Longman Science for AQA (AQA GCSE Science) Teacher's guide

Longman Science for AQA GCSE Science Extension Units

Series Editor: Nigel English

Edinburgh Gate Harlow, Essex

Muriel Claybrook Richard Grime Penny Johnson Sue Kearsey Penny Marshall

Pearson Education Edinburgh Gate Harlow Essex CM20 2JE UK www.longman.co.uk © Pearson Education Limited 2007 The right of Nigel English, Muriel Claybrook, Richard Grime, Penny Johnson, Sue Kearsey and Penny Marshall to be identified as the authors of this work has been asserted by them in accordance with the Copyright, Designs and Patents Act of 1988. All rights reserved. No part of this publication may be produced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording or otherwise without the prior written permission of the Publishers or a licence permitting restricted copying in the United Kingdom issue by the Copyright Licensing Agency Ltd, 90 Tottenham Court Road, London, W1P 9HE. First published 2007 ISBN 978 1 405 86187 8 Production and illustration eMC Design Ltd, www.emcdesign.org.uk Illustration Peters & Zabransky (UK) Ltd The publisher’s policy is to use paper manufactured from sustainable forests. Acknowledgments The publishers are grateful to the following for their collaboration in reviewing this book: Dr Peter Borrows, Director, CLEAPSS John Tranter, Senior Adviser, CLEAPSS Every effort has been made to trace the copyright holders and we apologise for any unintentional omissions. We would be pleased to insert the appropriate acknowledgement in any subsequent edition of this publication.

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AQA GCSE Extension Units Teacher’s Guide

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Contents Biology

Chemistry

B3.0

Exchange and balance

C3.0

Water

B3.0

Context page

C3.0

Context page

B3.1

Diffusion and active transport

C3.1

The water cycle

B3.2

Gas exchange in the lungs

C3.2

Purifying water

B3.3

Absorbing food

C3.3

Solubility

B3.4

Absorption in plants

C3.4

Saturated solutions

B3.5

Movement of water through plants

C3.5

Hard water

B3.6

Human blood circulation

C3.6

Types of hard water

B3.7

Travelling in the blood

C3.7

Should we remove hardness from water?

B3.8

Exercise and the body

C3.8

Flame tests

B3.9

Exercise fatigue and anaerobic respiration

C3.9

Detecting ions using sodium hydroxide solution

B3.10 Healthy kidneys B3.11 Dialysis treatment B3.12 Kidney transplants

C3.10 Looking at carbonates C3.11 Testing for other non-metal ions C3.12 Testing for acidity

B3.00 Exploiting microorganisms B3.00 Context page B3.13 Growing microorganisms

C3.13 Detecting organic chemicals C3.14 Detecting tiny amounts of chemicals C3.15 Instrumental analysis

B3.14 Aseptic technique B3.15 Biogenesis B3.16 Yoghurt and cheese B3.17 Yeast B3.18 The role of yeast in making alcoholic drinks B3.19 Fermenters and penicillin production B3.20 Mycoprotein by fungal fermentation B3.21 Biogas B3.22 Ethanol-based biofuels

C3.00 Driving chemistry further C3.00 Context page C3.16 The Periodic Table C3.17 Group 1 – the alkali metals C3.18 Transition metals C3.19 Group 7 – the halogens C3.20 The development of the Periodic Table C3.21 Solution calculations C3.22 Titrations C3.23 Choosing indicators for titrations C3.24 Energy transfers in reactions C3.25 Bond energies C3.26 Burning fuels C3.27 Using fuels C3.28 Energy in food C3.29 Reactions in solution

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AQA GCSE Extension Units Teacher’s Guide

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Physics P3.0

Forces and energy in space

P3.0

Context page

P3.1

Moments

P3.2

Centre of mass

P3.3

Stability

P3.4

Circular motion

P3.5

Gravity and the Solar System

P3.6

Changing ideas

P3.7

Satellites

P3.8

Stars and planets

P3.9

Life cycles of stars

P3.00 Investigating space P3.00 Context page P3.10 Plane mirrors P3.11 Curved mirrors P3.12 Refraction P3.13 Lenses P3.14 Cameras P3.15 Sound waves P3.16 Ultrasound P3.17 Electric motors P3.18 Making electricity P3.19 Generators P3.20 Transformers

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AQA GCSE Extension Units Teacher’s Guide

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Introduction Longman Science for AQA GCSE Science is the perfect accompaniment to the AQA Science GCSE specifications. The components work seamlessly together to offer you a fully supported and differentiated solution to help you deliver AQA Science GCSE specifications successfully from your first day of teaching. Series Editor Nigel English has led a team of experienced teachers to ensure that these materials are the perfect match to the AQA Science GCSE specifications. This is the Teacher’s Guide that accompanies the course. It contains Schemes of Work and lesson plans to get you started. The lesson plans include all the detail you would expect including ideas for starters and plenaries, practicals and ways to integrate How Science Works into your teaching. We have also included all the answers to the questions from both the Student’s Book and Copymaster File. In addition we have given you notes on how to integrate our exciting new ActiveTeach into your lessons. The course comprises: Component Student’s Book

An exact match to the AQA Science GCSE specifications. Supports student engagement with stimulating contexts.

Student’s ActiveBook

An electronic copy of the Student’s Book, which contains features such as target sheets and audio glossaries. Ideal for homework and revision.

Copymaster File

Photocopiable worksheets, practical activities and practice assessment materials. Completely differentiated to fully support the full range of student ability, materials are clearly marked to be suitable for Foundation or Higher tier students.

Teacher’s Guide

A source of lesson plans, teacher’s and technician’s notes, coursework help and of course full answers!

ActiveTeach

A unique electronic resource that contains the Student’s Book in electronic format with features such as zoom, audio glossary, video and Microsoft® PowerPoint presentations as well as interactive whiteboard animations.

Additional resources are also available to support your department. Please contact your local sales representative or email: [email protected] for further details. We hope that you enjoy using this course and that you will feel able to share your opinions, comments and suggestions with us. This will help us to ensure that this course continues to meet the needs of as many teaching professionals as possible. You can write to us at this address: The AQA Science team Longman Schools Division Pearson Education Edinburgh Gate Harlow CM20 2JE Or you can email us at [email protected]

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AQA GCSE Extension Units Teacher’s Guide



Course Structure The materials follow the pattern laid down in the AQA Biology, Chemistry and Physics GCSE specifications. The content is divided into three units.

Student’s Books Each unit has two context pages. These single pages help to introduce the unit, explain the context and set the objectives for the work ahead. Each subsequent topic is covered by one double page spread in the Student’s Book. These double pages contain the following features:

• Title

• Learning Objectives These

clearly explain what students should be able to do by the end of the topic. They are matched to the target sheets found in the Copymaster File (see below) and are directly related to the statements in the AQA Biology, Chemistry and Physics GCSE specifications.

• Key scientific words have been

highlighted in the text. They can also be found in a glossary at the end of each unit.



AQA GCSE Extension Units Teacher’s Guide

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At the end of each unit you will find a double page spread of sample questions. Sample questions provided are short answer questions reflecting the type of assessment that students will be given throughout the course. There are also two sample Individual Student Assessments (ISA) for each unit. ISAs require students to analyse data from a practical they have carried out in class and then answer questions on a related experiment. You will find that the ISAs provided in the Student’s Book provide students with the opportunity to answer some practice questions written in the style of an ISA. The full ISA can be found in the Copymaster File. For completeness we have included practicals not mentioned as potential ISA material by the AQA Biology, Chemistry and Physics GCSE specifications. This has been done to ensure that students have something relevant to work on in each unit. A glossary is provided at the end of each unit listing key words for the unit.

• Higher tier Content directly

related to higher tier specification statements are indicated by a small H icon next to the Learning objective and content.

• ActiveTeach icon Any links in

the ActiveBook or ActiveTeach are indicated in the print version by these icons. The links provide a wealth of activities, which will help to enrich your teaching. For more details on the ActiveTeach see pages 4–5.

• How Science Works Material on

How Science Works is included throughout the text. This icon indicates major links to such material. Where the whole topic is related to How Science Works there is a small HSW icon next to the Learning Objectives at the start.

• Questions can be found

throughout the text. They become increasingly difficult.

• Summary exercise The answer

to the last question in the topic summarises the whole of the topic. The exercise will also be useful for revision.

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AQA GCSE Extension Units Teacher’s Guide



ActiveBook and ActiveTeach Each Student’s Book in this series is accompanied by an ActiveBook. The ActiveBook is at the centre of the ActiveTeach that is a unique product enabling you to focus students’ attention on the content of the lesson and integrate multimedia into your teaching. The ActiveTeach contains the following features:

• An ActiveBook is the

heart of the ActiveTeach. The electronic version of the Student’s Book can be projected onto a whiteboard or through a digital projector. Every area of the book can be magnified by the interactive zoom feature. This means that students’ attention can be focused on a paragraph of text, a diagram or a question.

• All of the glossary terms in the book are available as audio files – just click on the word and both word and definition are played as sound files.



• The DigiList is a

quick way of finding your way around the interactive and electronic files. It works as a menu that enables you to locate a file quickly and see the full range of material available for each unit.

• The Teachers • The glossary • Target sheets are Notes give a short description of the electronic files in the ActiveTeach.

• The Interactive view allows you to gain access to the interactive features on the page. If you do not want the distraction of the multimedia assets then you can return the screen to Book View.

AQA GCSE Extension Units Teacher’s Guide

can also be accessed via this tab.

provided in electronic format for students to focus their own learning. The target sheets can be filled in on screen to provide a record of student’s achievements.

• Multimedia assets can be accessed via the pages of the book or via the DigiList. The assets include video clips, animations and interactive exercises, as well as presentations, documents and spreadsheets.

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Every copy of the print version of the Student’s Book contains a student’s ActiveBook. This contains the same electronic copy of the book plus the targets for each topic, summary exercises and editable word lists for the unit. Word lists for each unit contain the key words from the glossary and other words important in the unit.

Teacher’s Guide The Teachers Guide contains detailed information for each unit as well as these introductory notes. For each topic the pattern is as follows:

• Introduction This gives a brief overview of the unit and sets out the learning objectives. • Notes for each topic The notes are laid out along the lines of a lesson plan so that you can incorporate the material easily into your teaching. The following features are included for each topic:

• learning objectives

• a list of the

• points to note such

• higher tier, how

and key words

as common areas of confusion or detailed notes on the science

worksheets available for the topic

• suggestions

science works and ActiveTeach materials are highlighted

© Pearson Education Limited 2007

for learning activities

• ideas for starter and plenary activities

• ideas for additional homework or research activities

• a guide to running practicals and/or demonstrations, including apparatus list, timing and safety points.

AQA GCSE Extension Units Teacher’s Guide



At the end of the topic notes for each unit you will also find answers to the Student’s Book and Copymaster File questions, guidance on marking coursework ISAs (see note above) and a mark scheme for the end of unit test.

Copymaster File The Copymaster File provides all the worksheets and other materials intended to be photocopied for student use. The following worksheets can be found in the Copymaster File:

• Target sheets Each unit begins with a student target sheet. Students should look at the

statements and then record which statements they already understand. The target sheet also asks students for confidence levels. We would suggest that students are asked to fill in the target sheet at the beginning and end of the unit, and after they have revised for their end of unit test. This should provide them with a record of their own progress through the unit and increasing levels of confidence. This process of setting targets and monitoring progress themselves is a key feature of Assessment for Learning.

• Practical sheets and classwork sheets All topics have at least one worksheet to support classroom learning. These may be practical worksheets in some cases.

• Homework sheets Each topic is accompanied by a Homework sheet. The worksheets do not require the students to have access to the Student’s Book.

• Sample ISA ISAs require students to analyse data from a practical they have carried out

in class and then answer questions on a related experiment. The full ISA can be found in the Copymaster File. The practicals that may be used by AQA as the basis for ISA work are clearly laid out in the AQA Biology, Chemistry and Physics GCSE specifications. We have followed these as closely as possible but practicals used are not always those mentioned as potential ISA material by the specification. This has been done because they are only suggested ISAs and to ensure that students have relevant work for each unit.

• Unit assessment A practice short answer assessment is provided for each unit. These follow the style of the AQA sample materials.

The contexts In order to emphasise the importance of science in everyday life we have set each unit in two contexts. In each case the contexts are introduced by video footage that can be found on the ActiveTeach. The video clips show a series of individuals who are not necessarily scientists but who use science everyday as part of their occupation. Each individual explains what their job entails. The context is then used whenever appropriate in the Student’s Book to illustrate how their job uses scientific ideas. The contexts we have used are as follows: Biology B3 At the gym – exchange and balance and Industrial fermentation Chemistry C3 Water analysis and Chemistry in cars Physics P3 Forces and energy in Space and Investigating Space



AQA GCSE Extension Units Teacher’s Guide

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How Science Works The emphasis in all of the new science specifications is on building the skills and scientific literacy of candidates. There is now a much greater weighting towards this in the assessment process. All good teachers have always covered the essential areas of How Science Works (HSW) through their teaching methods. There is now an even greater imperative to do so with 60% of the overall assessment being for the application of knowledge, investigation skills and the ability of the candidates to see science in the wider context and understand current debate. There are areas detailed throughout the Student’s Book where HSW can be highlighted in the lesson. The Teacher’s Guide also highlights opportunities for introducing aspects of HSW. This includes a number of practical investigations that can be attempted, some of which are in the form of practice ISAs as well as material referring to scientific issues currently under debate. The context that each unit is set in also helps with the integration of HSW, providing a real flavour of science in everyday life. This integrates HSW closely into the teaching materials rather than it being a simple ‘bolt on’.

Foundation and Higher tiers The AQA Biology, Chemistry and Physics GCSE specifications allow students to enter either the Foundation or Higher tier for any of their assessments. Content aimed at Higher tier students only is indicated by an H icon. We have provided additional questions on the ActiveBook that are aimed at A*–A candidates. Worksheets that are aimed at Higher tier students only are indicated in the topic notes.

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AQA GCSE Extension Units Teacher’s Guide



Safety We have attempted to identify all the recognised hazards in the practical activities in this Teacher’s Guide, provide suitable warnings about them and suggest appropriate precautions. Teachers and technicians should remember, however, that where there is a hazard, the employer is required to carry out a risk assessment under either the COSHH Regulations or the Management of Health and Safety at Work Regulations. Most education employers have adopted a range of nationally available publications as model (general) risk assessments and, where such published assessments exist for the activity, our advice is believed to be compatible with them. Nevertheless, teachers and technicians must check whether what is proposed is indeed compatible with the requirements of the employer. In a few cases activities may be included that are not covered by widely-used model risk assessments. We have tried to identify these and in such cases teachers or technicians may need to check with their employer whether the activity is acceptable. If the employer is a member, they will often suggest consulting CLEAPSS. The proposed activities are likely to be acceptable to these organisations. Even where an activity is broadly in line with a model risk assessment, staff in a school will still need to consider whether their particular situation requires any adaptation. We have assumed that practical work is carried out in a properly equipped and maintained laboratory and that any field work takes account of the employer’s guidelines. In particular, we have assumed that any mains-operated electrical equipment is properly maintained, that students have been shown how to conduct normal laboratory operations safely (such as heating or handling heavy objects) and that good practice is observed when chemicals or living organisms are handled (see below). We have also assumed that classes are sufficiently small and well behaved for a teacher to be able to exercise adequate supervision of the students and that rooms are not so crowded that students’ activities pose a danger to their neighbours. The practical notes and worksheets have been checked by health and safety professionals who gave guidance on how to make this text conform to the above policy, and such recommendations were incorporated before publication.

Good laboratory practice A brief statement such as this can only be a summary. Any guidance issued by your employer must be followed, whatever is suggested here. It is expected that every school will have rules governing behaviour in the laboratory. No eating, drinking, smoking or the application of cosmetics should be allowed in laboratories. Interference with mains services or equipment should be strictly forbidden, as should running or foolish behaviour generally. Good hygiene is needed at all times, but especially when chemicals or living organisms are being used. Benches need to be wiped down after such activities and hands washed. Suitable eye protection must be worn whenever the risk assessment requires it, i.e. whenever there is a recognised risk to the eyes. This will certainly include activities in which chemicals are heated, heat is generated in a chemical reaction, or any activities involving chemicals with a hazard classification. Eye protection is also necessary when there are mechanical hazards, e.g. when stretching wires to breaking point or evacuating vessels. Many accidents occur during heating activities. Long hair should be tied back and ties, cardigans, scarves, etc. should not be allowed to hang freely. It is assumed that teachers will show and remind students how to safely heat small quantities of solids in test tubes and liquids in boiling tubes (wide diameter test tubes), using small quantities so that the tube is not more than one-fifth full, and pointing the tube away from their own and other people’s faces. The tube should be sloping so that the holder is not in a flame. For liquids, tubes should be gently shaken or a water bath used where appropriate. Students should stand, not sit, for most operations in which chemicals (and especially liquids) are handled. Teachers will need to show students how to smell the contents of a test tube or bottle safely. First, fill the lungs with (ordinary) air by breathing in deeply (so that only a small amount of chemical can subsequently be sniffed in). The container should then be held



AQA GCSE Extension Units Teacher’s Guide

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some distance from the face and pointing away from it, and the odours wafted gently towards the nose with a hand. Students need to be shown how to pour safely from bottles, pouring away from the label (so that it is not damaged by drips). Spills of chemicals should be wiped up at once. Some may require chemical treatment (e.g. neutralisation) but, in the quantities normally handled by students, a damp cloth is usually sufficient. The cloth should then be rinsed. Students should be trained to use a spatula or similar device, and never to handle chemicals with their fingers. Wherever possible, teat pipettes should be avoided. Even with well-behaved classes, too many accidents occur when liquids are squirted from them (e.g. when clearing up at the end of a lesson). Work in schools rarely requires the use of protective gloves. However, when chemicals have been used or living organisms handles, students should be trained to wash their hands afterwards. If the risk assessment requires the use of a fume cupboard, then this should meet the standard of Building Bulletin 88, Fume Cupboards in Schools (Architects and Buildings Branch, DfEE, HMSO, 1998) (previously Design Note 29). If safety screens are required for a demonstration, then they should be sufficient to protect the teacher and all the students. They should be sufficiently tall and close to the apparatus to prevent objects going over the top. There should be a gap of 2 m or more between any demonstration and the students. If microorganisms are in use, teachers unfamiliar with modern techniques may need training (see, for example, Topics in Safety, Safety in Science Education, or the CLEAPSS Laboratory Handbook). In any work in microbiology, risks can be reduced to an acceptable level by observing good practice and following simple precautions. Sterile technique is needed to prevent cultures from becoming contaminated and to stop microorganisms escaping from cultures. This will involve ensuring that materials that will contact microorganisms are sterile before and afterwards; a pressure cooker or autoclave is essential, complemented by the use of appropriate chemical disinfectants to deal with spills and to clean working surfaces. By choosing appropriate organisms and growth media, avoiding the culture of microorganisms from dangerous sources and incubating at room temperature, together with the correct handling and sealing of cultures, exposure to pathogens can be minimised or eliminated. Any culture of organisms that is to be consumed, e.g. yoghurt bacteria or baker’s yeast, should not take place in a science laboratory.

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AQA GCSE Extension Units Teacher’s Guide



B3

Biology

10

Topic

Learning outcomes and codes

1

13.1.2 Dissolved substances move by diffusion transport. H 13.1.3 Substances are sometimes absorbed against a concentration gradient. This requires the use of energy from respiration. The process is called active transport. It enables cells to absorb ions from very dilute solutions. Other substances, such as sugar and ions, can also pass through cell membranes.

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13.1.1 To explain how gas and solute exchange surfaces in humans and other organisms are adapted to maximise effectiveness. 13.1.4 Many organs are specialised for exchanging materials. 13.1.5 In humans: –  the surface area of the lungs is increased by the alveoli. 13.1.6 The lungs are in the upper part of the body (thorax) protected by the ribcage and separated from the lower part of the body (abdomen) by the diaphragm. 13.1.7 The breathing system takes air into and out of the body so that oxygen from the air can diffuse into the bloodstream and carbon dioxide can diffuse out of the bloodstream into the air. 13.1.8 The alveoli provide a very large, moist surface, richly supplied with blood capillaries so that gases can readily diffuse into and out of the blood.

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13.1.1 To explain how gas and solute exchange surfaces in humans and other organisms are adapted to maximise effectiveness. 13.1.5 In humans: –  the surface area of the small intestine is increased by villi. 13.1.9 The villi provide a large surface area with an extensive network of capillaries to absorb the products of digestion by diffusion and active transport.

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13.1.1 To explain how gas and solute exchange surfaces in humans and other organisms are adapted to maximise effectiveness. 13.1.4 Many organs are specialised for exchanging materials. 13.1.10 In plants: –  carbon dioxide enters leaf cells by diffusion –  most of the water and mineral ions are absorbed by root hair cells. 13.1.11 The surface area of the roots is increased by root hairs and the surface area of leaves by the flattened shape and internal air spaces. 13.1.12 Plants have stomata to obtain carbon dioxide from the atmosphere.

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13.1.13 Plants lose water vapour from the surface of their leaves. This loss of water vapour is called transpiration. Transpiration is more rapid in hot, dry and windy conditions. Most of the transpiration is through stomata. The size of stomata is controlled by guard cells that surround them. If plants lose water faster than it is replaced by the roots, the stomata can close to prevent wilting.

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13.2.1 The heart pumps blood around the body. Blood flows from the heart to the organs through arteries and returns through veins. In the organs, blood flows through capillaries. Substances needed by cells in the body tissues pass out of the blood, and substances produced by the cells pass into the blood through the walls of the capillaries. 13.2.2 There are two separate circulation systems, one to the lungs and one to all the other organs of the body.

AQA GCSE Extension Units Teacher’s Guide

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13.2.3 Blood plasma transports: –  carbon dioxide from the organs to the lungs –  soluble products of digestion from the small intestine to other organs –  urea from the liver to the kidneys. 13.2.4 Red blood cells transport oxygen from the lungs to the organs. Red blood cells have no nucleus. They are packed with a red pigment called haemoglobin. In the lungs haemoglobin combines with oxygen to form oxyhaemoglobin. In other organs oxyhaemoglobin splits up into haemoglobin and oxygen.

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13.3.1 To interpret data relating to the effects of exercise on the human body. 13.3.2 The energy that is released during respiration is used to enable muscles to contract. 13.3.3 During exercise a number of changes take place: –  the heart rate increases –  rate and depth of breathing increases –  the arteries supplying the muscles dilate. 13.3.4 These changes increase the blood flow to the muscles and so increase the supply of sugar and oxygen and increase the rate of removal of carbon dioxide. 13.3.5 Glycogen stores in the muscle are used during exercise.

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13.3.6 If muscles are subjected to long periods of vigorous activity they become fatigued, i.e. they stop contracting efficiently. If insufficient oxygen is reaching the muscles they use anaerobic respiration to obtain energy. H 13.3.7 Anaerobic respiration is the incomplete breakdown of glucose and produces lactic acid. As the breakdown of glucose is incomplete, much less energy is released than during aerobic respiration. Anaerobic respiration results in an oxygen debt that has to be repaid in order to oxidise lactic acid to carbon dioxide and water.

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13.4.2 A healthy kidney produces urine by: –  first filtering the blood –  reabsorbing all the sugar –  reabsorbing the dissolved ions needed by the body –  reabsorbing as much water as the body needs –  releasing urea, excess ions and water as urine. H 13.4.3 Sugar and dissolved ions may be actively absorbed against a concentration gradient.

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13.4.1 To evaluate the advantages and disadvantages of treating kidney failure by dialysis or kidney transplant. 13.4.4 People who suffer from kidney failure may be treated either by using a kidney dialysis machine or by having a healthy kidney transplanted. 13.4.5 In a dialysis machine a person’s blood flows between partially permeable membranes. The dialysis fluid contains the same concentration of useful substances as the blood. This ensures that glucose and useful mineral ions are not lost. Urea passes out from the blood into dialysis fluid. Treatment by dialysis restores the concentrations of dissolved substances in the blood to normal levels and has to be carried out at regular intervals.

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13.1.4 Many organs are specialised for exchanging materials. 13.4.6 A kidney transplant enables a diseased kidney to be replaced with a healthy one from a donor. However, the donor kidney may be rejected by the immune system unless precautions are taken. 13.4.7 To prevent rejection of the transplanted kidney: –  a donor kidney with a ‘tissue-type’ similar to that of the recipient is used –  the recipient is treated with drugs that suppress the immune system.

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AQA GCSE Extension Units Teacher’s Guide

11

12

13

13.7.1 Microorganisms can be grown in a culture medium containing carbohydrates as an energy source, mineral ions, and in some cases supplementary protein and vitamins. These nutrients are often contained in an agar medium that can be poured into a Petri dish. 13.7.3 In school and college laboratories, cultures should be incubated at a maximum temperature of 25 °C, which greatly reduces the likelihood of pathogens growing that might be harmful to humans. In industrial conditions higher temperatures can produce more rapid growth.

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13.7.2 In order to prepare useful products, uncontaminated cultures of microorganisms are required. For this: –  Petri dishes and culture media must be sterilised before use to kill unwanted microorganisms –  inoculating loops used to transfer microorganisms to the media must be sterilised by passing them through a flame –  the lid of the Petri dish should be sealed with adhesive tape to prevent microorganisms from the air contaminating the culture.

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13.5.1 To explain how scientists such as Spallanzani, Schwann and Pasteur were involved in the development of the theory of Biogenesis.

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13.5.2 Microorganisms are used to make food and drink: –  bacteria are used in yoghurt and cheese manufacture 13.5.7 In the production of yoghurt: –  a starter of bacteria is added to warm milk –  the bacteria ferment the milk sugar (lactose) producing lactic acid –  the lactic acid causes the milk to clot and solidify into yoghurt.

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13.5.2 Microorganisms are used to make food and drink: –  yeast is used in making bread and alcoholic drinks. 13.5.3 Yeast is a single-celled organism. The cells have a nucleus, cytoplasm and a membrane surrounded by a cell wall. 13.5.4 Yeast can respire without oxygen (anaerobic respiration), producing carbon dioxide and ethanol (alcohol). This is called fermentation. In the presence of oxygen yeast carries out aerobic respiration and produces carbon dioxide and water. Aerobic respiration provides more energy and is necessary for the yeast to grow and reproduce.

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13.5.5 In brewing beer and wine-making, carbohydrates are used as an energy source for yeast to respire. For making beer: –  the starch in barley grains is broken down into a sugary solution by enzymes in the germinating grains, in a process called malting –  the sugary solution is extracted then fermented –  hops are then added to give the beer flavour. 13.5.6 In wine-making the yeast uses the natural sugars in the grapes as its energy source.

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13.6.3 Microorganisms can be grown in large vessels called fermenters to produce useful products such as antibiotics. Industrial fermenters usually have: –  an air supply to provide oxygen for respiration of the microorganisms –  a stirrer to keep the microorganisms in suspension and maintain an even temperature –  a water–cooled jacket to remove heat produced by the respiring microorganisms –  instruments to monitor factors such as pH and temperature. 13.6.4 The antibiotic, penicillin, is made by growing the mould Penicillium, in a fermenter. The medium contains sugar and other nutrients, e.g. a source of nitrogen. The Penicillium only starts to make penicillin after using up most of the nutrients for growth.

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13.6.5 The fungus Fusarium is used to make mycoprotein, a protein-rich food suitable for vegetarians. The fungus is grown on starch in aerobic conditions and the biomass is harvested and purified.

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13.6.2 To evaluate the advantages and disadvantages of given designs of biogas generator. 13.6.6 Fuels can be made from natural products by fermentation. Biogas, mainly methane, can be produced by anaerobic fermentation of a wide range of plant products or waste material containing carbohydrates. 13.6.7 On a large scale, waste from, for example, sugar factories or sewage works can be used. On a small scale, biogas generators can be used to supply the energy needs of individual families or farms. Many different microorganisms are involved in the breakdown of materials in biogas production.

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13.6.1 To interpret economic and environmental data relating to production of fuels by fermentation and their use. 13.6.8 Ethanol-based fuels can be produced by the anaerobic fermentation of sugar cane juices and from glucose derived from maize starch by the action of carbohydrase. The ethanol is distilled from the products of the fermentation and can be used in motor vehicle fuels.

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AQA GCSE Extension Units Teacher’s Guide

13

B3.0

Exchange and balance Overview This unit starts with a revision of diffusion and introduces active transport, then builds on this to cover exchange and the adaptations of exchange surfaces in the lungs, the small intestine, plant leaves and root hair cells. It then describes the transport of water around plants and transpiration, and the transport of blood through the heart and human circulation. It continues by explaining how exercise affects the body during aerobic activity, and when muscles use anaerobic respiration. It ends with a section on kidneys, how they work normally and how dialysis and transplants are used to treat kidney failure.

Investigative Skills Assessment The ISA for Unit B3.0 is investigating the effect of environmental conditions on the rate of transpiration. In the Student’s Book, data is presented to the students and then they are asked a number of questions about the investigation. The Copymaster File provides questions for students to answer based on their own investigations into the rate of transpiration. Practical 1 in Topic B3.5 gives instructions for this investigation.

B3.0

Context page

Objectives for the unit

Notes on context

Students should know and understand:

• how the body responds to exercise to increase

This unit is presented in the context of fitness and exercise at the gym. The efficient exchange of gases in the lungs, and between cells and blood, is fundamental to being fit and healthy. Regular exercise improves the body’s response to increasing levels of activity, improving the strength of the heart and the response of the breathing and circulation systems to the transport of blood around the body. This supplies cells with the glucose and oxygen they need for aerobic activity.

• how muscle cells use anaerobic respiration when

AT The ActiveTeach component for this topic is a video introduction to what fitness really means.

• how exchange surfaces in animals and plants,

such as the lungs, small intestine, kidneys, plant leaves and root hair cells, are adapted for effective exchange

• how blood circulates through the heart and the two circulation systems of the human body

supply of oxygen and removal of carbon dioxide aerobic respiration cannot supply enough energy for activity

• different methods for treating kidney failure.

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AQA GCSE Extension Units Teacher’s Guide

© Pearson Education Limited 2007

B3.1

Diffusion and active transport

Worksheets available No. B3.1a

Title Diffusion questions

B3.1b

Transport across cell membranes

Type Classwork/homework (write-on) Classwork/homework (reusable)

Objectives Students should be able to:

• recall that dissolved substances move by diffusion transport

• H explain how active transport moves substances against a concentration gradient using energy.

Key words concentration gradient, diffuse, partially permeable membrane H active transport

Points to note

• Students may get the impression from articles

they read that ‘rate of diffusion’ relates to speed of movement of the particles. This is incorrect. Particles move at a speed that is related to the heat energy they have (i.e. the temperature). If that does not change, then the particles cannot move faster. Starting with a higher concentration gradient will not affect the distance that particles move over a given time. However, if you start with more particles in one area, then more will move to the area of lower concentration. Rate of diffusion is a rate of change of concentration. Practical 1 illustrates this, and can be used to dispel any misunderstanding.

Lesson ideas Starter

• Write the word ‘diffusion’ in the middle of the board or an OHT. Ask students to suggest words they associate with diffusion, and how they should be linked to build up a concept map for this topic. Much of the work on diffusion in this topic is revision of Topic B2.4 in the AQA Additional Science materials. This activity should revise the work they did then and identify any weaknesses or confusion in their knowledge. Keep the concept map for the plenary.

Learning activities

• Questions 1–4 in the Student’s Book could be used

Foundation 4

Higher 4 4

This will help you decide what needs covering in greater detail or can be glossed over. It is particularly important that students understand how the rate of diffusion is dependent on the concentration gradient, as this concept will be applied to specific examples in humans and plants in the following topics. If there is any confusion about rate of diffusion, ask students to carry out Practical 1.

• Worksheet B3.1a is a revision sheet about diffusion and could be used with Foundation and Higher students as classwork or homework, depending on their response to your initial assessment of their understanding.

• H Worksheet B3.1b is a Higher-level sheet on

diffusion and active transport that could be used as classwork or homework, as appropriate for your students. A suitable website for the final research question is Asthma UK, which can be accessed via www.longman.co.uk/AQAScience.

• AT The ActiveTeach includes a repeat of the

diffusion animation from the AQA Additional Science materials, for students who need to revise their understanding of this process.

• H

AT The ActiveTeach also includes an animation of active transport for students to compare with diffusion.

Plenary

• Return to the concept map produced in the starter. Ask students to identify any words that were misplaced then, and suggest where they should be placed correctly. They should also suggest any new words or ideas that they have come across in the lesson that could be added to the map.

Additional homework/research ideas

• ICT Key examples of diffusion and active transport

will be covered in following topics. However, you could ask students to research other examples here. For diffusion, students could research uptake of substances from the host by parasites such as tapeworms and flukes, and how this influences their body design. Higher-tier students could research the importance of active transport of sodium and potassium ions for the action of muscles and nerves.

as assessment of how well students remember and understand what they have learnt about diffusion.

© Pearson Education Limited 2007

AQA GCSE Extension Units Teacher’s Guide

15

Practicals and demonstrations 1 Diffusion in agar This practical will produce the results shown in Diagram B in the Student’s Book. Cut two identical wells in a non-nutrient agar plate using a cork borer. Seal the base of each well with a drop of liquid agar and leave to set. This will reduce the risk of leakage at the base of the well. Using a dropper, place similar amounts of dye solution in each well, using one concentrated and one dilute dye solution. Cover the plate and leave for 24–48 hours. This should show that in different concentrations the dye penetrates the same distance, but that the amount of dye that penetrates is greater for a higher concentration of solution. Discuss these results with

B3.2

students to make sure that they are clear that rate of diffusion is not speed of movement of the dye particles (as commonly believed) but the amount of particles that penetrate to any given depth. If it is not possible for students to set up and return to the practical within the time given, then the set up could be done for them, leaving them to look at the results. 15 minutes set up, leave for 24–48 hours, 5 minutes for results Apparatus (per group) Non-nutrient agar plate; cork borer; dye (food colouring); water; dropping pipette.

Gas exchange in the lungs

Worksheets available No. B3.2a B3.2b

Title Diseases of the lungs The structure of fish gills

Type Classwork (reusable) Homework (reusable)

Objectives Students should be able to:

• describe how the lungs are protected in the thorax and are separated from the abdomen by the diaphragm

• explain the role of the breathing system in the

exchange of gases between the air and the blood

Foundation 4 4

Higher 4 4

breathing. Then ask them to place one hand on their chest and one on their abdomen and see whether they can breathe in and out without moving the rib cage. What other part of the body moves with the breath during this kind of breathing?

Learning activities

• Although students do not need to understand the

mechanisms of ventilation for this specification, a demonstration using the apparatus below will help to reinforce the importance of the diaphragm in breathing and the fact that breathing in and out is the result of movements of the diaphragm (and rib cage) rather than the other way around.

• describe how the alveoli in the lungs are adapted for gas exchange in relation to surface area, thin walls and rich blood supply

• explain how these adaptations maximise the effectiveness of the lungs.

Key words

Y tube

abdomen, alveolus, bronchi, capillary, diaphragm, thorax

bell jar balloons fixed firmly to ends of Y tube

Points to note

• The specification refers to moistness of the alveolar

surface. Although there is some moisture in lungs (which is why exhaled air has a higher proportion of water than inhaled air), it is not a continuous layer and does not play a critical role in gas exchange.

Lesson ideas Starter

• Ask students to put their hands on their chest and

take a deep breath in and then out. Ask them to describe the movements of the rib cage during their

16

AQA GCSE Extension Units Teacher’s Guide

rubber sheet fixed firmly to base of bell jar



• Practical 1 reinforces the relationship between

surface area and rate of diffusion. This could be carried out during work on this topic or any of Topics B3.3–B3.5. Ask students to use their findings to explain the importance of increased surface area to alveoli in the lungs (or as appropriate for following topics).

• Worksheet B3.2a may be better used as a wholeclass activity with some students.

• Worksheet B3.2b looks at how the gills of fish are adapted for gas exchange.

© Pearson Education Limited 2007

• AT The ActiveTeach also contains a video clip that

discusses the importance of the breathing system during exercise, including the body’s response of breathing deeper and faster during activity to supply oxygen and remove carbon dioxide faster.

Plenary

• Carry out a connectives exercise with the class using

connective words, including ‘and’, ‘because’, ‘such as’, ‘to’ and ‘which’, to revise the adaptations of the lungs to exchange of gases. Suitable sentence starters are: ‘The alveoli increase the surface area of the lungs …’, ‘The breathing system takes air in and out of the body …’.

Additional homework/research ideas

• Ask students to research examples of lung diseases

that are caused by industrial pollution, such as pneumoconiosis and asbestosis. They should try to find the causes of these diseases, and which industries they are most closely related with. They could also research legislation that is aimed at reducing the risks to people working in industry from this kind of pollution.

Practicals and demonstrations 1 Surface area and rate of diffusion The effect of surface area on the rate of diffusion can be shown using identical lengths of different diameters of Visking tubing. Tie off one end of each tube and fill it with a solution of dye (food colouring). Wash the tubes under a running tap to remove any spills of colour on the outside. Then suspend the tubes to the same depth in different beakers of water. Differences in density of dye that diffuses into the water can be measured using a colorimeter.

You could ask Higher-level students to convert the tube diameters into surface areas for better analysis of the results. This could be extended by asking students to compare the rate of diffusion from the same volume of Visking tubing of different diameters. They will have to calculate first how many tubes of narrower diameter will be needed to hold the same volume of dye as one wide-diameter tube. 1 hour Apparatus (per group) Visking tubing of different diameters; dye (food colouring); beakers; water; clamp and clamp stands. 2 Demonstration of lung structure Ask your butcher for the lungs from a sheep or pig (alternatively, a ‘pluck’ includes the lungs and heart). Use these to help students identify the trachea (if still attached) and the two bronchi, and how these tubes divide and get narrower, the deeper you get in the lungs. Students should appreciate that the spongy texture of the lungs is due to the millions of alveoli at the ends of the bronchioles, though they will not be able to see alveoli clearly except with a magnifying glass. Students should also note the red colour of the lungs, which indicates the rich blood supply Wash hands thoroughly after handling lungs. Disinfect any dissecting boards used with 1% Virkon solution for 10 minutes. Alternatively, perform the demonstration on a sheet of plastic. After the demonstration, wrap the lungs in newspaper, place in a black plastic bin bag and place in normal refuse, preferably in a skip outside. Apparatus Lungs from a sheep or pig, dissecting board or plastic sheet, 1% Virkon solution, sharp knife or scalpel.

B3.3

Absorbing food

Worksheets available No. B3.3a B3.3b

Title Structures of the small intestine Adaptations of the intestine wall

Objectives Students should be able to:

Type Classwork (reusable) Homework (write-on)

Foundation 4 4

Higher 4 4

• explain how the adaptations of the small intestine maximise its effectiveness for absorption

• describe how the surface of the small intestine is

• H understand that some products of digestion are

• describe other adaptations of the small intestine

Key words

increased by villi

for absorption by diffusion, including the extensive network of capillaries

© Pearson Education Limited 2007

absorbed by active transport.

digest, microvillus, villus

AQA GCSE Extension Units Teacher’s Guide

17

Points to note

• You will find many different estimates of the length

of the small intestine and its surface area. The difficulty with length is that the muscles in the intestine wall relax after death, so measures taken then give lengths that are much longer than they are in life. Also, gut length naturally varies between individuals and may be affected by diet. Estimates of surface area make many assumptions, so will obviously vary depending on the assumptions made.

• H Active transport in the small intestine is

a confusing subject to research because of variations in terminology and accuracy of the detail that students will find. Glucose and other monosaccharides, and some amino acids, are actively transported, but only across one membrane of a cell and, in some cases, are not actively transported themselves but are cotransported with sodium ions that are actively transported. It is suggested that this detail is left to A-level to avoid confusing students.

Lesson ideas Starter

• Revise work on digestion from AQA Additional

Science by giving students 5 minutes to jot down notes to answer the question ‘What happens to your lunch inside your gut?’ Take answers from the class to assess what they remember about the structure of the gut, where enzymes are released and what they do.

Learning activities

Ask students to apply their findings to the structure of the small intestine and explain the importance of increased surface area to the absorption by diffusion of molecules released by digestion.

• Worksheet B3.3b could be used as either a classwork

or homework sheet as appropriate for your students.

• AT The ActiveTeach has an electron micrograph of

the microvilli on the cells of the surface of the small intestine for use with Worksheet B3.3a. This will need to be displayed on a whiteboard or screen while students complete this part of the worksheet as a classwork activity.

Plenary

• Write up the key words and other suitable words

from this topic on the board. Give students 5 minutes to write questions to which each word is an answer. Take examples from the class to discuss.

Additional homework/research ideas

• Not all the food substances that are absorbed in the

gut are absorbed in the small intestine. Students could research the few substances that are absorbed in the stomach (such as alcohol and aspirin) and try to find out why this is possible.

• Alternatively, students could research the effect of

diet on the intestine length, particularly in animals that vary their diet through the year (such as voles). Note that this research is not suitable for students who are upset by the thought of killing animals for study.

• If you have a 5-metre rope or flexible pipe, use it

Practicals and demonstrations

• Practical 1 and Worksheet B3.3a give students the

If using a microscope with a mirror, do not allow sunlight to shine directly through the microscope. 20 minutes

to demonstrate the length of the average human small intestine. Alternatively, get three students to lie down in a long line to give an idea of the length that you are describing. With the rope or pipe, students can attempt to ‘pack’ it so that it fits within the space of the abdomen. More able students could attempt to estimate the surface area of the inside of the small intestine if there was no folding. This will help give an idea of just how much the villi and microvilli increase the surface area. opportunity to study slides of the small intestine and assess the impact of villi and microvilli on surface area. Alternatively, a slide of small intestine could be projected on a whiteboard or screen and the calculations on the worksheet carried out as a whole-class activity.

18

• Practical 1 from Topic B3.2 could be used here also.

AQA GCSE Extension Units Teacher’s Guide

1 Structures of the small intestine In this practical, students observe a prepared slide of small intestine (ideally human, but any mammal will do) to look at the villi and microvilli (brush border). Note that they will be able to see little detail of microvilli using a light microscope. The ActiveTeach contains an electron micrograph of microvilli for use with Worksheet B3.3a to complete the practical.

Apparatus (per student) Microscope with low- and high-power objectives; light source; piece of thread or thin string; ruler; Worksheet B3.3a.

© Pearson Education Limited 2007

B3.4

Absorption in plants

Worksheets available No. B3.4a B3.4b

Title Diffusion and shape Getting enough carbon dioxide

Type Practical (reusable) Homework (reusable)

Objectives Students should be able to:

• describe how carbon dioxide enters leaves by diffusion through stomata

• describe how water and mineral ions enter plants through root hair cells

• explain how leaves and roots are adapted as exchange surfaces.

Key words root hair cells, stomata

Points to note

• Some of the features of leaves are adaptations to

other needs. For example, thin flat leaves are more effective for catching sunlight, and the control of stomatal opening is usually to control watervapour exchange with the air, not oxygen or carbon dioxide. You may wish to discuss these facts with students during this topic, but they will not need to remember them for the examination.

Lesson ideas Starter

• Briefly revise photosynthesis by giving students

5 minutes to jot down answers to the following questions: what is the equation for photosynthesis, where do the reactants for photosynthesis come from, which conditions affect the rate of photosynthesis, where does photosynthesis happen in a plant and why does it only happen here? Take answers from the class and tackle any weaknesses or misconceptions.

Learning activities

• Discuss the effect of shape in relation to diffusion

distance. Students should understand from the previous topics why diffusion distance affects the time it takes for a gas to diffuse from one place to another. So they should be able to explain why the flat shape of a leaf is an advantage for the effective exchange of gases.

• HSW Practical 1 and Worksheet B3.4a give students the opportunity to design and test models of

© Pearson Education Limited 2007

Foundation 4 4

Higher 4 4

different shapes to explore the effect of shape on diffusion.

• H With more able students, explore the relationship between surface area and volume by calculating the surface area of different-shaped blocks with the same volume. Start with a cube of side 2 cm2 and draw up a table of surface area, volume and SA/V ratio. Repeat with shapes that are increasingly flat, such as rectangular blocks of 42221 and 82121. Ask students to relate their findings to the shape of leaves.

• Practical 2 gives students the opportunity to look at the distribution of stomata on leaf surfaces.

• Plants that live in places where water is short

(such as dry places, or cold places where water is frequently frozen) have a conflict in need between getting carbon dioxide in through stomata for photosynthesis, but losing as little water vapour through the stomata as possible. Worksheet B3.4b explores some ways that plants are adapted to these conditions. This partly anticipates the work in the next topic on transpiration, and could be done then instead of here. This worksheet may be better used as a classwork activity with some students.

• AT The ActiveTeach includes an animation that

shows how the gases carbon dioxide and water vapour are exchanged between the cells inside the leaf, the air spaces and, through the stomata, with the air.

Plenary

• Play ‘traffic lights’ to test how well students have

learnt the features of absorption in plants. Give each student a red, a yellow and a green card. Ask them to hold up the red card if a statement is false, green if is true and yellow if they are not sure. Offer statements covered in this topic, such as ‘Stomata are holes in the leaf surfaces’ (true), ‘There are usually more stomata on the upper leaf surface than the lower surface’ (false), ‘Root hair cells are an adaptation for absorption’ (true).

Additional homework/research ideas

• Ask students to research the adaptations that plants have for keeping their stomata open in conditions when they need to reduce water loss. For example, they could consider cacti (hot/dry), conifers (cool/ dry) and epiphytes that live high in trees such as orchids and ‘airplants’ (hot/dry). AQA GCSE Extension Units Teacher’s Guide

19

Practicals and demonstrations

2 Leaf peels Students can study the stomata of leaves by looking at them under a binocular microscope, or by looking at leaf peels with a monocular microscope. Leaf peels are made by painting clear nail varnish thickly on to a leaf surface. Leave the peel at least two hours or, even better, overnight to harden. Cover the peel with clear sticky tape and then carefully peel the varnish from the leaf. The tape can then be stuck to a microscope slide for viewing.

1 Diffusion into 3D shapes Students can model the effect of 3D shape on the rate of diffusion by using different shapes of agar blocks. Higher-tier students should decide the thickness of the blocks in order to get some data to analyse in support of their conclusions. You may prefer to provide the agar blocks already prepared for Foundation students. The agar should be mixed with indicator solution before making the blocks. The blocks are then placed in dilute acid that will change the colour of the indicator. It should be possible to see when the acid reaches the centre of the blocks. Worksheet B3.4a supports the planning of this investigation. 1 hour

Ask students to compare the number of stomata on upper and lower leaf surfaces. If possible, they should also compare the leaves of different plant species. In most plants, they should find that upper leaf surfaces have relatively few stomata compared with the lower surface, and that different species show different distributions of stomata.

Apparatus (per group)

Apparatus

Non-nutrient agar blocks of different thicknesses including indicator, ideally a cube, e.g. 12121 cm, a half-cube, e.g. 1212½ cm, and a quarter-cube, e.g. 1212¼ cm; dish; dilute acid; ruler; knife; clock; Worksheet B3.4a.

B3.5

Selection of leaves from different plants; clear nail varnish, clear sticky tape, microscope and slides.

Movement of water through plants

Worksheets available No. B3.5a B3.5b

Title Investigating transpiration Transpiration and concentration gradients

Type Practical (reusable) Homework (reusable)

Objectives

Lesson ideas

Students should be able to:

Starter

•

describe how plants lose water from their leaves by transpiration

• suggest in which conditions transpiration is most rapid

• explain how and why a plant controls the rate of transpiration in some conditions.

Key words guard cell, osmosis, potometer, transpiration, wilt, xylem

Points to note

• The vascular tissue of a plant contains other types of

cells, such as phloem and cambium. Students do not need to know these for this specification. However, it is important that they don’t form the misconception that vascular tissue only contains xylem.

20

Foundation 4 4

AQA GCSE Extension Units Teacher’s Guide

Higher 4 4

• Use a potted plant as the basis for asking questions that revise how water gets into and is lost from a plant. A simple demonstration of a celery stalk that has been standing in a dyed solution for 24 hours will help students remember how the water gets from the roots to the leaves. It would be useful to introduce the term xylem at this point, to describe the tubes that carry the water up the plant.

Learning activities

• Some students may need a hint to help them

answer Question 5 in the Student’s Book. It refers to a factor that affects transpiration rate that hasn’t been mentioned in this topic, and that is the concentration gradient. This is discussed in more detail in Worksheet B3.5b.

• HSW Worksheet B3.5a supports Practical 1 in

investigating the effect of humidity on transpiration rate. Alternatives are suggested at the end of Practical 1.

© Pearson Education Limited 2007

• The Investigative Skills Assignment expects students to carry out an investigation into the effect of wind speed on the rate of transpiration.

• You may wish to use Worksheet B3.5b as a classwork sheet with Foundation students, in small-group or whole-class discussion of each situation, to help students’ understanding.

• AT The ActiveTeach includes animations that are an extension from Topic 4, to show how changes in temperature, wind speed and humidity affect transpiration rate.

• Sketch a graph like the one below on the board and

ask students to explain the shape in as many ways as they can. 100%

Transpiration rate

b fill the graduated capillary tube with water c under water, fit the shoot into the bung at the end of the potometer and seal it with Vaseline to make it airtight d join the potometer to the capillary tube using rubber tubing e submerge the whole apparatus in water to make sure that it is airtight f introduce an air bubble into the capillary tube

Plenary

75%

50%

25%



a cut a leafy shoot under water to stop the entry of air into the stem (Pelargonium is suitable for this)

6am

12 noon

6pm

12pm

Additional homework/research ideas

• Ask students to research all the adaptations of

desert-growing plants to enable them to survive in hot, dry conditions. This will extend work from the leaf adaptations researched in Topic B3.4, and should include form of growth, colour, root structure and life cycle.

Practicals and demonstrations

g use a syringe to move the bubble to the start of the scale. Note that potometer designs vary, so these instructions may need adapting. What is important is to make sure the equipment is airtight before starting, and to make sure the air bubble can be adjusted to a zero point before each experiment. If potometers are not available, a simpler set-up is to use a plant in a plant pot on weighing scales. The pot (not including the plant) will need to be sealed within a plastic bag to avoid water loss from the soil. However, even with sensitive weighing scales, this set-up will not give as precise measurements as using a potometer. This should be discussed with students if they use this set-up. Wash hands after handling plants. 1 hour Apparatus (per group) Potometer (including graduated capillary tube, rubber tubing, syringe, bung with hole); leafy shoot, e.g. Pelargonium; Vaseline; beaker; water; stopclock; Worksheet B3.5a.

1 Investigating transpiration Worksheet B3.5a supports this practical in the investigation of humidity on transpiration rate. Students will use a potometer to measure transpiration rate. This equipment will need to be set up for them as detailed below. You will also need to demonstrate how to move the bubble along the scale using the syringe so that the scale can be set to zero at the start of each experiment.

For investigating humidity: plastic bag and tie to place over shoot, humidity sensor and datalogging equipment. Humidity can be varied by spraying different (small) amounts of water into the bag before placing it over the plant.

To set up the potometer (see diagram on Worksheet B3.5a):

For investigating wind speed: small fan with several speed settings. Make sure the fan is not placed too close to the plant where it may cause physical damage at high speed.



© Pearson Education Limited 2007

For investigating temperature: source of heat such as within an incubator, or rooms of different temperature, thermometer or heat sensor with datalogging equipment.

AQA GCSE Extension Units Teacher’s Guide

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B3.6

Human blood circulation

Worksheets available No. B3.6a B3.6b

Title Structure of the heart Why two circulations?

Objectives Students should be able to:

• describe how the heart pumps blood through the

arteries to the organs that returns through veins to the heart

• identify two separate circulation systems in humans, one to the lungs and one to the rest of the body

• explain how substances are exchanged between body cells and the blood in capillaries.

Key words artery, vein

Points to note

• Worksheet B3.6b introduces mm Hg (millimetres of

mercury) as the measure of blood pressure. This is an old measure of pressure still used in the medical profession as it is linked to the use of mercury sphygmomanometers. If you have access to one of these, it would be useful to demonstrate to students so that they can understand the term more easily.

Lesson ideas Starter

• Write the word ‘heart’ on the board and, either as

a whole-class activity or pair work, ask students to suggest words that can be added to compile a concept map linked to this. After a few minutes, if they have not already been mentioned, introduce the words ‘circulation’ and ‘respiration’ and ask how they should be linked to the concept map. It is important at this stage to help students make the link to lungs and small intestine (as an example of a body organ) covered earlier. Keep the concept map to return to in the plenary.

Learning activities

• Question 4 in the Student’s Book refers back to work covered in Topic B3.2. Question 7 refers to work on diabetes that was covered in AQA GCSE Additional Science. If students have forgotten, you may have to remind them about how insulin is secreted from cells in the pancreas acts on cells in the liver and muscles.

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AQA GCSE Extension Units Teacher’s Guide

Type Classwork (write-on) Homework (reusable)

Foundation 4 4

Higher 4 4

• Worksheet B3.6a can be completed alongside

Practical 1 or, if preferred, through individual research. You will need to introduce the terms ‘oxygenated’ and ‘deoxygenated’ to describe blood that contains higher or lower concentrations of oxygen.

• Worksheet B3.6b could be completed as a classwork activity, if this will support your students better.

• The summary activity in the Student’s Book could be extended by asking students to write the essay.

• AT The ActiveTeach includes a video clip that discusses the importance of the heart and circulation in normal levels of activity.

• AT The ActiveTeach also includes an animation

that shows the circulation of the blood through the two circulation systems. There are close-up details in body tissue and in lungs to show exchange of materials with blood in relation to concentration gradients. This would be appropriate for either this or the next topic.

Plenary

• Return to the concept map developed in the starter activity and ask students to identify any errors and explain how to resolve them. They should then suggest further words and ideas from the topic to add to the concept map and explain how they should be linked.

Additional homework/research ideas

• ICT Ask students to research on the internet to find the heart and circulation structure of other groups of animals, such as fish, amphibians and reptiles. If possible, they should compare the effectiveness of the different kinds of circulation for delivering oxygenated blood to tissues.

Practicals and demonstrations 1 Dissection of a mammalian heart This practical can be done as a whole-class demonstration or, if appropriate for your students, as small-group work. Students will have to be shown how to dissect the heart and be made aware of safety procedures. You will need to ask a more experienced colleague if you have not dissected a heart before. Use a pig’s or sheep’s heart from the butchers. If possible, ask the butcher to leave the tubes attached to the heart rather than trimming them off as they are usually prepared, or buy a ‘pluck’ and cut out the heart with longer lengths of vessels. © Pearson Education Limited 2007

Help students to identify the left and right sides of the heart, using the thickness of the left ventricle as a guide. From this they should be able to work out which tubes are which, using Worksheet B3.6a. They should also be able to point out each of the atria and ventricles. Explain that blood movement through the heart starts with filling of the atria, then the atria contract to push the blood into the ventricles, then the ventricles contract to push the blood out into the arteries.

part of the circuit. The muscle of the left ventricle is thicker as it has to produce enough pressure to send blood around the whole body. The muscle of the right ventricle only has to produce enough pressure to send blood through the lungs (see Worksheet B3.6b). Use a metal seeker to help identify which tubes are connected to each ventricle.

Cut open the heart, from side to side in the position that it is found in the body (see Worksheet B3.6a). Help students to interpret the detail inside the heart, including the valves and ‘heartstrings’ that stop the valves turning inside out. Discuss how the valves and heartstrings mean that it is usually only possible for blood to flow one way through the heart.

Soak the dissecting board in 1% Virkon disinfectant for about 10 minutes afterwards. Wash hands thoroughly after practical. Dissecting instruments can be autoclaved afterwards. Treating with disinfectant will eventually cause corrosion. 1 hour Apparatus (per group) Sheep’s or pig’s heart (with tubes); dissecting board; scissors; metal seeker; disinfectant; Worksheet B3.6a.

Again, compare the thickness of the muscle in the walls of the atria and in each ventricle and relate this to the effort needed to push blood through the next

B3.7

Travelling in the blood

Worksheets available No. B3.7a B3.7b

Title Living at altitude Anaemia

Type Classwork (resuable) Homework (reusable)

Objectives Students should be able to:

• explain that blood plasma carries carbon dioxide

from the organs to the lungs, soluble products of digestion from the small intestine to other organs, and urea from the liver to the kidneys

• describe red blood cells as having no nucleus and being full of haemoglobin

• explain how oxygen is carried by haemoglobin in

red blood cells, as oxyhaemoglobin, from the lungs to tissues.

Key words haemoglobin, oxyhaemoglobin, plasma, red blood cell, urea

Lesson ideas Starter

• Before looking at the Student’s Book, ask students to jot down as many substances as they can remember that are transported in the blood. If possible, they should identify where in the body they enter the blood, and where they leave. Take answers from the class until you think they have covered everything –

© Pearson Education Limited 2007

Foundation 4 4

Higher 4 4

this should include oxygen, carbon dioxide, products of digestion and urea. (Note that urea was covered in Module B2.00 in AQA Additional Science.) If any of these have been missed, remind students of the name to prompt for details about where they enter and leave.

Learning activities

• The fact that red blood cells have no nucleus means

that they have a much shorter life-span than other cells in the body. Ask students to find out how long they survive in the body, what happens to them when they are beginning to break down, where new red blood cells are made and which substances are needed to make them.

• The worksheets provide examples of situations in

which the red blood cell count is changed (increased at altitude, decreased in anaemia) to give students further understanding of their importance in carrying oxygen around the body. Students could carry out their own research on either of these to learn more about the changes they cause within the body.

• Worksheet B3.7a may be better used as a wholeclass activity with some students.

• AT If you did not use the animation on the

ActiveTeach mentioned in the previous topic, then it would be useful to do so here. AQA GCSE Extension Units Teacher’s Guide

23

Plenary

are several kinds of white blood cell, for the purposes of this activity they can be considered under the one heading. If platelets are visible in the smear, you might like to explain their role in blood clotting.

• Write the key words and other related words from

the topic on the board. Give students 5 minutes to write questions to which each word is an answer. Take examples of questions from the class to discuss.

Additional homework/research ideas

• ICT Ask students to research other substances,



such as hormones, that dissolve in plasma and are transported around the body. Their research should include where the hormones are made, and where the target cells are that they affect.

H More able students could use a graticule to estimate the size of the different kinds of blood cell.

Students may need reminding of how to use a microscope safely. 15 minutes

Practicals and demonstrations

Apparatus

1 Investigating blood smears This is best done by looking at prepared slides of blood smears. To make slides of fresh blood, follow the instructions in CLEAPSS Laboratory Handbook, Section 14.4. Ask students to identify the different kinds of cells they can see in the smear, and roughly estimate the proportion of each kind. Note that although there

B3.8

Also ask students to look closely at single red blood cells and draw one cell from different angles so that they get a clear idea of its 3D shape.

Microscope with low- and high-power objectives (to give at least 2400); prepared slide of human blood smear.

Exercise and the body

Worksheets available No. B3.8a B3.8b

Title Exercise and heart rate Being healthy, being fit

Type Classwork (reusable) Homework (resuable)

Foundation 4 4

Objectives

Lesson ideas

Students should be able to:

Starter

• explain that some of the energy from respiration is used to make muscles contract

• describe changes that take place in the body during exercise, including increased heart rate, increased rate and depth of breathing, and dilation of arteries to muscles

• interpret data on the effects of exercise on the human body

• explain that the effect of these changes is to supply sugar and oxygen faster to muscles and remove carbon dioxide more rapidly.

• HSW interpret data relating to the effects of exercise on the body.

Key words dilate, glycogen

Higher 4 4

• Choose a relatively fit student who will not be

concerned by the attention. Quickly take their pulse and record it on the board. Then ask the student to carry out a simple exercise, such as 20 star jumps, and measure their pulse rate again. (It should have increased.) Ask students to suggest as many reasons as they can why this change has happened. They could also suggest any other changes they noticed, such as increased breathing rate and depth of breathing.

Learning activities

• Before using Worksheet B3.8a, students will need

to understand what an average heart rate is for a person of their age, how fitness affects heart rate during exercise (so they can identify those who are particularly fit or unfit) and what the dangers are of exercising too much when you are not fit. These answers can be found through research, or from the video clip on the ActiveTeach.

• Ask students to plan and possibly carry out an

investigation into the effect of exercise on heart rate and/or breathing rate. Note that depth of breathing changes as well as rate of breathing during exercise,

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© Pearson Education Limited 2007

so there is not such a clear-cut comparison of these factors with increasing exercise as there is with heart rate. Students could use their own data in the analysis given in Worksheet B3.8a. Alternatively, give them the data on the ActiveTeach to analyse. As before, be sensitive to any student who may have a medical condition that affects either heart rate or breathing rate.

• ICT The data on the ActiveTeach could be analysed using a spreadsheet program rather than by hand. This will simplify the graphing task.

• HSW Worksheet B3.8a gives students the

opportunity to identify anomalous results and decide how to handle them when calculating averages.

• Worksheet B3.8b introduces students to some of

the health and fitness statements that they may come across in their own research, and asks them to compare exercise for health with exercise for fitness (as these are not the same thing). This may be better used as a classwork activity with Foundation students.

• If appropriate for your students, ask them to carry

out their own ‘exercise audit’ and to think of simple ways in which they could increase their daily level of activity. (If they are already very active, they could consider other members of their family.) Explain how important it is to make exercise simple and easy to incorporate as part of normal life, otherwise you are much more likely to give up. Link any discussion on exercise to the reasons why it has an effect on health and fitness.

• ICT Students could also investigate the claim that

decreasing levels of fitness are reducing the nation’s health, or the current recommendations of exercise level for health/fitness and what judgements these are based on.

• AT The ActiveTeach includes a video clip interview

with a fitness instructor. In this, the instructor explains what an average heart rate is, how heart rate and breathing rate are affected by aerobic exercise, how being fit changes the body’s response to exercise by being better able to supply blood to muscles, and the dangers of exercising too much when you are not fit.

• AT

ICT The ActiveTeach also includes a spreadsheet of data on heart rate for a range of individuals at different levels of exercise. This can be used with Worksheet B3.8a so that the data can be analysed electronically rather than by hand.

© Pearson Education Limited 2007

Plenary

• On the board, sketch a graph of heart rate and

level of exercise like the one shown in Graph C for this topic in the Student’s Book. Ask students for suggestions on how to annotate the graph to explain the shape of the curve. Then ask how the curve might differ for someone who is very fit, or for someone who is unfit.

Additional homework/research ideas

• Question 8 in Worksheet B3.8a asks students to

research examples of moderate and vigorous exercise. They could combine this with their ‘exercise audit’ by identifying how easy it would be to include sufficient moderate exercise simply into their daily lives.

Practicals and demonstrations 1 Exercise and heart rate Students should plan and then, if appropriate, carry out an investigation into the effect of exercise on heart rate. Exercise should be restricted to light–moderate exercise, and carried out in an appropriate situation (such as the gym or playing field) and in suitable clothing (such as PE clothing). Manage this activity sensitively. Pairing students, so that those for whom exercise is inappropriate take readings while their partners exercise, is prudent. Students will need to consider which levels of exercise they will use, and how they can make the investigation fair and provide reliable data for analysis. This will mean taking repeat measurements, identifying anomalous results in the range, and taking averages of reliable results. This practical can be extended to look at the link between exercise and breathing rate. Simple exercises, such as jogging on the spot or walking up and down a short flight of stairs, for 3 minutes should produce a change in breathing rate. Note, however, that depth of breathing will change as well as rate, and this can only be quantified properly during activity using a spirometer. Students should not carry out this activity if they have a medical condition that will be affected by increased heart rate or blood pressure. Asthmatics should be warned to use their broncho-dilator inhalers before exercising. Do not allow exercise to become competitive, and ensure it is always done safely. Apparatus Watch or clock with second hand.

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B3.9

Exercise fatigue and anaerobic respiration

Worksheets available No. B3.9a B3.9b

Title Does lactic acid hurt Training for endurance swimming

Type Classwork (reusable) Homework (resusable)

Objectives Students should be able to:

• understand that muscles become fatigued after long periods of activity

Foundation

Higher 4 4

may already be aware that they occasionally use anaerobic respiration. If so, ask them to explain to the class what they know.

Learning activities

ICT Students could research the changes that • explain that anaerobic respiration supplies energy to • happen in muscle cells during prolonged activity. muscle cells if not enough oxygen is available

•

H describe how anaerobic respiration is the incomplete breakdown of glucose to produce lactic acid and some energy, though less energy than is produced by aerobic respiration

• H explain that anaerobic respiration results in an oxygen debt that has to be repaid.

Key words aerobic respiration, anaerobic respiration, fatigue H lactic acid, oxygen debt

Points to note

• Students may come across some ideas in their

research into anaerobic respiration on sports websites that are not very scientific. If appropriate to your students, warn them of this.

• There are no Foundation worksheets for this topic

as that material can be covered using the Student’s Book and activities suggested below.

• In their research, students may come across

reference to another system in muscles that supplies energy for movement, known as the phosphocreatine or creatine phosphate (CP) system. This is also anaerobic and supplies energy in the first 5–10 seconds of vigorous exercise, along with any ATP stored in the muscle cells. Students do not need to understand or explain this system separately for this specification.

Lesson ideas Starter

• Ask students what aerobic respiration is (the release of energy from food materials using air). Then ask them to suggest what anaerobic respiration is (release of energy from food without air), and to suggest situations when it might be needed. Note that any students involved in sports training

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AQA GCSE Extension Units Teacher’s Guide

This will result in many suggestions as to why cells fatigue. Some sources still suggest lactic acid from anaerobic respiration as the cause, although recent medical and scientific research shows that this is unlikely. Another suggested cause is the build-up of phosphate in muscle cells due to the breakdown of creatine phosphate, which is another source of energy in muscle cells. (Note that students do not need to remember this source for this specification.) An interesting debate topic for the class could be ‘How could scientists determine what causes muscle fatigue?’ This will illustrate the difficulty of identifying one factor from a number of changes that occur simultaneously, and help to explain the confusion about lactic acid for so long.

• It is important that students realise that anaerobic

respiration in muscles is used to supplement aerobic respiration when needed, and never replaces it. Even when exercising vigorously, aerobic respiration in cells will be supplying some of the energy need.

• H The understanding of when aerobic and

anaerobic respiration is used by an athlete is very important in sports training. An example of swimming is given in Worksheet B3.9b, though it is applicable to any endurance sport.

• H Students should be aware of the need to pant

or breathe heavily after finishing some strenuous exercise. If they seem uncertain, choose one of your fitter students and ask them to do something strenuous for several minutes, such as jumping up and down or jogging on the spot. This needs to be linked to the idea of ‘oxygen debt’ and the use of the oxygen to convert the lactic acid back to glucose.

• H

HSW At the end of the period of exercise, you could also ask the student how their leg muscles feel. They should answer that the muscles are tired, fatigued or ache. It was thought that this effect was caused by the build-up of lactic acid. However, recent research suggests that, contrary to having a negative effect on muscles, lactic acid is essential for continued functioning during prolonged strenuous exercise. The development of this idea is covered in more detail in Worksheet B3.9a. © Pearson Education Limited 2007

• AT The ActiveTeach contains a video clip that

Additional homework/research ideas

• ICT Ask students to research training for other

discusses the role of anaerobic respiration in vigorous activity.

endurance sports and the importance for trainers and athletes of understanding when anaerobic respiration is used so that they can improve performance.

Plenary

• Play ‘traffic lights’ to test how well students have

learnt the features of anaerobic respiration. Give each student a red, a yellow and a green card. Ask them to hold up the red card if a statement is false, green if is true and yellow if they are not sure. Offer statements appropriate to level covered in this topic, such as ‘Anaerobic respiration uses oxygen to break down glucose and release energy’ (false), ‘Muscle cells use anaerobic respiration to release energy when oxygen levels are low’ (true).

B3.10

• H

ICT Students could research further examples of where anaerobic respiration occurs in animals. Suggestions for topics to investigate are in diving, in low-oxygen (anoxic) conditions, in high-speed chases such as those of the cheetah after prey.

Practicals and demonstrations None suggested.

Healthy kidneys

Worksheets available No. B3.10a B3.10b

Title Testing urine Getting the right water balance

Type Classwork (reusable) Homework (write-on)

Foundation 4 4

Objectives

Lesson ideas

Students should be able to:

Starter

•

describe how a healthy kidney filters the blood, then reabsorbs sugar and any ions and water that the body needs

• explain that urine contains urea, excess ions and water

• H explain that sugar and dissolved ions may be actively absorbed in the kidneys.

Key words glomerulus, tubule, urine

Points to note

• During research, students may discover the fact

that up to 50% of the urea that is initially filtered from the blood into the kidney tubule is reabsorbed from the tubule. Since we talk about urea being a waste product that is removed by the kidneys, this can be confusing. The reason is that urea is a small molecule and moves back by diffusion along its concentration gradient. However, in the last stage of urine formation water is selectively reabsorbed from the tubule, meaning that the concentration of urea in urine increases even if the actual amount does not. The removal of urea from the blood is a gradual process. Students do not need to understand this for the specification.

© Pearson Education Limited 2007

Higher 4 4

• Start the lesson with a large flask of yellow-coloured

water (appropriately coloured for a normal urine sample). Tell students that it is a sample of urine and that they will be analysing it to see what it contains. Give them 5 minutes to jot down a list of substances that they would expect to find, and reasons why they would expect to find them in the urine. This should revise all earlier work on kidneys, the removal of waste products such as urea, and the control of water in the body.

Learning activities

• Practical 1 and Worksheet B3.10a both look at

urine testing. Following the practical work with the worksheet will help reinforce the reasons why the tests are indicative of problems. You could tell students that in the days before there were indicator strips, doctors often tasted a patient’s urine to test for diabetes. (It is not suggested that students attempt this with the artificial urine samples provided!) Students should be able to explain that urine from these patients should taste sweet due to high levels of glucose. This sheet may be better used as a whole-class activity with Foundation students.

• Worksheet B3.10b extends work from previous

courses on the maintenance of homeostatic balance of water in the body, and introduces the role of ADH (anti-diuretic hormone) as part of the feedback mechanisms that keeps the balance. If appropriate for your students, consider revising homeostasis and

AQA GCSE Extension Units Teacher’s Guide

27

feedback mechanisms from AQA Additional Science in class so that they have refreshed their knowledge before working on the worksheet.

• Glucose – Dip a Clinistix into a tube containing some of the sample for just a moment, then take it out. Count to ten, then check the colour with the chart. The darker the colour, the more glucose there is in the sample.

• AT The ActiveTeach includes an animation that

shows how the kidney filtrate is formed, and which substances are reabsorbed as it passes through the tubule.

• Protein – Place a tube containing the sample into

Plenary

• Give students lists of three words and ask them to

identify the odd one out, giving reasons for their answers. Suitable lists include: glucose, ions, urea; red blood cell, plasma, oxygen; red blood cell, plasma, carbon dioxide.

Additional homework/research ideas

• ICT Animals that live in desert conditions need to

1 Testing urine Ask students to carry out tests on various artificial urine samples to identify which is the one from a diabetic (+glucose), which from a patient with high blood pressure (+albumin), and which from a patient with a urinary tract infection (high pH). Students can use the following tests to identify the additional substances:

B3.11

indicator or non-bleeding pH strips. Normal urine has a pH between 4.5 and 8.0.

• ‘normal’ – dissolve 3 g sodium chloride and 5 g urea in 1 litre of water

mentioned in Worksheet B3.10a. Students could research a wider range of tests, to find out what they indicate.

Practicals and demonstrations

• pH – Test some of the sample using universal Artificial urine samples:

extract more water from the kidney tubule than those that live in wetter places. Ask students to research the differences in their kidneys which allows this to happen.

• ICT Doctors do more tests on urine than those

the water bath and leave for a few minutes. Remove the tube and compare with a tube containing some unheated sample. If there is cloudiness in the heated sample, then it contains protein. (The protein is coagulated with the heat, causing the cloudiness.) Alternatively, use Albustix strips if available.

• ‘diabetic’ – as normal with 1 g glucose powder • ‘protein’ – as normal with 1 g albumin powder • ‘high pH’ – as normal with 3 cm ammonia solution 3

Yellow food colouring can be added in varying amounts to give a more realistic appearance. 30 minutes Apparatus (per group) Artificial urine samples as above, labelled A–D; pipettes; test tubes, test tube rack; water bath at 70 °C; universal indicator or non-bleeding pH strips; Clinistix glucose test strips and chart; Albustix test strips.

Dialysis treatment

Worksheets available No. B3.11a B3.11b

Title Craig’s story Getting the concentration right

Objectives Students should be able to:

Type Classwork (reusable) Homework (write-on)

Foundation 4 4

Higher 4 4

• explain why dialysis has to be carried out at regular intervals

• describe how a person with kidney failure may be

• evaluate the advantages and disadvantages of

• describe how substances, including urea, are

Key words

treated using dialysis

exchanged between dialysis fluid and the patient’s blood across partially permeable membranes

dialysis treatment.

dialyser, haemodialysis, kidney failure

• explain how the dialysis fluid contains the same

concentration of useful substances as the blood to ensure that glucose and useful mineral ions are not lost

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© Pearson Education Limited 2007

Points to note

• H For more able students, this would be a useful

opportunity to extend understanding of the role of the kidneys beyond what is needed by the specification. For example, the kidneys play an important part in the formation of red blood cells (by producing erythropoietin) and in the production of vitamin D. Patients suffering from kidney failure and treated with dialysis need regular medication to protect against anaemia and calcium shortage.

• Students do not need to remember the details of

peritoneal dialysis for this specification. It has been included here because it helps to highlight some of the disadvantages of haemodialysis.

Lesson ideas Starter

• AT The ActiveTeach includes an animation that

• Ask students to work in pairs for 5 minutes to jot

shows how substances are exchanged between blood and dialysis solution in the dialyser. This can be compared with the animation of normal kidney function for the previous topic to highlight similarities and differences.

down what effect there would be if the kidneys suddenly stopped working. (Be sensitive to the possibility that a student, or someone they know, may have suffered kidney failure.) Take answers from the class to make sure that they have a clear understanding of the role of the kidneys from the last topic.

Plenary

• Give students 5 minutes to write down the key

Learning activities

• H Question 4b in the Student’s Book is for Higher-

tier students because it relates to active transport, which they learned about in the last topic. You could extend this question by relating it to the restrictions on diet, particularly foods that contain high levels of mineral ions.

• Worksheet B3.11a may be better used as a wholeclass activity with Foundation students.

• ICT Ask students to find out more about dialysis

using the internet or books to help them with their evaluation of the advantages and disadvantages of this treatment. Useful websites include the National Kidney Federation and Kidney Research UK, which can be accessed via www.Longman.co.uk/AQAScience.

problems with dialysis. Take examples from around the class, then ask students to judge whether dialysis is worth the effort. Again, take answers for both ‘yes’ and ‘no’ (if there are any), to evaluate this treatment for kidney failure.

Additional homework/research ideas

• Some children suffer kidney failure and have to face

a life of dialysis. Ask students to design a poster that is aimed at reassuring these children that dialysis will make it possible for them to lead a reasonably normal life.

• Alternatively, ask students to find out the link

between diabetes and kidney failure, and to consider how the increase in diabetes as a result of increase in obesity means that the need for treatment for kidney failure is likely to increase in the next few decades.

Practicals and demonstrations None suggested.

B3.12

Kidney transplants

Worksheets available No. B3.12a B3.12b

Title Not enough kidneys Craig’s transplant

Objectives Students should be able to:

• explain that a person with kidney failure may be given a healthy kidney in a transplant

• explain why the tissue of the kidney must be matched with the patient

Type Classwork (resuable) Homework (resuable)

Foundation 4 4

Higher 4 4

• HSW evaluate the advantages and disadvantages of kidney transplants.

Key words immunosuppressant drug, rejection, tissue type, transplant

• explain why the patient is treated with drugs to suppress the immune system

© Pearson Education Limited 2007

AQA GCSE Extension Units Teacher’s Guide

29

Points to note

• The specification says that diseased kidneys are

replaced by healthy ones in kidney transplants. This is true if the kidney failure was due to infection that is likely to spread to other parts of the body. However, in most cases kidney failure is the result of other causes (such as diabetes) that result in physical damage to the tissue. In these cases the patient’s kidneys are left intact, and the transplant is connected to the blood system in the patient’s groin. If a kidney has to be removed, this is done in a separate operation before the patient is considered for transplant.

Lesson ideas Starter

• Revise the last topic by asking students to suggest

quickly what the problems are when treating kidney failure with dialysis. Then ask them if they know of other ways to treat organ failure. It is highly likely that some students will suggest organ transplant. If not, offer a hint by asking what they would do if the batteries ran out in a torch, and whether we can do something similar for body parts. Ask students to suggest the advantages of replacing a diseased kidney rather than treating it with dialysis. This can be revisited in the plenary to make sure that students have learnt the correct answers.

Learning activities

• Worksheet B3.12a prepares students for a debate

on the topic of organ supply for transplants. This will require time to research further information about the suggestions mentioned in the worksheet. It can be carried out simply as a paper exercise, with students writing down their arguments for or

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AQA GCSE Extension Units Teacher’s Guide

against, or you could set up a true debate within class. In the latter case, consider splitting the class in two with each half working together for one side of the debate. Each half should appoint a spokesperson who will deliver the arguments, with support from a small group during the debate. The rest of the class can then act as ‘jury’ and vote on the question at the end of the debate.

• ICT The research activity needed to prepare for the

debate can be carried out using the Internet. For useful websites see www.longman.co.uk/AQAScience.

• Worksheet B3.12b extends the ‘case study’ of Craig

introduced in the previous topic. This sheet could be used as either classwork or homework and should help students appreciate the advantages and disadvantages of transplants, which can be compared directly with their answers to Worksheet B3.11a. This worksheet may be better used as a classwork activity with Foundation students.

Plenary

• Ask students to imagine that a friend’s sister is on

dialysis for kidney failure. The friend is thinking about offering to donate one of their kidneys to their sister. Give students 5 minutes to think of two reasons why they should donate, and two why they should not. Take answers from around the class, until you think all sensible examples have been covered.

Additional homework/research ideas

• ICT Students could research the increase in

numbers of organ transplants in pets, and consider what are the advantages and disadvantages of doing this.

Practicals and demonstrations None suggested.

© Pearson Education Limited 2007

B3.0

Answers

B3.1 Diffusion and active transport Student’s Book 1 a Dye particles have moved randomly from where they were placed at the start. This has resulted in their spreading out (diffusing) through the agar. b The area of dye may have spread out further. 2 a i Diagram showing beaker of water, with drop of colour added. ii

Diagram showing spread of colour from initial drop, still more concentrated near the original drop and getting less concentrated as you get further from the drop.

b Diagram should show even distribution of colour through water in beaker. c Particles of coffee dissolved in the warm water, and then moved through the water by random movement. 3 a There are small holes in the membrane that are large enough for the particles to move through. b The amount of a substance dissolved in a solution. c i Yes. ii Yes. d Particles move in both directions, but more move from the concentrated side to the dilute side.

iii Diagram showing even spread of colour throughout water in beaker, paler than original drop.

Worksheet B3.1b

b Movement should be a random, zigzag path within coloured area.

b Diffusion, because it is a small, non-ionic molecule.

3 a The particles are all moving at the same speed.

2 Diffusion when the concentration outside is greater than inside. Active transport when the cell needs glucose but the concentration outside is less than inside.

b More particles have moved from well A than from well B. c Rate of diffusion is the rate of change of concentration. 4 a A membrane that lets particles of small size through, but not larger particles. b All the particles are moving. c More of the particles from the concentrated solution pass through the membrane to the dilute side than particles pass in the opposite direction. This means the concentration gradient gets less and will eventually disappear when the solutions are the same concentration on each side. 5 a This means more move from the dilute to the concentrated solution than in the other direction.

1 a Through a protein pore, because it is ionic.

3 a To make the protein change shape. b Respiration. 4 The membranes around different organelles may contain different transport proteins, so it is possible to have different concentrations of substances inside organelles compared with the cytoplasm. This means different processes can go on inside the organelles.

B3.2 Gas exchange in the lungs Student’s Book 1 When you breathe in deeply, the rib cage lifts and gets a little wider and the diaphragm gets lower. When you breathe out, the rib cage collapses a little and the diaphragm is raised.

b Because diffusion results in more particles from the concentrated side moving to the dilute side than in the other direction.

2 Air, mouth, windpipe, bronchi, alveoli, blood in capillary.

6 a Mitochondria.

3 There is more area/blood to exchange gases with.

b Contains many mitochondria.

4 Sketch should show that greater surface area means that more exchange can happen at the same time.

Worksheet B3.1a 1 The particles of perfume diffused from the place where Paula sprayed them and spread through the air. It took a few minutes for some particles to diffuse as far as Gill. 2 a Diagram should show beaker with small pile of coffee at bottom.

© Pearson Education Limited 2007

5 The particles do not have far to move, so they get there faster. 6 a The blood is continually taking away oxygen and bringing in carbon dioxide, so that keeps O2 concentration low and CO2 concentration high on the blood side. Breathing replaces air in the lungs to keep O2 concentration high and CO2 concentration low in the alveoli. AQA GCSE Extension Units Teacher’s Guide

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B3.0

Answers

b Rate of diffusion depends on concentration gradient. If the blood flowed more slowly and breathing was slower, concentration gradients for the gases would get less and diffusion would be slower.

Worksheet B3.2a 1 Both reduce the exchange of air between the alveoli and the atmosphere, so carbon dioxide concentration in the alveoli will be higher than normal and oxygen concentration will be lower. This will slow down the exchange of gases with the blood. 2 It reduces surface area for exchange, so less can be exchanged in the same time.

b It can take more than would be available just by diffusion. c They carry out the process of respiration, releasing the energy needed for active transport.

Worksheet B3.3b 1 Adaptations: villi and microvilli for increased surface area; thin walls of capillaries and intestine surface to make diffusion distance as short as possible; lots of capillaries to take diffused products of digestion as quickly as possible. 2 All these adaptations increase rate of diffusion.

3 If alveoli are filled with liquid, they cannot exchange gases with the blood. Increasing the oxygen concentration in the air they breathe in will increase the rate of exchange in the alveoli that are still clear.

B3.4 Absorption in plants

Worksheet B3.2b

2 a Oxygen, carbon dioxide and water vapour.

1 a Lots of gills containing lots of gill plates. b Gill membranes very thin, well supplied with capillaries close to the surface. c Blood constantly flowing through capillaries, water constantly flowing over gills, blood flowing in opposite direction to water, so always a concentration gradient for gases. 2 All these factors increase the rate of diffusion of gases between the blood in the capillaries and the water. So this makes the gills effective exchange surfaces.

B3.3 Absorbing food Student’s Book 1 Being very long allows as much as possible to be absorbed from the digested food. 2 Increased surface area increases rate of absorption. 3 Brings them into contact with more of the digested food so absorption is faster. 4 a They increase the surface area even more. b Means rate of absorption can be even faster. 5 So substances can diffuse as fast as possible. 6 a The blood that has a high concentration of food products that have diffused into it moves away to be replaced with blood that has a low concentration. The concentration of food products remains high within the gut while digestion continues. So the concentration gradient is kept steep.

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7 a Glucose for carbohydrates such as starch, glycogen. Amino acids build into proteins.

Student’s Book 1 Being thin reduces distance for diffusion. b Oxygen out during day, in at night; carbon dioxide in during day, out at night; water vapour out. Oxygen and carbon dioxide at night as a result of respiration, during the day as a result of the balance between respiration and photosynthesis. Water vapour at higher concentration inside plant than outside most of the time. 3 Most leaves are wide and flat, giving as large a surface area as possible. 4 a Air, stoma, air space, cell membrane, cytoplasm, chloroplast (may be transfer between cells before reaching chloroplast). b One. c The shorter the distance for diffusion, the faster diffusion can happen. 5 Air, because carbon dioxide in the chloroplast is combined with water during photosynthesis. 6 a They greatly increase surface area. b The greater the surface area, the faster the rate of diffusion possible. 7 Active transport, because the ions are moving against their concentration gradient.

Worksheet B3.4b 1 Oxygen out, carbon dioxide in, water vapour in. 2 a Wide and flat, to give as large a surface area as possible and as short a diffusion distance as possible.

b Rate of diffusion is faster with a steeper concentration gradient.

b Leaves are the main surface for exchange of gases between the inside and outside of the plant and where photosynthesis (which uses and produces gases) occurs.

AQA GCSE Extension Units Teacher’s Guide

© Pearson Education Limited 2007

B3.0

Answers

3 a Rate of photosynthesis will decrease.

Worksheet B3.5a

b Closing stomata reduces rate of gas exchange. So carbon dioxide concentration inside the leaf will drop, which will reduce rate of photosynthesis.

1 A preliminary trial run would help to choose the range of humidities to use.

4 Photosynthesis only happens when it is light.

Worksheet B3.5b

5 a Water-vapour loss will be reduced so plant will not have to close stomata so soon if not enough water is available.

1 Transpiration is the diffusion of water from the leaf surface. Increasing concentration gradient increases rate of diffusion and vice versa.

b It reduces rate of exchange of other gases too.

2 a Increasing temperature increases evaporation from the cell surfaces inside the leaf, but decreases the number of water particles in the air (humidity).

6 Spruce, in cold temperate areas where ground may freeze during winter. Lavender in dry warm areas such as Mediterranean, where little rain falls during summer. Both environments will have little water available to plants at some times of the year so adaptations that reduce water loss at these times are essential. 7 Carbon dioxide can be captured at night, when temperatures are lower and loss of water by transpiration will be less. During the day, stomata are closed to prevent loss of large amounts of water due to the higher air temperatures, but photosynthesis can be carried out as the carbon dioxide is released inside the plant. 8 Dry and heat means the plants must have adaptations to reduce water loss but allow carbon dioxide in for photosynthesis: physical adaptations that reduce air movement over the leaf, or physiological adaptations such as those of the cacti, which allow carbon capture when it is cooler.

B3.5 Movement of water through plants

2–8 Students’ own answers.

b It will increase the rate of transpiration because it increases the concentration gradient between the inside and outside of the leaf. 3 a Increasing wind speed decreases the number of water particles outside the leaf. b This is because the moving air moves water particles away from the leaf faster. c It will increase the rate of transpiration because it increases the concentration gradient between the inside and outside of the leaf. 4 a There are more water particles in humid air than in dry air. b It will decrease the rate of transpiration because it decreases the concentration gradient between the inside and outside of the leaf. 5 Warm, windy and dry, because rate of transpiration would be highest in those conditions.

B3.6 Human blood circulation

Student’s Book

Student’s Book

1 Sketch annotated to show stages of osmosis from soil water to xylem in terms of concentration changes.

1 Because you would not be able to show all the capillaries as there are so many of them and they are so small.

2 It travels up the xylem tubes.

2 Arteries, large blood vessels that carry blood away from the heart; capillaries, very narrow blood vessels that supply cells in organs; veins, large blood vessels that carry blood back to the heart.

3 Sketch annotated in terms of concentration changes to show stages of osmosis from xylem to cell by air space, then to air space and out through stoma to air. 4 Plan to include use of potometer, several different air temperatures with same plant, and same light and other conditions. 5 Wind blows away any water particles next to the leaf, increasing the concentration gradient between the leaf and the air. A greater concentration gradient means greater rate of diffusion. 6 Dry and hot. 7 Stop photosynthesis as chloroplasts would run out of carbon dioxide to convert to glucose. © Pearson Education Limited 2007

3 Right side of heart, lung circulation through capillaries in lungs, left side of heart, body circulation through capillaries in other organs, right side of heart. 4 a Several possible answers including oxygen concentration in blood decreases, carbon dioxide concentration in blood increases, concentration of glucose (sugar) in blood decreases. b Oxygen concentration in blood increases, carbon dioxide concentration in blood decreases.

AQA GCSE Extension Units Teacher’s Guide

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B3.0

Answers

5 Layer of cells around capillaries only one cell thick, so short distance for diffusion. Very many capillaries increases surface area for exchange. 6 Because capillaries run close to most cells, walls very thin and distance for diffusion is very short. 7 Blood that has passed through the pancreas will also have exchanged gases with cells, so oxygen concentration will be low and carbon dioxide concentration high. By going through the lungs first, the oxygen and carbon dioxide can be exchanged between the blood and the alveoli, so that the blood going to the liver cells can supply oxygen as well as insulin.

Worksheet B3.6a 1 Arrows showing blood flowing in through vena cava to right aorta, down to right ventricle, out through pulmonary artery to lungs, back through left aorta and ventricle, out through aorta.

6 Left ventricle has to produce greater pressure to get blood all the way round the body, so muscle needs to be more powerful than in the right ventricle, which only has to get blood through lungs and back to the heart. 7 a Respiration. b The blood carries glucose and oxygen to the cells, and carries carbon dioxide from cells to lungs.

2 a Artery, because blood flows away from heart through it.

c Mammals and birds need more energy than other animals for maintaining body heat. A double circulation means you can have different pressures in the two circuits, so you get better exchange in each circuit. So cells can be supplied more efficiently.

b Deoxygenated, because it is bringing blood back from the body.

B3.7 Travelling in the blood

3 a Lungs. b Deoxygenated, because they are carrying blood that has come from body cells.

Student’s Book 1 It contains many red blood cells.

4 They stop blood flowing backwards when the muscles of the atria and ventricles contract.

2 Red blood cells.

5 a The atria only have to push blood into the ventricles. The ventricles have to push blood much further.

b Capillaries in small intestine.

3 a From cells in body organs. 4 a Capillaries in the lungs.

b The left ventricle has to push blood all the way round the body, the right ventricle only has to push blood through the lungs.

b Cells in body organs.

Worksheet B3.6b

b Oxygen needs to be exchanged by diffusion as rapidly as possible. The shorter the distance for diffusion, the faster the exchange.

1 a All the body except the lungs. b Lungs. 2 a Net diffusion of oxygen from alveoli into blood, net diffusion of carbon dioxide from blood into alveoli. b Net diffusion of oxygen from blood into cells, net diffusion of carbon dioxide from cells into blood. 3 a Capillaries. b There are many more capillaries than other blood vessels that pass close to all cells. They also have thin walls for faster diffusion. 4 They might burst because they have thin walls.

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5 The blood does not have to travel as far, and gets to capillaries in shorter distance so less pressure loss. If the pressure was the same as the body circulation, the capillaries would get a much higher pressure than capillaries in other organs, and so might burst.

AQA GCSE Extension Units Teacher’s Guide

5 It is soluble in water. 6 a It makes the distance as short as possible.

7 Contain haemoglobin, and no nucleus so more room for haemoglobin. 8 It can combine with oxygen to form oxyhaemoglobin, and oxyhaemoglobin easily gives up the oxygen when near cells to form haemoglobin again.

Worksheet B3.7a 1 Oxygen concentration in the air is low. Heart rate and breathing rate increase to try to supply the cells with the oxygen they need for normal activity. 2 The body diverts blood to the most important organs that need oxygen. The lungs have to get as much blood as possible so that they can supply it to the rest of the body. The brain needs a minimum level of oxygen to work properly, otherwise you fall unconscious. © Pearson Education Limited 2007

B3.0

Answers

3 a To carry oxygen around the body from lungs to cells.

B3.8 Exercise and the body

b The same volume of blood can carry a greater amount of oxygen.

Student’s Book

c At high altitudes the blood can extract less oxygen from the air. Having more red blood cells increases the amount of oxygen that can be extracted. 4 Red blood cells have no nucleus so they only last for a few months. At sea level the extra cells would not be replaced because they are not needed. 5 a Rosy cheeks indicate a lot of haemoglobin (red blood cells) in the blood. b It helps them extract more oxygen from the air at high altitude. 6 a It will help them increase the number of red blood cells in their blood. b They can extract more oxygen from the air so can compete for longer using aerobic respiration. c Only for a few weeks as red blood cell count will return to normal as red blood cells die off and are replaced.

Worksheet B3.7b 1 a They carry oxygen from the lungs to the cells in the organs. b Haemoglobin. 2 a Haemoglobin combines with oxygen to form oxyhaemoglobin. b Oxyhaemoglobin releases oxygen to form haemoglobin again. The oxygen is taken up by the cells in the organs. 3 Anaemia means that less oxygen is carried in the blood. Lack of oxygen means that respiration cannot be carried out at the same rate in body cells. Respiration produces energy, so less respiration means less energy, leading to tiredness. Lack of oxygen in the brain causes dizziness. If oxygen is low in the body, it responds by breathing faster to try to get more oxygen, so causing breathlessness. 4 Meat and green vegetables provide iron. Lack of meat and green vegetables means lack of iron, so lack of haemoglobin, leading to anaemia. 5 a They are absorbed from digested food in the small intestine. b They dissolve in the water in blood plasma. c Carbon dioxide and urea. (Other answers are possible.)

© Pearson Education Limited 2007

1 a Oxygen and glucose (sugar) for more respiration to produce more energy. b More carbon dioxide and water from respiration. 2 Oxygen in red blood cells from lungs, glucose dissolved in plasma absorbed from small intestine. 3 So they can get more glucose rapidly when needed in exercise and blood glucose concentration is low. 4 a Decreases. b Increases. 5 This shows what is happening in the body cells. Concentrations in the arteries reflect what is happening in the lungs. 6 Breathing faster and deeper exchanges more air in the alveoli for fresh air. This increases the oxygen concentration in alveoli and decreases the carbon dioxide concentration, which makes the concentration gradients between the blood and alveoli steeper for both gases, increasing the rate of exchange. 7 Lack of regular activity leads to health problems.

Worksheet B3.8a 1 a Correctly plotted graph of Heart rate (y-axis) against Exercise level (x-axis) with one line for each student. b Many possible reasons, including: different level of fitness, natural variation in measurement within an individual, mis-reading by recorder. 2 The results suggest that Tom, Claire and Leila are fitter than the others because their heart rate is generally lower than the others. Paul and Davey seem to be the most unfit because their heart rates increase the most with activity. 3 a Anomalous results: 68 for Jonathon level 2 (looks too low); 165 for Gary level 3 (looks too high); 112 for Sarah level 4 (looks too low). b Error in measurement. c Because they will make the average less accurate. 4 a Level 1, 75.1; level 2, 90.3; level 3, 117.0; level 4, 160.5. b Heart rate increases with increasing level of activity. 5 a 204. b Level 1, 36.8%; level 2, 44.3%; level 3, 57.4%; level 4, 78.7%. c Davey exceeds maximal heart rate on level 4 exercise. He should not exercise to this level until he has increased his fitness.

AQA GCSE Extension Units Teacher’s Guide

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Answers

6 Repeat measurements for each individual at each activity level to improve reliability of measurements. 7 Students should be very clear about what they have to do, follow sensible safety precautions when active and stop as soon as they feel uncomfortable or unwell.

Worksheet B3.8b 1 The activity is increasing the muscle cells’ need for oxygen and also the amount of carbon dioxide produced by the cells. Increased breathing rate and depth increases the rate of supply of oxygen and removal of carbon dioxide.

4 a Anaerobic respiration produces much less energy from the breakdown of one glucose molecule. b Supplies energy quickly, and when oxygen levels low. 5 a Breathing rate is as fast as possible to supply oxygen for aerobic respiration. b Breathing rate is still raised to supply oxygen for converting lactic acid back to glucose. 6 a The oxygen needed after anaerobic exercise to convert lactic acid back to glucose.

2 It improves circulation of the blood so the heart does not have to pump as hard to get blood round the body.

b The debt is built up during vigorous exercise. It is paid back once exercise has ended or reduced sufficiently for oxygen to be available for the conversion of lactic acid.

3 Maximal heart rate is 220 minus current age. Target heart rate during vigorous activity=70% of maximal heart rate.

7 It supplies energy when not enough can be supplied from aerobic respiration because of limits of oxygen supply through lungs and blood circulation.

4 a As the circulation improves with fitness, the heart rate will decrease. So as you get fitter, you will have to exercise harder to get to the target heart rate.

Worksheet B3.9a

b So as not to exceed the target heart rate at any point, which could be damaging. 5 Not on current recommendations. Exercise for health is less than for fitness. 6 To encourage everyone to do at least some exercise and so improve their health. 7 Many possible answers including: use motor transport too much, use machines to do physical work.

1 No it was not valid, because he had shown there was a correlation between the increase in lactic acid and loss of response, not that the lactic acid caused the loss of response. Another factor that Hill did not measure could also change at the same time and be the cause. 2 No, it is not. Possible reasons are: the original conclusion was not valid; Hill did not show that the development of pain was linked to the production of lactic acid. 3 It showed a possible way that lactic acid could cause the loss of response.

8 a Students’ own research.

4 a It was only carried out at low temperatures.

b i Many possible answers. Should include appreciation that little time is available, or that childcare will be needed.

b Later work at higher temperatures did not support the conclusion.

ii

Many possible answers. Should show understanding that exercise needs to be developed slowly, and aimed at cardiovascular endurance as well as general muscle fitness.

5 It shows that lactic acid is needed by muscle cells when fatigued to improve contraction response rather than damaging them.

B3.9 Fatigue and anaerobic respiration

6 Understanding that lactic acid is important could change exercise that only improves aerobic respiration over longer periods, to a mixture of that and improving the body’s response to higher levels of lactic acid from anaerobic respiration.

Student’s Book

Worksheet B3.9b

1 When the muscle stops responding properly due to over-use.

1 The release of energy from glucose using oxygen from air.

2 a They both release energy.

2 a To speed up heart and breathing rate so increasing rate of gas exchange.

b Several possible answers including: aerobic respiration uses oxygen, anaerobic does not; H anaerobic respiration produces lactic acid, aerobic respiration does not.

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3 Oxygen is being used rapidly in respiration to release lots of energy.

AQA GCSE Extension Units Teacher’s Guide

b It will make it more possible for the blood to deliver all the oxygen the cells need during the sprint. © Pearson Education Limited 2007

B3.0

Answers

3 Because they need to stay within the aerobic range of breathing for much longer. 4 a Produced in the cells. b As the result of anaerobic respiration. 5 Lactic acid levels would start at zero and only start to build when aerobic respiration was unable to supply all the energy the swimmer needed. Lactic acid levels would drop again only after the swim was over.

Worksheet B3.10a 1 Water, urea, and possibly water-soluble vitamins and sodium ions if the diet has included more than the body needs. Glucose is not normally excreted. 2 a The colour depends on the amount of water in the urine. This varies depending on how much the person has drunk recently, or how much water has been lost in sweating.

6 Curve A is a sprint swimmer and curve B is a distance swimmer, because A is faster but produces more lactic acid than B.

b Very pale after drinking large quantities of water, very dark after not drinking anything on a hot day or after lots of exercise, when water is lost in sweating.

7 a i A  ny point of the ‘after’ curve because it is all below the before-training curve.

3 a Visual check with microscope will show if red blood cells present in urine.

ii M  ark the end point of the ‘after’ curve, where it is higher than the end point of the ‘before’ curve.

b Cells cannot usually get into kidney tubules as they are too big. Presence in the urine indicates damage to the kidneys.

b Swimming faster aerobically means they can swim faster before adding in the energy from anaerobic respiration, so their top speed should be greater. Being able to tolerate higher levels of lactic acid means that they should be able to keep swimming faster for longer.

4 a Blood glucose concentration is not controlled properly and rises very high after a meal.

B3.10 Healthy kidneys Student’s Book 1 Many possible answers, including dissolved ions, urea, glucose, amino acids. 2 Blood cells, as they are too large to get through the holes. 3 For rapid exchange of substances by diffusion. 4 Glucose is normally all reabsorbed by the kidneys. Its presence in urine suggests blood glucose concentration is abnormally high. 5 Tiredness, because the glucose could not be used to release energy in respiration. 6 Some of the water in your blood will be lost through sweating, so more water will be reabsorbed from the kidney tubule to keep the balance of water in the body at the right level. 7 Urea and excess water and dissolved ions that the body does not need. These are what is left in the kidney tubule after everything that the body needs is reabsorbed. 8 a They will move by diffusion when the concentration in the blood is higher than the concentration in the kidney tubule. b The body needs to keep glucose and the right balance of ions. This means it will have to absorb some of these against the concentration gradient at times. This can only be done by active transport. © Pearson Education Limited 2007

b At a high concentration, the kidneys cannot reabsorb all the glucose, so some is left in the urine. 5 Only molecules below a certain size can be filtered out of the blood in the glomerulus. Proteins are usually larger than this limit. 6 If blood pressure is high, it could force larger molecules through the holes in the capillary membranes in the glomerulus. 7 a They are easy to do. b Ketones for diabetes; bilirubin for liver or gallbladder infection; HCG for pregnancy; NTP for Alzheimer’s syndrome.

Worksheet B3.10b 1 It could absorb too much water by osmosis and burst the cell membrane. 2 Osmosis from blood, and product of respiration. 3 As the blood flows past the cells, water is exchanged with the cells by osmosis. Water will move from the more dilute solution to the more concentrated solution. Keeping the amount of water in the blood at the right level will keep the amount of water in the cells at the right level. 4 The concentration of urine will increase. 5 a Jamie will produce more urine than Sam, and it will be paler in colour. b Sam, because he will need to absorb more water from his urine to prevent dehydration. 6 a The effect of any change is fed back to the control mechanism, so that a ‘normal’ or ‘set’ position is maintained.

AQA GCSE Extension Units Teacher’s Guide

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B3.0

Answers

b It makes it possible to keep the changes in water level in the body within limits so that cells can work properly. 7 Alcohol and tea are diuretics because they increase the amount or urine produced, by decreasing the amount of ADH produced by the hypothalamus. Aspirin is an anti-diuretic because it increases the release of ADH.

B3.11  Dialysis treatment Student’s Book 1 Because it sometimes does not produce any symptoms. 2 If it blocks the ureter, the urine cannot flow away. So urea and excess water and ions cannot be removed from the blood by that kidney. 3 a Substances that are produced by the body, such as urea, will increase in concentration in the blood. Substances that enter from the products of digestion will not be kept in balance, so concentrations will either increase or decrease much more than normal depending on how much is taken in. b This will change the concentration of the substances in the body cells, and possibly affect the way the cells work. 4 a It exchanges substances by diffusion with the blood. b It does not filter the blood like the glomerulus does, and there is no active transport across the membrane. 5 It keeps the concentration of substances such as urea, water and dissolved ions at levels that allow normal working of body cells.

3 Someone who is not very skilled or confident at changing the fluid, or someone who is not very disciplined and capable of changing the fluid frequently.

Worksheet B3.11b 1 a Particles move through the membrane, with more particles moving from the side where the concentration is higher than in the other direction. b It changes the rate of diffusion. c So that the blood returned to the patient has the right concentration of substances, such as water and mineral ions, in it. 2 a Glucose and ions will move out from blood into dialysing solution. b Glucose and ions will move into blood from dialysing solution. c In the kidney, substances are first filtered out and then reabsorbed into the blood; in dialysis, substances just diffuse out. In the kidney, substances are balanced by what the body needs; in the dialyser, substances are balanced by their concentrations in the dialysing solution. 3 No, because dialysis tries to remove as much urea as possible. 4 a Usually three times a week. b Continually, with solutions replaced four or five times a day.

6 Frequent regular dialysis means having to be near hospital or have lots of equipment at home; control of diet to stop some substances building up too rapidly; cannot travel away from dialysis equipment for long; takes a lot of time and care to do properly.

c Because substances are not allowed to build up in the blood as much as in haemodialysis.

Worksheet B3.11a

B3.12  Kidney transplants

1 He would fall into a coma and die.

Student’s Book

2 a Advantages: save life; lots of time to read. Disadvantages: must be done regularly at least three times a week; often done in hospital; takes a lot of time, so interferes with everyday life; equipment at home takes up lots of room; feel rough at end of treatment session due to blood pressure drop; difficult to go away from home for more than a day; limitations to fluid intake and diet.

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b Advantages: save life. Disadvantages: need to be very disciplined as needs doing four or five times a day; need to be very careful to prevent infections; fewer limitations on diet and fluid intake; can travel, as long as to places where can get dialysis solution.

AQA GCSE Extension Science Teacher’s Guide

5 A build up of toxins in the body, risking affecting the way cells work, or at worst coma.

1 a Because they may have a condition that would make the operation very risky. b Dialysis. 2 a It identifies any invading cells, such as those that cause disease. b Because the transplant comes from another person, but is something we want to keep working in the body.

© Pearson Education Limited 2007

B3.0

Answers

3 Because markers are dependent on genes, and you are more likely to share genes with someone close in your family than with someone who is not related to you. 4 Because the kidney can be kept alive long enough to transport that distance. 5 To give the greatest chance of success. 6 Because the cell markers are likely to be a close match to those of the patient. 7 Advantages: more normal life than on dialysis; do not have to have treatment every few days. Disadvantages: have to take immunosuppressant drugs for rest of life, which may allow other infections to get into body; no guarantee how long kidney will last; increased risk of some cancers.

Worksheet B3.12b 1 a The markers on Dave’s cells are likely to be a close match to Craig’s. b He did not want to take the risk that something might happen to Dave. 2 a Because the tissue type was a better match for him than for them.

7 Take the value for 5 minutes and divide by 5 to give cm/min. (1 mark) 8 Line graph. (1 mark) 9 Do a control experiment. (1 mark) 10 Repeat measurements and take averages for each time and setting. (1 mark) 11 Rate of transpiration increases from settings 0–2, and setting 3 shows transpiration has virtually ceased. (4 marks) Conclusion relates wind speed to the speed of removal of water particles from near the leaf, and increase of concentration gradient from leaf to air. (1 mark) Setting 3 shows the condition when the plant closes its stomata because rate of transpiration is greater than rate of supply of water from potometer, to avoid wilting. (1 mark) Quality of communication – correct use of two scientific terms, e.g. transpiration, diffusion, concentration gradient, rate. (1 mark)

b To give the best possible chance to success.

B3.0 Investigative Skills Assessment (Copymaster File)

3 a Student’s own answer.

Section 1

b Suitable justification for answer in a.

12 a Rate of transpiration. (1 mark)

4 a Advantages of dialysis: survival, for those who cannot have transplant. Disadvantages of dialysis: must be done regularly; major impact on life in time and restrictions on travel; control of diet.

b Wind speed. (1 mark)

Advantages of transplant: more normal life; fewer restrictions on diet. Disadvantages of transplant: must take immunosuppressant drugs for rest of life; catch more other infections; increased risk of some cancers, such as skin cancer; no guarantee how long kidney will last. b Any reasonable answer with suitable justification.

B3.0  Investigative Skills Assessment (Student’s Book) 1 Discrete. (1 mark) 2 Wind speed sensor and datalogger. (1 mark) 3 So the plant could adjust to the new conditions. (1 mark) 4 No, she has not made any effort to control other variables such as temperature or humidity. (2 marks)

13 a Temperature, humidity. (2 marks) b By shielding the plant from changes of air and temperature. (1 mark) 14 a Depending on method used: either the uptake of water by the plant from a potometer or loss of weight from the plant. (1 mark) b Depending on method used: either water is taken up by the plant as it loses water through transpiration or weight is lost as water evaporates from the leaves. (1 mark) 15 Suitable statement concerning the precision of measurements taken. (1 mark) 16 Correct identification of a clear anomaly or correct statement that there are no anomalies. (1 mark) 17 Pattern correctly identified, or statement that there is no pattern. (1 mark) Above but using terms linear/non-linear, or (not) directly proportional. (1 mark)

5 Her measurements are more precise. (1 mark) 6 Speed setting 1, 4 minutes. (1 mark)

© Pearson Education Limited 2007

AQA GCSE Extension Science Teacher’s Guide

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B3.0

Answers

18 No marks for yes/no. Judgement needed here. The explanation must match the answer and the data:

•

can suggest that extra evidence is (not) required (1 mark)

• can identify the extra evidence needed. (1 mark) 19 Suitable table of results with all relevant data included. (1 mark) Columns and rows correctly labelled. (1 mark) Units present and correct. (1 mark) Correct choice of bar chart or graph. (1 mark) Suitable scales chosen and labelled. (1 mark) Correct plotting. (1 mark) Section 2 1 Discrete. (1 mark) 2 Wind speed sensor and datalogger. (1 mark) 3 So the plant could adjust to the new conditions. (1 mark) 4 No, she has not made any effort to control other variables such as temperature or humidity. (2 marks)

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AQA GCSE Extension Units Teacher’s Guide

5 Her measurements are more precise. (1 mark) 6 Speed setting 1, 4 minutes. (1 mark) 7 Take the value for 5 minutes and divide by 5 to give cm/min. (1 mark) 8 Line graph. (1 mark) 9 Do a control experiment. (1 mark) 10 Repeat measurements and take averages for each time and setting. (1 mark) 11 Rate of transpiration increases from settings 0–2, and setting 3 shows transpiration has virtually ceased. (4 marks) Conclusion relates wind speed to the speed of removal of water particles from near the leaf, and increase of concentration gradient from leaf to air. (1 mark) Setting 3 shows the condition when the plant closes its stomata because rate of transpiration is greater than rate of supply of water from potometer, to avoid wilting. (1 mark) Quality of communication – correct use of two scientific terms, e.g. transpiration, diffusion, concentration gradient, rate. (1 mark)

© Pearson Education Limited 2007

B3.00

Exploiting microorganisms Overview This unit starts by exploring how we can be sure we are using microorganisms safely in the school laboratory. Students then look at the way Spallanzani, Schwann and Pasteur were involved in developing the theory of biogenesis. The next topic begins a study of how microorganisms are used to make food and drink. Starting with the involvement of bacteria in the dairy industry, yoghurt and cheese production are explored. Continuing with the traditional use of microorganisms, the structure of yeast is investigated and its role in bread making, wine making and brewing beer is examined. This leads to investigating how other useful substances can be made by culturing vast amounts of microorganisms in modern biotechnology industries. The fungal production of penicillin and mycoprotein is explored and we look at how fermenters supply optimal growth conditions. The last two topics focus on the production of fuels by fermentation. Small and large-scale biogas generators and the uses of the biogas are explored. Advantages and disadvantages of design features included in the biogas generators are presented. The concept of carbonneutral fuels is introduced and the increasing percentage of transport fuels produced by fermentation is investigated. Plans for expanding the production of ethanol-based biofuels in the United Kingdom is then explored. Financial data related to the plant source and cost of biofuel in various countries is presented. Data comparing carbon dioxide emissions of transport fuels is also included.

Investigative Skills Assessment The ISA for Unit B3.00 is using the aseptic technique to grow E. coli bacteria. In the Student’s Book, data is presented to the students from an investigation into the effect of temperature on the fermentation of yeast. Then they are asked a number of questions about the investigation. The Copymaster File provides questions for students to answer based on their own investigations into using the aseptic technique to grow E. coli bacteria.

B3.00

Context page

Practical 1 in Topic B3.14 gives instructions for this investigation.

Objectives for the unit By the end of this unit students should know and understand:

• how we can use microorganisms safely • the development of the theory of biogenesis • how microorganisms are used to make food and drink

• how industrial fermenters are used for the growth of the fungi Penicillium and Fusarium

• how fuels such as biogas and ethanol can be produced by anaerobic fermentation.

© Pearson Education Limited 2007

Notes on context The context for this unit is industrial biotechnology and the use of microorganisms to produce useful substances. Food production in the dairy industry is exemplified in the fermentation by Lactobacilli in yoghurt production. The operation of a large-scale industrial fermenter is outlined. Further information about biotechnology and other related websites for this unit can be accessed via www.longman.co.uk/ AQAScience.

Learning activities AT The context of this module is introduced via a video on the Active Teach. In the video, a scientist discusses the operation of an industrial fermenter. It provides an insight into the scale of production, equipment used and its operation.

AQA GCSE Extension Units Teacher’s Guide

41

B3.13

Growing microorganisms

Worksheets available No. B3.13a B3.13b

Title Growing microorganisms Growing microorganisms

Type Classwork (reusable) Homework (reusable)

Objectives Students should be able to:

• describe how microorganisms are grown in a culture medium

• describe the conditions that microorganisms need in order to reproduce

• explain why the incubation temperature is lower in the school laboratory than in industry.

Points to note

• The growth refers to the increase in population numbers throughout this unit.

• This topic only alludes to aseptic techniques when referring to incubation temperatures.

Key words agar, broth, culture medium

Lesson ideas Starter Write the word ‘Microorganism’ on the board. Ask students to suggest examples of microorganisms. Add the words ‘bacteria’ and ‘fungi’ to the board and ask students to list where examples of each of these can be found, e.g. disease – ‘sore throat’; food – mushrooms. This activity should give you knowledge of their prior understanding of the area of microorganisms.

Learning activities

• Show students two Petri dishes, one containing agar and one without it. Let them pass the Petri dishes round. The laboratory incubator should also be accessible for students to look at.

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AQA GCSE Extension Units Teacher’s Guide

Foundation

Higher 4 4

• Worksheet B3.13a will allow students an opportunity to present data on bacterial growth graphically as well as giving them practice at interpreting growth rates and explaining the changes in rate.

• AT Animation 1 from the Active Teach provides

reinforcement for the bacterial growth method and colony formation.

• Worksheet B3.13b provides students with

an opportunity to revise the substances and temperature needed for rapid bacterial growth leading to colony formation on agar.

Plenary

• Draw a surface view of a Petri dish containing agar

with colonies of bacteria on it. Elicit from students the conditions needed for these colonies to form in three days – list them on the board.

• Alternatively ask students to draw a growth curve to show the rate of increase in population growth. Ask them also to explain the changing rate at different times.

Additional homework/research ideas

• ICT

H Ask students to research agar, its origin, constituents and extraction. Also ask them to find out about Petri, the scientist who gave his name to the culture dishes.

Practicals and demonstrations 1 Demonstration of apparatus for growing microorganisms Show students an empty Petri dish and one containing agar. Arrange to have the school incubator accessible to students. 5 minutes Apparatus 2 Petri dishes: 1 containing agar and 1 without agar; incubator.

© Pearson Education Limited 2007

B3.14

Aseptic technique

Worksheets available No. B3.14a B3.14b

Title Using the aseptic technique to grow E. coli bacteria HSW Killing microorganisms

Objectives Students should be able to:

• recall that you need uncontaminated cultures of

microorganisms to get useful products from them

• describe how apparatus is sterilised and how this achieves a pure culture

• explain how to inoculate a culture medium. Points to note

• Safe working procedure must be stressed to

students. Petri dishes should only be incubated for 2–3 days and then stored in a refrigerator until students have the opportunity to see them again.

• Forward planning is essential as this practical requires significant technician support.

Key words aseptic, autoclave, pure culture, strain

Lesson ideas Starter Use the photograph in Display A from the Student’s Book showing a hospital operation in progress. Elicit from students why masks and green gowns are visible. Develop the notion of sterile practice and where microbes are in the surroundings.

Learning activities

• Discuss sterilisation of apparatus and liquids with

students and show them the autoclave. Emphasise the role of pressurised steam in the sterilising procedure.

• Use the diagrams in Display B of the Student’s Book in preparation for the practical work. Considerable dexterity is needed to pour a sterile plate and then inoculate it from a pure culture.

• Worksheet B3.14a provides support for the ISA for this unit.

• HSW Worksheet B3.14b provides an opportunity to

measure, rank and plot a histogram of data relating to chemical disinfectants. Students use the diameter of a circle to calculate the area of a circle.

© Pearson Education Limited 2007

Type Classwork/practical (reusable) Homework (reusable)

Foundation 4

Higher 4 4

• Question 3 is a short comprehension activity about the use of disinfectant alcohol hand gel and allows the opportunity to practice evaluation skills.

Plenary

• Write the words ‘aseptic technique’ on the board or

OHP. Underneath it on the same line add the words ‘Equipment. Why? How?’

• Invite contributions from students as to how plastic

apparatus, growth media, inoculating loops and hands are sterilised. Let them debate about hands being sterile and all the steps that could be taken to make hands sterile. This could be a good opportunity to return to the photograph of the operating theatre.

Additional homework/research ideas

• H

ICT Ask students to research MRSA infections in their local area health authority. More information can be found at www.longman.co.uk/AQAScience.

Practicals and demonstrations 1 Using the aseptic technique to grow E. coli bacteria This is the ISA for this unit. Details for carrying out the practical are given on Worksheet B3.14a. Pure cultures of E. coli must be available. If the control Petri dish grew bacteria, students should be encouraged to appraise their technique and speculate about the most likely point at which contamination occurred. Incubate agar plates at ambient temperature. All cuts should be covered with a plaster. Eye protection should be worn. Do not open Petri dishes once inoculated. Dispose of cultures safely by sterilising them in an autoclavable bag before placing in refuse. Count out agar plates for observation after incubation and count back in, to guard against theft. 20–25 minutes Apparatus Bunsen burner; heat-proof mat; inoculating loop; 2 sterile Petri dishes; pure culture of E. coli on agar in Petri dish or McCartney bottle; 2 sterile McCartney/ universal bottles of liquefied sterile agar held at 50 °C; small beaker of 1% Virkon disinfectant; paper towels; adhesive tape; scissors; waterproof marker pen; eye protection.

AQA GCSE Extension Units Teacher’s Guide

43

B3.15

Biogenesis

Worksheets available No. B3.15a

Title Using a swan-neck tube

B3.15b

Given the vowels

Type Practical/demonstration (reusable) Homework (write-on)

Objectives Students should be able to:

• describe Spallanzani’s challenge to the theory of ‘spontaneous generation’

• explain Schwann’s cell theory • describe how Pasteur’s experiments totally refuted spontaneous generation

• explain what is meant by ‘biogenesis’. Key words abiogenesis, biogenesis, cell theory, spontaneous generation, swan-neck tube

Lesson ideas Starter

• AT Use the ActiveTeach photograph of an egg

and sperm joining together to form a zygote. Ask students what develops from the zygote. Elicit from students the fact that it is a new individual of the same type as the parents who produced the gametes. Go on to tell them that until the eighteenth century people did not know this, but believed that fully formed living organisms could arise by spontaneous generation.

Learning activities

• Tell students the old myth that people in the

eighteenth century believed about the origin of mice: if a sweaty shirt and some wheat bran were placed in a wooden barrel, after 21 days mice would appear from the barrel. Let students suggest why mice were in the barrel.

• Explore displays A and B in the Student’s Book with students to clarify the theories of Spallanzani and Schwann

• H Worksheet B3.15a will give students the

opportunity to carry out, present and display the results, and make conclusions from an experiment with a swan-neck tube.

• Worksheet B3.15b can be used as revision for the

first three topics. It presents statements to match up to answers in which the vowels only are given and may need familiarisation before it is presented to the class for homework. You may wish to complete

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AQA GCSE Extension Units Teacher’s Guide

Foundation

Higher 4 4

two more answers as a class exercise before they attempt the worksheet as homework.

Plenary

• Ask students to write the word ‘abiogenesis’ at the

top of a sheet of paper and the word ‘biogenesis’ near the bottom. Ask them to draw a flow diagram between the words to illustrate the development of the theory about how living things come into existence. Finally, ask them to define abiogenesis and biogenesis.

Additional homework/research ideas

• ICT Students could be asked to research Pasteur’s

work on wine production or the development of the process of pasteurisation.

Practicals and demonstrations 1 Using a swan-neck tube Worksheet B3.15a has details of this practical. If preferred, this experiment could be done as a demonstration. Students use sterile nutrient broth and contain it in four tubes with different apparatus. After autoclaving, the tubes are left for one week before the results are seen. Do not uncover the broth in any tube after one week. Wash hands after handling the tubes. Typical results: Tube Contents number 1 open to air 2 tube closed 3 straight glass tubing 4

Results

broth cloudy/turbid broth clear broth eventually goes cloudy s-shaped glass tubing broth clear

Broth that turns cloudy contains bacteria from the air, with no guarantee of whether these are harmless or pathogenic. There is always a risk of tubes with cloudy broth being dropped, creating massive aerosol production and contaminating the room with bacteria. It is therefore recommended that tubes in which broth becomes turbid are treated to kill their contents before returning them to the students to observe. This is most easily done by adding two drops of 40% methanol solution (TOXIC) to the broth 24 hours in advance of the lesson. Technicians must wear goggles and gloves and use a fume cupboard when handling methanol solution. © Pearson Education Limited 2007

It is easiest to add drops of methanol solution using a Pasteur pipette, with the tip introduced into the tube without completely removing the cotton wool. 10 minutes to set up tubes; 5 minutes at the next lesson to note appearance of tubes after autoclaving; 5 minutes to note appearance of tubes again one week later after incubation.

B3.16

Apparatus Nutrient broth; 4 boiling tubes; test tube rack; nonabsorbent cotton wool; short, straight glass tube; short, S-shaped glass tube; cooking foil; stopwatch; waterproof marker; autoclave; 40% methanol solution.

Yoghurt and cheese

Worksheets available No. B3.16a B3.16b

Title Design a controlled experiment to produce yoghurt Manufacturing yoghurt.

Objectives Students should be able to:

• recall that bacteria are needed to manufacture yoghurt and cheese

• • describe the role of lactic acid in yoghurt

describe the role of bacteria in yoghurt production manufacture and where it comes from.

Points to note

• Milk is homogenised by being forced through tiny holes under pressure to break up fat globules.

• Set yoghurt is incubated in the pots it is sold in at the supermarket.

Key words curds, lactose, rennin, starters, whey

Lesson ideas Starter

• Show students an empty yoghurt pot and a

piece of packed cheese and ask them how they are produced. Elicit from students the idea that microorganisms are involved in their production and what their role is. Write the words ‘texture’, ‘pH’ and ‘keeping properties’ on the board. Ask students to suggest how these three features are different in milk and yoghurt/cheese. You may wish to keep a note of these and return to them for the plenary.

Learning activities

• Take time to explore Display A in the Student’s

Book with the class. An understanding of the four processes outlined here on the arrows is crucial for the rest of the topics in the unit.

© Pearson Education Limited 2007

Type Classwork (reusable) Homework (reusable)

Foundation 4

Higher 4 4

• AT The ActiveTeach has a video clip of industrial

yoghurt production and Display B in the Student’s Book shows a photograph of an industrial yoghurt fermenter.

• The flow diagram of yoghurt production in Display C should be explored with the students.

• Worksheet B3.16a supports students in designing a controlled experiment to produce yoghurt.

• Worksheet B3.16b gives students an opportunity to

revise yoghurt and cheese making and also extends their knowledge of additional microbes that may be involved in the processes.

Plenary

• Write: ‘Lactobacillus bulgaricus’ and ‘Streptococcus

cremoris’ in the middle of the board. Enlist student’s help in creating a spider diagram to show what the involvement of these bacteria is in yoghurt and cheese making.

• Alternatively, revisit the starter from this topic

and ask students to make any revisions they think necessary.

Additional homework/research ideas

• ICT Ask students to research three cheeses from their local area. Alternatively, they could research goat’s cheese and the nutrients it contains compared with cheese made from cow’s milk.

• Students could also be asked to research the

history of yoghurt making in third-world countries. Suggested sources of information can be found via www.longman.co.uk/AQAScience.

Practicals and demonstrations 1 A controlled experiment to produce yoghurt The practical designed in Worksheet B3.16a could be carried out if facilities and time allow.

AQA GCSE Extension Units Teacher’s Guide

45

Eye protection should be worn. Never taste food in the laboratory. Therefore it is much more appropriate if this activity is conducted in a food technology room or the school dining room. If hygenic conditions have been observed there is no reason why the yoghurt cannot be tasted. In this case, do not use laboratory equipment but appropriate utensils. 15–20 minutes to set up; 5 minutes to inspect

Apparatus Natural live yoghurt; UHT milk; 22250 cm3 beakers; measuring cylinder; small disposable container (plastic/paper cup); teaspoon; gauze; heat-proof mat; tripod; Bunsen burner; glass rod; clingfilm; water bath; pH papers; eye protection.

containers after 24 hours incubation (keep in fridge after this time)

B3.17

Yeast

Worksheets available No. B3.17a B3.17b

Title Experiment to investigate increase in the size of bread dough with time Living, respiring yeast

Objectives

Type Classwork/practical (reusable) Homework (reusable)

Foundation 4

Higher 4 4

Learning activities

Students should be able to:

• Take time to explore Display A in the Student’s

• describe the structure of yeast • describe how yeast can respire aerobically and

• AT The ActiveTeach has an animation to show the

• link the products of yeast’s anaerobic respiration to

• Worksheet B3.17a investigates the effect of yeast on

anaerobically

its use in making food and drink.

Points to note

• While fungi may be known to the class as

mushrooms and toadstools, the knowledge of a single-celled fungus will probably be new and may need time to develop.

Key words aerobic respiration, anaerobic respiration, budding, ethanol, fermentation

Lesson ideas Starter

• Before the lesson, mix up some dried yeast with

warm water and sugar in a beaker. Tell students that a harmless microscopic fungus has been mixed with warm water and sugar. Pass it round and ask students to smell it and ask what it reminds them of. Elicit what they know about bread making: what ingredients are used and what conditions are needed. You may find out that some students’ families have home bread-making machines.

Book with students to give them the opportunity to familiarise themselves with the structure of yeast. action of yeast in bread making.

a flour paste mixture. Students are asked to present data and draw conclusions before evaluating the way they carried out their experiment.

• Worksheet B3.17b gives students the opportunity to

revise the aerobic and anaerobic respiration of yeast. It highlights the amount of energy produced in each type of respiration.

Plenary

• Write the words ‘anaerobic respiration of yeast’

on the board. Ask students to help build up a word equation for respiration. Then ask them to help develop the diagram (in a similar way to that of Display B in the Student’s Book) in order to summarise how each of the products of respiration is used.

Additional homework/research ideas

• ICT Ask students to research the different types of yeast used in breweries.

Practicals and demonstrations 1 Investigating increase in the size of bread dough with time Worksheet B3.17a has all the details for this investigation. The ‘dough’ mixture used in Worksheet B3.17a contains more yeast than a bread dough mixture would. Do not taste the bread dough.

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AQA GCSE Extension Units Teacher’s Guide

© Pearson Education Limited 2007

40–45 minutes for the practical

could show the yeast suspension under low power and the other, under high power.

Apparatus

Do not angle the microscope mirror at the Sun, if using a microscrope of this type. 5 minutes to set up

Plain flour; sugar; yeast suspension; electronic balance; measuring cylinder; beaker; glass rod; stopwatch. 2 Demonstrating the appearance of yeast While students are completing the bread dough experiment you could set up two microscopes with slides of the yeast suspension. One microscope

B3.18

Apparatus 2 microscopes; 2 bench lamps; 2 microscope slides and cover slips; mounted needle.

The role of yeast in making alcoholic drinks

Worksheets available No. B3.18a

Title Fermentation of glucose by yeast

B3.18b

Wort, yeast and heat produce beer

Type Classwork/practical (reusable) Homework (reusable)

Objectives Students should be able to:

• describe what the energy source for yeast is in brewing beer and making wine

• explain that alcoholic fermentation is due to the anaerobic respiration of yeast

• describe and explain the stages in brewing beer. Points to note

• Brewing beer in breweries involves many different stages. The process has been simplified by concentrating on three main processes and the biological changes that occur there. Malting is not usually done at modern breweries but the malted barley grains are bought in

• A secondary fermentation process before bottling

makes beer fizzy. This has not been included in the production process outlined for simplicity.

Key words amylase, hops, malting, maltose, mash tun

Lesson ideas Starter

• Write the following true/false statements on the

board or OHP. a Yeast is a microscopic bacterium. b Yeast is a fungus. c Yeast is found in soil. d Dried yeast can be used for brewing beer or wine. e Fermenting yeast cannot grow. f Yeast needs warmth before it can ferment sugar.

© Pearson Education Limited 2007

Foundation

Higher 4 4

g Temperatures above 40 °C speed up yeast’s fermentation. h Yeast can ferment starch. i There are two useful products of yeast’s fermentation. j Ethanol is toxic to yeast cells. Ask students which statements are true and which false, and discuss their responses with them. This will act as revision for the last topic and allow you to assess their comprehension of fermentation so far.

Learning activities

• Use Display B in the Student’s Book to explore

together the commercial production of beer. Some students may be familiar with areas of the process if their family practice home brewing or wine making.

• Worksheet B3.18a is a practical to investigate the

fermentation rate of yeast. Students can work in groups of 3 or 4 if apparatus is in short supply, or it could be done as a demonstration. Students will need instructions on how to calculate the volume of gas collected in the test tube.

• Worksheet B3.18b provides a consolidation exercise on the brewing process.

Plenary

• Draw up the outline of the table, with headings, on

the board or OHP and fill it in with the students’ help. Brewing beer Making wine

When yeast is added Carbohydrate in barley/ grapes Carbohydrate fermented Other ingredients Product(s) of respiration in beverage

AQA GCSE Extension Units Teacher’s Guide

47

20–25 minutes

Additional homework/research ideas

• ICT Ask students to research yeast extracts

2 Fermentation of apple juice A simple demonstration of fermentation is to add a warm yeast suspension to apple juice in an unstoppered flask and watch the bubbles of gas given off.

• ICT Alternatively, ask students to research the

Do not taste anything in the laboratory. 20–25 minutes

Practicals and demonstrations

Apparatus

1 ICT Fermentation rate of yeast Worksheet B3.18a has all the details for a practical to measure the fermentation rate of yeast. This investigation provides the opportunity to use a datalogger and carbon-dioxide sensor if they are available.

150 cm3 clear apple juice; 10 cm3 5% glucose solution; 10 cm3 yeast suspension; flat-bottomed flask.

– obtained from brewery waste – and how they are used to enhance the nutrients in a wide variety of foods and/or in the pharmaceutical industry. production of alcohol-free beer.

B3.19

Fermenters and penicillin production

Worksheets available No. B3.19a B3.19b

Title The ins and outs of a fermenter Growing Penicillium mould and producing penicillin

Type Classwork (write-on) Homework (write-on)

Objectives Students should be able to:

• describe and explain the features of an industrial fermenter

• make clear how very large numbers of

microorganisms can be cultured safely in a fermenter

• list the specific needs of the mould Penicillium to produce penicillin

• specify when the release of penicillin from

Penicillium occurs during its growth in the fermenter.

Points to note

• Steam is used for sterilisation of the fermenter and associated pipework before a fermentation begins. The fermenter and pipework are usually made of polished stainless steel to make cleaning easier.

• It is important to stress here that the fermentation to produce penicillin is aerobic.

Key words bioreactors, isolated, penicillin

Foundation

Higher 4 4

Fermentation is useful: produce beer and yoghurt that involving Lactobacilli and yeast on a large scale it is used in the food and drinks industry many useful substances can be made by microorganisms all equipment must be sterilised before the process starts because, to, however, such as, therefore Ask students to add one of the words in the box before each statement. Then discuss the answers with them. Their results will help you to assess their learning so far.

Learning activities

• Take time with students to look at Display B in the

Student’s Book to familiarise them with the parts of the fermenter.

• AT The ActiveTeach has a video clip of an industrial fermenter.

• Worksheet B3.19a gives students an opportunity to engage with the structure and use of a fermenter.

Lesson ideas

• AT The ActiveTeach Animation 3 shows the

Starter

• Take time to discuss with students the graph in

• Write the following connectives quiz on the board or OHP:

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AQA GCSE Extension Units Teacher’s Guide

operation of an industrial fermenter.

Display C in the Student’s Book. It shows the time during the fermentation when the antibiotic is released from the fungus. © Pearson Education Limited 2007

• Worksheet B3.19b provides an opportunity to revise



the requirements for the growth of Penicillium and the point at which penicillin is released into the culture broth.

Plenary

c Aerobic. d Sugar and sources of nitrogen. e An antibiotic. f Removes heat produced by the respiring microbes.

Additional homework/research ideas

• Write the following answers on the board or OHP

• ICT Ask students to research other types of

and ask students to write down the question that was asked about Penicillium’s fermentation to get the answer.

medication produced in fermenters. Information can be found at www.longman.co.uk/AQAScience.

Practicals and demonstrations

a 28 °C. b When the mould is running out of nutrients.

None suggested.

Mycoprotein by fungal fermentation

B3.20

Worksheets available No. B3.20a B3.20b

Title How nutritious is mycoprotein? Producing food by fermentation

Type Classwork (reusable) Homework (reusable)

Objectives Students should be able to:

• define mycoprotein and recall which fungus produces it

• explain that the biomass of fungal hyphae is the product from the fermenter

•

describe the conditions needed to produce mycoprotein.

Points to note

• The Student’s Book provides nutrient data for freshly harvested mycoprotein. The Copymaster worksheets provide nutrient data for mycoprotein fillets, as they can be bought from a supermarket.

• Fibre, being carbohydrate, is part of the

‘carbohydrate total’ figures as well as being shown separately.

•

The whole fungal biomass is harvested from this fermentation.

Key words hyphae, mycoprotein

Lesson ideas Starter

• Hold up an empty packet or an advert for a

mycoprotein food (most well known are Quorn™ products). Write the word ‘mycoprotein’ on the board, divide the class into groups of four and give each group a different Quorn™ product box or cut-

© Pearson Education Limited 2007

Foundation

Higher 4 4

out advert. Give each group 5 minutes to write down what they already know about mycoprotein and what they have found out from the prop they have been given. Groups should then report their findings back to the rest of the class.

Learning activities

• It is worth taking time with students to explore Display B in the Student’s Book showing an alternative type of fermenter.

• ICT Worksheet B3.20a allows students to compare

nutrients in mycoprotein fillets, beef and lentils. Students can use Microsoft Excel for producing histograms in Worksheet B3.20a. If it is not convenient to do this during the science lesson, you may consider using that sheet for homework (private study in the computer department). Worksheet B3.20b could then be used for classwork.

• Worksheet B3.20b provides extension material

about other fermented food and drink products. It also presents a revision exercise about the loop fermenter in which mycoprotein is produced.

Plenary

• Ask students to make a concept map of fungal fermentation to produce mycoprotein.

Additional homework/research ideas

• ICT Ask students to research one (or more) of the foods or drinks in Figure 1 of Worksheet B3.20b, finding out how it was produced traditionally and how it is produced now.

AQA GCSE Extension Units Teacher’s Guide

49

Practicals and demonstrations 1 Demonstrating a bioreactor If the school has a classroom bioreactor, this could be demonstrated empty and a partially labelled diagram of it supplied to students. They could complete and annotate the diagram as you demonstrate it. Alternatively a diagram of a classroom bioreactor could be downloaded from the internet and used for

discussion. Further information about biotechnology and other related websites for this unit can be found at www.longman.co.uk/AQAScience. 10–15 minutes Apparatus Classroom bioreactor; diagrams of classroom bioreactor.

Biogas

B3.21

Worksheets available No. B3.21a B3.21b

Title Which biogas generator? Upgrading biogas generators

Objectives Students should be able to:

• describe how biogas can be produced from plant and animal waste by anaerobic fermentation

• give examples of small- and large-scale biogas production

• evaluate the advantages and disadvantages of the design of biogas generators.

Points to note

• Internet searches for information on biogas

generators are more productive if the term ‘biogas digesters’ is used.

•

Untreated biogas from rural generators containing impurities such as hydrogen sulfide has a low calorific value when combusted.

Foundation

Higher 4 4

copy of what you have written on the board or OHP to return to later.

Learning activities

• AT The ActiveTeach has an animation showing a small-scale biogas fermenter in action.

• Take time to explore Display B in the Student’s Book with students to help them appreciate the benefits biogas generation can bring to isolated third world villages.

• The table in the Student’s Book showing some

features of fermenters that maximise biogas production is worth discussing thoroughly with students.

• Worksheet B3.21a shows three designs of biogas

generator. Take time exploring these with students before they construct their table of advantages and disadvantages for each.

• Minworth sewage works on the eastern edge of

• Worksheet B3.21b will allow you to assess students’

• Students need time to access the internet, either

Plenary

Birmingham uses the sewage sludge produced from 2.5 million people. More information can be found via www.longman.co.uk/AQAScience. in school or at home, to research biogas generator designs.

Key words biofuel, biogas, sewage sludge

Lesson ideas Starter

• Ask students what a landfill site is. Let them suggest why these can be dangerous and elicit the fact that they produce biogas that can cause explosions if not controlled. Write the words ‘landfill’, ‘biogas’ and ‘hazard’ on the board or OHP. Then add ‘biogas flaring’ and ask students what this means. Save a

50

Type Classwork (reusable) Homework (reusable)

AQA GCSE Extension Units Teacher’s Guide

understanding of the fermentation process and provides an opportunity to research one type of biogas generator.

• Return to the words you used in the starter.

Annotate them with the students’ help to show what biogas contains, how it can be used and why it is a wasted resource if flared.

Additional homework/research ideas

• ICT Ask students to research small-scale biogas production in China or Sri Lanka and use their information in a PowerPoint presentation.

• Alternatively, ask students to research what happens to household waste or sewage sludge in their area and to produce a fact sheet of their findings.

Practicals and demonstrations None suggested. © Pearson Education Limited 2007

B3.22

Ethanol-based biofuels

Worksheets available No. B3.22 a B3.22 b

Title Bioethanol – an alternative fuel Promoting Biofuel

Type Classwork (reusable) Homework (reusable)

Objectives Students should be able to:

• describe how biofuels (ethanol-based fuels) are produced.

• interpret economic and environmental data about fuel production by fermentation and the use of these fuels.

Points to note

• Biofuel ethanol is 200 proof. • Economic data relating to production of fuels

is related to national situations, e.g. whether a particular country has a desire to be an independent producer of transport fuel, not reliant on oil imports. The situation is political and is in a state of change as we go to press.

• Hand in hand with national fuel transport policies are tax incentives or penalties, e.g. less tax on biofuels and flex-fuel cars.

• The price of biofuels and fossil fuels at the pump is very similar.

• Flex-fuel cars and biofuelled cars may cost more to buy than cars consuming fossil fuel, though tax on them is less.

• Lowest carbon emissions are obtained from ethanol

produced using lignocellulose from wood and straw, but the technology to do this is not so advanced, at present, as that for using cereals.

• HSW The availability of biofuels in 2007 in the UK is limited, but provision is already in hand to change this in the next decade.

Key words bioalcohols, flex-fuel

Lesson ideas Starter

• Write the term ‘transport fuels’ on the board or OHP.

Foundation

Higher 4

4

4

Learning activities

• AT Animation 5 illustrates the carbon-neutral concept.

• Display B in the Student’s Book is a horizontal

bar chart comparing CO2 emissions of fossil and renewable fuels. Students may not be familiar with this type of graphical presentation. It is used as there is a range of emissions depending on the manufacturing process.

• Display C in the Student’s Book is a conventional bar chart with information on country of production, source of biofuel/fossil fuel and cost in euros per litre. Note that petrol has fuel tax added. Some explanation of tax and discussion of units used in the table may be helpful.

• Worksheet B3.22a is a comprehension activity about

the use and availability of bioethanol. It will reinforce the students’ knowledge and understanding and extend it by looking at data from Brazil and the USA.

• ICT Worksheet B3.22b allows students to

incorporate information they have researched on the computer, and some that is supplied, into a poster to promote the use of biofuel.

Plenary

• Ask students to draw a concept map to show the

origins and advantages of biofuels. Their results will allow you to judge their understanding of the topic. Finally, ask them to think about when they will be car owners. Ask them to consider whether they would buy a flex-fuel car or not and their reasons why.

Additional homework/research ideas

• ICT Ask students to research Biofuel production and/or availability in their area.

• Alternatively, ask students to compare the price of a

new petrol/diesel car to one that uses biofuel. Also ask them to research the price at the pump for fossil fuels compared with biofuels.

Practicals and demonstrations None suggested.

Ask students to name some. You will probably have petrol, diesel and perhaps aviation fuel suggested. Add any suggestions to the board and then add ‘biofuels’. Invite suggestions as to what this might be.

© Pearson Education Limited 2007

AQA GCSE Extension Units Teacher’s Guide

51

B3.00

Answers

B3.00 Exploiting microorganisms Student’s Book 1 a Products listed may include:medicines,bread,wine, vinegar, cheese, yoghurt, fuel and many others from genetically engineered microorganisms.

B3.13 Growing microorganisms

2 c At X, there are plenty of nutrients available for the microbes to grow so they double their number every 20–30 minutes. At Z, the nutrients have been used up by the growing bacteria and their toxic waste products may have accumulated in the culture medium.

Worksheet 3.13b 1

Student’s Book 1 a Carbohydrates such as starch and glucose supply microbes with energy. b Mineral ions or urea supply microbes with a source of nitrogen. 2 Microbes can grow in it if nutrients are added.

Growth requirement Energy source Nitrogen source Warmth Moisture

Supplied as Starch/glucose Mineral ions/urea Incubator Culture medium

2 a F – optimal temperature, H – 15 °C, G – 25 °C.

3 A Petri dish is a round shallow dish made of clear plastic or glass with a lid. It is used for culturing microbes on agar.

b About 40 °C depending on the type of microbe.

4 25 °C is the maximum temperature used to incubate bacteria in school laboratories. It would minimise health risks if a pathogen was accidentally introduced into the culture medium as most pathogens have an optimum temperature of 37 °C.

3 c i A bacterial colony is a group of millions of bacteria.

5 A higher incubation temperature is used in industry to achieve a higher growth rate of microbes and a higher yield of microbial products. 6 a Region b. b The weight of cell numbers is increasing rapidly with time. 7 a A carbohydrate energy source, a source of nitrogen and perhaps other minerals, additional protein and vitamins.

c Many microbes can increase their growth rate up to 45 °C.

ii A colony originated from a single bacterium.

B3.14 Aseptic technique Student’s Book 1 Aseptic technique. 2 a It would multiply rapidly. b It would be a greater health risk than if it were a single cell. 3 a Glassware is sterilised in an autoclave. b Plastic equipment is sterilised by ultraviolet or ionising radiation.

b i The flask will be incubated in an incubator. ii So that the microbes will grow quickly enough for experimental results to be seen.

4 It would kill the microbes and melt the agar if it was too hot.

c i Agar is an alternative growth medium to broth.

5 If the Petri dish lid was removed completely, it would increase the chance of contaminating the agar with airborne microbes.

ii Agar is a solid at room temperature.

Worksheet B3.13a

6 a and b Wash hands and clean the working surface.

1

Assemble the apparatus. Light the Bunsen burner.

Time in minutes after start

30

60

90

120

150

180

210

240

Number of bacteria present

2

4

8

16

32

64

128

256

Pour the liquefied agar into the Petri dish – do not fully open the lid. Replace the lid and allow it to set. Flame the incubating loop and let it cool near to the Bunsen burner. Pick up some of the pure culture on the loop. Inoculate the Petri dish. Flame the loop again.

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AQA GCSE Extension Units Teacher’s Guide

© Pearson Education Limited 2007

B3.00

Answers

Tape up the plate and write details on the bottom of it.

2 Question, hypothesis, prediction, experiment, results, analysis, evaluation, conclusion.

Incubate the plate at 25 °C.

3 Tube 2 was boiled for 5 minutes and tube 3 was boiled for 60 minutes before being sealed.

c It would be autoclaved by a technician and then safely disposed of. d It will remain sterile.

Worksheet B3.14a

4 The broth would decay because microbes from the air had entered the broth. 5 Abiogenesis

1 Appearance of the plate; colour, number and distribution of colonies (if any) should be mentioned.

Disproved by Spallanzani

Life

2 The technique aims to be aseptic but depends on the user application. 3 Some basic suggestions include: wear protective coat, cover hair, wear a face mask, wear plastic gloves. In addition, a filtered air supply or working in a protective cabinet might be suggested.

Worksheet B3.14b 1 a Sterile means no living bacteria are present. b So that only the bacteria required will be present to grow. 2 a i A control is a check on the experimental technique. It is needed to eliminate other explanations of experimental results. ii To prove that the paper discs did not kill the bacteria.

Devised by Schwann



Cell theory – all cells come from pre-existing cells

Microorganisms must be present if decay occurs

Worksheet B3.15a 1 The microbes are killed. 2 Tubes 1 and 3. 3 Tubes 2 and 4. 4 The microbes had come from the air. 5 When microbes in nutrient broth have been killed, the broth will stay fresh if air is excluded. 6 Louis Pasteur developed a swan-neck flask with an S bend in it to trap bacteria.

Worksheet B3.15b

b and c Disc A B C D

Chemical

Rank

Diameter, Clear area, cm cm2 Sterile water control – – ‘HYPERKILL’ 1 2.5 4.9 ‘CLEANSO’ 2 1.6 2.0 ‘NOGERM’ 3 0.8 0.5

3 Advantages Alcohol gel Soap Takes less time to use Removes visible dirt Kills bacteria rapidly Dries quickly Can be used anywhere

Proved by Pasteur

Answer 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

I A P A L B I S S U T M P A B

N G E U O I N W P P H I U D A

C A T T U O O A A W E C R H C

U R R O I G C N L A O R E E T

B J I C S E U N L R D O C S E

A E D L P N L E A D O O U I R

T L I A A E A C N D R R L V I

O L S V S S T K Z R S G T E A

R Y H E T I I F A A C A U T L

E S N L N U H N R A C

Statement Letter D L O J U R N M G L O O P I A S K K I G G H T E W A N N A I S M S B E H P E C O L O N Y F

Disadvantages are the converse of the advantages above

B3.16 Yoghurt and cheese

B3.15 Biogenesis

Student’s Book

Student’s Book

1 Bacteria use enzymes to digest their food.

1 The mistaken belief that living organisms could come into existence from non-living matter.

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2 Digestion by the enzymes has made the food soluble.

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3 A starter culture is a culture of bacteria added to milk to produce yoghurt or cheese.

4 Aerobic respiration.

4 Milk is incubated at 40–46 °C for 4–6 hours.

5 a The ethanol evaporates during baking at 180 °C.

5 a Lactose is the sugar in milk.

b The bubbles of carbon dioxide escape during the fermentation process.

b It supplies energy to bacteria. 6 Anaerobic respiration releases energy. 7 a Lactic acid producing bacteria (Streptococcus cremoris) and rennin. b They curdle milk so that it separates into curds and whey. 8 a Whey is a watery liquid and curds are solid white particles. b Cheese is made from curds. 9 d Incubation temperature is 40–46 °C. The pH drops from 6.3 to 4.6.

Worksheet B3.16a

3 Respiration in the absence of oxygen.

6 a In aerobic respiration, when oxygen is present, much more energy is released than in anaerobic respiration. This is because, in the absence of oxygen, not all of the energy in sugars can be fully released. b Yeast is killed in bread making because of the high temperature in baking. Yeast is killed in wine making because the ethanol released is toxic to the cells. c Bread dough rises because bubbles of carbon dioxide released get trapped in the elastic dough.

2 A Label the two beakers to show which is the control and which is the experimental beaker.

Worksheet B3.17a

B Put three teaspoons of yoghurt into each beaker.

4 Perform the experiment in a water bath set at different temperatures.

C Heat one beaker (the control) gently over the Bunsen burner, stirring it until the yoghurt boils.

3 The bread dough increases in volume with time.

D Leave the control to cool.

5 The mean of a large number of results would help to minimise any inaccuracies and anomalous results.

E Add 125 cm3 of UHT milk to each beaker and stir it.

Worksheet B3.17b

F Cover each beaker with clingfilm and keep it in a water bath at 40 °C for 24 hours.

1 a Aerobic respiration.

G If it is not possible to take the results after 24 hours, keep the beakers in a fridge until the next lesson.

b Sugar+oxygen water+energy.

carbon dioxide+

2 a Anaerobic respiration.

H Record pH, smell and appearance of the contents of each beaker.

b Sugar

3 a The pH should fall.

b It has plenty of oxygen around it for aerobic respiration.

b Lactic acid. c The bacteria in the starter culture of yoghurt. 4 Other harmful chemicals or microorganisms might have accidentally been introduced into the yoghurt.

Worksheet B3.16b 1 a Lactic acid.

ethanol+carbon dioxide+energy.

3 a The first diagram.

B3.18 Yeast and making alcoholic drinks Student’s Book 1 a Cereal grains are seeds.

b Lactose, the milk sugar.

b They will develop into the same type of plant as the parents that produced them.

c The lower pH causes the protein in the milk to turn to a gel and the milk partially clots, or solidifies, into yoghurt.

2 Starch is a carbohydrate. It provides a chemical store of energy, which is needed for the seeds to sprout or germinate.

B3.17 Yeast

3 a The enzyme amylase converts the starch into sugar.

Student’s Book 1 The skin of fruits, plant leaves, flowers and in the soil.

b It is necessary because starch is a large insoluble molecule that cannot be transported to respiring cells and is not used in respiration.

2 Oxygen.

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B3.00

Answers

4 Malting is the process used in brewing beer when barley grains germinate.

b To provide a useful product and increase yield, respectively.

The barley grains must be damp and spread out in a thin layer at 10–15 °C.

2 They are performing aerobic respiration and growing quickly.

5 a In the mash tun, enzymes change starch into sugar. In the boiler, the wort is flavoured with hops and it is sterilised.

3 By a water-filled jacket surrounding the fermenter.

b From the sugary liquid called wort.

b Paddles disperse the foam.

6 Hops are dried flower heads of a climbing plant. They give flavour to the beer.

5 pH – most microbes are pH sensitive.

7 Sugar

ethanol+carbon dioxide+energy.

8 a Hops are filtered out.

4 a Bubbles of carbon dioxide become trapped on the surface of the culture broth.

Temperature – microbial growth has an optimum temperature.

b Dead yeast cells are filtered out.

Oxygen – microbes use it rapidly when respiring aerobically.

9

6 In the culture broth.

Process

Reason Enzymes change starch in maize Malting to sugar Mashing A sugary liquid is produced Flavour is added and the sugary Boiling liquid is sterilised Yeast ferments the sugar to Fermenting ethanol and carbon dioxide

Worksheet B3.18a 3 As yeast ferments sugar it releases carbon dioxide. As the sugar is used up, less carbon dioxide is released. 4 a Use boiled yeast. b To prove that the yeast is causing the release of carbon dioxide. 5 When all the sugar is used up and/or when the level of ethanol increases and kills the yeast cells.

7 Penicillium grows slowly at first and does not produce any penicillin. Penicillium mould releases most penicillin when its growth rate is slowing down or has stopped. 8 a Clockwise from top right: gas/CO2 out; stirrer; water jacket; culture broth; sterile air; harvesting drain; microbes and nutrients. b i If the stirrer stopped working, the microbes would settle at the bottom of the fermenter and their growth rate would fall. ii If the airflow decreased by 80%, aerobic respiration would slow down and the yield of penicillin would be reduced.

Worksheet B3.19a 1 A and B – Microbes and nutrients inlet. C – Gas/CO2 outlet. D – Sterile air inlet. E – Harvesting drain for microbial product.

Worksheet B3.18b

3 X – To keep the microbes and culture broth in close contact.

2 The barley seeds are germinated in a process called malting. The seeds are crushed and added to the mash tun with warm water so enzymes can change the starch in the seeds to sugar. The filtered wort is transferred to the boiler and hops and sugar are added. It is boiled for 2½ hours. After filtering and cooling, the wort goes into the fermenter and yeast is added. After eight days, the beer is ready for packaging.

Y – To provide the optimal temperature for microbial growth.

B3.19 Fermenters and penicillin production Student’s Book

Z – So that conditions inside the fermenter can be maintained at optimum levels.

Worksheet B3.19b 1 a Sugar and a source of nitrogen. b The Penicillium has used the nutrients up for its growth. c i Penicillin. ii In the culture broth. 2 b It has used up most of the nutrients.

1 a Keep contaminating microorganisms out and provide optimal growth conditions.

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B3.20 Mycoprotein by fungal fermentation Student’s Book

b Air pumped in near the base of the fermenter reduces the density of the broth so it rises in the fermenter. Gas is removed from the top of the fermenter and causes the broth to become denser, so it falls to the base.

1 Fusarium venenatum.

c i Glucose, ammonia, compressed air.

2 A plentiful supply of nutrients and oxygen.

ii Fusarium venenatum biomass.

3 Cooling coils full of cold water take heat away from the fermenter.

d i Aerobic respiration.

4 It supplies oxygen for respiration and it gently agitates the culture broth. 5 a Glucose and ammonia. b To maintain the growth rate of the fungus.

ii Air is added to the fermenter.

B3.21 Biogas Student’s Book 1 A mixture of mostly methane and carbon dioxide.

6 The product of the fermentation is the fungal body or biomass of Fusarium venenatum. It is made up of microscopic thread-like hyphae.

2 Plant material or animal waste, such as sewage sludge.

7 a Mycoprotein consists of a microscopic fungus.

3 Anaerobic fermentation.

b It is grown under carefully controlled conditions in enormous industrial fermenters and supplied with oxygen and nutrients.

4 a Cooking, lighting or electricity generation.

c In pies, sausages and burgers or with pasta, rice and potatoes, etc.

b As a fertiliser. c Animal and human excreta will be used and not left to cause disease.

Worksheet B3.20a

5 a Automatic mixing system, heating system and agitation system.

2 a Beef sirloin.

b Energy costs.

b Lentils.

c Heating system in the fermenter. This would speed up the fermentation rate to give a high yield of biogas when it is needed most as a fuel, in winter.

c Lentils. d Lentils. e Mycoprotein fillets. f Beef sirloin. 3 Mycoprotein is the fungal body of Fusarium venenatum. It is made by growing the fungus aerobically in a fermenter.

Worksheet B3.21a 1 X

b It has low fat and energy values. c It has a slightly lower value than beef. 5 Several different types of units are used in the table.

Worksheet B3.20b

Advantages

4 a It involves no animal products but has a similar texture to meat and can be flavoured to taste like meat.

1 a Cheese, yoghurt.

Pump to force organic matter into the fermenter

Mixing system in feed tank

Heating in fermenter

Agitator in slurry store

Gas used to generate electricity

Gas collected from Heating in slurry store fermenter

Heating in fermenter

Agitator in slurry store

Only one building to maintain

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Disadvantages

d Soy sauce, miso, tempeh.

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Gas used to generate electricity Gas used for agitation in fermenter

c Rice.

2 a The arrows represent the circulation of culture broth in the fermenter.

Z

Pump to force organic matter into fermenter

b Bread, beer.

e Cider, wine.

Y

Three buildings to Underground maintain construction is expensive

Gas from slurry store not collected

Gas not used to generate electricity

Feed not pumped into fermenter

Difficult to access plastic gasholders for maintenance

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B3.00

Answers

Worksheet B3.21b

c There is a high fuel tax on it.

1 a

d Maize.

No.

Replacement

Reason

1

Pumps will force raw waste into the fermenter

A constant supply of material will be fed to the fermenter

2

Gas mixers or mechanical More contact between stirrers microbes and organic matter

3

Wall and floor heating and insulation to outer walls of fermenter

Fermentation rate will be speeded up

4

Three

A higher yield of biogas will be produced

5

Two flexible polyethylene Greater volume of gas gas holders, one above collected. Easier to the slurry store maintain gas holders

e 0.5€ per litre. 7 a To cut down on carbon dioxide emissions and because of the high price of fossil fuels. b Anaerobic fermentation of glucose from sugar beet or wheat by yeast followed by distillation of the ethanol produced. c E85 fuel contains 15% petrol and 85% ethanol. Flex-fuel cars have engines that can be adjusted according to the fuel in the tank.

Worksheet B3.22a 1 5%. 2 Taking into account all carbon emissions involved in the production and transport between extraction at the oil well head and driving a car. 3 46.5% reduction.

b i There was plenty of waste organic matter to feed into the fermenter.

4 £500.

ii Short distance to transport waste from the source to the biogas facility.

6 a 45%.

5 Petrol containing 25% ethanol and 100% ethanol

c i Odour control, less unsightly.

b 60%.

ii Revenue from sales of electricity to the National Grid. Safe disposal of wastes.

7 6 million.

2 Advantages of balloon biogas digester plants include: prefabricated and low cost; not below ground; relatively simple maintenance; most plants can be used as feed for the fermenter. Disadvantages of balloon biogas digester plants include: low gas pressure; the plastic balloon has a relatively short life span; local craftsmen cannot usually repair a balloon.

B3.22 Ethanol-based biofuels

8 a Advantages 70% CO2 emission reduction Fully renewable fuel

Disadvantages Vehicles that use it cost £500 more Not widely available in UK in 2007

Produced from UK crops Less reliant on oil imports

Student’s Book

B3.00 Investigative Skills Assessment (Student’s Book)

1 a Fuels that are obtained from carbohydrate-rich crops.

1 What effect temperature has on the fermentation of yeast. (2 marks)

b By anaerobic fermentation into ethanol.

2 Volume of gas released. (1 mark)

c They are used as transport fuels in motor vehicles instead of petrol.

3 a 2–12 minutes. (1 mark)

2 There is no net effect on carbon dioxide levels in the atmosphere.

4 a No anomalous results. (1 mark)

3 They are fully renewable.

b By repeating the experiment. (1 mark) b Measurement of gas volumes. (1 mark)

b Ethanol from wood.

5 a Concentration of glucose solution, volume of glucose solution, Volume/weight of yeast suspension. Type of yeast. (any 2) (2 marks)

5 Ethanol from wheat.

b Appropriate measurements. (1 mark)

6 a Bioalcohol from wheat.

c Fermentation rate is related to quantities of sugar and yeast used. (1 mark)

4 a Petrol.

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6 At temperatures between 28 °C and 32 °C increasing the temperature; causes an increase in the volume of carbon dioxide released by yeast. (2 marks)

Section 2

7 Axes X and Y (one mark each) correct drawing and labelling. (2 marks)

12 Volume of gas released. (1 mark)

Correct plots – all (2 marks) four or five (1 mark)

b By repeating the experiment. (1 mark)

11 What effect temperature has on the fermentation of yeast. (2 marks) 13 a 2–12 minutes. (1 mark) 1 4 a No anomalous results. (1 mark)

B3.00 Investigative Skills Assessment (Copymaster File)

b Measurement of gas volumes. (1 mark)

Section 1

1 5 a Concentration of glucose solution, volume of glucose solution, Volume/weight of yeast suspension. Type of yeast. (any 2) (2 marks)

1 How to grow/culture E. coli bacteria; only. (2 marks)

b Appropriate measurements. (1 mark)

2 To prevent harmful microbes being accidentally introduced; and multiplying so that it became a health risk. (2 marks)

c Fermentation rate is related to quantities of sugar and yeast used. (1 mark)

b To prove there were no microbes present before they were introduced. (1 mark)

16 At temperatures between 28 °C and 32 °C increasing the temperature; causes an increase in the volume of carbon dioxide released by yeast. (2 marks)

4 Experiment and control mentioned appropriately. (2 marks)

17 Axes X and Y (one mark each) correct drawing and labelling. (2 marks)

5 If the control was bacteria free; then the technique has been justified. If the control grew microbes; the technique used was not aseptic. (2 marks)

Correct plots – all (2 marks) four or five (1 mark)

3 a A sterile agar plate. (1 mark)

6 Suitable improvement; appropriate benefit. For example, repeat the experiment with two more Petri dishes. This should confirm the results and make the conclusion more valid. (2 marks) 7 The class results. (1 mark) 8 Perform the experiment again. Ask another group to check the results. (1 mark) 9 Too low a temperature and they would only grow very slowly. A temperature above 25 °C increases health risks. (1 mark) 10

Colour of agar

Clarity of agar

Number of bacterial colonies present

Experimental plate Control plate Suitable table. (1 mark) All columns complete. (1 mark)

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B3

Answers

B3 Assessment exercises Question 1 a b c d

Answer To average so she could increase the accuracy of her results. 70.3, 86.7, 114.0. Heart rate increases with level of activity. Phil’s results are lower, so he may be fitter than Marie.

2 a

Diagram labelled correctly.

b c d

Blood vessel taking blood away from heart. Capillary. Very thin walls.

3 a

Rate of transpiration increases during daylight because stomata are open Using a potometer. Temperature lower so rate of evaporation from leaf slower; humidity higher so rate of evaporation lower. Sketch should show lower rate of transpiration; fewer stomata to reduce water loss

b c d

4 a b c

d e

Reached maximum level of supply of oxygen to muscles Glucose/sugar lactic acid (+energy released) The glucose molecule is only partly broken down. or Energy still locked in bonds in lactic acid. Lactic acid is transported to liver, there converted back to glucose using oxygen Oxygen is required after activity to convert lactic acid back to glucose.

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Extra information at least 2 correct 1 mark for answer, 1 for reason allow 1/2 mark for each correct

Mark 1 1 1 2 Total 5 2

1 mark for each point

1 1 1 Total 5 2

1 mark for each point

1 2

1 mark for sketch; 1 mark for explanation

Either answer.

2 Total 7 1 1 1

2 1 mark for each point.

1 1 Total 7

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Question Answer Uncontaminated or pure cultures. 5 a Agar, inoculating loop, Petri dish, McCartney bottle. b

Extra information

c

Pressurised steam – culture medium. Ultraviolet light – plastic culture dish. Bunsen burner flame – inoculating loop.

1 mark for each correct pair 3

6 a b

Boiled chicken broth sealed in glass phial did not decay. Living organisms produce other living organisms of the same type. Swan-neck flask containing boiled chicken broth; no decay after two days; air could enter flask but microbes settled on neck of flask.

c

7 a b c

d e 8 a b

All 4 correct (2 marks); 3 correct (1 mark)

Total 6 1 1 1 mark for each point.

3

Total 5 1 1 3

Milk and bacteria. 6.3 and 4.6. Lactose is used as an energy source; by the bacteria that ferment it; producing lactic acid. 38–44 °C (any temperature in this range). An experiment with milk but no microbes. Bioethanol/biobutanol/biodiesel – anaerobic fermentation. CO2 absorbed from atmosphere by wheat/sugar cane. Fermentation and distillation produce bioalcohols. Exhaust gases from vehicles release CO2 back into the atmosphere.

Mark 1 2

1 mark for each point.

1 1 Total 7 2 3

Total 5 47 marks

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B3 Unit test Question Answer Oxygen from alveolus to blood; 1 a carbon dioxide from blood to alveolus The membranes between the blood and alveoli are partially b permeable membranes.

Extra information 1 mark for each point

c

Horizontal line to show higher concentration in plasma (no change or lower concentration in alveolus, with steeper line joining the two). Concentration in plasma higher due to more carbon dioxide produced by muscle cells.

Mark for correct plasma line 1

1 mark for each point

2

To get more oxygen into blood through lungs; get more oxygen to cells Lower Any two from: contain haemoglobin, which carries oxygen; thin disc shape for rapid diffusion/exchange or increased SA/V ratio; no nucleus so more space for haemoglobin. Blood can carry more oxygen so can run faster or further than before increase in red blood cells.

1 mark for each point

Total 6 2

1 mark for each point

2

To get more organs for transplant. or Not enough organs for transplant. It goes to the patient with the best tissue match. Dialysis. Any one from: more normal life; less control of diet; or any other sensible answer. Any one from: take immunosuppressant drugs for life; more infections than other people; greater risk of some cancers.

either answer for mark

Total 7 1

d

2 a b c

d

3 a

b c d e

4 a b

c

Root hair cell. Water enters by osmosis because solution of soil water is more dilute than solution inside cell. Mineral ions by active transport / using energy because concentration outside is lower than inside, so cannot enter by diffusion.

Mark 2 1

1 mark for each point, allow 1/2 mark for adaptation without explanation.

1 2

1 1 1 1

1 for osmosis, 1 for explanation 1 for active transport/using energy, 1 for explanation

Total 5 1 2

2

Total 5

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Question Answer Labels are: bud, cell wall, cytoplasm, nucleus. 5 a b

c d 6 a b c

AEROBIC RESPIRATION sugar+oxygen carbon dioxide+water+energy ANAEROBIC RESPIRATION sugar ethanol+carbon dioxide+energy More energy is released in aerobic respiration. On the grape skins. Penicillium and Fusarium. Penicillin and mycoprotein. Component of fermenter Water jacket Temperature probe Stirrer Sterile air

7 a b

Extra information All correct – 2 three correct – 1 All correct – 2 three correct – 1

Reason needed to maintain a constant temperature in the fermenter to monitor conditions in the culture medium to keep microbes and nutrients in close contact for respiration of microbes

1 mark for each correct pair

2

1 1 Total 6 1 1 4

Total 6 1 6

Methane, carbon dioxide Any 3 for both Third-world farmer

Mark 2

European farmer – community biogas

• protection of forests • income from power sales • improvement in hygiene • no need to treat farm waste • yields fertiliser • yields fertiliser • provides lighting 8 a b c

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Beer making is starch in barley grains; wine making is sugar in grapes Enzymes break starch down to sugar Hops add flavour to the beer

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1 mark for each point.

Total 7 2 1 1 Total 4 46 marks

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C3

Chemistry Topic

Specification learning outcomes and codes

1

13.3.3 Water in rivers, lakes and the oceans is evaporated by the heat of the Sun. This forms water vapour that rises in the atmosphere and cools so that it condenses to form clouds. The water droplets in the clouds join together to produce rain. This is known as the water cycle.

2

13.3.2 To consider and evaluate the environmental, social and economic aspects of water quality and hardness. 13.3.14 Water of the correct quality is essential for life. For humans, drinking water should have sufficiently low levels of dissolved salts and microorganisms. This is achieved by choosing an appropriate source, passing the water through filter beds to remove any solids and then sterilising with chlorine. 13.3.15 Water filters containing carbon, silver and ion-exchange resins can remove some dissolved substances from tap water to improve the taste and quality. 13.3.16 Pure water can be produced by distillation.

3

13.3.4 Many substances dissolve in water. Most ionic compounds are soluble in water. Some molecular substances are soluble but many covalent compounds are insoluble in water. 13.3.5 The solubility of a solute in water, or any other solvent, is usually given in grams of solute per 100 grams of water (or solvent) at that temperature. 13.3.8 Many gases are soluble in water. Their solubility increases as the temperature decreases and as the pressure increases. –  Dissolving carbon dioxide in water under high pressure makes carbonated water. When the pressure is released, the gas bubbles out of the solution. Carbonated water is used to make fizzy drinks. –  Dissolved oxygen is essential for aquatic life. If the temperature of the water increases, the amount of oxygen that is dissolved decreases.

4

13.3.1 To interpret solubility curves and explain when crystallisation may occur. 13.3.5 The solubility of most solutes that are solids increases as the temperature increases. 13.3.6 A saturated solution is one in which no more solute will dissolve at that temperature. When a hot saturated solution cools, some of the solute will separate from the solution.

5

13.3.9 Soft water readily forms lather with soap. Hard water reacts with soap to form scum and so more soap is needed to form lather. 13.3.10 Hard water contains dissolved compounds, usually of calcium or magnesium. The compounds are dissolved when water comes into contact with rocks.

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13.3.10 Hard water contains dissolved compounds, usually of calcium or magnesium. The compounds are dissolved when water comes into contact with rocks. 13.3.11 Using hard water can increase costs because more soap is needed. When hard water is heated it can produce scale that reduces the efficiency of heating systems and kettles. 13.3.13 Hard water can be made soft by removing the dissolved calcium and magnesium ions. This can be done by: –  adding sodium carbonate that reacts with the calcium and magnesium ions forming a precipitate of calcium carbonate and magnesium carbonate –  using an ion-exchange column containing hydrogen ions or sodium ions that replace the calcium and magnesium ions when hard water passes through the column.

7

13.3.2 To consider and evaluate the environmental, social and economic aspects of water quality and hardness. 13.3.11 Using hard water can increase costs because more soap is needed. When hard water is heated it can produce scale that reduces the efficiency of heating systems and kettles. 13.3.12 Hard water has some benefits because calcium compounds are good for health. 13.3.13 Hard water can be made soft by removing the dissolved calcium and magnesium ions. This can be done by: –  adding sodium carbonate that reacts with the calcium and magnesium ions forming a precipitate of calcium carbonate and magnesium carbonate –  using an ion-exchange column containing hydrogen ions or sodium ions that replace the calcium and magnesium ions when hard water passes through the column.

8

13.5.1 To interpret results of the chemical tests in this specification. 13.5.4 Flame tests can be used to identify metal ions. Lithium, sodium, potassium, calcium and barium compounds produce distinctive colours in flame tests.

9

13.5.1 To interpret results of the chemical tests in this specification. 13.5.7 Aluminium, calcium and magnesium ions form white precipitates with sodium hydroxide solution but only the aluminium hydroxide precipitate dissolves in excess sodium hydroxide solution. Copper(II), iron(II) and iron(III) ions form coloured precipitates with sodium hydroxide solution. 13.5.10 Ammonium ions react with sodium hydroxide solution to form ammonia.

10

13.5.1 To interpret results of the chemical tests in this specification. 13.5.5 Carbonates react with dilute acids to form carbon dioxide. Carbon dioxide turns limewater milky. 13.5.6 Copper carbonate and zinc carbonate decompose on heating and can be identified by the distinctive colour changes.

11

13.5.1 To interpret results of the chemical tests in this specification. 13.5.8 Halide ions in solution produce precipitates with silver nitrate solution in the presence of dilute nitric acid. Silver chloride is white, silver bromide is cream and silver iodide is yellow. 13.5.9 Sulfate ions in solution produce a white precipitate with barium chloride solution in the presence of dilute hydrochloric acid. 13.5.11 Nitrate ions are reduced by aluminium powder in the presence of sodium hydroxide solution to form ammonia.

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13.2.1 To evaluate the contributions of Arrhenius, Lowry and BrØnsted to our understanding of acid-base behaviour. H 13.2.2 To suggest why the work of some scientists, for example Arrhenius, took much longer to be accepted than the work of others, for example, Lowry and BrØnsted H 13.2.4 An acid can be defined as a proton donor. A base can be defined as a proton acceptor. 13.2.5 Water must normally be present for a substance to act as an acid or as a base. 13.2.6 Acids produce hydrogen ions in aqueous solution. The H+ ion is a proton. In water this proton is hydrated and is represented as H+(aq). 13.2.7 Alkalis produce hydroxide ions, OH-(aq), in aqueous solutions. 13.2.8 Acids and alkalis are classified by the extent of their ionisation in water. –  A strong acid or alkali is one that is completely ionised in water. Examples of strong acids are hydrochloric, sulfuric and nitric acids. Examples of strong alkalis are sodium and potassium hydroxide. –  A weak acid or alkali is only partially ionised in water. Examples of weak acids are ethanoic, citric and carbonic acids. An example of a weak alkali is ammonia solution. 13.5.1 To interpret results of the chemical tests in this specification.

13

13.5.1 To interpret results of the chemical tests in this specification. 13.5.12 Organic compounds burn or char when heated in air. H 13.5.13 The empirical formula of an organic compound can be found from the masses of the products formed when a known mass of the compound is burned. 13.5.14 Unsaturated organic compounds containing double carbon– carbon bonds decolourise bromine water.

14

13.5.1 To interpret results of the chemical tests in this specification. 13.5.2 To evaluate the advantages and disadvantages of instrumental methods of analysis and the features that influence that development. 13.5.3 To interpret and evaluate the results of instrumental analyses carried out to identify elements and compounds for forensic, health or environmental purposes. 13.5.15 The development of modern instrumental methods has been aided by the rapid progress in technologies such as electronics and computing. 13.5.16 Elements and compounds can be detected and identified using a variety of instrumental methods. Instrumental methods are accurate, sensitive and rapid and are particularly useful when the amount of a sample is very small.

15

13.5.3 To interpret and evaluate the results of instrumental analyses carried out to identify elements and compounds for forensic, health or environmental purposes. H 13.5.17 Some instrumental methods are suited to identifying elements, such as atomic absorption spectroscopy used in the steel industry. Other instrumental methods are suited to identifying compounds, such as infrared spectrometry, ultraviolet spectroscopy, nuclear magnetic resonance spectroscopy and gas-liquid chromatography. Some methods can be adapted for elements or compounds, such as mass spectrometry.

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13.1.5 When electrons, protons and neutrons were discovered early in the 20th century, the Periodic Table was arranged in order of atomic (proton) numbers. When this was done, all elements were placed in appropriate groups. 13.1.6 The modern Periodic Table can be seen as an arrangement of the elements in terms of their electronic structures. Elements in the same Group have the same number of electrons in their highest occupied energy level (outer shell). 13.1.13 In the Periodic Table between Groups 2 and 3 is a block of elements known as the transition elements. These elements are all metals.

17

H 13.1.7 The trends in reactivity within Groups in the Periodic Table can be explained because the higher the energy level: –  the more easily electrons are lost –  the less easily electrons are gained. 13.1.8 The elements in Group 1 of the Periodic Table (known as the alkali metals): –  are metals with low density (the first three elements in the Group are less dense than water) –  react with non-metals to form ionic compounds in which the metal ion carries a charge of+1. The compounds are white solids that dissolve in water to form colourless solutions –  react with water releasing hydrogen –  form hydroxides that dissolve in water to give alkaline solutions. 13.1.9 In Group 1, the further down the group an element is: –  the more reactive the element –  the lower its melting point and boiling point.

18

H 13.1.13 The transition elements have similar properties and some special properties because a lower energy level (inner shell) is being filled in the atoms of the elements between Groups 2 and 3. This is because the third energy level can hold up to 18 electrons, once two electrons have occupied the fourth level. 13.1.14 Compared with the elements in Group 1, transition elements: –  have higher melting points (except for mercury) and higher densities –  are stronger and harder –  are much less reactive and so do not react as vigorously with water or oxygen. 13.1.15 Many transition elements have ions with different charges, form coloured compounds and are useful as catalysts.

19

13.1.10 The elements in Group 7 of the Periodic Table (known as halogens): –  have coloured vapours –  consist of molecules that are made up of pairs of atoms –  form ionic salts with metals in which the chloride, bromide or iodide ion (halide ion) carries a charge of –1 –  form molecular compounds with other non-metallic elements. 13.1.11 In Group 7, the further down the group an element is: –  the less reactive the element –  the higher its melting point and boiling point. 13.1.12 A more reactive halogen can displace a less reactive halogen from an aqueous solution of its salt.

AQA GCSE Extension Units Teacher’s Guide

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13.1.1 To explain how attempts to classify elements in a systematic way, including those of Newlands and Mendeleev, have led through the growth of chemical knowledge to the modern Periodic Table. 13.1.2 To explain why scientists regarded a periodic table of the elements first as a curiosity, then as a useful tool and finally as an important summary of the structure of atoms. 13.1.3 Newlands, and then Mendeleev, attempted to classify the elements by arranging them in order of their atomic weights. The list can be arranged in a table so that elements with similar properties are in columns, known as Groups. The table is called a Periodic Table because similar properties occur at regular intervals. 13.1.4 The early Periodic Table were incomplete and some elements were placed in inappropriate Groups if the strict order of atomic weights was followed. 13.1.5 Mendeleev overcame some of the problems by leaving gaps for elements that he thought had not been discovered.

21

H 13.2.3 To calculate the chemical quantities in titrations involving concentrations (in moles or mass per unit volume) and masses.

22

H If the concentration of one of the reactants is known, the results of a titration can be used to find the concentration of the other reactant.

23

13.2.9 The volumes of acid and alkali solutions that react with each other can be measured by titration using a suitable indicator: –  strong acid+strong alkali . any acid-base indicator –  H strong acid+weak alkali . methyl orange indicator –  H weak acid+strong alkali . phenolphthalein indicator.

24

13.4.10 During a chemical reaction: –  energy must be supplied to break bonds –  energy is released when bonds are formed. These changes can be represented on an energy-level diagram.

25

H To calculate the energy transferred in reactions, using simple energylevel diagrams or supplied bond energies. 13.4.11 In an exothermic reaction, the energy released from forming new bonds is greater than the energy needed to break existing bonds. 13.4.12 In an endothermic reaction, the energy needed to break existing bonds is greater than the energy released from forming new bonds.

26

13.4.5 The relative amounts of energy released when substances burn can be measured by simple calorimetry, e.g. by heating water in a glass or metal container. This method can be used to compare the amount of energy produced by fuels and foods. 13.4.1 To compare the energy produced by different fuels and foods.

27

13.4.2 To consider the social, economic and environmental consequences of using fuels.

28

13.4.6 Energy is normally measured in joules (J). Some dietary information is given in calories, which are equal to 4.2 joules. 13.4.7 Different foods produce different amounts of energy. Foods with high proportions of carbohydrates, fats and oils produce relatively large amounts of energy. 13.4.8 Eating food that provides more energy than the body needs can lead to obesity.

29

13.4.9 The amount of energy produced by a chemical reaction in solution can be found by mixing the reagents in an insulated container and measuring the temperature change of the solution. This method can be used for reactions of solids with water or for neutralisation reactions.

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C3.0

Water Overview This unit looks at water. It starts with where water comes from and how it is purified. It then goes on to discuss the effect of increasing temperature on the solubility in water of both gases and solid solutes, including the use of solubility curves. Hard water is then examined – its origins, its effect on soap, its benefits and disadvantages, and methods of removing hardness. The detection of dissolved ions in water is then studied in depth. This includes flame tests for the identification of some metal ions, and the effect of sodium hydroxide solution on solutions of some metal ions. The simple chemistry of carbonates is then studied, followed by the detection of halide, sulfate and nitrate ions in solution. Strong and weak acids and alkalis are then covered, including the contributions of Arrhenius, Brønsted and Lowry to our understanding of acid–base reactions at Higher level. The unit then continues by looking at the simple detection of some organic functional groups, including combustion analysis at Higher level. The unit ends by describing how modern instrumental methods can be used to detect and identify tiny amounts of substances quickly and accurately, including the specific use of some instruments at Higher level.

Investigative Skills Assessment The ISA for Unit C3.0 is investigating the differing hardness of samples of water. In the Student’s Book, data is presented to the students and then they are asked a number of questions about the investigation. The Copymaster File provides questions for students based on their own investigation into comparing the hardness of a number of samples of water. Practical 1 in Topic C3.6 gives instructions for this investigation.

C3.0

Context page

Objectives for the unit Students should know and understand:

• how water is cycled and purified • how the solubility of gases and solids changes with increasing temperature

• why soap reacts with the ions in hard water to form a scum

• how both permanently and temporarily hard water are formed and the hardness can be removed

• the benefits and disadvantages of hard water • how to carry out flame tests or use sodium •

determine the empirical formula of an organic compound

• the use of some instrumental methods for identifying compounds

• H the specific use of some instrumental methods. Notes on context The context for this unit is a water company. Here water is purified and then analysed for both purity and hardness.

hydroxide solution to identify some metal ions

Learning activities

how to test for carbonate, halide, sulfate and nitrate ions

• AT The ActiveTeach component for this topic is a

• the difference between strong and weak acids and alkalis

• H the influence of Arrhenius, Brønsted and Lowry on ideas about acids

• how to distinguish some organic compounds 68

• H how to use combustion analysis data to

AQA GCSE Extension Units Teacher’s Guide

video about the treatment of water to make it fit for use. It shows the extraction of water from aquifers and rivers, followed by purification. The small scale and accurate analysis of water is also shown.

• Students should realise that water is not an infinite resource, and should be encouraged to consider methods of conserving this essential resource.

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C3.1

The water cycle

Worksheets available No. C3.1a C3.1b

Title Water for life Rainfall statistics HSW

Type Classwork (reusable) Homework (reusable)

Objectives

Higher 4 4

water shortage found in other parts of the world, especially developing countries.

Students should be able to:

• AT The ActiveTeach has an animation showing the

• explain how water is cycled by a continuous

water cycle.

process involving evaporation, condensation and precipitation.

• ICT The Homework sheet gives statistics for rainfall in this country. It gives students an opportunity to plot bar charts and also to analyse data. The bar charts could be plotted using ICT.

Key words water cycle

Plenary

• Ask students to note down what would happen if we

Lesson ideas

ran out of water, or if it were severely rationed. Some students living in the south east of England will have experienced the hosepipe bans of 2006.

Starter Fill a beaker with water from the tap. Ask students to make a list of what they know about water. Give them two minutes and then pool their ideas into a class list. They should have some ideas from previous years, and also from Geography.

Additional homework/research ideas

• ICT Use the internet to gather more data about

water availability and consumption in developing countries.

Learning activities

Practicals and demonstrations

• Worksheet C3.1a is based on the United Nations

None suggested.

‘Water for Life’ campaign. It illustrates the severe

C3.2

Foundation 4 4

Purifying water

Worksheets available No. C3.2a C3.2b

Title Filtering dirty water Bottled water

Type Practical Homework

Foundation 4 4

Objectives

Lesson ideas

Students should be able to:

Starter

•

explain that our water must be of the correct quality with sufficiently low levels of dissolved salts and microorganisms

• explain how this is achieved by filtration and chlorination

• describe how water filters remove dissolved substances from tap water

•

describe how pure water is obtained by distillation.

Key words

Higher 4 4

Show students some muddy water and ask them if it is fit to drink. If they say it is not, ask them what must be done to it to make fit for drinking and how they will be able to tell when it is fit to drink.

Learning activities

• HSW The method by which water is purified by the

water companies is described in the Student’s Book.

• The practical (Worksheet C3.2a) gives students an

opportunity to try to purify water on a much smaller scale.

chlorinate, filter beds, water filter © Pearson Education Limited 2007

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Additional homework/research ideas

• AT The ActiveTeach has a video clip showing the

• ICT Research more uses of activated charcoal.

removal of water from aquifers and rivers. It also shows the purification of water so that it is fit to drink.

Students could start off by looking at its use in Second World War gas masks.

• The purity of water can be checked using water-

testing kits bought in garden centres or aquarium shops. Water-testing kits are available to allow you to test for pH, ammonia, nitrate, and copper. Oxygentesting kits are also available.

• ICT The summary question (Q7) could be completed using a computer presentation package.

• The homework sheet (Worksheet C3.2b) gives

students data about bottled water and asks them to compare three types on sale.

1 Filtering dirty water This straightforward experiment lets students make a simple model of water filtration. 30 minutes Students must wash their hands after using dirty water and should take care with the sharp tool. Apparatus (per group) Small yoghurt pot; sharp tool for making holes in the yoghurt pot; coarse gravel; fine gravel; fine sand; beaker; sample of dirty water (this could be just mud mixed with water); Worksheet C3.2a.

Plenary

• Give students the sentence ‘Clean water is essential

because …’ and ask them to complete it in as many ways as possible.

C3.3

Practicals and demonstrations

Solubility

Worksheets available No. C3.3a C3.3b

Title Dissolving air in water Cleaning up the Thames HSW

Type Classwork Homework

Objectives Students should be able to:

Foundation 4 4

Higher 4 4

be determined. This experiment may be done practically if the correct apparatus is available, but it is difficult to set up. Practical details have therefore not been given.

• describe how many substances dissolve in water • describe how most ionic compounds are soluble in

• AT The ActiveTeach has a video showing the

• express solubility as grams of solute per 100 g of

• The homework sheet (Worksheet C3.3b) gives

water, while many covalent substances are insoluble water (or solvent) at a given temperature

• describe how the solubility of gases changes as the temperature and pressure change.

Key words solubility, solute, solvent

Lesson ideas Starter Boil a beaker of water and watch how bubbles of gas leave as the temperature increases. Explain that this is because the gas is less soluble in hot water than in cold water.

Learning activities

analysis of oxygen levels in water.

information about how oxygen levels in the Thames have changed over the past 100 years. Students could be told that it is now quite usual to find salmon swimming in the Thames.

Plenary

• Ask students to draw a poster or mind map to

summarise what they know about the effect of increasing temperature on the solubility of gases. This can be completed after the next topic.

Additional homework/research ideas

• ICT Ask students to research how the ‘fizz’ is put into fizzy drinks.

Practicals and demonstrations None suggested.

• Worksheet C3.3a has information from which the relative solubilities of oxygen and nitrogen may

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C3.4

Saturated solutions

Worksheets available No. C3.4a C3.4b

Title Measuring the solubility of copper sulfate HSW A solubility curve for potassium chloride HSW

Type Practical Homework

Objectives

Foundation 4

Higher 4

4

4

• ICT The homework sheet (Worksheet C3.4b) gives

Students should be able to:

• describe how the solubility of solid solutes increases as the temperature increases

• explain that a saturated solution is one in which no

students an alternative method of measuring solubility. It also gives students practice in plotting and interpreting graphs. These could be done using ICT.

Plenary

more solute will dissolve at that temperature

• Complete the poster or mind map started at the

• interpret solubility curves and explain when

end of the last topic, in this case showing how the solubility of solid solutes varies with temperature.

crystallisation will occur.

Additional homework/research ideas

Key words crystallise, saturated solution

• Find out if the solubility of liquids varies with

Lesson ideas

Practicals and demonstrations

temperature.

1 Measuring the solubility of copper sulfate Although copper sulfate is expensive, this practical is more memorable than one using white crystals, and the copper sulfate obtained can always be reused. 1 hour

Starter Write the word ‘solubility’ on the board and ask students to jot down as many words and phrases that they associate with it as possible. Use this to revise first the solubility of gases covered in the last topic, and then any differences when solid solutes dissolve in water at different temperatures.

Copper sulfate is harmful. Eye protection should be worn at all times. Ensure that students wash their hands at the end of the practical.

Learning activities

• The theory of solubility and saturated solutions is

Apparatus (per group)

covered in the Student’s Book. The use of solubility curves is covered in some detail, with examples given.

• Practical 1 (Worksheet C3.4a) allows students to find the solubility of copper sulfate at different temperatures.

C3.5

9 g copper sulfate (hydrated); boiling tube; 25 cm3 measuring cylinder; 250 cm3 beaker; tripod; gauze; Bunsen burner; heat-proof mat; thermometer (0–100oC); access to a balance; eye protection; Worksheet C3.4a.

Hard water

Worksheets available No. C3.5a C3.5b

Title Finding the ions that cause hard water Soaps and detergents HSW

Objectives Students should be able to:

• describe the effects of both hard and soft water on soap

© Pearson Education Limited 2007

Type Practical Homework

Foundation 4 4

Higher 4 4

• explain that hard water contains dissolved

compounds, usually of magnesium or calcium, which dissolved when the water came into contact with rocks.

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Key words

Plenary

• Ask students to jot down individually what they

hard water, soft water

know about water now. They can then share their ideas with other people before contributing them to a list written on the board. Ask them to compare this to the list that they wrote in Topic 1.

Lesson ideas Starter Demonstrate to students what happens if soap is added to hard water. If you live in an area where there is hard water, use tap water. If you live in a soft water area, add a little calcium sulfate to some tap water before the lesson.

Learning activities

• ICT The effect of soap on both hard and soft water

is covered in the Student’s Book. If a turbidity meter is available this could be used with datalogging software to make a more accurate comparison.

• AT The ActiveTeach contains a video about the

analysis of water during the purification process.

• The Worksheet C3.5a gives students an opportunity to find out which ions cause hardness.

• HSW The homework sheet (Worksheet C3.5b)

extends the idea of soaps further by discussing the difference between soaps and detergents.

C3.6

Additional homework/research ideas

• Find out what else is added to soap.

Practicals and demonstrations 1 Finding the ions that cause hardness This is a simple experiment in which students add solutions containing various ions to soap and find which ones form a lather easily (are soft) and which ones do not form a lather (are hard). This could be extended to other compounds should you wish. 30 minutes Eye protection should be worn. Most soap solutions are made up in ethanol and water and so are highly flammable. Apparatus (per group) 0.1 mol/dm3 sodium chloride; 0.1 mol/dm3 calcium chloride; 0.1 mol/dm3 magnesium chloride; 0.1 mol/ dm3 potassium chloride; soap solution; 1 cm3 syringe; 10 cm3 measuring cylinder; 4 test tubes; test tube rack; Worksheet C3.5a.

Types of hard water

Worksheets available No. C3.6a C3.6b

Title Comparing the hardness of water Hard water

Objectives

Foundation 4 4

Higher 4 4

Learning activities

Students should be able to:

• The Student’s Book explains the difference between

• explain how hard water is formed • explain the difference between permanently hard

• Practical 1 (Worksheet C3.6a) gives students an

Key words

• The differences between permanently hard water

water and temporarily hard water.

calcium hydrogencarbonate, calcium sulfate, permanently hard water, temporarily hard water

Lesson ideas Starter Write the words ‘Hard water’ on the board and ask students to note down words and phrases that they associate with this. Most students will not have had experience of both hard and soft water, as this will depend on where they have lived.

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Type Practical Homework

AQA GCSE Extension Units Teacher’s Guide

permanently hard water and temporarily hard water. opportunity to test different waters for hardness, both before and after boiling. This practical can be used to provide data for the ISA element of the coursework. and temporarily hard water are reinforced in the homework sheet (Worksheet C3.6b)

Plenary

• Revisit the starter activity, asking students to revise their definitions. If ideas are shared between the class and then written on the board, they can be used to provide revision notes.

© Pearson Education Limited 2007

Additional homework/research ideas

• ICT Research areas of the country where the water

Apparatus (per group)

is permanently hard and where it is temporarily hard.

Practicals and demonstrations 1 Comparing the hardness of water This experiment may be used to provide data for the ISA element of the coursework. 1 hour

Permanently hard water (or calcium sulfate solution); temporarily hard water (or calcium hydrogencarbonate solution); distilled water; a mix of permanently hard and temporarily hard water; 100 cm3 conical flask; 25 cm3 measuring cylinder; burette; soap solution; clamp stand; boss; clamp; Bunsen burner; tripod; gauze; eye protection; Worksheet C3.6b.

Students must take care when boiling the water to try to soften it. Eye protection should be worn. The soap solution is probably highly flammable.

C3.7

Should we remove hardness from water?

Worksheets available No. C3.7a C3.7b

Title Softening water Other ways of softening water

Objectives Students should be able to:

Type Practical Homework

Foundation 4 4

Higher 4 4

• AT The ActiveTeach has an animation showing how an ion-exchange column works.

• describe the advantages to health of drinking hard

• The homework sheet (Worksheet C3.7b) gives

• explain the disadvantages of using hard water • describe how to remove the hardness from water

Plenary

Key words

Additional homework/research ideas

water

students other methods of removing hardness.

• Make a summary of the advantages and

disadvantages of hard water on the board.

ion-exchange column, limescale, sodium carbonate, soften

• Look at packets of washing powder to find out if

Lesson ideas

Practicals and demonstrations

Starter Ask students if hard water is a good or a bad thing. Depending on their experiences of their local water supply, they may realise that hard water affects washing and if the water is temporarily hard, there is a problem with limescale. This is often apparent on beakers used to boil water.

Learning activities

• Practical 1 (Worksheet C3.7a) allows students to

show the effect of adding washing soda (sodium carbonate) to water.

• The class could be encouraged to debate the

advantages and disadvantages of hard and soft water.

© Pearson Education Limited 2007

they contain any softening ingredients.

1 Softening water This experiment could be combined with that from the previous topic. 1 hour Sodium carbonate can irritate the eyes. Eye protection should be worn. The soap solution is probably highly flammable. Apparatus (per group) 100 cm3 permanent and temporary hard water (calcium sulfate solution and calcium hydrogencarbonate solution); sodium carbonate crystals; 100 cm3 measuring cylinder; 22250 cm3 beakers; spatula; filter funnel; filter paper; burette; clamp stand; boss; clamp; soap solution; eye protection; Worksheet C3.7a.

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C3.8

Flame tests

Worksheets available No. C3.8a C3.8b

Title Carrying out flame tests The origin of flame colours

Objectives Students should be able to:

• describe how flame tests can be used to identify some metal ions

• know the flame colours for lithium, sodium,

potassium, calcium and barium compounds.

Key words flame tests Points to note Chlorides are used for flame tests as they are more volatile and therefore give more intense flame colours.

Lesson ideas Starter Ask students to list everything that could be in river water, and everything that could be in drinking water. From here you could go on to talk about how those things that can be seen could be tested for.

Learning activities

Foundation 4 4

Higher 4 4

• For homework Worksheet C3.8b explains in simple terms why flames’ colours are observed.

Plenary

• Write up some colours (red, lilac, orange, green,

brick-red) on the board and ask students to match the colour with the metal ion.

Additional homework/research ideas

• Find out if transition metals give characteristic flame colours.

Practicals and demonstrations 1 Carrying out flame tests This experiment should be set up as a ‘circus’, with students moving from one station to another. Not only is this quicker, it is also safer and removes the chances of nichrome wire becoming contaminated with more than one type of metal compound. The acid should be put out for students and removed either by the teacher or a lab technician to avoid spillages of concentrated acid. Magnesium chloride has been included to show that this method cannot be used for all metal ions. 30 minutes

• Demonstrate how to carry out a flame test.

Concentrated hydrochloric acid is corrosive, lithium chloride is harmful, calcium chloride is an irritant and barium chloride is toxic. Goggles should be worn at all times.

• Students have an opportunity to carry out flame

Apparatus per station

Emphasise the importance of having clean nichrome wire and also the dangers of concentrated hydrochloric acid. tests. You may wish to do the whole experiment as a demonstration with some classes. Details are given on Worksheet C3.8a.

• AT The ActiveTeach has a video showing how

fireworks depend on different elements giving different flame colours.

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Type Practical Homework

AQA GCSE Extension Units Teacher’s Guide

Sample of lithium chloride, sodium chloride, potassium chloride, magnesium chloride, calcium chloride, or barium chloride; small amount of concentrated hydrochloric acid in a small beaker; Bunsen burner; nichrome wire; heat-proof mat; eye protection; Worksheet C3.8a.

© Pearson Education Limited 2007

C3.9

Detecting ions using sodium hydroxide solution

Worksheets available No. C3.9a C3.9b

Title Using sodium hydroxide to identify metal ions Camelford HSW

Objectives Students should be able to:

• distinguish between some metal ions by their reaction with sodium hydroxide solution

• test for ammonium ions using sodium hydroxide solution.

Key words precipitate, sodium hydroxide solution

Lesson ideas Starter Ask students for any drawbacks of flame tests that they can think of. They should include the fact that not all metals give a coloured flame. Students should then be encouraged to think of other methods of distinguishing between different metal ions – by chemical means.

Learning activities

• The Student’s Book gives full details of how

to distinguish between calcium, magnesium, aluminium, copper, iron(II) and iron(III) ions. It also describes how to identify ammonium ions.

• The practical (Worksheet C3.9a) gives students an opportunity to distinguish between metal ions practically.

• You could demonstrate the reaction of sodium

hydroxide solution on ammonium chloride. See Practical 2.

• AT The ActiveTeach contains a PowerPoint

presentation summarising the reactions of calcium carbonate.

• HSW For homework Worksheet C3.9b gives

students details about the water pollution incident at Camelford in 1988. This can be tied in with the general water treatment and analysis context, and also as an example of ions that can be tested in aqueous solution.

Type Practical

Foundation 4

Higher 4

4

4

Homework

• Alternatively, write the colours of some precipitates

on the board and ask students to identify the metal ions that cause them.

Additional homework/research ideas

• Research the colour of precipitates formed by

other transition metal ions when they are reacted with sodium hydroxide solution. They may need to consult A-level texts for this.

Practicals and demonstrations 1 Using sodium hydroxide to identify metal ions This experiment shows students how to distinguish between different metal ions. They should follow the instructions carefully, or the aluminium hydroxide will not redissolve. 1 hour Sodium hydroxide is an irritant. Eye protection should be worn. Apparatus per group 0.1 mol/dm3 aluminium sulfate; 0.1 mol/dm3 calcium chloride; 0.1 mol/dm3 copper sulfate; 0.1 mol/dm3 iron(II) sulfate; 0.1 mol/dm3 iron(III) sulfate; 0.1 mol/ dm3 magnesium chloride; 0.1 mol/dm3 sodium hydroxide solution; 7 test tubes; test tube rack; teat pipette; eye protection; Worksheet C3.9a. 2 Testing for ammonium ions Place a 2 cm depth of ammonium chloride in a test tube and add a 2 cm depth of sodium hydroxide solution. Warm the tube gently and hold a piece of damp litmus paper in the mouth of the tube. It will go blue as ammonia is produced. 10 minutes Sodium hydroxide is an irritant. Eye protection should be worn. Apparatus 0.1 mol/dm3 ammonium chloride; 0.1 mol/dm3 sodium hydroxide; test tube; Bunsen burner; test tube holder; damp litmus paper; eye protection.

Plenary

• Draw a flow diagram on the board, showing how to differentiate between the metal ions studied, and ask students to complete it.

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C3.10

Looking at carbonates

Worksheets available No. C3.10a C3.10b

Title Comparing samples of copper carbonate Heating carbonates

Type Practical Homework

Objectives Students should be able to:

• describe how carbonates react with acids to form carbon dioxide

• describe how carbon dioxide turns limewater milky • describe how zinc carbonate and copper carbonate decompose when they are heated

• identify these carbonates by their distinctive colour changes.

Key words carbonates

Lesson ideas Starter Ask students what is in ionic compounds as well as positive metal ions. They should remember that nonmetal ions are negatively charged. Elicit the names of anions they have already met. They should remember carbonates, chlorides, sulfates, nitrates (and possibly hydrogencarbonates). They should then be encouraged to think about how these can be identified.

Learning activities

• The general chemistry of carbonates is covered in the Student’s Book.

• Practical 1 gives details of heating both copper carbonate and zinc carbonate.

• Practical 2 (Worksheet C3.10a) shows students

how the purity of samples of malachite (copper carbonate) can be compared by heating them and finding mass loss.

• The ideas given in this topic are reinforced on the

Foundation 4

Higher 4

4

4

Additional homework/research ideas

• Find out if acid can be used to compare the purity of carbonate rocks, e.g. limestone, chalk (both calcium carbonate) or malachite (copper carbonate).

Practicals and demonstrations 1 Heating carbonates This simple experiment illustrates the colour changes that occur when copper carbonate and zinc carbonate are heated. Place a 1 cm depth of copper carbonate in a test tube. Using a test tube holder, hold the tube over a blue Bunsen burner flame until there is no further change. Repeat this with zinc carbonate. 30 minutes Copper carbonate is harmful. Eye protection should be worn. Apparatus (per group) Copper carbonate; zinc carbonate; spatula; test tubes; test tube holder; test tube rack; Bunsen burner; heat-proof mat; eye protection. 2 Comparing samples of copper carbonate Students are given three samples of ‘malachite’. This can be copper carbonate with added sand. They can heat each sample and find out how much carbon dioxide is formed. The purer a sample is, the more gas is lost. Details of the experiment are on Worksheet C3.10a. 1 hour Copper carbonate is harmful. Eye protection should be worn at all times. Apparatus (per group) 1 g of each of three samples of powdered copper carbonate (pure, with 20% sand, with 40% sand); crucible; balance; Bunsen burner; tongs; tripod; gauze; heat-proof mat; eye protection; Worksheet C3.10a.

homework sheet (Worksheet C3.10b)

Plenary

• Draw a mind map of all of the reactions of

carbonates. This should include the action of heat and the action of hydrochloric acid; it could also include the relationship between calcium hydrogencarbonate and calcium carbonate.

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C3.11

Testing for other non-metal ions

Worksheets available No. C3.11a C3.11b

Title Testing inorganic compounds Identifying inorganic compounds

Type Practical Homework

Objectives Students should be able to:

•

describe how to test for halide ions using silver nitrate solution

• describe how to test for sulfate ions using barium chloride solution

• describe how to test for nitrate ions using

aluminium powder and sodium hydroxide solution.

Key words halide, nitrate, sulfate

Lesson ideas Starter Show students solutions of sodium chloride, sodium nitrate and sodium sulfate, and ask them if they could distinguish between them. They will probably say ‘No’. You could try adding dilute hydrochloric acid to show that they do not react like carbonates. Elicit the idea that chemical tests are needed to detect non-metal ions.

Learning activities

• The theory behind the tests for halides, nitrates and sulfates is covered in the Student’s Book.

• Worksheet C3.11a gives students an opportunity to try the tests for all three halides, nitrates and sulfates. Details are given as Practical 1.

• You could demonstrate the use of ammonia to

further distinguish between the halides. Silver chloride dissolves in dilute ammonia solution, silver bromide dissolves in concentrated ammonia solution and silver iodide does not dissolve in concentrated ammonia. See Practical 2.

Foundation 4 4

Higher 4 4

Additional homework/research ideas

• Ask students to find out how to distinguish between

carbonates and hydrogencarbonates (add sodium carbonate solution – carbonates give a precipitate of calcium carbonate, hydrogencarbonates do not give a precipitate); or sulfates and sulfites (sulfates do not react with dilute hydrochloric acid, sulfites do). They may need to consult A-level texts to do this.

Practicals and demonstrations 1 Testing inorganic compounds This gives students an opportunity to test for inorganic ions. You could start by giving them known compounds (for example, sodium chloride, sodium bromide, sodium iodide, sodium nitrate and sodium sulfate) before giving them compound X. X should be a soluble Group 1 or 2 or zinc halide, nitrate or sulfate. 1 hour Eye protection should be worn at all times. Ammonia is a very smelly and toxic gas. Make certain that the lab is well ventilated. Sodium hydroxide and nitric acid are irritants, and barium chloride is harmful. Wipe up any spills at once. Aluminium powder is highly flammable. Silver nitrate stains skin and clothing. Hands should be washed thoroughly after this experiment. Apparatus (per group) Solid X; 0.1 mol/dm3 barium chloride solution; 0.1 mol/dm3 sodium hydroxide solution; litmus paper; aluminium powder; 0.1 mol/dm3 nitric acid; 0.1 mol/dm3 silver nitrate solution; test tubes; test tube rack; teat pipettes; test tube holder; Bunsen burner; heat-proof mat; eye protection; Worksheet C3.11a. 2 Using ammonia to differentiate between halide ions

• The homework sheet (Worksheet C3.11b) is synoptic

Once a silver halide has been made, add dilute ammonia solution. If the solid does not dissolve, add concentrated ammonia. 10 minutes

Plenary

8 mol/dm3 ammonia is corrosive. This experiment should be done in a fume cupboard. Goggles should be worn.

in nature and encourages students to use flametest results as well as chemical-test results to help identify unknown compounds.

• Write up some results on the board and ask students to identify the ions present.

• Alternatively, draw an incomplete flow diagram

showing how to identify an unknown compound, and ask students to pool ideas to complete it. Students could work as a class or in small groups.

© Pearson Education Limited 2007

Apparatus Samples of silver chloride, silver bromide, silver iodide; test tubes; dilute ammonia solution; 8 mol/ dm3 ammonia. AQA GCSE Extension Units Teacher’s Guide

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C3.12

Testing for acidity

Worksheets available No. C3.12a C3.12b

Title Comparing strong and weak acids Naturally occurring acids

Type Practical Homework

Objectives Students should be able to:

• explain that water must be present for a substance to act as an acid or an alkali

• explain that acids produce hydrated ions in aqueous solution, and alkalis produce hydroxide ions in solution

• explain the difference between strong and weak acids and alkalis, giving examples of each

• H evaluate the contributions of Arrhenius, Brønsted and Lowry to our understanding of acid–base behaviour

• H define an acid as a proton donor and a base as a proton acceptor.

Key words hydrated, ionise, proton donor, proton acceptor Points to note The difference between a strong acid or alkali and a concentrated acid or alkali should be emphasised. Similarly, the difference between a weak acid or alkali and a dilute acid or alkali should also be emphasised.

Lesson ideas Starter Ask students how acids and alkalis could be detected in water. They should be familiar with the pH scale.

Learning activities

• The difference between strong and weak acids and alkalis is explained in the Student’s Book.

• Demonstrate that water is necessary for acids to

work by dissolving some dry citric acid in some water and also in some dry propanone. Then test each for acidic properties. Details are given as Practical 1.

• Practical 2 (Worksheet C3.12a) emphasises the

difference in hydrogen ion concentration between strong and weak acids. Many students are surprised that vinegar is more concentrated (approx. 1 mol/ dm3) than bench hydrochloric acid. You may need to remind students about the effect of concentration on rates of reaction before doing this practical.

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Foundation 4 4

Higher 4 4

• AT The ActiveTeach has a video showing pH analysis in a water-company’s labs.

• H The ideas of Arrhenius, Brønsted and Lowry are

also explained in the Student’s Book. This could be used as an opportunity to discuss how scientific ideas have changed over the years.

Plenary

• Repeat the starter activity from this topic asking

students how to detect acids and alkalis in water. This will enable you to see how much they have learnt.

Additional homework/research ideas

• Find the names of three strong acids and three weak acids.

Practicals and demonstrations 1 Water and acids Dissolve a spatula of citric acid powder in 50 cm3 of water in one beaker and in 50 cm3 of dry propanone in a second beaker. Then test for acidic properties by adding universal indicator solution to a sample of each. Repeat with magnesium ribbon and marble chips. The solution in propanone shows no acidic properties, demonstrating that water is needed for an acid to work. 40 minutes Apparatus (per group) Citric acid powder; dried propanone; distilled water; 50 cm3 measuring cylinder; 22100 cm3 beakers, 2 glass stirring rods, 6 test tubes, universal indicator solution, 2 pieces of magnesium ribbon, 4 marble chips. Citric acid powder is an irritant. Dried propanone is an irritant and is also highly flammable. Magnesium ribbon is highly flammable. 2 Comparing strong and weak acids Hydrochloric acid is used as an example of a fully ionised strong acid, and ethanoic acid as a partially ionised weak acid. Details are given on Worksheet C3.12a. 1 hour Magnesium ribbon is highly flammable. Eye protection should be worn. Apparatus (per group) 0.5 mol/dm3 hydrochloric acid; 0.5 mol/dm3 ethanoic acid; magnesium ribbon; marble chips; universal indicator solution; test tubes; test tube rack; eye protection; Worksheet C3.12a. © Pearson Education Limited 2007

C3.13

Detecting organic chemicals

Worksheets available No. C3.13a C3.13b

Title Identifying alkenes Alkanes and alkenes

Type Practical Homework

Objectives Students should be able to:

• describe how organic compounds burn or char • explain that unsaturated organic compounds

containing a double bond decolourise bromine water

• H find the empirical formula of an organic

compound from the masses of the products formed when a known mass of the compound is burned.

Key words H empirical formula, organic compounds, unsaturated Points to note While organic chemistry is considered to be the chemistry of carbon and its compounds, it does not include the chemistry of inorganic salts containing carbon (carbonates and hydrogencarbonates) or carbon dioxide, carbon monoxide or carbon disulfide.

Lesson ideas Starter Burn a candle and ask why the flame is smoky. You should elicit from students the idea that wax contains carbon, and is a hydrocarbon.

Learning activities

• The Student’s Book gives a simple introduction to organic chemistry.

© Pearson Education Limited 2007

Foundation 4 4

Higher 4 4

• The practical (Worksheet C3.13a) is revision of work carried out on alkenes in Year 10. It involves the reaction of alkenes with bromine water.

• For homework Worksheet C3.13b reinforces ideas about alkanes and alkenes.

• H Combustion analysis is covered in some detail.

Its importance in establishing empirical formulae is stressed.

Plenary

• Ask students to write down three differences between organic compounds and inorganic compounds. Produce a class list agreed by all students.

Additional homework/research ideas

• ICT Find out about alcohols or another functional group, e.g. aldehydes or carboxylic acids.

Practicals and demonstrations 1 Identifying alkenes As this is revision of work carried out in Year 10, it could be omitted if time is short. Other alkanes and alkenes could be used if they are available. 30 minutes Bromine water is very toxic (0.06 mol/dm3) or irritant (0.06 mol/dm3). Cyclohexane is highly flammable. Cyclohexene is highly flammable and harmful. Eye protection should be worn. Apparatus (per group) Cyclohexane; cyclohexene; bromine water; teat pipette; test tubes; test tube rack; eye protection; Worksheet C3.13a.

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C3.14

Detecting tiny amounts of chemicals

Worksheets available No. C3.14a C3.14b

Title Analysis – old and new Testing for illegal drugs

Type Classwork Homework

Objectives Students should be able to:

• describe how the development of modern

instrumental methods has been aided by the rapid progress in technology

Foundation 4 4

Higher 4 4

Learning activities

• The Student’s Book gives students an idea of the tiny amounts of metal ions found in water samples.

• The calculation of parts per million (ppm) may need some time.

• explain that instrumental methods are accurate,

• The material covered in this topic is extended at

• explain that instrumental methods are particularly

• The Worksheet C3.14a compares modern methods

Key words

• AT

sensitive and rapid

useful when the amount of sample is very small.

no new words Points to note Water companies provide very accurate data giving average amounts of a number of substances in their tap water. These include about 15 metals, a number of non-metal ions, at least 20 different pesticides, organic residues and bacterial counts.

Lesson ideas Starter Remind students that they have been analysing solutions where the concentration is about 0.1 mol/ dm3. What would they do if the solution was 1/1000 of that concentration? Elicit the idea that analysis must be much more accurate.

Higher level in the next topic

of analysis with those used in earlier topics. Students are asked to select the most appropriate method for a number of different examples. ICT The ActiveTeach contains a video of an analytical chemist using modern chemical analysis techniques, including the use of ICT, in their work.

• The homework sheet (Worksheet C3.14b) uses drug testing as an example of where tiny amounts of substances must be very accurately analysed.

Plenary

• Give students the sentence ‘We need to know about

the presence of tiny amounts of substances because …’, and ask them to complete it in as many ways as possible.

Additional homework/research ideas

• ICT Search the website of the student’s local water

supplier to find out what they can about the content of their water.

Practicals and demonstrations None suggested.

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C3.15

Instrumental analysis

Worksheets available No. C3.15a C3.15b

Title Using infrared spectroscopy H Using mass spectra H

Type Classwork Homework

Objectives Students should be able to:

• describe how some instrumental methods are suited to identifying elements

• describe how some instrumental methods are suited to identifying compounds

• describe how some methods can be adapted for elements or compounds.

Key words Atomic spectrometer, gas–liquid chromatography, infrared spectroscopy, line emission spectrum, mass spectrometer, nuclear magnetic spectroscopy, ultraviolet spectroscopy

Lesson ideas Starter Building on the plenary session from the last topic, ask students how they think that rapid analysis is carried out. Brainstorm their ideas on the board. This leads into the main part of the lesson.

Learning activities

• AT The ActiveTeach has a video of instrumental

methods being used in a water analysis laboratory. Ask students for their impressions – for example, the amount of instrumentation, the speed of obtaining the results …

© Pearson Education Limited 2007

Foundation

Higher 4 4

• Worksheet C3.15a outlines how infrared

spectroscopy works. It gives students infrared spectra for ethanol and ethanoic acid, two compounds that they should be familiar with, and asks them to identify the infrared absorption due to the functional groups.

• If you can access any infrared or mass spectra, they should be of interest to students. Some may be obtained from A-level texts.

• For homework Worksheet C3.15b gives further details of mass spectrometry and fragmentation patterns. It then asks students to predict the fragments produced from ethanol.

Plenary

• Write the six main methods of instrumental analysis

on the board and ask students what each one is used for. Alternatively, you could write up the names of a number of elements and compounds (both organic and inorganic), and ask students which method they would use to analyse each.

Additional homework/research ideas

• ICT Research one of the methods not covered

by Copymaster sheets. For example, NMR or UV spectroscopy.

Practicals and demonstrations None suggested.

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Answers

C3.1 The water cycle

C3.2 Purifying water

Student’s Book

Student’s Book

1 a Sodium and chloride.

1 It has filtered through rocks.

b Calcium and hydrogencarbonate.

2 From farming and industry.

2 a Sea water=1.124.

3 There is more contact between the surface and the water being filtered.

Fresh water=0.002 12. b Sea water contains ions that have dissolved in water in rivers and streams and has passed through rocks. Also salts from the sea bed.

4 Advantages: taste and water quality improve.

3 Distillation.

5 Substances dissolved in the water as it flows over rocks.

4 More showers and baths, swimming pools, etc. 5 Demand for water would increase even more. 6 Turn taps off, have showers rather than baths, recycle water by using bath/washing-up water on gardens. Credit any sensible suggestions.

6 Water filter is probably cheaper to run – though adverts quote 4p per litre of water. Distillation apparatus needs electricity. 7 Summary.

Worksheet C3.1a

Worksheet C3.2a

1 Extra 1.0 billion people. Therefore % increase=1.0/6. 22100=16%.

1 Cloudy or brown. 2 Clear.

2 60270/100=42%.

3 Filter through activated carbon.

3 Overuse of baths, showers, in gardens, general waste.

4 Check its boiling point (should be 100 °C).

4 Water for drinking, washing and sanitation. 5 Industrialisation and increased population.

5 No – the dissolved salts will remain dissolved in the water.

6 Decrease in fatalities if better water supplies.

Worksheet C3.2b

7 If more people ate vegetarian food, less water would be wasted in converting vegetable matter into meat.

1 It has not been chemically treated.

8 Personal responses, with examples.

Worksheet C3.1b 1 Bar charts. 2 Temperature – rise in summer, peaking in July and August. Sunshine – rise in summer – peaking in May. Rainfall – decrease in summer – lowest in May. Days of rainfall – decrease in summer – lowest in July. 3 a 1125.2 mm. b 112.5 cm. 4 Higher than hotter countries. 5 More hours of sunshine in May than in June or July. More mm of rainfall in June than in May or July. More days of rainfall in June than in May or July. 6 Would expect maximum temperature and hours of sunshine to increase. Probably cannot predict effect on rainfall.

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Disadvantages: expensive to replace cartridges and may have adverse effect on health.

AQA GCSE Extension Units Teacher’s Guide

2 Limestone. 3 It has been filtered through the rocks. 4 Calcium and hydrogencarbonate. 5 The total mass of ions is greater than dry mass as the calcium hydrogencarbonate decomposed when heated and lost carbon dioxide – and hence mass. 6 Table water – it may be tap water. 7 Matter of opinion (the author thinks yes).

C3.3 Solubility Student’s Book 1 Calcium carbonate and sugar. 2 158/5=31.6 g/100 g water.

3 a i 0.0036 g/100 g water ii 0.0030 g/100 g water (Each +/– 0.0002). b Values would be lower. 4 There is insufficient oxygen. 5 It will increase.

© Pearson Education Limited 2007

C3.0

Answers

6 More gas will dissolve at the lower temperature of the fridge. Therefore more bubbles will be produced than from a can kept at room temperature. 7 All oxygen has been boiled out of the water.

Worksheet C3.3a 1 As temperature increases, solubility of gases decreases. 2 a Copper+oxygen b 2Cu+O2 3

copper oxide.

2CuO.

33 cm3.

Worksheet C3.4b 1 A solution that cannot contain any more dissolved solute at a given temperature. 2 To prevent spitting – and loss of mass. 3 Find the mass of solid and then reheat for 5 minutes more. Continue until the mass stays the same. 4 Mass of evaporating basin. Mass of basin+saturated solution. Mass of basin+solid. 5 Graph of results – correctly plotted.

4 33%.

6 48.5 g/100 g water.

5 Oxygen – there is more in the gas boiled out of water than in air.

7 36.5 g/100 g water.

6 Increase the amount of gases dissolved in the blood. 7 It is less soluble in water. 8 Helium must be less soluble in water.

Worksheet C3.3b

8 48.5−36.5=12.0 g crystals.

C3.5 Hard water Student’s Book

1 More sewage in 1900 than 2000.

1 They dissolve in rain water as it seeps through rocks in the ground.

2 a 12–13 km after London Bridge.

2 Add soap and see if there is a scum.

b A lot of sewage and other waste entering the Thames from London.

3 Calcium and magnesium.

3 Less pollution.

4 Calcium stearate or magnesium stearate.

4 There is now a lot more oxygen for fish to use.

5 Probably – elements in the same group tend to have similar properties.

5 Decrease fish populations.

6 A measure of the hardness of water.

6 a Could lead to illness from contaminated sewage.

7 Summary – hard water.

b Rowing, swimming, fishing.

Worksheet C3.5a

7 Prevent sewage release, or divert it to an area where it has fewer harmful effects.

1 Table of results.

C3.4 Saturated solutions

2 Calcium and magnesium. They did not form a lather with soap solution.

Student’s Book

3 Volume of soap solution, concentration of soap solution, volume of test solution.

1 Potassium bromide.

4 Metal ion in compound.

2 Potassium nitrate. 3 33 °C (+/–2).

5 Use chloride of other metals and repeat experiment – keeping above variables constant.

4 85.522=171 g.

6 Use sodium salts with other negative ions.

5 400 g water.

Worksheet C3.5b

6 75 °C (+/–2 °C).

1 Similarities: remove grease and dirt.

7 40.0−17.4=22.6 g solid.

Differences:

8 Summary.

Worksheet C3.4a

soaps made from animal fats or vegetable oils+sodium hydroxide; can be alkaline; soapless detergents made from oil

1 Results table.

soaps form scum, soapless detergents do not

2 Graph of results.

soaps are not biodegradable, detergents are.

3 Solubility increases as temperature increases. 4 Read off graph. 5 Read off graph. © Pearson Education Limited 2007

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Answers 2 B. Little soap needed to form a lather.

2 Charged end of detergent attracted to water, while other end attracted to grease. Hence molecules penetrate grease and surround it.

3 A. Same amount of soap needed after boiling – therefore not softened by boiling.

3 Oil not a raw material in Middle Ages, while sodium hydroxide (Lye) and animal fats were available.

4 C. The amount of soap needed after boiling was considerably reduced.

4 Saponification.

5 a D.

5 List of household items with detergents – washingup liquid, shampoo, etc.

b After boiling it had lost some hardness, but still needed much more soap than softened water.

6 Soapless detergents do not form scum in hard water, while soaps do. But too many soapless detergents cause foaming and may poison aquatic life.

6 Calcium sulfate.

C3.6 Types of hard water

7 a Calcium hydrogencarbonate. b Ca(HCO3)2(aq)

CaCO3(s)+CO2(g)+H2O(l).

Student’s Book

C3.7 Should we remove hardness from water?

1 a Magnesium carbonate+carbon dioxide+water magnesium hydrogencarbonate.

Student’s Book

b MgCO3(s)+CO2(g)+H2O(l)

1 Calcium hydrogencarbonate calcium carbonate+carbon dioxide+water.

Mg(HCO3)2(aq).

2 The calcium ions are no longer in solution – and therefore cannot react with soap. 3 The electricity would have to heat the limescale as well as the water. 4 Boiling temporarily hard water removes hardness. 5 As a control. 6 The constituents in the water. 7 a Similar to distilled water. b Similar to unboiled temporarily hard water. 8 Temporarily hard water Permanently hard water Similarities Contains calcium ions Contains calcium ions Makes a scum with soap Makes a scum with soap Differences Contains hydrogenContains sulfate ions carbonate ions Not softened by boiling Softened by boiling

2 More soap is needed for it to act as a cleaning agent and extra expense occurs because it reduces the efficiency of the heating system. 3 a Build strong bones and teeth, prevent heart disease. b Scum formed during washing, limescale in kettles, hot water pipes and boilers. 4 a Magnesium sulfate+sodium carbonate magnesium carbonate+sodium sulfate. b MgSO4(aq)+Na2CO3(aq) MgCO3(s)+Na2SO4(aq). 5 No scum would form and it would form a lather quickly. 6 So that hard water is available for drinking – and to prevent harmful sodium ions being drunk. 7 Appropriate letter of explanation.

Worksheet C3.7a 1 Results obtained. 2 The water that had had sodium carbonate added to it. The calcium ions had been removed.

Worksheet C3.6a

3 To remove solid calcium carbonate.

1 Results table.

4 To make it a fair test.

2 Depends on samples.

5 a Calcium sulfate+sodium carbonate calcium carbonate+sodium sulfate.

3 Depends on samples. 4 Depends on samples. 5 Depends on samples.

Worksheet C3.6b

b CaSO4(aq)+Na2CO3(aq) Na2SO4(aq).

CaCO3(s)+

6 The calcium carbonate formed might damage the clothes.

1 a D, C, A, B. b The hardest water will need most soap to form a lather.

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Answers

Worksheet C3.7b 1 Calcium phosphate. 2 a calcium sulfate+sodium phosphate phosphate+sodium sulfate. b 3CaSO4(aq)+2Na3PO4(aq) 3Na2SO4(aq).

calcium

Ca3(PO4)2(s)+

C3.9 Using sodium hydroxide solution to detect positively charged ions Student’s Book

3 Eutrophication.

1 Aluminium nitrate+sodium hydroxide aluminium hydroxide+sodium nitrate.

4 So no other ions are present in experiments.

2 No. No insoluble hydroxide formed.

5 Cost of electricity.

3 Magnesium – none; calcium – brick-red. H2O(l).

4 a FeCl2(aq)+2NaOH(aq)

Fe(OH)2(s)+2NaCl(aq).

7 This ion-exchange column replaces calcium and magnesium ions with hydrogen ions. A home ionexchange column replaces calcium and magnesium ions with sodium ions. This column also exchanges negative ions – which home ones do not.

b FeCl3(aq)+3NaOH(aq) 3NaCl(aq).

Fe(OH)3(s)+

6 H+(aq)+OH–(aq)

8 Good for bones, teeth and the heart.

C3.8 Flame tests Student’s Book 1 To identify toxic metals. 2 Water evaporated off. 3 It is cheaper. 4 To remove any impurities. 5 It would get covered in soot. 6 Lithium – red; sodium – orange; potassium – lilac; calcium – brick-red; barium – green. 7 Appropriate diagrams.

Worksheet C3.8a 1 Results table. Colours – red, orange, lilac, none, brick-red, green. 2 Magnesium. 3 Many flame colours are red – therefore we cannot distinguish between these metals. 4 To make it a fair test.

Worksheet C3.8b 1 Electrons gain energy and jump from lower energy levels to higher ones. 2 Electricity. 3 They give out light energy. 4 a 12. b Not in visible part of spectrum. 5 a 2.

5 Ammonium nitrate+sodium hydroxide ammonia+sodium nitrate+water. 6 Ion present Aluminium Ammonium Calcium Copper Iron(II) Iron(III) Magnesium

Observation White precipitate that dissolves in excess Ammonia produced – litmus goes blue White precipitate, insoluble in excess Blue precipitate Green precipitate Brown precipitate White precipitate, insoluble in excess

Worksheet C3.9a 1 Compound being tested Aluminium sulfate

Metal ion Observations present Al3+ White precipitate, soluble in excess Calcium chloride Ca2+ White precipitate, insoluble in excess 2+ Copper sulfate Cu Blue precipitate 2+ Iron(II) sulfate Fe Green precipitate Iron(III) sulfate Fe3+ Brown precipitate 2+ Magnesium chloride Mg White precipitate, insoluble in excess 2 Calcium chloride would give a brick-red flame colour; magnesium chloride would not give a flame colour. 3 If too much solid is used, it may not dissolve in excess. 4 It has been oxidised to form an iron(III) compound.

b 1. c Must be other unfilled electron energy levels.

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Answers

Worksheet C3.9b

2 Diagram showing delivery tube going into limewater.

1 Neutralisation. 2 a Calcium hydroxide+hydrochloric acid chloride+water. b Ca(OH)2(aq)+2HCl(aq)

calcium

CaCl2(aq)+2H2O(l).

3 Through filter beds. 4 The aluminium is included in the clumps. 5 Copper compounds were present. 6 Less of the toxic chemical is needed to kill fish because fish are smaller. 7 At first a white precipitate forms. This dissolves in excess sodium hydroxide solution. 8 a Aluminium sulfate+sodium hydroxide aluminium hydroxide+sodium sulfate. b Al2(SO4)3(aq)+6NaOH(aq) 2Al(OH)3(s)+3Na2SO4(aq).

C3.10 Looking at carbonates

5 A=sodium carbonate; B=sodium chloride; C=calcium carbonate; D=zinc carbonate; E=zinc oxide; F=copper carbonate; G=copper sulfate.

C3.11 Testing for other non-metal ions Student’s Book 1 Yellow precipitate. 2 The blue colour would obscure the colour of the precipitate. 3 White precipitate (of barium sulfate). BaSO4(s)+2KCl(aq).

5 They both produce solid precipitates.

1 a Calcium carbonate+hydrochloric acid calcium chloride+carbon dioxide+water. CaCl2(aq)+CO2(g)+

2 Limescale contains calcium carbonate – therefore reacts with acids. 3 In (temporarily) hard water. 4 FeCO3(s)

4 Although it is a carbonate, it did not decompose when heated.

4 BaCl2(aq)+K2SO4(aq)

Student’s Book b CaCO3(s)+2HCl(aq) H2O(l).

3 Limewater contains calcium hydroxide, which reacts with carbon dioxide to form insoluble calcium carbonate.

FeO(s)+CO2(g).

6 Ammonium ions. 7 No. 8 Outline summary of tests for halides, nitrates and sulfates.

Worksheet C3.11b A=lithium sulfate; B=calcium nitrate; C=sodium carbonate; D=barium chloride; E=potassium sulfate.

5 Zinc carbonate goes yellow when heated, calcium carbonate does not.

C3.12 Testing for acidity

6 Physical – no chemical change occurs.

Student’s Book

7 Reactions of calcium carbonate. To include formation of calcium hydrogencarbonate (and reverse reaction), reaction with acids and thermal decomposition.

Worksheet C3.10a 1 Table of results. 2 Green to black. 3 Green copper carbonate has turned into black copper oxide. 4 Mass loss calculated. 5 a The more copper carbonate present, the more carbon dioxide is produced. b Purest sample should lose most carbon dioxide. 6 Only if they decompose when heated.

Worksheet C3.10b

1 pH<7, litmus or indicator goes red, reactive metals hydrogen, bases salt+water, carbonates salt+carbon dioxide+water. 2 H+ ions: formed in all acidic solutions; strong acid: fully ionised in water; weak acid: partially ionised in water; strong alkali: fully ionised in water; weak alkali: partially ionised in water. 3 People did not believe that molecules could be ionised. 4 More knowledge available. 5 a No water present. b The HCl acts as an acid and donates the proton to the ammonia, which acts as a base and accepts it. 6 Summary. At Higher level this should include Arrhenius and Brønsted–Lowry definitions.

1 a A, C, D, F. b They fizzed when acid was added.

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C3.0

Answers

Worksheet C3.12a

Worksheet C3.13a

1

1 No reaction.

Test pH Action of magnesium Action of marble chips

With hydrochloric acid 1 Rapid bubbling

With ethanoic acid 4 Slow bubbling

2 Bromine water decolourised / went from brown to colourless. 3 Carbon–carbon double bonds must lead to reactivity. 4 C6H10+Br2

Rapid bubbling

Slow bubbling

C6H10Br2.

Worksheet C3.13b 1 Ethene. It reacts with bromine water and acidified potassium permanganate.

2 Experiment should have worked well. The strong acid reacts faster than the weak acid as there are more hydrogen ions in solution.

2 The presence of a carbon–carbon double bond gives reactivity.

3 Volume and concentrations of acids.

3 a Ethane+oxygen

Worksheet C3.12b

b 2C2H6+7O2

carbon dioxide+water.

4CO2+6H2O.

1 White wine has more ethanol than cider or malt.

4 Add bromine water. Butene will decolourise it, butane will not.

2 a Something else that is formed in a chemical process other than the main product.

5 Alkanes end in –ane; alkenes end in –ene.

b Save money / make money / avoid waste. 3 More – they taste sourer. 4 Bee stings and nettle stings are acidic – therefore they are neutralised by alkalis.

6 5.6 g P

17.6 g carbon dioxide+7.2 g water.

Mass carbon=12/44217.6=4.8 g. Mass hydrogen=2/1827.2=0.8 g. Moles carbon=4.8/12=0.4.

5 The acid reacts with the calcium carbonate and removes it.

Moles hydrogen=0.8.

6 Ethanoic acid+magnesium carbonate magnesium ethanoate+carbon dioxide+water.

7 Moles carbon=3.6/12=0.3. Moles hydrogen=0.8.

7 From the Latin formica (ants).

Moles oxygen=1.6/16=0.1.

C3.13 Detecting organic chemicals

Empirical formula=C3H8O.

Empirical formula=CH2.

8 0.46 g R

0.88 g carbon dioxide+0.54 g water.

Mass carbon=12/4420.88=0.24 g.

Student’s Book

Mass hydrogen=2/1820.54=0.06 g.

1 Any carbonate.

Mass oxygen=0.46−(0.24+0.06)=0.16 g.

2 Not totally – there are exceptions.

Moles carbon=0.24/12=0.02.

3 Add bromine water. Hexane has no effect; hexene will decolourise it.

Moles hydrogen=0.06.

4 a C3H7.

Empirical formula=C2H6O.

b CH. 5 0.112 g hydrocarbon

0.352 g CO2+0.144 g H2O.

Mass carbon=12/4420.352=0.096 g. Mass hydrogen=2/1820.144=0.016 g. Moles carbon=0.096/12=0.008. Moles hydrogen=0.016/1=0.016. Empirical formula=CH2. 6 Detection of toxic organics in water.

© Pearson Education Limited 2007

Moles oxygen=0.16/16=0.01.

C3.14 Detecting tiny amounts of chemicals Student’s Book 1 0.005 ppm. 2 Fertilisers. 3 Accurate, sensitive, rapid, use tiny amounts of sample.

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4 Expensive and high level of training required.

Worksheet C3.15a

5 Nuclear power stations, hospitals. 6 Public health.

1 Carbon–carbon; carbon–hydrogen; carbon–oxygen; oxygen–hydrogen.

7 Appropriate leaflet.

2 Broad trough above 3000 cm–1.

Worksheet C3.14a

3 Carbon–oxygen double bond.

1 It can only be used to detect metal ions. 2 If the flame is red, you cannot determine which metal is present.

5 Same as ethanoic acid.

3 They are more specific.

1 a C4H8O.

Worksheet C3.15b

4 Anything that does not contain ions.

b 48+8+16=72.

5 The cost of computers and all of the electronic software.

2 Ion on right-hand side.

6 a Any of these. b Testing for ions in solution or modern methods. c Modern methods. d Modern methods.

Worksheet C3.14b 1 It is cheating. Also harmful to the body. 2 Increases body mass and muscle strength. 3 For reliable results. 4 Otherwise people may be wrongly accused. 5 To prevent people performing again with drugs in their bodies. 6 Probably not as sophisticated drugs had not been invented.

C3.15 Instrumental analysis Student’s Book 1 a Flame tests. b Finding the presence of certain metal ions. 2 Detection of tiny amounts of lead in water; analysis of amounts of trace elements in steel. 3 a Infrared spectroscopy, nuclear magnetic spectroscopy and gas–liquid chromatography. b Probably all. Water contains both inorganic and organic impurities. 4 They will show each isotope as a line, so count the lines. 5 Can detect elements and compounds; and measures relative formula mass. 6 Appropriate article.

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4 a+b Sharp one at 1700 cm–1.

AQA GCSE Extension Units Teacher’s Guide

3 15. 4 57. 5 The ion at 15 and the ion at 57. 6 C2H6O+−46. CH3+−15. CH3O+−31. OH+−17. C2H5+−29.

C3.0 Investigative Skills Assessment (Student’s Book) 1 D, A, C, B. (1 mark) 2 A=23.8 and 24.0 B=1.3 and 1.3 C=22.25 and 1.45 D=26.9 and 13.75 (all cm3). (2 marks) 3 a=A, b=C, c=B, d=D. (4 marks) 4 Distilled water. (1 mark) 5 Do more repeats. (1 mark) 6 Difficult to say when there is a permanent lather. (1 mark) 7 Ask another group to repeat them. (1 mark) 8 Make certain that the temperature was constant, and check that the same concentration of soap solution was used for each experiment. (2 marks) 9 Probably – there is a wider range of results and any anomalies could be discounted. (2 marks) 10 No continuous variable. (1 mark) 11 Bar chart. (1 mark) 12 Measure the turbidity of the water. Or similar to rates disappearing-cross experiment, where a cross could be drawn and the volume of soap needed to form enough scum to obscure it could be measured. (2 marks)

© Pearson Education Limited 2007

C3.0

Answers

C3.0 Investigative Skills Assessment (Copymaster File) Section 1 1 To compare the hardness of a number of samples of water. (2 marks) 2 a Volume of water, concentration of soap solution. b Either have same volume of water by using a measuring cylinder or have same concentration of soap solution throughout. c If more water used, more soap would be needed. If soap was more concentrated, less would be needed. (4 marks) 3 Type of water. (1 mark) 4 Do more repeats. (1 mark) 5 Difficult to state when a lather had been formed. (2 marks) 6 Table of results. (2 marks) 7 Bar chart showing results. (3 marks) 8 Conclusion. (2 marks) Section 2 9 D, A, C, B. (1 mark) 10 A=23.8 and 24.0 B=1.3 and 1.3 C=22.25 and 1.45 D=26.9 and 13.75 (all cm3). (2 marks) 11 a=A, b=C, c=B, d=D. (4 marks) 12 Distilled water. (1 mark) 13 Do more repeats. (1 mark) 14 Difficult to say when there is a permanent lather. (1 mark) 15 Ask another group to repeat them. (1 mark) 16 Make certain that the temperature was constant, and check that the same concentration of soap solution was used for each experiment. (2 marks) 17 Probably – there is a wider range of results and any anomalies could be discounted. (2 marks) 18 No continuous variable. (1 mark) 19 Bar chart. (1 mark) 20 Measure the turbidity of the water. Or similar to rates disappearing-cross experiment, where a cross could be drawn and the volume of soap needed to form enough scum to obscure it could be measured. (2 marks)

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C3.00

Driving chemistry further Overview This unit develops ideas from Units C1 and C2 about the Periodic Table, acids and energy changes in reactions. Students will learn more about the structure and development of the Periodic Table as well as Group 1, Group 7 and the transition metals in detail. They will learn how to perform mole calculations in solution and how to carry out an acid–alkali titration. Finally, students will learn how to calculate energy changes in reactions using bond energies and how to do simple calorimetry to calculate energy changes when burning fuels and foods, and for reactions in solution.

Investigative Skills Assessment The ISA for Unit C3.00 is based around energy changes in reactions. In the Student’s Book, data is presented to the students and then they are asked a number of questions about the investigation. The Copymaster File provides questions for students to answer based on their own investigation in which they carry out an experiment to measure the temperature change when copper sulfate solution reacts with zinc metal to see how it is affected by changing the mass of zinc. The ISA worksheets give instructions for this investigation.

Points to note

• This unit involves a number of calculations, many involving moles from Unit C2. • The work on acids is linked on the specification to some of the material in Unit C3.0. C3.00

Context page

Objectives for the unit

Notes on context

Students should know and understand:

The context for this unit is cars and the context video looks at various aspects of cars. The Periodic Table is considered by examining the use of some transition metals in cars, including iron in the body, platinum and palladium in the catalytic converter, chromium and nickel in many alloys for engine parts. Acids are dealt with by looking at the use of sulfuric acid in car batteries. Energy changes are considered in relation to the use of petrol and diesel as fuels.

• how elements are arranged in the Periodic Table

and be able to link the position of an element in the Periodic Table to its properties

• the chemical and physical properties of the

elements in Group 1 and Group 7, and the transition metals

• how the Periodic Table developed from early ideas about the elements

• how to perform mole calculations for reactions in solution

• how to perform an acid–alkali titration, choosing a suitable indicator

• how to calculate the energy change in a reaction

Learning activities

• AT The context for this unit is introduced via a video on the ActiveTeach.

• Students could be asked to brainstorm as many

ways as possible that chemistry is involved in cars.

using bond energies

• how to perform experiments to calculate the energy

change for a chemical reaction in solution or when a fuel or food is burned

• how to evaluate issues surrounding the use of fuels • which foods contain most energy and how this is linked to obesity.

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© Pearson Education Limited 2007

C3.16

The Periodic Table

Worksheets available No. C3.16a C3.16b

Title The Periodic Table 1 The Periodic Table 2

Type Classwork (write-on) Homework (write-on)

Objectives

Groups 0, 1 and 7 of the Periodic Table. For each group they are asked to find out five things that the elements have in common. Students could report their findings to another student in pairs, and then their combined findings to the class

• describe how elements are arranged in the Periodic Table

to its electronic structure.

Higher 4 4

• ICT Worksheet C3.16a asks students to research

Students should be able to:

• link the position of an element in the Periodic Table

Foundation 4 4

• For homework, Worksheet C3.16b reinforces the work from the lesson.

Key words atomic number, element, group, period, Periodic Table, transition metals

Points to note

• Different Periodic Tables show hydrogen in different places. Some have it at the top of Group 1, but the AQA data sheet has it in the more common position on its own apart from any other group.

• New elements are being created and detected in nuclear reactions. Elements 112–116 have been detected but not fully authenticated, with some argument about element 118.

Plenary

•

AT Students decide whether a series of statements are true or false. Suggested statements are given below and on the ActiveTeach:

a Elements are listed in mass number order. (false – atomic number order) b Elements in Group 6 have 6 electrons in their outer shell. (true) c The transition metals are between Groups 1 and 2. (false – between Groups 2 and 3) d Just over three-quarters of elements are nonmetals. (false – just over three-quarters of elements are metals)

Lesson ideas

e The element with the electron structure 2,8,5 is in Group 5. (true)

Starter

f The element with the electron structure 2,8,5 is in Period 3. (true)

•

Ask students to list 10 things they know about the Periodic Table. Ask them to compare their list with someone else’s from the class.

Learning activities

• Students could be presented with samples of

various substances around the room, which should be labelled with names and formulas (Experiment 1). They should decide whether each one is an element or a compound. This could be followed up by asking whether the elements are metals or non-metals. Students should be allowed access to a Periodic Table. You may wish to extend this activity further by asking students to explain how they arrived at their answers.

• Use the Student’s Book to discuss the basic features of the Periodic Table.

• Worksheet C3.16a has a variety of activities and

questions about the Periodic Table, leading into the link between electron structure and position in the Periodic Table.

© Pearson Education Limited 2007

g Elements in the same group have similar chemical properties because they have the same number of electrons. (false – they have the same number of electrons in their outer shell) h The elements in Group 7 are known as the noble gases. (false – they are the halogens)

Additional homework/research ideas

• ICT Students could be asked to use the internet

to find out about the formation of new elements in nuclear reactions. Element 118 is an interesting one to suggest.

Practicals and demonstrations 1 Elements or compounds? Samples of various elements and compounds could be placed around the room. Each one should be labelled with its name and formula and relevant hazard symbol. Examples are ammonia (NH3, compound, toxic), argon (Ar, element, non-metal), glucose (C6H12O6, compound), AQA GCSE Extension Units Teacher’s Guide

91

iron oxide (Fe2O3, compound), magnesium (Mg, element, metal, highly flammable), methane (CH4, compound, extremely flammable), nickel (Ni, element, metal), oxygen (O2, element, non-metal, oxidising), sodium chloride (NaCl, compound), sulfur (S8, element, non-metal). For colourless gases (ammonia, argon, methane and oxygen) simply use a gas jar of air. As students look at each substance, they should write down in a suitable table whether it is an element or a compound, and for each element whether it is a metal or a non-metal.

harmful (do not use powder). Eye protection should be worn. 10 minutes Apparatus Beakers labelled glucose (C6H12O6), iron oxide (Fe2O3), magnesium (Mg), nickel (Ni), sodium chloride (NaCl), sulfur (S8) containing samples of those substances; gas jars labelled ammonia (NH3), argon (Ar), methane (CH4), oxygen (O2) containing air; eye protection.

Use air in place of ammonia, argon, methane and oxygen. Magnesium is highly flammable. Nickel is

C3.17

Group 1 – the alkali metals

Worksheets available No. C3.17a C3.17b

Title The alkali metals 1 The alkali metals 2

Type Classwork (write-on) Homework (reusuable)

Objectives Students should be able to:

• describe the physical and chemical properties of the alkali metals

Foundation 4

Higher 4 4

• H

AT Students should explain why the alkali metals become more reactive down the group. There is an animation in the ActiveTeach to help.

• Worksheet C3.17a reinforces much of the work from the lesson by considering the chemistry of caesium.

• H explain the trend in reactivity of the alkali metals. • For homework, Worksheet C3.17b involves Key words alkali metals

Lesson ideas Starter

• Ask students to list the properties of common metals.

Learning activities

• Show students the metals lithium, sodium and

potassium, including cutting them with a knife (Practical 1). This should reinforce the ideas about the physical properties of the alkali metals shown in the Student’s Book.

•

Use the Student’s Book to look at the reactions of Group 1 metals with non-metals and reinforce this by demonstrating the reaction of sodium with chlorine (Practical 2).

• Use the Student’s Book to look at the reactions

of Group 1 metals with water. Demonstrate the reactions of lithium, sodium and potassium with water (Practical 3). Students could make a table to describe what they see and write an equation for each reaction. There are DVDs available from the RSC showing the more reactive elements in Group 1.

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some data analysis and graph drawing to make predictions about francium.

Plenary

• Rubidium is the fourth member of the group.

Students should predict the chemical and physical properties of rubidium.

• An alternative is to carry out a connectives exercise.

Give students the start of a sentence such as ‘Rubidium and sodium are similar …’, then give them connective words such as ‘to’, ‘so’, ‘such as’, ‘therefore’, ‘but’ and ‘however’. Ask them to complete the sentence in as many different ways as possible using the connective words.

Additional homework/research ideas

• ICT The alkali metals have not been known for that long. Students could research their discovery. This links to the work on electrolysis from Unit C2.

Practicals and demonstrations 1 Looking at the alkali metals Show students samples of lithium, sodium and potassium. Handle each one with tweezers and cut off a small piece using a scalpel on a tile. Keep the metals away from water. Lithium, sodium and potassium are highly flammable and corrosive. Use small pieces of each metal (no bigger than pea © Pearson Education Limited 2007

sized). Do not touch the metals, use tweezers to handle them. Goggles should be worn. 5 minutes Apparatus Lithium; sodium; potassium; tile; scalpel; tweezers; filter paper; goggles. 2 Reaction of sodium and chlorine Place a small piece of sodium on a non-porous brick. Heat it directly with a Bunsen flame until it melts and catches fire. Then place a gas jar of chlorine on top of the brick. Chlorine is toxic so the reaction must be carried out in a fume cupboard. Sodium is highly flammable and corrosive. Goggles should be worn. The brick should be placed in a bowl of cold water to remove any unreacted sodium. 5 minutes Apparatus Gas jar of chlorine gas; sodium; filter paper; scalpel; tweezers; non-porous brick; goggles.

The reactions should be done behind safety screens. Lithium, sodium and potassium are highly flammable and corrosive. Use small pieces of each metal (sodium no more than 4 mm cube; potassium no more than 3 mm cube). The test for hydrogen should only be done for lithium. No attempt should be made to restrain the movement of sodium or potassium. Any flame should be extinguished before the reactions of sodium and potassium. Goggles should be worn. 15 minutes Apparatus

3 Reaction of alkali metals with water Fill a large glass trough with water. Handle each metal with tweezers and cut off a small piece (no bigger than a small pea) using a scalpel on a tile. Wipe off the oil using filter paper. The reaction with lithium should be

C3.18

done first and used to test for hydrogen. The lithium can be held in place in an inverted test tube of water to collect the hydrogen. In a test tube rack, away from the alkali metals, a burning splint can be put into the test tube; it will give a squeaky pop. Sodium and potassium can then be reacted with water (do not test for hydrogen with sodium and potassium). Once all three reactions have been done, universal indicator should be added to the water to show that it is alkaline.

Large glass trough; safety screens; lithium; sodium; potassium; filter paper; scalpel; tweezers; test tube; test tube bung; splint; matches; test tube rack; universal indicator solution and colour chart; goggles.

Transition metals

Worksheets available No. C3.18a C3.18b

Title Looking at metal compounds Transition metals and alkali metals

Objectives Students should be able to:

• describe the physical and chemical properties of the transition metals and compare them with the alkali metals

Type Classwork (write-on) Homework (reusable)

Foundation 4

Higher 4 4

electrons), 3p (which holds eight electrons) and the 3d (which holds ten electrons) sub-levels. The 4s sub-level is lower energy than the 3d sub-level and so electrons fill the 4s sub-level before 3d. Students do not need this much detail, just the idea that there is a sub-level within the 3rd energy level that fills after two electrons have gone into the 4th energy level.

• describe special properties of the transition metals • H explain why the transition metals have special

• Not all transition-metal compounds are coloured,

Key words

Lesson ideas

no new words

Starter

properties.

Points to note

• Electron energy levels are made up of sub-levels

(except the first energy level). The 3rd energy level of electrons is made up of the 3s (which holds two

© Pearson Education Limited 2007

although most of them are.

• Ask students to list ten commonly used metals (as

metals rather than in compounds). Then ask them to find them on the Periodic Table and note down what they are used for. Most of them are likely to be transition metals.

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Learning activities

Practicals and demonstrations

• AT The ActiveTeach has a video showing the use of

1 Looking at the transition metals Show students samples of transition metals, e.g. chromium, copper, gold, iron, zinc. Put them into water to show they react very slowly, if at all.

a variety of transition metals in cars.

• Show students some samples of transition metals

and discuss their physical properties. Put these metals into water to show their low reactivity (Practical 1). Compare the chemical and physical properties with those of the alkali metals. The Student’s Book also gives details of this and can be used alongside the examples.

Eye protection should be worn. 5 minutes Apparatus Chromium; copper; gold (e.g. wedding ring); iron; zinc; beaker; eye protection.

• Practical 2 involves looking at some compounds

containing alkali metals and/or transition metals. Worksheet C3.18a can be used to deduce that compounds containing transition-metal compounds are coloured (usually).

• Use the Student’s Book to look at other special

properties of transition metals, including their use as catalysts and the fact that they can form ions with different charges.

• H Students should be made aware of the electronic structure of the transition metals in Period 3.

• For homework, Worksheet C3.18b reinforces the work from this lesson.

Plenary

• Ask students to prepare five quiz questions about

the transition metals and then ask those questions of at least one other student.

Additional homework/research ideas

• ICT Students could find more uses of transition metals as catalysts.

C3.19

2 Looking at compounds containing metals Place ten metal compounds around the room. Each sample should be a solid and labelled with both name and formula. Give students Worksheet C3.18a to use to deduce that compounds containing transition-metal compounds are coloured. Students should not touch the compounds. Cobalt chloride is toxic and potassium dichromate (VI) is very toxic and oxidising; both should be sealed inside beakers or see-through containers. Copper sulfate and nickel sulfate are harmful. Potassium manganate (VII) is oxidising and harmful. Sodium carbonate is an irritant. Eye protection should be worn. 15 minutes Apparatus Samples (in beakers labelled with name and formula) of cobalt chloride (with sealed top), copper sulfate, iron(III) oxide, nickel sulfate, potassium dichromate (VI) (with sealed top), potassium hydrogencarbonate, potassium iodide, potassium manganate (VII), sodium carbonate, sodium chloride; Worksheet C3.18a; eye protection.

Group 7 – the halogens

Worksheets available No. C3.19a C3.19b

Title Halogen displacement reactions The chemistry of astatine

Foundation 4

Higher 4 4

Objectives

Points to note

Students should be able to:

• Many students mistakenly think that bromine is a

• describe the chemical and physical properties of the halogens

• H explain the trend in reactivity of the halogens. Key words displacement reaction, halogens

94

Type Classwork (write-on) Homework (reusable)

AQA GCSE Extension Units Teacher’s Guide

gas at room temperature and iodine is a liquid.

• Many students struggle with the idea of halogen

displacement reactions. They confuse which element is displaced by the halogen. It helps to think of these reactions as non-metal displacement reactions where a more reactive non-metal displaces a less reactive non-metal.

© Pearson Education Limited 2007

Lesson ideas

Practicals and demonstrations

Starter

• Ask students to list the properties of Group 1

elements and then write a list of opposite properties. Point out that many of the properties of Group 7 elements are the opposite of Group 1 elements.

Learning activities

• Use the Student’s Book to look at the physical

properties of the halogens and reinforce this with Practical 1. properties of the halogens. This can be reinforced by Practical 2, which involves halogen displacement reactions. Worksheet C3.19a uses this to work out the order of reactivity of the halogens. It may be best to do this before looking at the reactivity order in the Student’s Book.

Chlorine gas in gas jar; bromine in sealed glass vial (colourless glass); iodine crystals; watch glass; boiling tube; boiling tube holder; tweezers; Bunsen burner; heat-proof mat; matches; eye protection. 2 Halogen displacement reactions Students react solutions of potassium chloride, potassium bromide and potassium iodide with solutions of chlorine, bromine and iodine. They use the results to put the halogens into order of reactivity. Instructions are on Worksheet C3.19a.

• H

AT Students should explain why the halogens become less reactive down the group. There is an animation in the ActiveTeach to help.

• For homework, Worksheet C3.19b reinforces much

of the work from the topic, in part by predicting the chemistry of astatine.

Chlorine vapour is toxic. Chlorine water is an irritant and harmful. Bromine water is very toxic (0.06 mol/dm3) or harmful (0.006 mol/dm3). Iodine water is harmful. Eye protection should be worn. The experiments should be done in a well ventilated room. 20 minutes

Plenary

• The element below astatine in the Periodic Table

has yet to be detected. Ask students to predict the chemical and physical properties of this element.

Apparatus

• ICT Students could research the use of chlorine as a chemical weapon in the First World War.

C3.20

The halogens should only be handled in a fume cupboard. Chlorine is toxic and an irritant. Bromine is very toxic and corrosive. Iodine is harmful. Eye protection should be worn. 5 minutes Apparatus

• Use the Student’s Book to look at the chemical

Additional homework/research ideas

1 Looking at the halogens Show students a gas jar of chlorine, a sealed vial of bromine and some iodine crystals. One crystal of iodine could be warmed gently in a boiling tube to show the purple vapour formed on heating.

Chlorine (aq); bromine (aq); iodine (in aqueous potassium iodide); potassium chloride (aq); potassium bromide (aq); potassium iodide (aq); test tubes; test tube rack; teat pipettes; Worksheet C3.19a; eye protection.

The development of the Periodic Table

Worksheets available No. C3.20a C3.20b

Title Mendeleev and Meyer HSW The Periodic Table 3

Type Classwork (reusable) Homework (reusable)

Foundation 4 4

Objectives

Lesson ideas

Students should be able to:

Starter

•

describe the development of the Periodic Table, including the work by Mendeleev and Newlands.

Key words

Higher 4 4

• Select a few elements students will know little

about, for example strontium, vanadium, selenium and xenon. Ask them to use their knowledge of the Periodic Table to list properties of these elements.

no new words

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Learning activities

d Elements in Group 7 get more reactive as you go down the group. (false – they get less reactive)

• HSW

ICT Students could use the internet to find out what Newlands and Mendeleev contributed to the development of the Periodic Table. Students could present their findings back to the class as a PowerPoint presentation.

e Non-metals are on the left-hand side of the table. (false – right-hand side) f Just over three-quarters of the elements are metals. (true)

• HSW Worksheet C3.20a looks at how Meyer is

g The element with the electronic structure 2,8,8,2 is in Group 2. (true)

thought to have had the same ideas as Mendeleev but because Mendeleev published his ideas first he was credited with them.

h The elements in Group 7 are known as the alkali metals. (false – they are the halogens)

• HSW For homework, Worksheet C3.20b reinforces

i Transition metals have higher melting points than the alkali metals. (true)

much of the work about the whole topic of the Periodic Table.

j Melting points increase as you go down Group 7. (true)

Plenary

• AT Students decide whether a series of statements

Additional homework/research ideas

about the Periodic Table are true or false. Suggested statements are given below and on the ActiveTeach:

• ICT Students could use the internet to obtain

a Elements are listed in atomic mass order. (false – atomic number order)

copies of Meyer’s original table and compare it with Mendeleev’s.

b Newlands left gaps for undiscovered elements in his table. (false – Mendeleev did this)

Practicals and demonstrations None suggested.

c Elements in Group 1 get more reactive as you go down the group. (true)

C3.21

Solution calculations

Worksheets available No. C3.21a C3.21b

Title Solution calculations 1 Solution calculations 2

Type Classwork (reusable) Homework (reusable)

Objectives

Lesson ideas

Students should be able to:

Starter

•

H calculate the chemical quantities for reactions in solution.

Key words titration

Points to note H This spread is Higher Tier only.

• The units mol/dm

3

are used for concentration (not M

or mol/litre).

• The specification states that students should be able to do reactions of solutions with other solutions as well as with solids.

• 96

Foundation

It is best to learn how to do solution calculations before students learn how to do titrations, so that they can perform the calculation linked to their own titration. AQA GCSE Extension Units Teacher’s Guide

Higher 4 4

• Ask students to do some mole calculations based

on masses (done in Unit C2). This will revisit the equation mass=Mr 2moles so that they are well practised when needed in this topic. Students will also need the following relative atomic masses: H=1, C=12, O=16, Na=23, Cl=35.5, K=39, Ca=40, Fe=56, Br=80). Some examples include:

a Calculate the number of moles: 72 g of H2O (moles=72/18=4) 8 g of Br2 (moles=8/160=0.05) 1.43 kg of Na2CO3 (moles=1430/286=5 moles) b Calculate the mass: 0.10 moles of KCl (mass=74.520.1=7.45 g) 1.50 moles of Fe2O3 (mass=16021.5=240 g) 0.25 moles of Ca(OH)2 (mass=7420.25=18.5 g)

© Pearson Education Limited 2007

Plenary

c What mass of oxygen reacts with 78 g of potassium? 4K+O2

• Students could be asked the following question.

2K2O

Calculate the concentration of sodium carbonate solution given that 25.0 cm3 of it reacts with 28.0 cm3 of 1.00 mol/dm3 hydrochloric acid solution. (answer: 0.56 mol/dm3)

(moles K=2, moles O2=0.5, mass O2=3220.5= 16 g)

Learning activities

Na2CO3(aq)+2HCl(aq)

• Use the Student’s Book for worked examples of

2NaCl(aq)+H2O(l)+CO2(g)

Practicals and demonstrations

calculating chemical quantities for reactions in solution.

None suggested.

• This can be reinforced by using Worksheets C3.21a

and C3.21b, which contain more practice calculations.

C3.22

Titrations

Worksheets available No. C3.22a C3.22b

Title Finding the concentration of an acid Titrations 1 HSW

Type Practical (reusable) Homework (reusable)

Objectives

Foundation 4

Higher 4 4

Plenary

• H Students should do the calculation at the end

Students should be able to:

• describe how an acid–alkali titration can be carried out.

of the titration experiment on Worksheet C3.22a. You could also find the class mean and let students compare their results to the mean.

• As an alternative, ask students one by one to give

Key words burette, end point, indicator, pipette

the next step in carrying out a titration. This could be done several times.

HT

Practicals and demonstrations

Lesson ideas

1 Finding the concentration of sulfuric acid Students perform a titration to find the concentration of a solution of sulfuric acid. It is best to demonstrate the titration first. Instructions for the experiment are on Worksheet C3.22a.

Starter

• H Students could be asked the following question. Calculate the concentration of sodium hydroxide given that 25.0 cm3 of it reacts with 21.6 cm3 of 0.500 mol/dm3 sulfuric acid solution. (answer: 0.864 mol/dm3)

H2SO4(aq)+2NaOH(aq)

Na2SO4(aq)+2H2O(l)

• As an alternative, a range of apparatus for measuring volumes could be put out (e.g. 100 cm3 measuring cylinder, 10 cm3 measuring cylinder, 250 cm3 beaker, 100 cm3 beaker, burette, pipette) and students asked which they think is the most accurate and why.

Learning activities

• Worksheet C3.22a gives instructions for students to

Sodium hydroxide solution is an irritant. Eye protection should be worn. 50 minutes Apparatus 0.100 mol/dm3 sodium hydroxide; approximately 0.05 mol/dm3 sulfuric acid; burette stands/clamps; 50 cm3 burettes; 25 cm3 pipettes; pipette fillers; 250 cm3 conical flasks; small beakers; funnels for burettes; marker pens for glassware; wash bottles with distilled water; white tiles; methyl orange indicator; Worksheet C3.22a; eye protection.

do a titration. It is best to demonstrate the titration to students before they do it themselves.

• HSW For homework, Worksheet C3.22b looks at

issues surrounding accuracy, precision and reliability in titrations.

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C3.23

Choosing indicators for titrations

Worksheets available No. C3.23a C3.23b

Title Making a pH curve Titrations 2

Type Practical (reusable) Homework (reusable)

Objectives Students should be able to:

• choose a suitable indicator for a titration.

Foundation 4

Higher 4 4

Plenary

• Students should suggest suitable indicators for a

number of titrations, choosing from methyl orange and phenolphthalein. Suitable examples are:

Key words

sulfuric acid+potassium hydroxide (methyl orange or phenolphthalein)

no new words

citric acid+sodium hydroxide (phenolphthalein)

Points to note

ethanoic acid+potassium hydroxide (phenolphthalein)

• The specification does not cover titrations between

nitric acid+ammonia (methyl orange)

weak acids and weak alkalis for which there are no suitable indicators.

Lesson ideas Starter

• Draw two axes for a graph. Label the x-axis ‘volume

of alkali added’ and the y-axis as ‘pH’. Ask students to draw similar axes and then draw a graph to predict how the pH changes as a strong alkali is added slowly to a strong acid to excess. Students could also be asked to explain why they have drawn the graph as they have. The graph may be revisited as a plenary at the end of the lesson.

Learning activities

• It may be best to do the experiment to produce

a pH curve before looking in the Student’s Book. Worksheet C3.23a has instructions for this. The experiment is done using pH probes attached to dataloggers, but if suitable apparatus is not available, pH sticks could be used and the results recorded every 1 cm3 of alkali added. The data could then be plotted on a graph.

• Once students have the shape of the pH curve, use the Student’s Book to look at indicators and why they work in titrations between strong acids and strong alkalis. Then examine the narrower range of pH change in other titrations and why not all indicators work.

nitric acid+sodium hydroxide (methyl orange or phenolphthalein)

• As an alternative, you may wish to revisit the graph that students sketched at the start of the lesson. Students could be asked to say what was right and what was wrong with their graphs.

Practicals and demonstrations 1 Making a pH curve Students use pH probes and dataloggers to record the pH curve for the reaction of a strong acid and a strong alkali. Some students could do curves for strong acid – weak alkali or weak acid – strong alkali. If suitable pH probes are not available, the experiment can be done by using pH sticks and recording the pH every 1 cm3 of alkali that is added to acid. A graph can then be plotted. Worksheet C3.23a has details of the practical. Sodium hydroxide solution is an irritant. Eye protection should be worn. 40 minutes Apparatus 0.1 mol/dm3 sodium hydroxide; 0.1 mol/dm3 hydrochloric acid; burette stands/clamps; 50 cm3 burettes; measuring cylinder (to measure 25 cm3); wide neck 250 cm3 conical flasks; small beakers; funnels for burettes; marker pens for glassware; pH probes; dataloggers; Worksheet C3.23a; eye protection.

• AT There is a useful animation showing how indicators change colour during titrations.

• For homework, Worksheet C3.23b covers the whole topic area of titrations.

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C3.24

Energy transfers in reactions

Worksheets available No. C3.24a C3.24b

Title Endothermic or exothermic? Useful energy transfers

Type Practical (write-on) Homework (reusable)

Objectives Students should be able to:

• describe the energy changes involved in exothermic and endothermic reactions

• draw an energy diagram to represent the energy changes in a reaction, including the activation energy.

Key words activation energy, endothermic, exothermic

Lesson ideas Starter

• Students could try to draw an energy transfer diagram for burning natural gas (methane).

• As an alternative, give students the two words

‘endothermic’ and ‘exothermic’ and ask them to write definitions of each of these words. You may wish to revisit these definitions at the end of the topic.

Learning activities

• It may be best to do the experiment before using

the Student’s Book. Students carry out some test tube reactions and feel the tube to see if they are endothermic or exothermic. A simple explanation of these terms is on Worksheet C3.24a.

• Use the Student’s Book to look at the differences

between endothermic and exothermic reactions in terms of energy changes and the relevant amount of chemical energy of the reactants and products.

Foundation 4 4

Higher 4 4

Plenary

• Give students some reactions for which they have to draw suitable energy diagrams, for example:

Ca+H2SO4 ZnCO3

CaSO4+H2 (exothermic) ZnO+CO2 (endothermic)

2Na+2H2O

2NaOH+H2 (exothermic).

Practicals and demonstrations 1 Endothermic or exothermic? Students carry out a series of test tube reactions to see whether each reaction is endothermic or exothermic. They feel the outside of the test tube to judge whether it has got hotter or colder. When they have finished, ask students to write word equations for each reaction using the symbol equation supplied. Students should not hold test tubes during reactions; they should be carried out in a test tube rack. Students should feel the tubes only after the reaction has ended. Hydrochloric acid is an irritant. Magnesium and zinc are highly flammable. Ammonium chloride is harmful. Calcium is highly flammable (handle with tweezers, not hands). Do not touch calcium with your fingers. Eye protection should be worn. 20 minutes Apparatus 2.0 mol/dm3 hydrochloric acid; magnesium ribbon (strips about 3 cm long); sodium hydrogencarbonate; ammonium chloride; 0.5 mol/dm3 copper sulfate; zinc powder; calcium (small granules); test tubes; bungs; tweezers (for calcium); test tube rack; spatulas; eye protection; Worksheet C3.24a.

• For homework, Worksheet C3.24b reinforces the

ideas from the lesson by looking at the use of exothermic reactions in self-heating cans and of endothermic reactions in ice packs.

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C3.25

Bond energies

Worksheets available No. C3.25a C3.25b

Title Bond energies 1 Bond energies 2

Type Classwork (reusable) Homework (reusable)

Objectives

Higher 4 4

• AT There is an animation on the ActiveTeach

Students should be able to:

• H calculate the energy change in a reaction using bond energies.

showing how to do these calculations.

• Worksheets C3.25a and C3.25b provide further practice at bond-energy calculations.

• The reason for a reaction being endothermic or

Key words

exothermic in terms of bond energies should be discussed. In an exothermic reaction, more energy is released forming bonds than is required to break bonds. In an endothermic reaction, less energy is released forming bonds than is required to break bonds.

bond energy

Points to note

• Students struggle with the idea that energy is

released when bonds are made. This often is seen when students are asked why a reaction is exothermic in terms of bond making and breaking. The commonest wrong answer is ‘the energy to make bonds is more than the energy to break bonds’ rather than ‘the energy released making bonds is more than the energy needed to break bonds’.

Plenary

• Ask students to work out the energy change in this reaction using bond energies. Extend this further by asking them to draw an energy diagram. Bond energies: O–H=463, O–O=146, O=O=498 kJ/mol. (answer: –206 kJ/mol)

Lesson ideas

O

H

H This topic is Higher-tier only. 2

O

2 H

O

H + O

O

H

Starter

• Give students some more reactions for which they

have to draw suitable energy diagrams, for example:

2NaHCO3

Na2CO3+H2O+CO2 (endothermic)

2HCl+Zn

ZnCl2+H2 (exothermic)

C3H8+5O2

Foundation

Practicals and demonstrations None suggested.

3CO2+4H2O (exothermic).

Learning activities

• Use the Student’s Book to discuss the idea of energy changes in terms of bond making and breaking. This can be taken further by doing bond-energy calculations as worked through in the Student’s Book.

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C3.26

Burning fuels

Worksheets available No. C3.26a C3.26b

Title Burning alcohols 1 Burning alcohols 2 HSW

Objectives Students should be able to:

• describe how simple calorimetry can be used to

measure the energy released when a fuel or food is burned.

Key words calorimeter, calorimetry, specific heat capacity

Points to note

• A common error in calorimetry calculations is to use the mass of the fuel burned rather than the mass of water in the equation to work out heat released.

Lesson ideas Starter

• Give students the information that it takes 4.2 J of

energy to make 1 g of water 1 °C hotter. Ask them to suggest ways of finding out how much heat is given out by 1 g of a fuel using this information.

Learning activities

• Use the Student’s Book to look at the principles

of calorimetry and how we can measure the heat released when a fuel is burned. Reinforce this using the experiment on Worksheet C3.26a in which students measure the heat released by burning alcohols.

• HSW For homework, Worksheet C3.26b looks

further at calorimetry experiments with fuels, with an emphasis on the experimental aspects of How Science Works.

© Pearson Education Limited 2007

Type Practical (reusable) Homework (reusable)

Foundation 4 4

Higher 4 4

Plenary

• Ask students to work out the heat released by

burning hexan-1-ol (C6H13OH) in terms of kJ/g and kJ/mol. When 0.15 g of hexan-1-ol is burned, it makes 80 g of water 15 °C hotter (answers: 33.6 kJ/g and 3427 kJ/mol). Extend this further by asking why this information would be useful.

Additional homework/research ideas

• ICT Ask students to use the internet to find out

about bomb calorimeters, which give much more accurate results.

Practicals and demonstrations 1 Burning alcohols Students burn three different alcohols in spirit burners under a copper calorimeter to work out the heat released from each alcohol in terms of kJ/g and kJ/mol. Details are given on Worksheet C3.26a. The alcohols are highly flammable. Students should not re-fill the burners, it must be done by the teacher, if necessary. Methanol is toxic, ethanol and propan-1-ol are harmful. The apparatus will be very hot. Ensure safe design of spirit burners. The wick should fit tightly in the wick holder and the wick holder should fit tightly in the burner. If the capacity of the burner is large (more than 50 ml), reduce it by partially filling with epoxy resin or glass wool or similar material. Eye protection should be worn. 40 minutes Apparatus methanol spirit burners; ethanol spirit burners; propan-1-ol burners; copper can calorimeters; stands; clamps; bosses; matches; balances (0.01 g sensitivity); 100 cm3 measuring cylinders; thermometers; Worksheet C3.26a; eye protection.

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C3.27

Using fuels

Worksheets available No. C3.27a C3.27b

Title Burning fuels Hydrogen – fuel of the future HSW

Type Classwork (write on) Homework (reusable)

Objectives Students should be able to:

• evaluate the social, economic and environmental consequences of using fuels.

Key words non-renewable, renewable

Points to note

• Nuclear fuels produce heat by radioactive decay

rather than burning, but they are included here to contribute to the general discussion of meeting the world’s energy needs.

Lesson ideas Starter

• Ask students to get into pairs. Ask one of each pair

to list the advantages of using fuels and the other to list the disadvantages of using fuels. After a few minutes, ask them to swap their lists and to add or delete items from them. They must be able to give a reason for any deletion.

Learning activities

• AT There is a context video on the ActiveTeach looking at the use of fuels in cars.

• The Student’s Book gives some social, economic

and environmental consequences of using fuels. Students could discuss or debate one or more of the examples in detail or be encouraged to think of further consequences. For example, they could discuss in detail ways in which we could lower our energy demands, or whether we should use nuclear fuels or not.

Foundation 4 4

Higher 4 4

Plenary

• Ask students, in their pairs, to revisit their lists of

advantages and disadvantages of using fuels. Ask them to add or delete items from their list as they think necessary. Again, they should be able to give a reason for any deletion.

Practicals and demonstrations 1 Burning fuels Demonstrate how some different fuels burn. The fuels should be placed in a crucible in a pipe clay triangle on a gauze. The crucible should be no more than a third full with liquid fuels. Try to light each one first by bringing a burning splint near it, then by holding the burning splint against it for a short time, then for a longer time, and then by aiming a Bunsen burner directly at it. Observe how easily each fuel lights and how smoky the flame is. Students use this information along with data on Worksheet C3.27b to select suitable fuels for various uses. The first fuel is methane, so light a Bunsen burner for this. Do not use commercial petrol – its use is banned in schools – pet. ether 60–80 is a good substitute. Similarly, use paraffin in place of fuel oil. Ethanol, pet. ether, and paraffin are flammable and harmful. Wear eye protection. 20 minutes Apparatus Ethanol; pet. ether 60–80 (labelled ‘petrol’); paraffin; coal; Bunsen burner; heat-proof mat; splints; tripod; pipe clay triangle; crucible; eye protection.

• There is an experiment on Worksheet C3.27a

involving the burning of some fuels. Students are asked to use the results to decide which fuel to use in different circumstances, giving reasons for their decisions.

• HSW For homework, Worksheet C3.27b explores the possible use of hydrogen in fuel cells in the future.

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C3.28

Energy in food

Worksheets available No. C3.28a C3.28b

Title HSW Burning food Energy in foods

Type Practical (reusable) Homework (reusable)

Objectives Students should be able to:

• identify types of food that contain a lot of energy • explain the link between energy in food and obesity • calculate the energy stored in some foods. Key words calories, obese

Points to note

• The calorie is the imperial unit for energy. When

people refer to the calories in food, they are actually referring to kilocalories. People may say that a biscuit contains 80 calories when actually it contains 80 kilocalories (80 000 calories). The joule (or kilojoule) should be used as the unit for energy.

Lesson ideas Starter

• Ask students to make a list of high-energy foods and

a list of low-energy foods. Once they have done this, ask them to identify which food type (carbohydrates, fats, fibre, minerals, protein, vitamins) is in each food. They should be able to identify what the highenergy foods have in common.

Learning activities

•

Use the Student’s Book to discuss energy in foods, including which foods are high in energy. The starter can be used as a starting point for this discussion, leading on to how eating food with too much energy can make us overweight or obese, and some of the consequences of this.

• HSW There is an experiment on Worksheet C3.28a

in which students measure the energy in some foods by burning them and using the heat energy to warm up some water. They compare their results to the correct values and are asked about the types of errors involved.

Foundation 4 4

Higher 4 4

Plenary

• Students should try to rank the following food

items in energy-content order (highest to lowest): chocolate biscuit, cheeseburger, bowl of cornflakes with milk, apple, banana, turkey and salad sandwich (from 1 slice of bread), packet of crisps, can of cola, slice of pizza, low-fat yoghurt. The answer depends on exact portion sizes, but typical sizes give this answer: (1) cheeseburger (1 507 kJ, 360 kcal), (2) pizza slice (1 172 kJ, 280 kcal), (3) cornflakes with milk (837 kJ, 200 kcal), (4) turkey and salad sandwich (733 kJ, 175 kcal), (5) can of Cola (670 kJ, 160 kcal), (6) packet of crisps (628 kJ, 150 kcal), (7) chocolate biscuit (502 kJ, 120 kcal), (8) low fat yoghurt (419 kJ, 100 kcal), (9) banana (377 kJ, 90 kcal) (10) apple (209 kJ, 50 kcal). Once they have their order ask them how they decided on it. This should give the idea of food types and how some food types have more energy than others.

Additional homework/research ideas

• ICT Students could use food labels and the internet to try to work out their energy intake on a typical day. This could be presented using a spreadsheet.

Practicals and demonstrations 1 Burning foods Students burn pieces of different foods under a test tube containing 10 cm3 of water and use the results to work out the energy released in kJ per 100 g. Instructions are given on Worksheet C3.28a. Avoid using nuts because of food allergies. Eye protection should be worn. 40 minutes Apparatus Foods to burn (e.g. crisps, bread, mini marshmallows, pasta, bacon, dried broad beans); mounted needles to hold food; teaspoons; test tubes; stands; clamps; bosses; matches; balances (0.01 g sensitivity); 10 cm3 measuring cylinders; thermometers; Bunsen burners; heat-proof mats; matches; Worksheet C3.28a; eye protection.

• For homework, Worksheet C3.28b looks further at energy in foods. It looks closely at the correlation between the energy content of foods and the amount of carbohydrate/fat.

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C3.29

Reactions in solution

Worksheets available No. C3.29a C3.29b

Title Finding the energy change for a reaction in solution HSW Energy changes in solution

Type Practical (reusable) Homework (reusable)

Objectives Students should be able to:

•

calculate the energy change for reactions in solution.

Key words no new words

Points to note

• The calculation of energy changes for reactions

in solution is quite a high-level skill, although it is not indicated as Higher tier only. Most calculations would involve the use of moles. To simplify matters, you may wish to tell students the number of moles.

Lesson ideas Starter

• Magnesium reacts vigorously when added to acid.

The solution gets hot. You could show students this reaction to remind them of all the things that happen during a reaction. Ask students to suggest a way of measuring the energy change for the reaction.

Learning activities

• Use the Student’s Book to discuss how to measure energy changes for reactions in solution.

• HSW Material from the Student’s Book can be

reinforced by doing the experiment on Worksheet C3.29a, in which students are asked to measure the energy change for a neutralisation reaction.

Foundation 4

Higher 4 4

Plenary

• Ask students what the energy change would be

when 0.02 moles of copper sulfate in 25 cm3 of solution reacts with an excess of zinc, given that the temperature rises by 41 °C. (∆H=–215 kJ/mol)

Additional homework/research ideas

• ICT Students could use the internet or data books to find the energy change for other neutralisation reactions. For strong acids and alkalis, they are all about the same. Students could try to explain why this is the case (the same reaction takes place: H+(aq)+OH–(aq) H2O(l)).

Practicals and demonstrations 1 Finding the energy change for a reaction in solution Students react hydrochloric acid with sodium hydroxide solution to calculate the energy change for this neutralisation reaction. Instructions are on Worksheet 3.29a. Sodium hydroxide at this concentration is corrosive and very damaging to eyes. Goggles should be worn. 30 minutes Apparatus Polystyrene cups and lids (with hole for thermometer); tripods; thermometers (sensitivity of at least 0.5 °C, but preferably 0.1 or 0.2 °C); plastic beakers (to sit the cup in); 1.0 mol/dm3 sodium hydroxide solution; 1.0 mol/dm3 hydrochloric acid; measuring cylinders (to measure 25 cm3); Worksheet C3.29a; goggles.

• Worksheet C3.29b contains further examples of calculations for homework.

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Answers

C3.0

C3.16 The Periodic Table

2 1

Student’s Book 1 Lists all the elements.

2,1

2,2

2,8,1

2,8,2

2 2,3

2,4

2,5

2,6

2,7

2,8

2,8,3 2,8,4 2,8,5 2,8,6 2,8,7 2,8,8

2,8,8,1 2,8,8,2

2 Atomic number order. 3 a O, S, Se, Te or Po. b Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd, La, Hf, Ta, W, Re, Os, Ir, Pt, Au, Hg, Ac, Rf, Db, Sg, Bh, Hs, Mt, Ds, Rg or Uub. c Al.

3 a B. b Sb, Bi or Uup. c Mg.

e N, P or As.

d Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd, La, Hf, Ta, W, Re, Os, Ir, Pt, Au, Hg Ac, Rf, Db, Sg, Bh, Hs, Mt, Ds, Rg or Uub.

4 Group 2.

4 a

d Ge, Sn, Pb or Uuq.

5 They have the same number of electrons in their outer energy level (shell).

Li+

6 a Group 3. b Period 3.

F-

S2-

Cl-

Mg2+

K+

Ca2+

Br-

Sr2+

I-

c 13.

Al3+

O2-

Na+

Worksheet C3.16a 1 1

2

3

4

5

6

7

0

1 1

3 4 2,1 2,2 11 12 2,8,1 2,8,2 19 20 2,8,8,1 2,8,8,2

2 2 5 6 7 8 9 10 2,3 2,4 2,5 2,6 2,7 2,8 13 14 15 16 17 18 2,8,3 2,8,4 2.8.5 2,8,6 2,8,7 2,8,8 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36

b Groups 1, 2, 3: charge=group number; Groups 6, 7: charge=8 – group number. c Cs+, Ba2+, At–.

C3.17 Group 1 – the alkali metals Student’s Book 1 Alkali metals. 2 Any three from: soft, low density, conductor, low melting points.

2 Group number=number of electrons in outer energy level (shell).

3 Li, Na, K.

3 Any five from: Group 1=metals, soft, low density, low melting points, conductors, react with water, very reactive, form 1+ions, react with non-metals to form ionic compounds; Group 7=non-metals, toxic, coloured vapours, diatomic molecules, react with metals to form ionic compounds, react with nonmetals to form molecular compounds, insulators; Group 0=unreactive, gases, monatomic, low density, colourless, used in discharge tubes.

Worksheet C3.16b 1 1 3

4

11 12

2 5

6

7

8

9

Key

Group 7

13 14 15 16 17 18

Group 0

© Pearson Education Limited 2007

5 a Potassium bromide. b Ionic. c K+. d White. e Dissolve to form colourless solution. 6 a Lithium+water

lithium hydroxide+hydrogen.

b Lithium hydroxide is an alkali.

c Lithium atoms smaller than sodium atoms, stronger attraction between nucleus and outershell electron, outer-shell electron lost less easily. Group 1

10

19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36

4 Decrease.

7 Ten key facts about Group 1.

Transition metals

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Answers

Worksheet C3.17a

2 a

1 One.

250

2 Lower. 3 a Caesium+chlorine

caesium chloride. 200

b White. d CsCl. e Ionic. f Dissolve to give colourless solution. 4 a Caesium+water

caesium hydroxide+hydrogen.

Atomic radius (pm)

c Cs+. 150

100

b More. c Caesium atoms bigger than sodium atoms, weaker attraction between nucleus and outer-shell electron, outer-shell electron lost more easily.

50

d i Blue/purple. ii Caesium hydroxide is an alkali.

0

0

20

Worksheet C3.17b

40 60 Atomic number

80

100

b Atomic radius=around 247 pm.

1 a

3 a 200 2.5 175

2.0

150

Density (g/cm3)

Melting point (°C)

125

100

75

1.5

1.0

50 0.5 25

0

0 0

20

40 60 Atomic number

80

100

0

20

40 60 Atomic number

80

100

b Density=around 2.35 g/cm3. b Melting point=around 27 °C.

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4 Trend in density is not as clear-cut as the others.

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Answers

C3.18 Transition metals

2 a White.

Student’s Book

c Coloured.

b Coloured.

1 Any three named transition metals from: scandium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, yttrium, zirconium, niobium, molybdenum, technetium, ruthenium, rhodium, palladium, silver, cadmium, lanthanum, hafnium, tantalum, tungsten, rhenium, osmium, iridium, platinum, gold, mercury, actinium, rutherfordium, dubnium, seaborgium, bohrium, hassium, meitnerium, darmstadtium, roentgenium or ununbium. 2 a Any two from: conduct heat, conduct electricity, malleable, ductile. b Any two from: higher density, higher melting points, stronger, harder. 3 a Slowly, if at all. b Much less reactive than the alkali metals. 4 Act as catalysts, form coloured compounds, form ions with different charges. 5 2,8,12,2. 6 Electrons are filling an inner electron level (shell). 7 Similarities: metals, conduct heat, conduct electricity, solids, malleable, ductile. Differences: potassium much more reactive, potassium has lower melting point, cobalt can form different ions, cobalt compounds coloured, cobalt acts as catalyst.

Worksheet C3.18a

Coloured (4)

Does it contain a transition metal? (4)

CoCl2

4

4

Copper sulfate

CuSO4

4

4

Iron(III) oxide

Fe2O3

4

4

Nickel sulfate

NiSO4

4

4

4

4

Potassium dichromate K2Cr2O7 (VI)

Does it contain an alkali metal? (4)

Formula

Cobalt chloride

White (4)

Name

1

3 Transition metals=2 (gold), 3 (nickel), 4 (iron), 5 (copper), 8 (mercury); alkali metals=1 (lithium), 6 (sodium), 7 (any alkali metal).

Worksheet C3.18b 1 Group 1

Transition metals

• they have relatively low • they have high melting melting points points • they are very reactive • they are not very reactive • their compounds are white • they are useful as catalysts • they form ionic compounds on • their compounds are reaction with nonmetals they are good thermal and electrical conductors they are soft and can be cut with a knife they have a low density and some float on water they react with water forming an alkaline solution they react with water releasing hydrogen gas they form 1+ions

•  •  •  •  •  •

coloured they form ionic compounds on reaction with nonmetals they are good thermal and electrical conductors they are strong and hard they have a high density they can form different ions

•  •  •  •  • 

2 a Does not react with water, malleable. b Conducts electricity, ductile. 3 a Coloured compounds, act as catalysts, form ions with different charges. b As an inner energy level of electrons is being filled.

4

C3.19 Group 7 – the halogens Student’s Book

Potassium hydrogencarbonate

KHCO3

4

4

1 Halogens.

Potassium iodide

KI

4

4

2 Any three from: low melting/boiling points, thermal insulators, electrical insulators, coloured vapours.

Potassium manganate KMnO4 (VII)

4

4

4

3 Increase.

Sodium carbonate

Na2CO3

4

4

4 a Ionic.

Sodium chloride

NaCl

4

4

b Molecular. c Ionic.

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Answers

5 a Bromine. b Bromine atoms are smaller, the electron gained is closer to the nucleus, there is a stronger attraction to the nucleus, the electron is gained more easily. 6 a No reaction. b Fluorine+potassium chloride potassium fluoride+chlorine. c Bromine+sodium iodide sodium bromide+iodine. 7 Ten key facts about Group 7.

Worksheet C3.19a Cl2(aq)

Br2(aq)

KCl(aq)

Is there a reaction?

I2(aq) no

Word equation. What it tells us.

KBr(aq)

KI(aq)

Is there a reaction?

Is there a reaction? Word equation.

bromine is probably less reactive than chlorine

yes

What it tells us.

iodine is probably less reactive than chlorine

Is there a reaction?

no

chlorine+potassium bromide potassium Word chloride + bromine equation.

Word equation.

What it tells us.

chlorine is more reactive than bromine

What it tells us.

Is there a reaction?

yes

Is there a reaction?

iodine is probably less reactive than bromine

yes

chlorine+potassium iodide potassium Word chloride + iodine equation.

bromine+potassium iodide potassium Word bromide + iodine equation.

What it tells us.

What it tells us.

chlorine is more reactive than iodine

no

bromine is more reactive than iodine

Order of reactivity=chlorine > bromine > iodine.

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Answers

Worksheet C3.19b

b Properties repeated every eighth element.

1 a

c It only works for the first few elements. 2 a Left gaps for elements yet to be discovered.

350

b He predicted the existence and properties of undiscovered elements that were later discovered and whose properties closely matched his predictions.

300

Boiling point (°C)

3 a Atomic number. b Some elements in wrong groups, i.e. their properties were different from other elements in the same group.

200

c Protons had not been discovered. 100

0

4 Newlands – if elements are arranged in atomic mass order, properties repeat at intervals. 0

20

40 60 Atomic number

80

100

-100

-200

Mendeleev – left gaps for undiscovered elements whose existence he predicted and put elements in atomic number order (without knowing it).

Worksheet C3.20a 1 Mainly in order of atomic mass leaving gaps for undiscovered elements. 2 Predictions about the existence of and properties of undiscovered elements were found to be correct.

b Boiling point=around 322 °C.

3 Short reports about scientific research.

2 a Solid.

4 Small booklets containing papers that are published regularly, often monthly, by scientific organisations.

b At2. c Non-metal. d Coloured. 3 a Ionic. b Ionic. c Molecular. 4 a At–. b CaAt2.

5 Reviewed by other scientists before they are published to judge if they are scientifically sound and worthy of inclusion in the journal. 6 a 1869. b 1870. c He might have just copied Mendeleev’s ideas.

Worksheet C3.20b

5 a No reaction.

1 As / Sb / Bi.

b Chlorine (aq)+sodium astatide (aq) sodium chloride (aq)+astatine (aq).

2 As / Se / Te / F / At / Ar.

c Iodine (aq)+potassium astatide (aq) potassium iodide (aq)+astatine (aq).

4 Fe / Co / Ni / Pt.

6 a Iodine.

6 Ar.

b iodine atoms are smaller, the electron gained is closer to the nucleus, there is a stronger attraction to the nucleus, the electron is gained more easily.

7 Te / Po.

C3.20 The development of the Periodic Table

3 F / At. 5 Li / Fr.

8 Te. 9 Ar. 10 F. 11 Li / Fr. 12 F / At.

Student’s Book

13 Fr.

1 a Atomic mass.

14 Li. 15 F.

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Answers

16 At.

7 0.154 dm3.

17 Fe / Co / Ni / Pt.

8 0.157 dm3.

18 Al. 19 Ar.

C3.22 Titrations

20 Fe / Co / Ni / Pt.

Student’s Book

21 Li. 22 F / At.

1 Experiment to measure the concentration of a solution.

23 Ar.

2 a Point at which the acid/alkali is exactly neutralised.

24 Fe / Co / Ni / Pt.

b When the indicator changes colour.

25 Li / Fr.

3 To improve reliability and accuracy.

C3.21 Solution calculations Student’s Book 1 0.25 mol/dm3. 2 0.10 moles. 3 0.30 dm3. 4 0.148 mol/dm3. 5 0.050 dm3. 6 Flow diagram showing how to perform mole calculations: step 1 – calculate moles of substance whose quantity is known; step 2 – use equation to find moles of required substance; step 3 – calculate quantity of required substance.

Worksheet C3.21a 1 a 2.0 mol/dm3.

b 0.2 mol/dm3.

2 a 0.25.

4 They are more precise. 5 Flow diagram showing stages of a titration: (1) measure out alkali (or acid) into a conical flask using a pipette; (2) add some indicator; (3) put the acid (or alkali) into a burette; (4) add the acid (or alkali) dropwise until the indicator changes colour; (5) record the reading on the burette; (6) repeat the titration.

Worksheet C3.22b 1 Burettes and pipettes measure volumes more precisely. 2 Added acid quickly, not dropwise; did not use wash bottle. 3 We have measured the volume to that higher level of precision, 23.80 cm3 rather than 23.8 cm3. 5 Titration 1=23.55 cm3 ; titration 2=23.25 cm3 ; titration 3=23.50 cm3 ; titration 4=23.60 cm3. 6 a Yes, they are reliable.

b 0.1.

b Three of the four results are very close together (i.e. they are repeatable).

3 0.111 mol/dm3.

7 a Titration 2.

4

0.172 mol/dm3.

b Random error.

5

0.0300 dm3.

6

0.031 25 dm3.

c Because it is different from titrations 1, 3, 4, which are all similar to each other.

8 6.5 g.

d May have not washed out the equipment properly, may have misread the burette, may have used the pipette incorrectly.

9 23.6 dm3.

8 23.55 cm3.

10 Mr=286, x=10.

9 0.212 mol/dm3.

Worksheet C3.21b

10 a Yes, it is accurate.

7 300 g.

1

0.0167 mol/dm3.

2

0.0500 mol/dm3.

b Value measured is very close to the actual value.

3 0.0400 dm3. 4 0.0225 dm3. 5 200 g. 6 6.3 g.

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C3.23 Choosing indicators for titration

3 chemical energy

Student’s Book 1 Substance that is one colour in acid and one colour in alkali.

CH4+2O2

2 a Has lots of different colours at different pHs.

CO2+2H2O

b It is a mixture of indicators. 3 a Methyl orange. b Phenolphthalein.

4 a Reaction that gets colder.

c Any indicator.

b Reactants have less chemical energy than products, so some heat energy is transferred to chemical energy.

4 a It changes from one colour to another at the end point. b It does not change from one colour to another at the end point (it would change after the end point).

Worksheet C3.23a

5 chemical energy

1 pH rises slowly at first, increases rapidly around the end point, and then increases slowly after the end point.

CuO+CO2

CuCO3

2 Any indicator (not universal indicator).

Worksheet C3.23b 1 a Methyl orange.

6 a Minimum energy needed to start a reaction.

b Any indicator.

b They provide an alternative route with a lower activation energy.

c Phenolphthalein. d Any indicator. 2 a Phenolphthalein. b Put vinegar into conical flask, using pipette; add indicator; add alkali from burette, dropwise, until colour changes; record result; repeat.

7 a Exothermic reactions get hotter, endothermic reactions get colder. b Exothermic reaction: chemical energy transferred to heat energy; endothermic reaction: heat energy transferred to chemical energy.

c 0.900 mol/dm3.

Worksheet C3.24a

3 a Methyl orange.

Exothermic reactions=A, D, E

b 1.06 mol/dm3.

Endothermic reactions=B, C

C3.24 Energy transfers in reactions Student’s Book 1 a Example of exothermic reaction, e.g. burning methane, magnesium+acid. b Example of endothermic reaction, e.g. sodium hydrogencarbonate+acid. 2 a Reaction that gets hotter. b Reactants have more chemical energy than products; chemical energy transferred to heat energy.

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1 Reactants have more chemical energy than products; chemical energy transferred to heat energy. 2 Reactants have less chemical energy than products, so some heat energy is transferred to chemical energy. 3 A chemical energy

Mg(s)+2 HCI(aq)

MgCI2(aq)+H2(g)

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B

c Reactants have more chemical energy than products; chemical energy transferred to heat energy.

chemical energy

NaCI(aq)+H2O(I)+CO2(g)

2 a Endothermic. b chemical energy

NaHCO3(s)+HCI (aq)

NH4NO3(aq)

C NH4NO3(s) chemical energy

NH4CI(aq)

NH4CI(s)

c Reactants have less chemical energy than products, so some heat energy is transferred to chemical energy.

C3.25 Bond energies Student’s Book

D

1 a 498 kJ/mol of energy is needed. chemical energy

b 498 kJ/mol of energy is released. 2 a N≡N.

Zn(s)+CuSO4(aq)

b Br–Br. ZnSO4(aq)+Cu(s)

E chemical energy

4 a Flow diagram showing these three steps: (1) calculate the energy required to break all the bonds in the reactants; (2) calculate the energy released making all the bonds in the products; (3) energy change (∆H)=energy required to break bonds – energy released making bonds.

Ca(s)+2H2O(I)

Ca(OH)2(aq)+H2(g)

b The energy released making bonds is more than the energy required to break bonds. c The energy released making bonds is less than the energy required to break bonds.

Worksheet C3.24b

Worksheet C3.25a

1 a Exothermic.

1 a 678 kJ/mol.

b chemical energy

3 a i –103 kJ/mol. ii –95 kJ/mol. b i Exothermic. ii Exothermic.

b 862 kJ/mol. c –184 kJ/mol. d Exothermic.

CaO(s)+H2O(l)

e Energy released making bonds is greater than energy needed to break bonds. Ca(OH)2(aq)

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2 a 2238 kJ/mol.

c +45 kJ/mol.

b 2610 kJ/mol.

d Endothermic.

c –372 kJ/mol.

e Energy released making bonds is less than energy needed to break bonds.

d Exothermic. e Energy released making bonds is greater than energy needed to break bonds.

5 a 3868 kJ/mol.

3 a 6482 kJ/mol.

c –124 kJ/mol.

b 8162 kJ/mol.

d Exothermic.

c –1680 kJ/mol. d Exothermic.

e Energy released making bonds is greater than energy needed to break bonds.

e Energy released making bonds is greater than energy needed to break bonds.

C3.26 Burning fuel

4 a 3625 kJ/mol.

Student’s Book

b 3720 kJ/mol.

1 a 210 J.

c –95 kJ/mol.

b 4200 J.

d Exothermic.

c 33 600 J.

e Energy released making bonds is greater than energy needed to break bonds.

2 a Methane: 52.5 kJ/g; pentane: 46.6 kJ/g.

5 a 6381 kJ/mol.

b 3992 kJ/mol.

b Methane: –840 kJ/mol; –3353 kJ/mol.

c 0 kJ/mol.

3 A known mass of fuel is used to heat a known mass of water; we know how much heat is required to make 1 g of water 1 °C hotter.

d No energy change.

Worksheet C3.26a

b 6381 kJ/mol.

e Energy released making bonds is the same as the energy needed to break bonds.

Worksheet C3.25b

2 a The alcohol. b Categoric.

b 1852 kJ/mol.

3 Same calorimeter, same distance between burner and calorimeter, same volume of water, heated until the same temperature.

c –482 kJ/mol.

Worksheet C3.26b

d Exothermic.

1–4

1 a 1370 kJ/mol.

e Energy released making bonds is greater than energy needed to break bonds.

Alcohol

2 a 3754 kJ/mol. b 4824 kJ/mol. c –1070 kJ/mol. d Exothermic. e Energy released making bonds is greater than energy needed to break bonds. 3 a 2208 kJ/mol. b 2796 kJ/mol. c –588 kJ/mol. d Exothermic. e Energy released making bonds is greater than energy needed to break bonds. 4 a 3231 kJ/mol. b 3186 kJ/mol.

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Butan-1-ol, C4H9OH

Pentan-1-ol, Hexan-1-ol, C5H11OH C6H13OH

Mass of spirit burner at start

110.65 g

123.36 g

108.23 g

Mass of spirit burner at end

111.04 g

123.70 g

108.56 g





Mass of alcohol burned

0.39 g

0.34 g

0.33 g

Mass of water

100 g

100 g

100 g

Temperature of water at start

21 °C

22 °C

21 °C

Temperature of water at end

48 °C

47 °C

47 °C

Temperature rise

27 °C

25 °C

26 °C

Energy released 11.3 kJ

10.5 kJ

10.9 kJ

Energy released 29.1 kJ/g

30.9 kJ/g

33.1 kJ/g

Energy released 2152 kJ/mol 2718 kJ/mol

3375 kJ/mol

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C3.00

5 Hexan-1-ol.

1 Natural gas: cheap, clean flame, ignites easily and can be piped to the house.

6 Hexan-1-ol. 7 Repeat it. 8 The masses are quite small and that much precision is needed to detect differences in mass otherwise significant percentage errors would arise.

2 Coal or fuel oil: cheap and can be transported by road. 3 Natural gas: can be used in cylinder, clean flame, ignites easily and cheaper than ethanol.

9 a They show the relative amount of energy released.

4 Fuel oil: cheap, flows into engines.

b The values of energy released are inaccurate.

Worksheet C3.27b

c Systematic, they are all out by a similar amount.

1 Hydrogen+oxygen

d Heat loss.

2 The only product is water.

C3.27 Using fuels

3 Device in which hydrogen reacts with oxygen to make electricity.

Student’s Book

4 a Too expensive.

1 To provide heat to keep us warm, to generate electricity (by heating water to make steam to drive turbines), and to fuel cars and lorries. 2 Global warming from carbon dioxide produced. 3 Carbon, carbon monoxide, sulfur dioxide, nitrogen oxides. 4 a Fuel that cannot be replaced.

water.

b They will become cheaper as technology develops. 5 Main method of making hydrogen (from methane) uses a non-renewable resource and requires energy.

C3.28 Energy in food

b Any fossil fuel.

Student’s Book

5 a Fuel that can be replaced.

1 Eat food providing too much energy.

b Wood.

2 Very overweight.

6 Advantages: does not produce carbon dioxide; fuel will last for thousands of years.

3 Increases risk of illness.

Disadvantages: problem of storage of nuclear waste.

5 Food containing carbohydrates, fats and oils.

7 Key issues: pollution, using up fuels, lowering energy requirements.

6 a 1680 kJ per 100 g.

Worksheet C3.27a

7 Too much energy in food leads to people becoming overweight, increasing risk of many illnesses.

Fuel

4 Eat food providing less energy.

b 400 kcal per 100 g.

Natural gas

Ethanol Fuel oil

Coal

Petrol

Cost (p per MJ)

0.7

4.3

0.6

0.6

2.5

5 a No, they are a long way out.

Ease of lighting

very easy very easy

quite hard

very hard

easy

b Heat loss.

very smoky

a little smoky

Worksheet C3.28a

Cleanliness very of flame clean

very clean

quite smoky

Transport

by road tanker (as liquid)

by road by road/ tanker or rail (as pipeline solid) (as liquid)

by pipeline or cylinders (as gas)

by road tanker (as liquid)

c Systematic, they are all out by a similar degree. d Use a bomb calorimeter; shield the experiment set up.

Worksheet C3.28b 1 Milk chocolate. 2 532 kJ. 3 Generally, the higher the mass of carbohydrates, the higher the energy. 4 In many cases, the higher the mass of fat, the higher the energy.

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Answers C3.29 Reactions in solution

5 a Nutritional details (per 100 g) Apples Bran flakes Bread (white) Carrots Cheese Chicken (roasted) Chocolate cake Cola drink Diet cola drink Digestive biscuits Milk Milk chocolate Oven chips Potatoes Skimmed milk Sugar-coated corn flakes

Energy (kJ)

Carbohydrates +fat (g)

Student’s Book 1 –52.1 kJ/mol.



206 1331 1015 172 1004 281 1541 756 2 2090 274 2247 548 391 144



14.0 80.6 46.7 10.1 26.0 8.9 70.3 10.6 0 85.5 8.5 90.0 25.2 21.3 5.1

b Flow diagram showing the following steps: (1) calculate the heat released/absorbed; (2) calculate the number of moles reacting; (3) calculate the heat released/absorbed for one mole.



1578



87.6

Worksheet C3.29b

2 +30.8 kJ/mol. 3 a The heat released from (or absorbed by) a reaction used to heat up (or cool down) the water in the solution; we know how much heat is required to make 1 g of water 1 °C hotter.

Worksheet C3.29a 3 Moles HCl=0.025, moles NH3=0.025. 7 Repeat the experiment. 8 b Could not detect the temperature with enough precision.

1 –213 kJ/mol. 2 +28 kJ/mol.

b

3 –367 kJ/mol.

2500

4 –57.1 kJ/mol. 5 –55.0 kJ/mol.

2000

energy (kj)

6 –57.1 kJ/mol. 1500

C3.00 Investigative Skills Assessment (Student’s Book)

1000

1 a 1 g. (1 mark)

500

0

b 1 g to 5 g. (1 mark) 2 0

20

40 60 carbohydrates + fat (g)

80

100

c Generally, the higher the total mass of carbohydrates and fat, the higher the energy.

Mass of zinc (g)

1.0 2.0 3.0 4.0 5.0 23 35 38 37 13 34 37 38

Temperature Experiment 1 12 rise (°C) Experiment 2 11

6 High carbohydrate (sugar) content.

(1 mark)

7 a Someone who is significantly overweight.

3 a Experiment 2, 2.0 g. (1 mark)

b Eating food containing too much energy.

b Random error, does not fit in with other results. (2 marks)

c Foods containing a lot of fat and/or carbohydrates.

c Less than 2.0 g of zinc used, misread thermometer, more than 50 cm3 of copper sulfate used. (1 mark) 4 Mass of zinc (g) 1.0 2.0 3.0 4.0 5.0 Temperature rise (°C) 11.5 23 34.5 37.5 37.5 (1 mark)

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Answers

5 Line graph. (1 mark)

Section 2

6 Repeat their results more times (or get someone else to do the experiment). (1 mark)

8 a 1 g. (1 mark)

7 a Yes, increasing the mass of zinc beyond 4 g makes no difference. (1 mark)

9

b Any answer in the range 3 to 4 g. (1 mark) c Do more experiments; between 3 and 4 g (or plot a graph, see where it levels off ); correct use of at least one scientific term. (3 marks)

b 1 g to 5 g. (1 mark) Mass of zinc (g)

1.0 2.0 3.0 4.0 5.0 23 35 38 37 13 34 37 38

Temperature Experiment 1 12 rise (°C) Experiment 2 11

(1 mark) 10 a Experiment 2, 2.0 g. (1 mark) b Random error, does not fit in with other results. (2 marks)

C3.00 Investigative Skills Assessment (Copymaster File)

c Less than 2.0 g of zinc used, misread thermometer, more than 50 cm3 of copper sulfate used. (1 mark)

Table Suitable table of results with all relevant data included.

11



Columns and rows correctly labelled, units present and correct. (2 marks)

Graph Suitable scale for mass of zinc on x-axis and labelled with units.

Mass of zinc (g) 1.0 2.0 3.0 4.0 5.0 Temperature rise (°C) 11.5 23 34.5 37.5 37.5 (1 mark) 12 Line graph. (1 mark)



Suitable scale for temperature rise on y-axis and labelled with units.

13 Repeat their results more times (or get someone else to do the experiment). (1 mark)



Points plotted correctly.



Suitable best fit line. (4 marks)

14 a Yes, increasing the mass of zinc beyond 4 g makes no difference. (1 mark)

Section 1 1 Mass of zinc and temperature rise identified as variables. (2 marks) The link between the two must be evident to award both marks. 2 a Independent variable=mass of zinc. (1 mark)

b Did not use high enough masses of zinc / only did experiments before the point at which changing the mass of zinc makes no difference. c Any answer in the range 3 to 4 g. (1 mark) d Do more experiments; between 3 and 4 g (or plot a graph, see where it levels off ); correct use of at least one scientific term. (3 marks)

b Continuous. (1 mark) 3 a Any two from: volume of copper sulfate; concentration of copper sulfate; apparatus used; type/surface of zinc. (2 marks) b To make it a fair test / valid as they could affect the temperature rise / dependent variable. (1 mark) 4 Sensitivity of the thermometer they used. (1 mark) 5 Masses being measured are less than 1 g. (1 mark) 6 Use more sensitive balance, use more sensitive thermometer, measure copper sulfate solution with burette / pipette, etc. (1 mark) 7 Simple correct statement=1 mark, e.g. different masses of zinc give different temperature rises. Amplified correct statement=2 marks, e.g. the more zinc used, the larger the temperature rise. (2 marks)

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C3

Answers

C3 Assessment exercises Question 1 a b c d e f

Answer Correctly plotted graph. Axes labelled and units inserted. 9 g per 100 g of water. Solubility of solids increase with increasing temperature. Solubility of gases decreases with temperature. 62–63 °C. 17.5 g.

2 a b c d e

Calcium. Carbonate. CaCO3. Decomposition of calcium hydrogencarbonate. Ca(HCO3)2(aq) CaCO3(s)+CO2(g)+H2O(l).

3 a b

A proton donor. Arrhenius said that acids split up into hydrogen ions in water. Brønsted and Lowry’s theory explained that water is not necessary. An alkali that is only partially ionised in water.

c 4 a

b

1.32 g carbon dioxide=1.32 × 12/44=0.36 g carbon. 0.54 g water=0.54 × 2/18=0.06 g hydrogen. Moles carbon=0.36/12=0.03 moles. Moles hydrogen=0.06. Empirical formula=CH2. Mass spectrometer.

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Extra information

Mark 4 1 1 1 1 1 Total 9 1 1 1 1 2 Total 6 1 2

1 Total 4 3

1 Total 4

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C3

Answers

Question Answer Atomic number order. 5 a Predicted the properties of new elements, b which were then discovered and fitted his predictions. c

Group 4.

6 a b i ii

Alkali metals. More reactive. Potassium atoms are bigger so the outer-shell electron is further from the nucleus, weaker attraction between the nucleus and outer-shell electron, outer-shell electron is easier to lose.

7 a b i ii iii

B. Being significantly/very overweight. Taking in more energy from food than we use up. A.

8 a

Non-renewable fuels. Any air pollution issue (e.g. CO2 contributing to global warming, CO is toxic, SO2 causes acid rain / respiratory problems, NOx causes acid rain / respiratory problems). Only H2O formed.

b 9 a b c

10 a b

118

Any indicator, e.g. methyl orange or phenolphthalein (except universal indicator). To improve accuracy/reliability. Moles HCl=0.061 moles NaOH=0.061 concentration NaOH=2.44 mol/dm3. q=mc∆T 9600 J. 64.4 kJ/g.

AQA GCSE Extension Units Teacher’s Guide

Extra information

Mark 1 2 1 Total 4 1 1 3

Total 5 1 1 1 1 Total 4 2

1 Total 3 1 1 3

Total 5 2 1 Total 3 47 Marks

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C3

Answers

C3 Unit test Question Answer Extra information Magnesium or calcium. 1 a Nichrome wire is cleaned by dipping it in concentrated b i hydrochloric acid and then holding it in a blue flame. When clean, the wire is dipped into the sample and held in a flame. Magnesium ions. ii Iodide ions. c Magnesium iodide. d MgI2(aq)+2AgNO3(aq) 2AgI(s)+Mg(NO3)2(aq). e 2 a

Soap reacts with calcium ions and magnesium ions in the water to form scum.

b c

Permanent hardness. It was not removed by boiling. In an ion-exchange column, the calcium ions and magnesium ions are exchanged by sodium ions. Calcium ions in hard water are good for health (bones, teeth and heart). Sodium ions in softened water can lead to high blood pressure and heart disease.

d

3 a b i ii c

Arrhenius. A weak alkali is only partially ionised in water, while a strong alkali is fully ionised in water. NaOH or KOH. It is accepting protons (H+) from the hydrogen chloride.

4 a b c

C 2H 4O 2. Mass spectrometer. Infrared spectroscopy.

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Mark 1 3

1 1 1 2 Total 9 1 2 2 2

Total 7 1 1 1 1 Total 4 1 1 1 Total 3

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C3 Question 5 a b c

d

6 a i ii b c

7 a b c d e

8 a b

c i ii

120

Answers Answer Pipette is more accurate. Phenolphthalein. Sodium hydroxide in burette; add until colour changes; note reading; repeat; accuracy mark (e.g. drop wise near end, use a white tile). Moles of CH3COOH=0.0235; concentration of CH3COOH= 0.94 mol/dm3. Elements with similar properties in same column/group / grouped together. Copper does not have similar properties to other elements in group/column. Undiscovered elements. Predicted the existence / properties of undiscovered elements; properties of those elements matched his predictions when discovered 2252 kJ/mol 2328 kJ/mol –76 kJ/mol Exothermic. Energy released forming bonds is more than energy needed to break bonds. C=36.7, D=25.3 C, there is some uncertainty due to poor reliability of results / food A produced a bigger temperature rise in one experiment. 1483 J 3.71 kJ/g

AQA GCSE Extension Units Teacher’s Guide

Extra information

Mark 1 1 5

2 Total 9 1 1 1 2

Total 5 1 1 1 1 1 Total 5 1 2

1 1 Total 5 47 marks

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P3

Physics Topic

Learning outcomes and codes

1

H 13.1.2 To calculate the size of a force, or its distance from an axis of rotation, acting on a body that is balanced 13.1.4 The turning effect of a force is called the moment. 13.1.5 The size of the moment is given by the equation: moment=force × perpendicular distance from the line of action of the force to the axis of rotation perpendicular distance from the moment = force × line of action of the force to the axis of rotation (newton metre, Nm) (newton, N) (metre, m) H 13.1.9 If a body is not turning, the total clockwise moment must be exactly balanced by the total anti-clockwise moment about any axis.

2

13.1.1 To describe how to find the centre of mass of a thin sheet of a material. 13.1.6 The centre of mass of a body is that point at which the mass of the body may be thought to be concentrated. 13.1.7 If suspended, a body will come to rest with its centre of mass directly below the point of suspension. 13.1.8 The centre of mass of a symmetrical body is along the axis of symmetry.

3

H 13.1.3 To analyse the stability of bodies by considering their tendency to topple. H 13.1.10 Recognise the factors that affect the stability of a body. H 13.1.11 If the line of action of the weight of a body lies outside the base of the body there will be a resultant moment and the body will tend to topple.

4

13.2.1 To identify which force(s) provide(s) the centripetal force in a given situation. 13.2.2 To interpret data on bodies moving in circular paths. 13.2.3. When a body moves in a circle it continuously accelerates towards the centre of the circle. This acceleration changes the direction of motion of the body, not its speed. 13.2.4 The resultant force causing this acceleration is called the centripetal force. 13.2.5 The direction of the centripetal force is always towards the centre of the circle. 13.2.6 The centripetal force needed to make a body perform circular motion increases as: –  the mass of the body increases –  the speed of the body increases –  the radius of the circle decreases.

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122

5

13.3.1. To interpret data on planets and satellites moving in orbits that approximate to circular paths. 13.3.2 The Earth, Sun, Moon and all other bodies attract each other with a force called gravity. 13.3.3 The bigger the masses of the bodies the bigger the force of gravity between them. 13.3.4 As the distance between two bodies increases the force of gravity between them decreases. 13.3.5 The orbit of any planet is an ellipse (slightly squashed circle), with the Sun at one focus. 13.3.6 Gravitational force provides the centripetal force that allows planets and satellites to maintain their circular orbits. 13.3.7 The further away an orbiting body is the longer it takes to make a complete orbit. 13.3.8 To stay in orbit at a particular distance, smaller bodies, including planets and satellites, must move at a particular speed around larger bodies.

6

13.3.1 To interpret data on planets and satellites moving in orbits that approximate to circular paths.

7

13.3.9 Communications satellites are usually put into a geostationary orbit above the equator. 13.3.10 Monitoring satellites are usually put into a low polar orbit.

8

13.10.1 To explain how stars are able to maintain their energy output for millions of years. 13.10.5 Stars form when enough dust and gas from space is pulled together by gravitational attraction. Smaller masses may also form and be attracted by a larger mass to become planets. 13.10.6 Gravitational forces balance radiation pressure to make a star stable.

9

H 13.10.2 To explain why the early Universe contained only hydrogen but now contains a large variety of different elements. 13.10.3 Our Sun is one of the many billions of stars in the Milky Way galaxy. 13.10.4 The Universe is made up of billions of galaxies. 13.10.7 A star goes through a life cycle (limited to the life cycle of stars of similar size to the Sun and stars much larger than the Sun). H 13.10.8 Fusion processes in stars produce all naturally occurring elements. These elements may be distributed throughout the Universe by the explosion of a star (supernova) at the end of its life.

10

13.4.1 To construct ray diagrams to show the formation of images by plane, convex and concave mirrors. 13.4.5 The normal is a construction-line perpendicular to the reflecting/ refracting surface at the point of incidence. 13.4.6 The angle of incidence is equal to the angle of reflection. 13.4.7 The nature of an image is defined by its size relative to the object, whether it is upright or inverted relative to the object and whether it is real or virtual. 13.4.8 The nature of the image produced by a plane mirror.

11

13.4.1 To construct ray diagrams to show the formation of images by plane, convex and concave mirrors. 13.4.4 To calculate the magnification produced by a lens or mirror using the formula: image height magnification= object height 13.4.9 The nature of the image produced by a convex mirror. 13.4.10 The nature of the image produced by a concave mirror for an object placed at different distances from the mirror.

AQA GCSE Extension Units Teacher’s Guide

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13.4.11 Refraction at an interface. 13.4.12 Refraction by a prism.

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13.4.2 To construct ray diagrams to show the formation of images by diverging lenses and converging lenses. 13.4.3 To explain the use of a converging lens as a magnifying glass and in a camera. 13.4.4 To calculate the magnification produced by a lens or mirror using the formula: image height magnification= object height 13.4.13 The nature of the image produced by a diverging lens. 13.4.14 The nature of the image produced by a converging lens for an object placed at different distances from the lens.

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13.4.15 The use of a converging lens in a camera to produce an image of an object on a detecting device (e.g. film).

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13.5.1 To compare the amplitudes and frequencies of sounds from diagrams of oscilloscope traces. 13.5.2 Sound is caused by mechanical vibrations and travels as a wave. 13.5.4 Sound cannot travel through a vacuum. 13.5.5 The pitch of a note increases as the frequency increases. 13.5.6 The loudness of a note increases as the amplitude of the wave increases. 13.5.7 The quality of a note depends upon the waveform. 13.5.8 Sound waves can be reflected and refracted.

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13.5.3 Sounds in the range 20–20 000 Hz can be detected by the human ear. H 13.6.1 To compare the amplitudes and frequencies of ultrasounds from diagrams of oscilloscope traces. H 13.6.2 To determine the distance between interfaces in various media from diagrams of oscilloscope traces. 13.6.3 Electronic systems can be used to produce ultrasound waves that have a frequency higher than the upper limit of hearing for humans. 13.6.4 Ultrasound waves are partially reflected when they meet a boundary between two different media. The time taken for the reflections to reach a detector is a measure of how far away such a boundary is. 13.6.5 Ultrasound waves can be used in industry for cleaning and quality control. 13.6.6 Ultrasound waves can be used in medicine for pre-natal scanning.

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13.7.1 To explain how the motor effect is used in simple devices. 13.7.2 When a conductor carrying an electric current is placed in a magnetic field, it may experience a force. 13.7.3 The size of the force can be increased by: –  increasing the strength of the magnetic field –  increasing the size of the current. 13.7.4 The conductor will not experience a force if it is parallel to the magnetic field. 13.7.5 The direction of the force is reversed if either the direction of the current or the direction of the magnetic field is reversed.

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13.8.2 If an electrical conductor ‘cuts’ through magnetic field lines, an electrical potential difference is induced across the ends of the conductor. 13.8.3 If a magnet is moved into a coil of wire, an electrical potential difference is induced across the ends of the coil. 13.8.4 If the wire is part of a complete circuit, a current is induced in the wire. 13.8.5 If the direction of motion, or the polarity of the magnet, is reversed, the direction of the induced potential difference and the induced current is reversed. 13.8.6 The generator effect also occurs if the magnetic field is stationary and the coil is moved. 13.8.7 The size of the induced potential difference increases when: –  the speed of the movement increases –  the strength of the magnetic field increases –  the number of turns on the coil increases –  the area of the coil is greater.

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H 13.8.1 To explain from a diagram how an a.c. generator works, including the purpose of the slip rings and brushes.

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13.9.1 To determine which type of transformer should be used for a particular application. 13.9.2 The basic structure of the transformer. 13.9.3 An alternating current in the primary coil produces a changing magnetic field in the iron core and hence in the secondary coil. This induces an alternating potential difference across the ends of the secondary coil. H 13.9.4 The potential difference (p.d.) across the primary and secondary coils of a transformer are related by the equation: p.d. across primary = number of turns on primary p.d. across secondary number of turns on secondary 13.9.5 In a step-up transformer the potential difference across the secondary coil is greater than the potential difference across the primary coil. 13.9.6 In a step-down transformer the potential difference across the secondary coil is less than the potential difference across the primary coil. 13.9.7 The uses of step-up and step-down transformers in the National Grid.

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P3.0

Forces and energy in space Overview This unit looks first at moments, centre of mass and stability, and then at the forces involved in circular motion. The latter is then applied to the Solar System, where gravity provides the centripetal force. The unit concludes by looking at how stars can produce energy for billions of years, and at the life cycle of stars.

Investigative Skills Assessment The ISA for Unit P3.0 is set in the context of moments. In the Student’s Book, data is presented to the students and then they are asked a number of questions about the investigation. The Copymaster File provides questions for students to answer based on their own investigation into centripetal force. Practical 1 in Topic P3.4 gives instructions for this investigation.

P3.0

Context page

Objectives for the unit

Notes on context

Students should know and understand:

The context for this unit is forces and energy in space.

• how to calculate the moment of a force • what the centre of mass of a body is, and how to

Learning activities

find the centre of mass for a thin sheet of material

• H the factors affecting the stability of an object • that circular motion involves a centripetal force,

and how to identify the centripetal force in various situations

• the factors affecting the size of the centripetal force • the factors affecting the size of a gravitational force • how the period and speed of an object in orbit

• AT The context for this unit is introduced via a video on the ActiveTeach.

• The AfL questions are intended to help students to

recall some of their Key Stage 3 work on forces and the Earth in space. Students’ answers could be used for formative assessment.

depend on its distance from the parent body

• different types of orbit for satellites and why they are used

• how the Sun and the planets were formed • the life cycles of stars • H that new elements are formed in stars.

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P3.1

Moments

Worksheets available No. P3.1a P3.1b

Title Moments 1 Moments 2

Type Classwork (reusable) Homework (reusable)

Objectives Students should be able to:

• recall that the turning effect of a force is called the moment

• use the equation: moment=force2perpendicular distance from the line of action of the force to the axis of rotation

• H explain why, if a body is not turning, the total

clockwise moment must be exactly balanced by the total anti-clockwise moment about any axis

• H calculate the size of a force, or its distance from

an axis of rotation, acting on a body that is balanced.

Key words moment, newton metre

Points to note

• Moments were covered in Key Stage 3, so much of this topic should be revision.

• Students will not be required to recall equations for

assessment purposes. Rearrangement of equations is Higher Tier only.

Lesson ideas Starter

• Use Practical 1 as a starter. Learning activities

• Follow up the starter by asking students to suggest applications of turning forces. They should be able to suggest things such as spanners, door handles, etc. Ask why a longer spanner is more useful for applying a large turning moment.

• Use Practical 2 to demonstrate that the moment of a force depends on the perpendicular distance to the axis of rotation.

• AT

H ActiveTeach provides an equation triangle that will help Higher-tier students to rearrange the moment equation.

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Higher 4 4

• H Practical 3 suggests that students make a

balance to find the weight of small or large objects. This will help to reinforce the idea that objects that are not turning have balanced moments, and will give students practice in calculating forces.

Plenary

• Ask students to write a set of three bullet points to summarise the lesson. Give them a few minutes to do this, and then ask for contributions to make a class summary.

Additional homework/research ideas

• Ask students to design a mobile. If necessary, show

them an example and sketch one. Ask them to produce a drawing that is approximately to scale, showing how each arm of the mobile would be balanced by the arms or objects suspended from it.

Practicals and demonstrations 1 Demonstrating turning forces Ask for a volunteer from the class, and ask them how many stacking masses they think they can hold in an outstretched hand. Allow them to test their prediction by asking them to hold out their hand and then gradually add small masses until the student can no longer keep their arm level. Then ask them to hold one end of a metre rule, and gradually add masses to the other end. See how many masses can be added before the student can no longer hold the ruler horizontal. Ask what would need to be done to allow more masses to be supported, and elicit the idea that the turning force depends on the number of masses applied and also on how far they are from the turning point (the student’s hand). 10 minutes Ensure that masses cannot fall on feet or break metre rule. Apparatus Metre rule; stacking masses. 2 Perpendicular distances Ask students to devise a way of demonstrating that the distance used in the moment equation must be perpendicular to the line of action of the force. This could be done by using a set-up such as that shown below and pulling on the forcemeter at different angles, noting the force needed to hold the metre rule balanced in each

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case and also measuring the distance between the forcemeter and pivot point, as shown. wooden block with G-clamp fastening it to the bench

nce

r dista

dicula

n perpe

bench

20 minutes

However, this will be more a challenging activity if students are challenged to use the apparatus to find the weight of something heavier than the weight of the masses available, or much lighter than the forcemeter smallest mass available. They can do this by putting the known masses and the unknown objects at different distances from the pivot, and calculating the weight of the unknown object from the weight weights hanging of the masses used and the distances from the pivot from metre rule when the ruler is balanced. Note that this method will ignore the mass of the metre rule itself, so you may wish to revisit it after students have studied the next topic. 30 minutes

Ensure that masses cannot fall on feet. Apparatus (per group) 2 metre rules; wooden block; G-clamp; forcemeter; stacking masses.

Ensure that masses cannot fall on feet. Apparatus (per group)

3 H Make a balance Challenge students to make a balance to find the weights of various objects. At its simplest, this could just be a metre rule balanced in the middle, with the object to be weighed on one side and known masses on the other (remind students that a mass of 100 g has an approximate weight of 1 N). At this level, the activity will reinforce the idea that objects that are not turning have balanced forces on them.

P3.2

Metre rule; triangular block to act as pivot; masses; unknown objects to weigh. Optional: card, sticky tape, etc. to make a ‘pan’ on which to put masses or objects to be weighed.

Centre of mass

Worksheets available No. P3.1a P3.1b

Title Balancing acts Centre of mass

Type Classwork (reusable) Homework (reusable)

Objectives Students should be able to:

• recall that the centre of mass of a symmetrical body is along the axis of symmetry

• describe how to find the centre of mass of a thin sheet of a material

• recall that the centre of mass of a body is that point

at which the mass of the body may be thought to be concentrated

• explain that, if suspended, a body will come to rest with its centre of mass directly below the point of suspension.

Key words centre of mass

Points to note

• The terms ‘centre of gravity’ and ‘centre of mass’ are

often used interchangeably. For most purposes, this

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Foundation 4 4

Higher 4 4

causes no problem, as the centre of gravity is only in a different place to the centre of mass for objects so large that the force of gravity varies from one part of it to another. If you were to try to find the centre of gravity of Ben Nevis, for example, it would be slightly below its centre of mass.

• Centre of mass and stability are looked at in more detail in Topic P3.3.

Lesson ideas Starter

• Make a cut-out shape from cardboard, such as the

parrot shown on Worksheet P3.2a, and ask a student to try to get it to balance on a finger. Add a lump of Plasticine to the tail, and show them that the object now balances. Ask for suggestions for why adding the Plasticine helps.

Learning activities

• Show students that you can balance a ruler on a

finger by putting your finger under the centre of the ruler. Repeat this with an object whose mass is not AQA GCSE Extension Units Teacher’s Guide

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symmetrical about its centre, such as a rounders or baseball bat. Ask students why you have to balance this with your finger/hand nearer to the wide end, and elicit the idea that there is more mass near that end of the bat.

• Practical 1 allows students to find the centre of mass of a sheet of card, and Practical 2 demonstrates ways of finding the centre of mass of other objects, illustrating the fact that a centre of mass could be at a point where there is no material. You could extend Practical 1 by asking students to find the centre of mass of symmetrical card shapes, and to confirm that the centre of mass lies on lines of symmetry.

• Practical 3 (and Worksheet P3.2a) show a number

of other ‘balancing tricks’ that rely on adjusting the position of the centre of mass of objects. If time is short, the worksheet can be used alone, and students just asked to explain why each object will balance.

• H You may wish to reinforce the learning from

Topic P3.1 by talking about a balanced object having equal turning forces in each direction about the centre of mass. You could also revisit Practical 3 in Topic P3.1 and ask students to repeat the calculations for any balances they made and used that did not have the pivot in the centre of the ruler, taking into account the centre of mass of the ruler.

Plenary

• Set up the apparatus below, and show students that

the funnels appear to move uphill. You may need to test this beforehand, to make sure you have the sticks at a suitable angle. Ask them to explain what is happening.

Additional homework/research ideas

• Ask students to sketch five different objects at home, and to indicate the centre of mass of each one.

Practicals and demonstrations 1 Centre of mass of a thin sheet Ask students to find the centre of mass of an irregular-shaped piece of card. You could provide them with the shapes, or students could cut out their own shapes, ensuring that they do not have any lines of symmetry. Possible shapes could be an approximate outline of mainland UK (or any other country), the outline of a footballer in action or an animal in an unsymmetrical position. Students could follow the method shown in the Student’s Book, or more able students may be able to work the method out for themselves before using the textbook if you discuss the fact that objects hang with their centre of mass below the point of suspension. 15 minutes Apparatus (per group) Card; scissors; plumb line (string and weight); cork mounted in a clamp stand; pin. 2 Centre of mass of objects Ask students to work out the approximate positions of the centres of mass for various objects. For example, use a cup or mug and hang it by the handle from a finger. The centre of mass must lie somewhere along the axis of symmetry that goes through the handle, and students should be able to see that a vertical line down from their finger would intersect the plane of symmetry somewhere in the hollow inside of the cup. A similar process can be used for other objects, although if using heavy items, such as chairs or stools, you may wish to demonstrate rather than risk students dropping them on their feet. 15 minutes Ensure heavy objects cannot drop on feet and that the objects have no sharp points. Apparatus (per group) Selection of objects of different shapes. Optional: plumb line.

• Alternatively, show students a metre rule balanced

on two fingers, with one finger at each end. Bring your hands together, and they will always meet in the middle of the ruler. Ask students to use ideas about centre of mass and moments to explain what is happening. The explanation is that if one hand gets closer to the centre than the other, there will be a higher proportion of the weight of the ruler resting on that finger and so the friction will increase and allow the other finger to get nearer to the centre.

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3 Balancing acts Worksheet P3.2a shows a number of different balancing ‘tricks’ that students can set up. In each case, ask them to explain why the objects will balance, although at first glance most look as if they will not. Students could also be encouraged to invent their own tricks. If time is available, students could invent their own animal shapes similar to the parrot and decorate them. Alternatively, you could give students items such as the potato, toothpick, beaker and forks from B on the worksheet, and challenge them to make it balance. In this case, the worksheet could be used as a source of possible solutions to the problems. © Pearson Education Limited 2007

10–30 minutes

A: Card; scissors; Plasticine or Blu-Tack.

C: String tied between 2 fixed objects; toy holding bent wire (see worksheet – you may be able to use figures from a Lego set, or make the toy out of thin wood or thick card); lumps of Plasticine.

B: Beaker; potato; 2 forks; toothpick.

D: Ruler; hammer; string or rubber band.

Apparatus (per group)

P3.3

Stability

Worksheets available No. P3.3a P3.3b

Title Aeroplane stability Centre of mass and stability

Objectives Students should be able to:

Type Classwork (reusable) Homework (reusable)

Foundation

Higher 4 4

Learning activities

• H Challenge students to balance a pencil vertically

• H recognise the factors that affect the stability of a

on the end of one finger. Some may be able to manage it for a few seconds if they move their hands to attempt to keep their finger beneath the centre of mass of the pencil. Ask students to explain what is happening in terms of centre of mass.

• H explain that if the line of action of the weight of

• H In this topic the stability of bodies is approached

•

H analyse the stability of bodies by considering their tendency to topple body

a body lies outside the base of the body, there will be a resultant moment and the body will tend to topple.

Key words H stable, unstable

Points to note

•

H The content of this whole topic is suitable for Higher-tier students only.

•

H Students are not required to recall the details of aircraft stability on the classwork sheet.

Lesson ideas Starter

• H Ask for a volunteer who wants to earn £5 (or

£1 if you only have coins available). Tell them they can have the money if they can pick it up without touching the floor with their hands or raising their heels from the floor. The only other condition is that they have to stand with their back to a wall with their heels against it. Place the coin about 10 cm in front of their toes. It is impossible to pick up an object in such a position without falling over (and therefore putting a hand on the floor). Ask students to try to explain why the money cannot be picked up – their explanations can be jotted down on scrap paper to be revisited later.

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by considering whether the centre of mass remains above part of the base. Stability can also be assessed by determining whether a movement of the body would raise or lower the position of the centre of mass. If the centre of mass is lowered when the body is displaced, the body is unstable. Raising the centre of mass takes work, so objects where this would happen are stable. You may wish to discuss this aspect of stability with some more able students.

• AT

H ActiveTeach provides an animation illustrating stability and toppling.

• H Worksheet P3.3a looks at the stability of aircraft

as an application of the ideas in this topic. Students will not be expected to recall this information.

Plenary

• H Ask students to modify their explanations for

the starter activity, if necessary, and then ask some students to read out their explanations.

Practicals and demonstrations None suggested.

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P3.4

Circular motion

Worksheets available No. P3.4a P3.4b P3.4c

Title Factors affecting centripetal force Centripetal forces Moving in circles

Type Practical (reusable) Classwork (card sort) Homework (reusable)

Objectives Students should be able to:

• identify which force(s) provide(s) the centripetal force in a given situation

• interpret data on bodies moving in circular paths • recall that when a body moves in a circle it

continuously accelerates towards the centre of the circle. This acceleration changes the direction of motion of the body, not its speed

• describe what centripetal force is and the direction in which it acts

• explain that the centripetal force needed to make

a body perform circular motion increases as the mass of the body increases, as the speed of the body increases and as the radius of the circle decreases.

Key words acceleration, centripetal force, velocity

Points to note

• The term ‘centrifugal force’ is often used, but

actually the force does not exist. What we feel as ‘centrifugal force’ are the effects of momentum. For example, if we are in a car moving around a sharp bend, momentum would tend to make us travel in a straight line. As the car is turning, we feel as if we are being pushed outwards. You may wish to discuss this with some students as a way of revising momentum.

Lesson ideas Starter

• Ask students to define velocity and acceleration,

and ask them to explain the factors that affect the acceleration of an object. This will allow you to assess how much they recall from work on forces and movement from earlier units.

Learning activities

• Practical 1 asks students to investigate the factors

that affect the size of the centripetal force required to keep an object moving in a circle. This practical can be used as the basis of the Investigative Skills Assessment.

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• Worksheet P3.4b provides a set of scenes showing

circular motion. Students can sort them into order of the size of the centripetal force involved. There may be some they have to guess at, but they should explain their reasoning for any they do put in order. Students can also be asked to suggest how the centripetal force is being provided in each situation.

• AT Students can then use the spreadsheet provided on the ActiveTeach to calculate the centripetal force in each case.

• AT The spreadsheet could also be used by students in place of the practical activity to produce enough data to plot graphs of mass, speed and radius against centripetal force, and so determine the relationship between the different factors and the force needed. Note that students are not expected to use or recall the equation for calculating centripetal force.

Plenary

• Ask students to finish off the sentence ‘Centripetal force …’ in as many different ways as they can.

Practicals and demonstrations 1 Factors affecting circular motion Instructions for an investigation are provided on Worksheet P3.4a. More able students can be encouraged to gather results for a range of values of each factor and to plot graphs to determine whether or not the relationships they find are linear. They should find that the centripetal force needed is proportional to the mass of the object, proportional to the velocity squared, and inversely proportional to the radius of the circle. 30–60 minutes, depending on depth of investigation Eye protection should be worn. Ensure sensible behaviour and allow enough space for swinging the bungs. It may be best to do this practical out of doors or in a hall, to allow for plenty of space between different groups. Apparatus (per group) Hollow tube about 30 cm long; 3 rubber bungs with holes; 1.5 m string; forcemeters; crocodile clip; stopwatch; metre rule; eye protection.

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P3.5

Gravity and the Solar System

Worksheets available No. P3.5a P3.5b

Title Orbits, speeds and times A new planetary system

Type Classwork (reusable) Homework (reusable)

Objectives Students should be able to:

• recall that the Earth, Sun, Moon and all other bodies attract each other with a force called gravity

• recall that the bigger the masses of the bodies, the

bigger the force of gravity between them, and that, as the distance between two bodies increases, the force of gravity between them decreases

• recall that the orbit of any planet is an ellipse

(slightly squashed circle), with the Sun at one focus

• explain that gravitational force provides the

centripetal force that allows planets to maintain their orbits

Foundation 4 4

Higher 4 4

Learning activities

• Show students how to draw ellipses using a loop of

string around two pins (the foci). More able students could be asked to find out what the terms ‘semi-major axis’, ‘semi-minor axis’ and ‘eccentricity’ mean, and what the values of these are for the orbit of the Earth or one of the other planets. Note that it is the semimajor axis that is normally quoted as the distance of a body from the Sun. Students will not be required to recall this information, but it should help them to understand what is meant by an ellipse, or by the ‘eccentric’ orbits of dwarf planets such as Pluto.

The ActiveTeach activities discussed below should be used before students work through the material in the Student’s Book.

• explain that the further away an orbiting body is, the • AT ActiveTeach provides an animation explaining longer it takes to make a complete orbit • explain that, to stay in orbit at a particular distance, smaller bodies, including planets, must move at a particular speed around larger bodies

• interpret data on planets moving in orbits that approximate to circular paths.

Key words elliptical, focus, gravity

Points to note

• The Solar System has been considered to have

nine planets since the discovery of Pluto in 1930. However, in 2006 Pluto was reclassified as a ‘dwarf planet’, as was Ceres and a body orbiting beyond Pluto informally known as Xena. At the time of writing, other Solar System bodies were being considered for inclusion in the category of dwarf planets.

Lesson ideas Starter

• Ask students to draw concept maps to show what

they recall about the Solar System from Key Stage 3 work or from Module P1. This will allow you to assess how much they recall from earlier work. Students could keep their maps and add to them as they work through the next few topics to form a record of what they have learnt.

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what an ellipse is, and also illustrates how the elliptical orbits of the planets are almost circular.

• AT

H The final part of the animation shows how the speed of a body changes during an elliptical orbit – students are not required to know about this, but it will be useful to show more able students how the assumption of a circular orbit is actually simplifying the situation.

• AT ActiveTeach provides a spreadsheet that allows

students to put in the masses of two objects and the distance between them, and to work out the gravitational force. This can be used before students work through the material in the book to illustrate that the force increases if either of the two masses increases, and to show that the force decreases with distance. It can also be used to calculate the weight of different masses on the Earth, the Moon or one of the inner planets, by entering the radius and the mass of the relevant body. This is a good place to reinforce the idea of centre of mass – when working out the weight of a 1 kg mass on the surface of the Earth, the distance needed is the distance between the centres of mass of the two bodies. Note that Foundation-tier students may need help understanding the scientific format in which the data about the planets is presented.

• AT

H More able students can use the spreadsheet to work out the force between two bodies at different distances and plot a graph of force against distance. Students are not required to recall that the force decreases with the square of the distance, but knowing this will help them to understand how the speed of an object in orbit changes with distance (see below). AQA GCSE Extension Units Teacher’s Guide

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• H You may wish to show more able students

Newton’s equation for gravitational attraction: Gm1m 2 F= r 2 , where m1 and m2 are the masses of the two objects, and r is the distance between them. This should help students to understand that the force of gravity depends on the masses of both bodies involved, and that the force decreases with the distance squared. Students will not be expected to recall these details.

• AT ActiveTeach provides a second spreadsheet that allows students to enter the distance of an orbiting body from the body around which it is orbiting. The spreadsheet returns its speed and period. There are also fields for the masses of the bodies to be entered, demonstrating that the orbital period or speed does not depend on the mass of the orbiting body.

Plenary

• Ask students to alter their concept maps to reflect what they have learnt during this topic.

• Alternatively, ask students to write a statement

about gravity or the Solar System that is wrong in some way. Ask students to read out their sentences, in turn, and ask the rest of the class what is wrong with each one.

Additional homework/research ideas

• Gravity also controls the orbits of moons around

• Worksheet P3.5a also allows students to work out

for themselves the approximate speed at which each planet moves around its orbit, if access to the ActiveTeach is not possible. More able students could be given just the top portion of the worksheet that contains the data, and asked to work out the speed and plot graphs to show the relationships

P3.6

between distance from the Sun, speed and orbital period. The questions on the worksheet provide more help for students.

other planets. Ask students to find out about the other planets in our Solar System that have moons, and suggest how the forces of gravity between these planets and their moons compare with the gravity between the Earth and the Moon, and between the Sun and the planets.

Practicals and demonstrations None suggested.

Changing ideas

Worksheets available No. P3.6a P3.6b

Title What are nebulae? HSW Reverseword

Type Classwork (reusable)

Foundation 4

Higher 4

Homework (reusable)

4

4

Objectives

Lesson ideas

Students should be able to:

Starter

•

HSW distinguish between models based on evidence and those based on non-scientific ideas

• HSW explain that hypotheses or scientific models

can be used to make predictions that can be tested

• HSW explain that, if the theories and models we

have available to us do not completely match our data or observations, then we need to check the validity of our observations or data, or amend the theories or models.

Key words model

Points to note

• The content of this topic illustrates the aspects of

How Science Works listed above. Students will not be required to recall details of changing ideas about the Solar System, or the material on Worksheet P3.6a.

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• Ask students to suggest how we know how the Solar

System is arranged and how the planets move. Collect ideas and note them down for discussion later.

Learning activities

• ICT

Either before or after using the Student’s Book, ask students to use the internet or reference books to find out more about Ptolemy, Copernicus, Galileo, Brahe, Kepler and Newton. Students could be asked to find out brief biographical details, but the main focus of their research should be on the evidence that each one gathered or used, how (or whether) evidence led them to adapt or change existing models of the Solar System, and whether any part of their model was based on non-scientific ideas (for example, Copernicus still considered that the planets must move in circles).

• Students could also be asked to find out more

about why ideas such as those of Copernicus were not accepted immediately, including the role of the Catholic Church. © Pearson Education Limited 2007

Additional homework/research ideas

• Worksheet P3.6a looks at a later controversy in

• Ask students to find out more about ways of

astronomy – a debate that took place in 1920 about the nature of nebulae and the size of the galaxy.

measuring distances to the stars. They could be asked to research the parallax method, or to find out more about Cepheid variables and why they are useful for distance measurements.

Plenary

• Ask students to write definitions of the following

words: observations, evidence, experiment, hypothesis, theory, model, prediction. If necessary, discuss the meanings with the class and how they apply to the material in this topic.

P3.7

Practicals and demonstrations None suggested.

Satellites

Worksheets available No. P3.7a P3.7b

Title Orbits and distances Satellites and orbits

Type Classwork (reusable) Homework (reusable)

Objectives Students should be able to:

• interpret data on satellites moving in orbits that approximate to circular paths

• recall that, the further away an orbiting body is, the longer it takes to make a complete orbit

• explain that, to stay in orbit at a particular distance smaller bodies, including satellites, must move at a particular speed around larger bodies

• recall that communications satellites are usually put

into a geostationary orbit above the equator and monitoring satellites are usually put into a low polar orbit.

Key words communications satellite, geostationary orbit, monitoring satellite, polar orbit, satellite

Points to note

• ICT Geostationary orbits are sometimes referred

to as geosynchronous or just synchronous orbits. Students may come across these terms if looking for information on the internet.

• Monitoring satellites usually follow a Sun

synchronous orbit, which is an almost polar orbit whose altitude is chosen so that the satellite will always fly over a particular location at the same local time, so the Sun angle is always the same.

Lesson ideas Starter

Foundation 4 4

Higher 4 4

list, or ask students to jot their ideas down on scrap paper for use later.

Learning activities

• AT ActiveTeach provides an animation showing

different types of orbits, illustrating their periods and coverage of the surface of the Earth.

• Help students to draw a scale diagram of Earth, the

orbit of a satellite in low Earth orbit, and the orbit of a geostationary satellite (or part of its orbit, at least). Worksheet P3.7a provides the necessary data and instructions.

• ICT The NASA website provides a Java applet that

shows the orbits of various satellites. For more information see www.longman.co.uk/AQAScience. The view shows real-time positions or can be speeded up to show the satellites moving. Particular satellites can be selected and tracked, and data obtained about them, including their ground track. Students could be asked to find (for example) what the orbits of GPS satellites are like, the names of some satellites in geostationary orbits and what they are used for, the names and uses of some satellites in polar orbits, etc.

• ICT Students could look into the uses of satellites,

for example by using Google Earth to look at satellite mapping imagery. Alternatively, the NASA Earth Observatory has a huge collection of satellite imagery that students may be interested to look at, including the ability to create animations showing how things such as snow cover change throughout the year. For more information see www.longman. co.uk/AQAScience. Encourage students to relate the data to the sensors needed on satellites to gather the data, and to the type of orbit the satellites would have needed to be in.

• Ask students to give as many different uses for

satellites as they can. Collect ideas to make a class

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Additional homework/research ideas

• AT ActiveTeach provides a selection of images for

• ICT Ask students to find out about the kind

use if access to the internet is difficult.

of equipment needed on satellites. For more information see www.longman.co.uk/AQAScience.

Plenary

• Revisit the list that students made for the starter

Practicals and demonstrations

activity, and ask them to expand the list of uses if necessary. Ask them to note what kind of orbit each satellite has.

P3.8

None suggested.

Stars and planets

Worksheets available No. P3.8a P3.8b

Title Solar System story Space true or false?

Type Classwork (card sort) Homework (reusable)

Objectives Students should be able to:

• explain how stars are able to maintain their energy output for millions of years

• describe how stars form when enough dust and

gas from space is pulled together by gravitational attraction, and how smaller masses may also form and be attracted by a larger mass to become planets

• recall that gravitational forces balance radiation pressure to make a star stable.

Key words fuse, nebular hypothesis, nuclear fusion reactions, nucleus, radiation pressure, star

Lesson ideas Starter

• Ask students to give three reasons why the Sun is

important. Possible answers include providing light to enable us to see, providing heat, and providing light for photosynthesis, without which we would not have any food.

Learning activities

Foundation 4 4

Higher 4 4

• AT ActiveTeach provides an animation showing the nebular hypothesis of how the Solar System formed.

• ICT Worksheet P3.8a provides a set of cards

showing diagrams and explanations of various stages in the formation of the Solar System for students to match up and put into order. More able students can be given only the diagrams and asked to write the accompanying descriptions themselves. Students could also use the drawings (or coloured images from the internet) to make posters illustrating how the Solar System was formed.

Plenary

• Ask students to finish off the sentence ‘The Sun …’ in as many different ways as they can. Give them a few minutes to think of some sentences, then go round the class asking for examples.

Additional homework/research ideas

• Ask students to find out how many planets have

been discovered around other stars, what these planets are like, and some information about how they were detected (they cannot be seen directly through telescopes).

Practicals and demonstrations None suggested.

• ICT An animation illustrating the formation of the

Solar System can be downloaded from the internet. For more information see www.longman.co.uk/ AQAScience.

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P3.9

Life cycles of stars

Worksheets available No. P3.9a P3.9b

Title Eyewitness account A sunny story

Objectives Students should be able to:

• recall that our Sun is one of the many billions of

stars in the Milky Way galaxy and that the Universe is made up of billions of galaxies

• describe the life cycles of stars of similar size to the Sun and stars much larger than the Sun

• H explain that fusion processes in stars produce

all naturally occurring elements. These elements may be distributed throughout the Universe by the explosion of a star (supernova) at the end of its life

• H explain why the early Universe contained only hydrogen but now contains a large variety of different elements.

Key words black hole, galaxy, life cycle, neutron star, planetary nebula, red giant, supernova, Universe, white dwarf

Points to note

• The term ‘life cycle’ as used for stars does not imply

reproduction/rebirth in the same way that this word does when used for living things. It might be worth emphasising this point to students.

Lesson ideas Starter

• Put a set of initial letters on the board for the key words from the last topic (or from earlier topics in the module as well, if you wish). Ask students to suggest what the words might be, and to give meanings for them.

Learning activities

• AT ActiveTeach provides an animation illustrating the life cycles of stars of different masses.

•

ICT Worksheet P3.9a asks students to imagine they have a time machine, and asks them to write an ‘eyewitness’ account of the life of the Sun and of a star more massive than the Sun. Some illustrations are included for students to use in their accounts

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Type Classwork (reusable) Homework (reusable)

Foundation 4 4

Higher 4 4

if they wish, or they could find images from the internet. The ‘life stories’ could be made into posters, or students could use the information provided to make PowerPoint presentations to tell the life story of the Sun.

• ICT Students could also be asked to find images

from the internet to illustrate their ‘life story’ posters or presentations. Key words to use in searches include ‘protosun’, ‘Solar System formation’, ‘planetesimal’ and ‘moon formation’.

• Discuss how astronomers know about the life

cycles of stars, as this is something they cannot experiment on directly, and the timescales are far too long actually to observe a star through its life cycle. Information is gathered about many different stars, and astronomers look for links between the brightness and composition of stars, together with other information they can use to deduce what happens as the star ages. This is backed up with theoretical calculations about the nuclear reactions going on inside the star.

Plenary

• Ask students to work in groups to decide on a set

of key facts – for example, three key facts about the current topic, or ten key facts about the unit as a whole. If time permits, students could then share their ideas and produce an agreed class list of key facts.

Additional homework/research ideas

• Ask students to find out how massive (compared

with the Sun) a star has to be for it to become a red supergiant rather than a red giant, and how massive it has to be to end up as a black hole. (Stars of above about eight stellar masses become red supergiants, if what is left after the supernova explosion is greater than around two stellar masses, it is likely to become a black hole.)

Practicals and demonstrations None suggested.

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P3.0

Answers

P3.0 Forces and energy in space Student’s Book 1 Concept maps should include types of force, and how forces can affect the movement of objects. 2 Bullet points should include the names of the planets and what they are made of, the Sun as a light source, a description of what a moon is, and details of days/nights/years. A very good answer would also describe solar and lunar eclipses. 3 It provides the energy needed to keep the Earth warm enough for life, and the light needed for photosynthesis, without which we would not have any food.

P3.1 Moments Student’s Book 1 If you push close to the hinges, the perpendicular distance between the force from your hand and the hinge is small, so the moment is small. 2 The force you apply is further from the pivot so the moment is bigger. 3 Moment=20 N×0.5 m=10 Nm. 4 At the ends of the handles/bars, so the distance between force and pivot will be as big as possible, to make the moment as big as possible. 5 Moment from load=100 N×0.2 m=20 Nm 20 Nm Force on handle= =20 N 1.0 m 6 Ben’s moment is 600 Nm. Jill’s distance needs to be 600 Nm/300 N=2 m. 7 a With a longer spanner, the force can be applied further from the pivot, so the moment is bigger. b Pick a place for one person to sit, and work out their moment by multiplying their weight (in N) by their distance from the pivot (in m). Divide this by the weight of the second person to find out how far they should sit from the pivot. Accept any similar explanation.

Worksheet P3.1a 1 The tube effectively extends the spanner, so the force he/she applies will be at a greater distance from the nut, so the moment for a given force will be greater. 2 a 86 cm – it is the perpendicular distance between the force and the hinge.

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e It will be the same. The perpendicular distance between the line of the force and the hinge will be less when the door is further up, but the distance between the line of action of the weight and the hinge will be reduced in similar proportion. 3 Clockwise moment from Holly’s weight is 1.5 m×200 N=300 Nm. Dad must be applying a 300 Nm moment if she is stationary. Force= moment =300 Nm=120 N. 2.5 m distance 4 a The moment would be greater for a given force (or a smaller force would be needed for the same moment, because the distance would be greater). b The arms would be too long, or similar answer.

Worksheet P3.1b 1 a Moment – Nm; force – N; distance – m. b The distance between force and pivot, at right angles to the line of action of the force. Students should include a diagram in their answer. 2 a 500 N×0.5 m=250 Nm. b 750 Nm. c 0.8 m×800 N=640 Nm. 3 a 50 N×2 m=100 Nm. b The weight of B and C, and their distances from the pivot. c The anti-clockwise moment from B (and part of C) almost balances the clockwise moment due to the weight of the bridge and the part of arm C above it, so that only a little additional force on the left-hand side is enough to unbalance it in the other direction, so the bridge will rise. d Less force will be needed, because the moment due to B (and the left-hand part of C) will be larger. 4 a Force marked along the direction of the rope. b Pivot marked at the bottom of the vertical post. c Distance marked from pivot, perpendicular to the line of the force.

P3.2 Centre of mass Student’s Book

b 150 N × 0.86 m=129 Nm.

1 The point at which we can think of all the mass of an object being concentrated.

c They are equal and in opposite directions.

2 a Point marked in centre of square.

d Force=moment/distance=129 Nm/0.43 m= 300 N.

b The centre is where the lines of symmetry cross, and there is the same mass either side of each line of symmetry. Accept any equivalent explanation.

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Answers

3 a Suspend the object from any point on it, and use a plumb line to mark the line of the vertical. Suspend the object from a different point, and mark the vertical again. The centre of mass is where the two lines cross. b A suspended object will hang with its centre of mass below the point of suspension, so the centre of mass must be somewhere on each of the vertical lines drawn.

3 b

centre of mass c

4 A hexagon is a regular shape, so its centre of mass can be found by drawing lines of symmetry to find the centre of the shape. centre of mass

5 a Point marked in centre of plate. b Point marked in centre of doughnut (i.e. in the hole in the middle). c

d



centre of mass centre of mass 6 The shopping has been put in with all the heavy things to one end. The centre of mass is towards one end of the basket. It hangs with the centre of mass below the handle, which it is why it is hanging at an angle.



Worksheet P3.2a

Student’s Book

In all cases the centre of mass of the balancing object is below the point of suspension.

Worksheet P3.2b 1 a Centre of the circle. b Centre of the shape. c Centre of the cross bar of the H. d Centre of the square. In all cases, the centre of mass is where lines of symmetry cross. 2 a

P3.3 Stability 1 The base of the pencil is very narrow when it is standing on end, so the pencil does not have to be tilted very far before the line of action of the weight passes outside the base. 2 With a wider base, the object has to be tilted further before the line of action of the weight passes outside the base, so it is harder to tip over. 3 The centre of mass is to the left of the point where the stone is supported, and the mass of the people is not enough to move the centre of mass to the right of the support. 4 a An unstable bus could topple over when going round a corner and injure people. b On the bottom deck, as this will keep the centre of mass as low as possible. 5 a A, D or F b C or E

b It will hang with the centre of mass below the suspension point.

c Glasses A, D and F are more stable because their centres of mass are low compared to their bases. Glasses C and E have high centres of mass compared to their bases. 6 A full glass will be less stable than an empty glass, because the mass of the liquid will make the overall centre of mass higher.

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P3.0

Answers

7 Answers depend on the objects students suggest. Explanations should involve wide bases and/or low centres of mass, as both these features mean that the object has to be tilted a long way before the line of action of the weight passes outside the base.

Worksheet P3.3a

control surfaces. This kind of system can prevent stalling (when the aircraft loses lift) or other manoeuvres that may be dangerous. For military aircraft, the system can also supply continuous corrections to maintain the flight conditions without bothering the pilot, so the airframe can be designed to be unstable (and hence more manoeuvrable).

1 The force on the fin would produce a moment about the centre of mass, and turn the aircraft back to face in the original direction.

Examples of fly-by-wire aircraft include many of the Airbus passenger aircraft, and most recent military fighters.

2 It is further from the centre of mass, and therefore produces a bigger moment for a given force.

Worksheet P3.3b

3 You can think of the aeroplane as being ‘suspended’ by the upwards force from the wings. When it is flying level, the anti-clockwise moment from the weight is balanced by the clockwise moment from the down force on the tailplane.

1 a Sketch of Bunsen burner.

If the front of the aeroplane pitches up, there is less down force on the tailplane, so the clockwise moment is no longer enough to balance the anti-clockwise moment from the weight, and the aircraft returns to its original position. Note that:

• clockwise and anti-clockwise refer to the diagram as given on the worksheet

• the situation is actually more complicated than

this, as pitching up will also change the amount of lift from the wing, and move the centre of pressure.

4 It is further from the centre of mass, and therefore produces a bigger moment for a given force (or a bigger reduction in moment for a given reduction in force). 5 If the nose pitches down (which means the tail will go up), the downwards force from the tailplane will increase, producing a moment that will pull the tail down again. Suitable diagram. 6 A stable aircraft is harder to turn or manoeuvre than an unstable one. This is an advantage for passenger aircraft, where steady level flight is the norm. However, a fighter aircraft needs to be able to turn quickly, so inherent stability is not an advantage. 7 ‘Fly-by-wire’ aircraft use computers to control the aircraft. The pilot uses a stick (as in normal aircraft) to signal to the computer the need to climb/ dive/turn, etc., but the computer converts these commands into electronic signals sent to the

b If it got knocked over while lit, it could start a fire/be dangerous. c The base is wide, which increases stability. The base is also the heaviest part of the burner, so its centre of mass is low. 2 If the top drawer is filled and the bottom drawers are empty, the centre of mass of the cabinet will be very high. The centre of gravity will move when the drawer is opened and may not stay above the base, so the cabinet may tip over. Even if all the drawers were filled properly, having (say) the two top drawers open at once could move the centre of mass beyond the base of the cabinet. 3 Adults can sit still on a chair, so the line of action of their weight will normally stay within the base of the chair or stool. Babies do not usually sit very still, and often rock themselves or move around. If a high chair did not have a base wider than the seat, it might be possible for a baby to tip the chair over and hurt themselves. 4 a Tom’s centre of mass will be in his body somewhere. Dick’s centre of gravity will be below the level of the wire. b Dick – as he (and the weights) are effectively suspended from the wire (because the centre of mass is below the wire) rather than being balanced on top of it. Tom has a high centre of mass inflatable toy above a very narrow base, and so is unstable. 5 The centre of mass is very low because of the water in the base. Tilting the toy will result in the line of action of the weight not being above the point of contact with the floor, and the resulting moment will return the toy to the upright position.

point of contact

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P3.0

Answers

P3.4 Circular motion

3 a The man, because he has a bigger mass.

Student’s Book

b The car doing the catching up, because it is moving faster.

1 A force that makes things move in a circle. It acts towards the centre of a circle.

c The one going round the sharp bend, because the radius is smaller.

2 Yes. They are accelerating because they are changing direction.

d The ones on the faster roundabout.

3 Force in the cables/ropes. 4 a It would be greater. b It would be less. c It would be greater as the mass would be greater. 5 The lorry, because it has the bigger mass. 6 a The greater the mass, the greater the centripetal force needed. The greater the speed, the greater the centripetal force needed. The greater the radius, the less the centripetal force needed. b Any three examples, such as: road vehicle, friction from tyres; aeroplane, force from the wings; fairground ride, force in the structure of the ride.

Worksheet P3.4b The centripetal forces on each object are: Card A B C D E F G H I J K L M N

Force (N) 220 000 180 000 720 000 360 000 1920 960 4320 2160 2600 520 4680 12 000 2400 21 600

Worksheet P3.4c 1 a It is changing direction. b Friction between the tyres and the road. 2 a Friction between the snow and the skis. b Force from the track. c Force in the structure of the roundabout.

© Pearson Education Limited 2007

e You can’t say without further information. The one sitting near the middle has a smaller radius of turning circle, but the one on the outside is moving faster. It depends on the exact speeds and distances available. The children may also have different masses. 4 If the track is banked, the reaction force from the track will be pointing partly towards the centre of the turning circle, and so will contribute to the centripetal force. This means that cars can go round the corners faster without exceeding the amount of friction needed from their tyres to provide the centripetal force. 5 The article should mention that the force required to turn a car depends on the sharpness of a turn and the speed; so if the turn is sharper, the speed needs to be reduced. It should also point out that this force comes from friction between the tyres and the road, which will be less if there is water on the road, and so a slower speed will help to ensure that the friction limit is not exceeded.

P3.5 Gravity and the Solar System Student’s Book 1 a An ellipse. b Because the orbit is almost circular. 2 Gravity. 3 Between the Earth and the Sun, because the Earth has a bigger mass than the Moon. 4 a Neptune. b The further the planet from the Sun, the longer the year. 5 a 200 years or more. b 7 years (accept any answer between about 3 years and 10 years). (The actual orbital periods are 248 years for Pluto and 4.6 years for Ceres. Note that both of these bodies have much more elliptical orbits than most of the planets.) 6 a Mars and the Earth have different masses, and they are also different distances from the Sun. b Mars moves more slowly than Earth, and takes longer to complete one orbit, because the orbit of Mars is further from the Sun. AQA GCSE Extension Units Teacher’s Guide

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Answers

Worksheet P3.5a 1 to 3 Planet

Mercury Venus Earth Mars Jupiter Saturn Uranus Neptune 

Distance from Sun (km)

Length Distance (km) of year (Earth days)

Time (h)

57 900 000 108 200 000 149 600 000 227 900 000 778 300 000 1 427 000 000  870 000 000 2 4 497 000 000

88 363 796 429 225 679 840 650 365 939 964 522 687 1431 937 932 4332 4 890 203 125 10 760 8 966 105 433 30 685 18 032 741 832 60 190 28 255 484 326

2112 5400 8760 16 488 103 968 258 240 736 440 1 444 560

Speed (km/h)

72 252 1 25 896 1 107 302 86 847 47 036 34 720 24 486 19 560

4 Suitable graph. Give marks for drawing suitable scales, labelling the axes, plotting points correctly and joining them with a smooth curve.

Worksheet P3.5b

4 He saw moons around Jupiter, which demonstrated that not everything revolved around the Earth (as was then thought). 5 a He said the orbits of the planets were ellipses, not circles. b It made the model match actual observations. c It provided lots of data that he could use to work out and to test his model against. 6 It continues to match observations of the movements of the planets. Since Newton’s work, we also have an explanation of why the planets move in the way they do. 7 a Ptolemy’s, Copernicus’ or Kepler’s models were all based on evidence, although with varying degrees of accuracy. b The Church’s idea that the Earth was in the centre of the Universe.

1 a Time for one orbit (Earth days) 200 790 2230 6310 50 500

c Copernicus’ change to Ptolemy’s model, or Kepler’s change to Copernicus’ model.

b The closer the planet is to the star, the faster it goes, and the shorter the time it takes for one orbit (or vice versa).

2 a The band of light we can see across the sky, which can be explained if we are part of a disc. When we look ‘along’ the disc, we see the band of concentrated stars; when we look ‘out of’ the disc, there are fewer stars.

Planet

Alzog 1 Alzog 2 Alzog 3 Alzog 4 Alzog 5

Distance from Alzog (million km) 100 250 500 1000 4000

Speed of planet (m/s)

36 440 23 047 16 296 11 523 5762

2 Gravity. 3 a W. It is the furthest from its planet.

Worksheet P3.6a 1 We see stars as points of light; we can see fuzzy patches called nebulae; some nebulae are collections of stars; we can see a band of light across the sky, which we can see is made of a concentrated area of stars; Cepheid variables vary in brightness.

b X and Z. They are the closest to their planets.

b We need a telescope to see that the band of light is actually caused by millions of stars.

c Z. It is close to its planet, and it is bigger than X so will have more mass.

3 Other galaxies like our own; smaller clusters of stars; gas clouds.

P3.6 Changing ideas Student’s Book 1 We can see them apparently moving. 2 a The Earth was in the centre, with the planets and the Sun moving around it. b The positions of the planets on future dates could be predicted. c No. Epicycles were added to try to make Ptolemy’s model a better match for observations, but the revised model was still inaccurate.

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3 Copernicus. His idea was based on trying to make the model match actual observations. The Church’s idea was based on what was written in their scriptures.

AQA GCSE Extension Units Teacher’s Guide

4 a Curtis. 30 000 light years was the size he suggested for our galaxy, and he suggested that some nebulae were beyond our galaxy, so some would be found to be more than 30 000 light years away. b Shapley. He suggested that the whole Universe was 300 000 light years across, and so any objects within it must be less than 300 000 light years away. 5 a The current estimate is about 100 000 light years in diameter, and 1000 light years thick. b It is a spiral galaxy (similar to the photo on page 144 in the Student’s Book). The Sun is in one of the spiral arms. © Pearson Education Limited 2007

P3.0

Answers

6 Shapley was partly right because he said the Sun was not in the centre of the galaxy. Curtis was partly right because he said that some of the nebulae were beyond our galaxy.

Worksheet P3.6b

b If the orbit is not tilted, the satellite stays above the same point on the Earth all the time. 2 Echostar 10 and Insat 4A 1440 minutes is 24 hours. 3 About 98 minutes, as it is at approximately the same altitude as IKONOS, which takes 98 minutes.

ny sensible clues for the words given. The clues A should be related to the content of this unit.

4 More time; it is higher.

P3.7 Satellites

b Monitoring, because it can cover all the Earth over a series of orbits.

Student’s Book

6 a Echostar 10 and Insat 4A.

1 a It takes 24 hours to complete one orbit, so it stays over the same point on the Earth (as long as its orbit is not tilted). b Geostationary orbit. c Satellite dishes, etc. will always point to the satellite once set up properly (or similar answer). 2 a Less time. b The one in the lower orbit. 3 a You can get more detail in photos without needing zoom lenses (or similar answer). b So it can cover all places on the Earth over a series of orbits. 4 a It can continuously monitor the same part of the Earth. b It could monitor weather over all parts of the Earth (although the records would not be continuous).

5 a IKONOS, Iridium 12 and SSETI Express.

b Broadcasting TV programmes or other communications tasks.

P3.8 Stars and planets Student’s Book 1 About 4.5 billion years ago. 2 Nuclear fusion reactions. 3 It will run out of hydrogen for fusion. 4 a Radiation pressure. b Gravity. 5 a Gas and dust was pulled together into a disc when the Sun was formed, and the dust gradually clumped together into bigger and bigger lumps until planets were formed. b Because it cannot be tested, so it cannot be called a theory.

5 a A polar orbit, so it can overfly the poles to take pictures.

6 Fact sheets / web pages should include all the key points given in the answer to question 5.

b A geostationary orbit, so satellite dishes will always be pointing at it.

Worksheet P3.8a

c Either answer is acceptable as long as it is explained. A geostationary orbit, so continuous pictures can be taken, or a polar orbit, if the country is not near the equator or if better pictures can be obtained from a lower orbit.

C–J

Worksheet P3.7a

B – O, I

1 To get them from the orbit of the shuttle to higher orbits. (Some also have thrusters to allow them to adjust their orbit or maintain their position in orbit.)

Worksheet P3.8b

2 Geostationary, because it has to be positioned furthest from Earth. 3 The geostationary satellite, because it is further away.

Worksheet P3.7b 1 a An orbit where the satellite takes 24 hours to complete one orbit.

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E–L A–K D – G, P, N, M F–H

1 True. 2 False. The force of gravity between two bodies gets bigger if one of the masses gets bigger. 3 False. The force of gravity between two masses decreases as the distance between them increases. 4 False. Gravity provides the centripetal force that keeps planets orbiting around the Sun (or that keeps moons orbiting around planets. 5 True. 6 False. The Sun is at one focus of the Earth’s orbit.

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7 True.

Worksheet P3.9b

8 False. The force of gravity between Jupiter and the Sun is smaller than the force of gravity between the Earth and the Sun.

1 B, as the Sun is expected to end its life cycle as a white dwarf.

9 True. 10 False. Jupiter moves slower in its orbit than the Earth, because it is further from the Sun. 11 False. Mars has a longer year than Earth because it is further from the Sun than the Earth.

b It would be more massive. 3 a Star in both charts. (Some hydrogen is still being converted in the red giant phases, but students are not expected to know this.) b Red supergiant and red giant (both charts).

12 False. A satellite in a geostationary orbit is above the equator.

c Neutron star (chart A).

13 True.

d Star stage in both charts.

14 False. Stars shine because nuclear fusion reactions inside them release lots of energy.

e Planetary nebula (chart B).

15 True.

g Protostar stage in both charts.

16 False. The planets formed when a cloud of dust and gas clumped together.

h Red supergiant in chart A.

P3.9 Life cycles of stars

4 In biology, ‘life cycle’ refers to a continuous cycle of birth to death that also includes reproduction. For stars, there is no reproduction involved.

Student’s Book

f Red supergiant and red giant stages in both charts.

i Supernova in chart A.

b Milky Way.

P3.0 Investigative Skills Assessment (Student’s Book)

2 a A star that has swelled up after using up most of its hydrogen fuel.

1 a Type of wall. (1 mark)

1 a A collection of stars.

b A cloud of dust and gas thrown off by a red giant.

b Categoric. (1 mark)

c What is left after a red giant has thrown off a planetary nebula.

d The weight at which the shelf failed. (1 mark) e Continuous. (1 mark)

3 A red supergiant exploding.

f Bar chart. (1 mark)

4 It does not have enough mass.

2 a No. (1 mark)

5 a Helium and all the elements up to oxygen in the Periodic Table.

b The results are all very similar. (1 mark)

c The distance of the weight from the wall. (1 mark)

b In larger stars or in supernova explosions.

3 It is the moment at the fixing that causes the fixing to fail (1 mark)

6 a and b Flow charts similar to Diagram D in the Student’s Book.

and the moment is greatest when the weight is furthest from the wall (1 mark)

7 Hydrogen was present at the beginning of the Universe. Elements up to oxygen could have been formed in Sun-sized stars or bigger ones. Elements up to iron could have been formed in bigger stars, and elements heavier than iron would have been formed in supernova explosions.

and so they are testing the worst case. (1 mark)

Worksheet P3.9a 1 Eyewitness accounts should include the basic facts about the life cycle of the Sun. 2 Students should explain the differences in the life cycle of a star the size of the Sun and a bigger star, including the formation of a red supergiant, a supernova explosion, and the formation of a neutron star or black hole.

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2 a A.

AQA GCSE Extension Units Teacher’s Guide

4 Ask another team to test the same shelves. (1 mark) 5 a Kilograms are a unit of mass, not of weight (or equivalent answer). (1 mark) b A kilogram has a weight of 10 N on Earth, so the management are effectively giving the same information, and most people are not used to using newtons as a unit of weight. (2 marks) Quality of written communication. (1 mark)

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P3.0

Answers

P3.0 Investigative Skills Assessment (Copymaster File) Section 1 1 Clear statement of question to be investigated. (2 marks)

Section 2 11 a Type of wall. (1 mark) b Categoric (1 mark) c The distance of the weight from the wall. (1 mark) d The weight at which the shelf failed. (1 mark)

2 a Correct dependent variable, e.g. mass, radius of circle. (1 mark)

e Continuous. (1 mark)

b Correct dependent variable, e.g. force. (1 mark)

12 a No. (1 mark)

3 Correct classification of independent variable. (1 mark)

b The results are all very similar. (1 mark)

4 Explanation of how range was chosen, e.g. did a trial run to see what lengths of string were practical. (1 mark) 5 a Forcemeter or stopclock/stopwatch named. (1 mark) b Correct variable named (e.g. force or time). (1 mark) 6 Either: any anomalous results circled, or: correct statement that no results looked anomalous. (1 mark) 7 Conclusion consistent with student’s own results. (2 marks)

f Bar chart. (1 mark)

13 It is the moment at the fixing that causes the fixing to fail (1 mark) and the moment is greatest when the weight is furthest from the wall (1 mark) and so they are testing the worst case. (1 mark) 14 Ask another team to test the same shelves. (1 mark) 15 a Kilograms are a unit of mass, not of weight (or equivalent answer). (1 mark) b A kilogram has a weight of 10 N on Earth, so the management are effectively giving the same information, and most people are not used to using newtons as a unit of weight. (2 marks) Quality of written communication (1 mark)

8 Either: yes, with a valid reason, such as having repeated results, or having compared results with other groups, or: no, with explanation that repeating results or comparing results would improve reliability. (1 mark) 9 Suitable table of results with all relevant data included, (1 mark) columns and rows correctly labelled, (1 mark) units present and correct. (1 mark) 10 Correct choice of bar chart or graph, (1 mark) suitable scales chosen and labelled, (1 mark) correct plotting. (1 mark)

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P3.00

Investigating space Overview This unit covers aspects of optics, including plane and curved mirrors, refraction, and converging and diverging lenses. Students learn how to construct ray diagrams to show the formation of images. The unit goes on to look at how sounds can be described, and at how ultrasound is used in medicine and industry. The final section of the unit looks at the motor effect and electromagnetic induction, including transformers.

Investigative Skills Assessment The ISA for Unit P3.00 is investigating the effect of tension in a string on the wavelength of the sounds produced by the string. In the Student’s Book, data is presented to the students and then they are asked a number of questions about the investigation. The Copymaster File provides questions for students to answer based on their own investigation into factors affecting the size of an induced potential difference (suggested in Topic P3.18).

B3.00

Context page

Objectives for the unit

Notes on context

Students should know and understand:

The context for this unit is using light to explore space. This is extended to look at how sound waves are used to investigate things that cannot be seen, and linked to motors and generators that are needed to provide electricity to control scientific equipment.

• how light is reflected and refracted by plane and curved mirrors and by lenses

• how to construct ray diagrams to show image formation by mirrors and lenses

• how to calculate the magnification of an image • that sounds can be described in terms of frequency, amplitude and waveform, and how to interpret oscilloscope traces

•

how ultrasound can be used in medical imaging, cleaning and manufacturing quality control

• H how to determine the distances between

interfaces in various media from oscilloscope traces

• how the motor effect is used in electrical devices • the factors affecting electromagnetic induction • H how induction is used to generate electricity • how transformers work and why they are used.

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Learning activities

• AT The context for this unit is introduced via a video on the ActiveTeach.

• The AfL questions are intended to find out how

much students recall of work on light, sound and electromagnetism from Key Stage 3 work. Note that the last question is not intended to elicit details of how series and parallel circuits work, although there is no harm in students doing this as well if you have sufficient time.

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P3.10

Plane mirrors

Worksheets available No. P3.10a P3.10b

Title Ray diagrams Images and plane mirrors

Type Classwork (write-on) Homework (write-on)

Objectives

Foundation 4 4

Higher 4 4

Students should be able to:

Key Stage 3, but it is worth repeating, emphasising the need for accuracy when marking the rays and measuring angles.

• recall that the normal is a construction line

• HSW Even the most careful students will have

perpendicular to the reflecting/refracting surface at the point of incidence

• recall that the angle of incidence is equal to the angle of reflection

• explain that the nature of an image is defined by its size relative to the object, whether it is upright or inverted relative to the object and whether it is real or virtual

inaccuracies in their measurements of angles. You could use the opportunity to discuss the source of the errors, and whether they are random or systematic errors. You could also ask students to explain why they were asked to make several measurements at different angles.

• Practicals 2 and 3 allow students to discover some of the properties of images in plane mirrors.

• describe the nature of the image produced by a

• Help students to remember what a virtual image is

• construct ray diagrams to show the formation of

• Worksheet P3.10a gives students practice in

plane mirror

images by plane mirrors.

Key words angle of incidence, angle of reflection, image, normal, object, plane, ray diagram, real image, upright, virtual image

Points to note

• The law of reflection and some of the properties of images in mirrors were covered in Key Stage 3.

Lesson ideas Starter

• Ask students to draw a diagram showing how they

can read a book in a room lit only by a reading lamp. Students should show light radiating in straight lines from the lamp, reflecting from the book and entering the eyes. This should allow you to detect any misconceptions about the propagation of light and how we see. Follow this up by reminding students that we see all non-luminous objects by reflected light, but mirrors and other shiny surfaces reflect light evenly and allow us to see images.

Learning activities

•

Practical 1 asks students to plot incident and reflected rays for a plane mirror. Students are likely to have carried out a practical activity such as this in

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by relating it to ‘virtual reality’, which is a reality that is not physically there. drawing accurate ray diagrams. Students will need a protractor to help them to draw the angles correctly.

Plenary

• Give students a list of some of the key words in

this topic, and tell them that these are the answers to questions. Ask them to suggest one or more questions that would lead to the ‘answers’ given.

Practicals and demonstrations 1 Angles of incidence and reflection Remind students (if necessary) how to set up a ray box and mirror to investigate the relationship between the angles of incidence and reflection. Explain that such angles are always measured from the normal, and emphasise the need for accuracy in plotting the rays and measuring the angles. Students should draw a line along the back of the mirror, so they can replace it in the same place if it gets moved (if the silvering is on the rear surface, this line will represent the plane at which the light rays are reflected). Use of a collimating lens in the ray box will allow a narrower beam and help students to mark the rays accurately. Students should measure rays at several different angles. 15 minutes Ensure sensible behaviour if the room is darkened and keep floor area clear. Apparatus (per group) Ray box, slit, lens and power supply; mounted plane mirror; A4 plain paper; pencil, ruler and protractor. AQA GCSE Extension Units Teacher’s Guide

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2 Nature of image Give each student a plane mirror, and ask them to use it to answer questions such as ‘where does the image appear to be?’ and ‘if you close your right eye, which eye closes on the image?’. 10 minutes Apparatus (per student) Plane mirror. 3 Distance of image Set up a plane mirror mounted vertically on the bench. Use a Bunsen burner, or a pencil mounted vertically in Plasticine or Blu-tack, as the object, and set up a similar item behind the mirror. Get students to move the item behind the mirror until it appears to be an extension of the image in the mirror. Check that the image and the item behind the mirror still appear to be in the same place when the student moves their head. Explain that the item behind the mirror is therefore in the same position as the image in the mirror. Measure the distance from the mirror to the object in front of the mirror, and also from the mirror to the item behind the mirror.

10 minutes Apparatus (per group) Plane mirror and mounting; 2 Bunsen burners, or 2 pencils and Plasticine or Blu-Tack; ruler. 4 The candle trick Mount a sheet of glass vertically on the bench. Take two candles and place them at equal distances on either side of the glass. Light one candle and show students that, when viewed through the glass, the other candle also appears to be lit. This activity further demonstrates that an image is the same distance from the mirror as the object. Students could follow this up by drawing ray diagrams to explain what they have seen. 10 minutes Make sure no one’s hair gets too close to the candle. Ensure sensible behaviour if the room is darkened and keep floor area clear. Apparatus Sheet of glass; G-clamps or other means of mounting the glass vertically; 2 candles.

pencil mounted in Plasticine behind mirror



P3.11

Curved mirrors

Worksheets available No. P3.11a P3.11b

Title Mirrors and rays Using curved mirrors

Foundation 4 4

Higher 4 4

Objectives

Key words

Students should be able to:

concave, converge, convex, diminished, diverge, focal length, focus, inverted

• describe the nature of the image produced by a convex mirror

• describe the nature of the image produced by a concave mirror for an object placed at different distances from the mirror

• calculate the magnification produced by a lens or mirror using the formula: magnification=image height/object height

• construct ray diagrams to show the formation of images by convex and concave mirrors.

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Type Practical (reusable) Homework (reusable)

AQA GCSE Extension Units Teacher’s Guide

Points to note

• The curved mirrors discussed in this topic are

spherical or cylindrical mirrors. You may wish to discuss the difference between spherical/cylindrical and parabolic mirrors with more able students.

• The practical activities and the classwork sheet

introduce the principles of ray tracing for curved mirrors, and are best used before students use the Student’s Book.

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Lesson ideas Starter

• Use Practical 1 as a starter. Learning activities

• Practical 2 asks students to use ray boxes and mirrors to trace rays, and introduces the three primary rays used in constructing ray diagrams for curved mirrors.

• Follow this up by asking students to draw ray

diagrams on graph paper to help them to answer the following questions. The sizes and distances have been chosen so that the scale drawing will fit on a piece of A4 graph paper. Some groups may find this work easier if they can also use ray boxes and mirrors to check their work.



a A 1 cm object is placed at 18 cm from a concave mirror with a focal length of 10 cm.

i How big is the image formed? (1.2 cm) ii Where is the image formed? (22.5 cm from the mirror) iii What is the magnification of the image? (1.2)

b A 2 cm object is placed 5 cm from a convex mirror with a focal length of 10 cm. (Students will need to mark the axis and focal point behind the mirror to help them to draw their rays.)

i How big is the image formed? (1.3 cm) ii Where is the image formed? (approx 3.2 cm behind the mirror) iii What is the magnification of the image? (1.3/2=0.65)

• Note that it is not necessary to draw the shape of a

concave mirror accurately for the ray diagrams, as the positions of the rays are worked out by reference to the F and 2F points. Students will find the ray diagrams easier to draw on graph paper, and can answer most of the questions by drawing only the ray passing through F and the ray parallel to the axis.

• You may also wish to point out that a ray along the

axis of the mirror will be reflected back along the axis, which is why all ray diagrams are generally drawn with one end of the object on the axis so that only rays from the top of the object need to be drawn.

• AT The ActiveTeach provides software that draws

ray diagrams to show students how the different images are formed in curved mirrors. However, students should still produce some diagrams of their own using pencil, paper and ruler, to ensure that they can do this if they need to in an examination.

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• You could link the work in this topic to the context for this unit by asking students to find out about the mirrors used in reflecting telescopes. Note that astronomical telescopes have wide apertures to collect more light – a function as important as magnification.

Plenary

• Ask students to work in small groups and to make a table with ‘plane’, ‘concave’ and ‘convex’ as the headings, and to put uses of the different types of mirror in the columns. Uses could include makeup/shaving (plane), focusing light in spotlights (concave), and mirrors at blind bends in roads (convex). Share ideas, and ask some students to explain why they have chosen a particular type of mirror for a particular use.

Additional homework/research ideas

• Ask students to find out what a parabolic mirror is. Ask them to explain how they are different from a concave mirror, and to suggest some uses for parabolic mirrors.

Practicals and demonstrations 1 Images in curved mirrors Give students a spherical concave and a spherical convex mirror (or a plastic curved mirror that is reflective on both sides), and check that they know what concave and convex mean. Ask them to describe the images in terms of which way up they are, whether they are magnified or not, and at what distance from the mirror they appear to be. 10 minutes Apparatus (per student) Concave mirror; convex mirror. 2 Ray tracing with mirrors Instructions are provided on Worksheet P3.11a, asking students to find the focal point of a cylindrical convex and a cylindrical concave mirror, and to use ray tracing to work out the position and magnification of an image in a concave mirror. 30 minutes Ensure sensible behaviour if the room is darkened and keep floor area clear. Apparatus (per group) Ray box, collimating lens and slits; concave mirror; convex mirror; plain paper; ruler and pencil.

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P3.12

Refraction

Worksheets available No. P3.12a P3.12b

Title Refraction effects Refraction questions

Objectives Students should be able to:

• describe how light is refracted when it passes from one material to another

• describe how light is refracted by a prism. Key words disperse, interface, refraction, spectrum

Points to note

• Students will have studied refraction in Key Stage 3,

although not in terms of waves. Students will not be expected to recall the explanation for refraction in terms of waves in an examination.

Lesson ideas Starter

• Have a pencil standing in a beaker of water for

students to look at (or have several around the room), or show them the coin trick – see Practical 1. Ask students to explain why the pencil appears to bend as it comes out of the water, in as much detail as they can, or to explain why adding water to the mug allows them to see the coin. This exercise will help you to find out how much they recall of Key Stage 3 work on refraction.

Learning activities

• Help students to understand how changing speed at a wavefront can cause a change of direction by discussing what would happen if a car ran into a muddy field at an angle. The wheel that went into the mud first would slow down, and the car would turn towards that side.

• AT ActiveTeach provides an animation illustrating refraction.

• Practical 2 asks students to trace rays to find out what happens as light passes through a glass or Perspex block.

• Worksheet P3.12a asks students to construct ray

diagrams to explain various phenomena connected with refraction. Although this work is not explicitly required by the specification, it will help to develop students’ skills in drawing ray diagrams to explain phenomena.

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Type Classwork (write-on) Homework (reusable)

Foundation 4 4

Higher 4 4

Plenary

• Give students the statement ‘light should not

change direction as it goes from one material to another’ and ask them to think of a positive point, a minus point and an interesting point related to the statement. Possible answers are: P – we would be able to see clearly underwater, M – spectacles/ telescopes/microscopes would not be possible, I – how much of today’s scientific knowledge would we have if lenses had never been developed?

Practicals and demonstrations 1 Refraction effects Stand a pencil in a beaker of water, and ask students to suggest why the pencil appears to be bent. Put a coin in a mug touching the side of the mug, and ask a student to move their head so they can only just not see the coin – see the diagram on Worksheet P3.12a. Ask the student to keep their head still while you add water to the mug, and ask them what has changed. They should now be able to see the coin. Ask students to suggest why this has happened. 10 minutes Clear up spills. Apparatus (per group) Beaker; pencil; mug (or other opaque container); coin. 2 Refraction ray tracing Ask students to trace the path of a ray through a glass block. Show them how to do this if necessary, but if they have completed practical work in the preceding topics they should be able to work out how to do this for themselves. Ask students to draw around the block first, and to mark the rays going into and out of the block. They can then remove the block and mark where the ray travelled through it. Students should be able to work out whether the ray bends towards or away from the normal at each interface. Note that the mathematical relationship between the angles of incidence and refraction involves sines, and is beyond the scope of this specification (although sines are in the maths GCSE (Higher)). 15 minutes Ensure sensible behaviour if the room is darkened. Apparatus Ray box, collimating lens, slit and power supply; glass or Perspex block; plain paper. © Pearson Education Limited 2007

P3.13

Lenses

Worksheets available No. P3.13a P3.13b

Title Telescopes Using lenses

Type Practical (reusable) Homework (reusable)

Objectives Students should be able to:

• describe the nature of the image produced by a diverging lens

• describe the nature of the image produced by a

converging lens for an object placed at different distances from the lens

• construct ray diagrams to show the formation of

images by diverging lenses and converging lenses

• explain the use of a converging lens as a magnifying glass

• calculate the magnification produced by a lens using the formula magnification=image height/object height.

Key words converging, diverging, lens

Points to note

• Students are not required to recall details about the use of lenses in telescopes.

• Long refracting telescopes were built in an attempt

to reduce chromatic aberration (the fringes of coloured light formed because the different wavelengths in visible light are refracted by different amounts). Chromatic aberration was less if thinner lenses were used, but this necessitated a longer telescope. These telescopes were very unwieldy and difficult to use, and became redundant with the invention and development of reflecting telescopes.

Lesson ideas Starter

• Use Practical 1 as a starter. Learning activities

• Revise the work on prisms from the last topic by

asking students to think of a lens as two prisms with bases together (for a converging lens) or with points together (for a diverging lens). Draw these models on the board and ask students to suggest how rays of light will be affected when they pass through the lens.

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Foundation 4 4

Higher 4 4

• As with mirror ray diagrams, the Student’s Book

describes three rays that can be used to locate the image formed by a lens. In practice, only two are needed, but drawing three rays can act as a check on the accuracy of the drawing; if they all cross at a single point, the drawing is likely to be accurate.

• Ask students if the magnification can be worked

out by comparing the distances of the object and image, and ask them to justify their answer. They can do this by drawing some ray diagrams to scale and comparing the magnification worked out using image sizes with that calculated using image distances, or they could use arguments involving similar triangles and the ray of light that goes through the centre of the lens to demonstrate that both methods will yield the same answer.

• AT The ActiveTeach provides an animation to show what happens as light passes through lenses from objects at different distances.

• H With some students, you may wish to discuss the

problem of chromatic aberration, although they will not be required to recall this. Remind students that prisms can be used to split white light into different colours, and ask them to suggest what effect this might have on the image seen through a lens. Link this work to reflecting telescopes (which students may have researched in Topic P3.11) – using a curved mirror to gather light instead of a lens avoids the problem of coloured fringes around images.

Plenary

• Revise some of the terms connected with refraction

and lenses by writing up the initial letters of key words on the board. Ask students to suggest what the words are, and to write definitions for them. Suitable words include: angle of incidence, angle of refraction, converge, diverge, focal length, focus, lens, normal, refract.

Additional homework/research ideas

• Ask students to find out what astigmatism is, what

causes it and what the symptoms are. This is best done after students have completed the homework sheet (Worksheet P3.13b), which looks at correcting long and short sight.

Practicals and demonstrations 1 Images in lenses Give students a spherical converging and a spherical diverging lens, and ask AQA GCSE Extension Units Teacher’s Guide

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Students can then be asked to draw ray diagrams for the situations described in Table D in the Student’s Book, using their ray boxes and lenses to show that the ray diagrams do show what really happens. 30 minutes

them to describe the images formed by the lenses (in terms of magnified/diminished, upright/inverted and real/virtual). For the last option, they should see if they can form an image on a piece of card. If necessary, prompt students to move the object they are looking at to different distances from the lens to see how this affects the image formed. Students could jot down their findings for later comparison with the information in the Student’s Book or with the findings from the practical activities below.

Ensure sensible behaviour if the room is darkened and keep floor area clear. Apparatus (per group) Ray box, collimating lens and slits; power supply; concave mirror; convex mirror; plain paper; ruler and pencil.

10 minutes Apparatus (per student) Converging spherical lens; diverging spherical lens; card. In addition, several lamps may be needed around the room to act as objects. 2 Ray tracing for lenses Use cylindrical lenses and ray boxes to produce ray diagrams for converging and diverging lenses. Start by asking them to find the focal lengths of the lenses they are using by shining parallel rays of light towards the lens and seeing where they converge, then ask them to find out what happens to:

Apparatus (per group) 2 spherical lenses, one with a longer focal length than the other; metre rule; Blu-Tack or Plasticine; graph paper.

a a ray aimed at the centre of the lens b a ray parallel to the axis of the lens c a ray aimed at the lens through the focal point.

P3.14

3 Telescopes Students use two lenses to make a telescope, and draw ray diagrams to help them to understand how it works. Instructions are provided on Worksheet P3.13a. You can save some time by telling students what the focal lengths of the two lenses are (so they can omit step A on the worksheet). 30 minutes

Cameras

Worksheets available No. P3.14a P3.14b

Title Pinhole cameras Light reverseword

Type Practical (reusable) Homework (reusable)

Objectives Students should be able to:

• explain the use of a converging lens in a camera

to produce an image of an object on a detecting device (e.g. film).

Key words no new words

Lesson ideas Starter

• Ask students to work in small groups to list as many

different uses and types of camera as they can. Share the ideas, and then ask students to suggest what all cameras have in common. The main common features are a light-proof box with a lens set into an opening, and a means of recording light (film or electronic sensors).

150

AQA GCSE Extension Units Teacher’s Guide

Foundation 4 4

Higher 4 4

Learning activities

• Practical 1 allows students to work out for

themselves why lenses are needed in cameras, and is best used before students study the material in the textbook. Students may have used pinhole cameras when studying light in Key Stage 3, but the practical is still worth repeating as it can be extended to incorporate ideas about the focal length of lenses.

• Students may be more used to digital cameras than

cameras using film, so it may be useful to show them a film, plus developed negatives.

• Photo D in the Student’s Book shows an image

of colliding galaxies taken by the Hubble Space Telescope. Images such as this need a long exposure time to gather enough light to form an image – several hours in this case. Revise earlier parts of Unit P3.0 by asking students to suggest possible problems with this approach – the main one being that the direction in which the telescope is pointing has to be continually changed to allow for the © Pearson Education Limited 2007

Practicals and demonstrations

movement of the Earth (or the movement of the satellite, if taken by the Hubble Space Telescope). A further point is that cameras can be used with filters to take pictures at different wavelengths to show up features that would not be visible to the human eye (even if the eye could take in enough light).

• ICT Interested students could look for images on

the Hubble Heritage website, which gives exposure times and other details about how the photographs were taken. For more information see www.longman. co.uk/AQAScience.

Plenary

Ensure sensible behaviour if the room is darkened and keep floor area clear. Do not put the camera too close to the filament bulb. Apparatus (per group)

• Ask students to write an exam question worth

Pinhole camera; pin; access to filament lamp or other bulb to be used as an object; selection of converging and diverging lenses (one converging lens should have a focal length similar to the length of the pinhole camera, so it can be used to focus the image from a large hole).

4 marks on any part of the work they have done on light, mirrors and lenses. They should also write a mark scheme. When this is done, ask some students to read out their questions and challenge the rest of the class to answer them.

P3.15

1 Pinhole cameras Worksheet P3.14a asks students a set of questions that they can answer with the aid of a pinhole camera. This is best done before using the Student’s Book. Some darkening of the room will be necessary, and you will need a bright source against a dark ground. 20 minutes

Sound waves

Worksheets available No. P3.15a P3.15b

Title Oscilloscope traces Sound questions

Type Classwork (card sort) Homework (reusable)

Foundation 4 4

Objectives

Lesson ideas

Students should be able to:

Starter

•

recall that sound is caused by mechanical vibrations, travels as a wave, and cannot travel through a vacuum

• recall that sound waves can be reflected and refracted

• explain the link between frequency and pitch, and between amplitude and loudness

• Ask students to write three questions for a quiz

on sound, and to also jot down the answers. Give them a few minutes for this and then collect questions from the class, challenging others to answer them. This should allow you to assess how much Key Stage 3 work on sound the class remembers.

• compare the amplitudes and frequencies of sounds

Learning activities

• explain that the quality of a note depends upon the

through a vacuum.

from diagrams of oscilloscope traces waveform.

Key words amplitude, frequency, hertz (Hz), medium, pitch, qualaity, vibrate, waveform

Points to note

• Much of this topic is revision of material originally studied in Key Stage 3.

• Refraction of sound is difficult to demonstrate. Note that when we hear sound but are not in the line of sight to the source of the sound, this is usually because of diffraction, not refraction.

© Pearson Education Limited 2007

Higher 4 4

• Practical 1 demonstrates that sound does not travel • Practical 2 introduces students to the use of an

oscilloscope to visualise sound waves, and reinforces the material on pitch, loudness and quality of sounds.

• Worksheet P3.15a gives students practice with

interpreting oscilloscope traces. There are some questions on the sheet, but you could extend the activity by asking further questions similar to questions 5 and 6.

• AT The ActiveTeach provides an animation

that illustrates aspects of sound waves and their description.

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Plenary

2 Oscilloscope demonstrations Set up an oscilloscope and microphone. Use a signal generator and loudspeaker to show students the shape of the oscilloscope trace produced by a single frequency. Vary the pitch and loudness of the sound and relate this to the changes in the waveform on the oscilloscope screen.

• Play true/false by asking students to make

statements about sound. As you go round the class, say ‘true’ or ‘false’ to each student – they then have to make a statement that is true or false, as appropriate. For false statements, ask the rest of the class to suggest a true version. If you have mixed abilities, it is best to limit the ‘false’ requests to more able students, to avoid possible confusion.

Follow this by demonstrating how the waveform changes with other sources of sound. If any musical instruments are available, you could play the same notes on several different instruments to demonstrate the different waveforms. Note that it is very difficult to hold a steady trace because of varying phase(s).

Additional homework/research ideas

• Ask students to find out the range of frequencies

that humans can hear, and how this changes with age (this looks forward to the next topic).

Students will also be interested to see the waveform produced when they speak, whistle or sing. Reinforce ideas about the relationship between pitch and frequency, and between loudness and amplitude by showing them a wave on the screen and challenging them to whistle or sing a note with a higher/lower frequency or higher/lower amplitude. 20 minutes

Practicals and demonstrations 1 Sound and vacuum Demonstrate that sound does not travel through a vacuum by using a vacuum pump to remove the air from a bell jar with a working electric bell suspended inside it. 5 minutes Apparatus Bell jar and stand; vacuum pump; electric bell; elastic suspension for bell; power supply/cells; connecting wires.

P3.16

Apparatus Oscilloscope; microphone; signal generator; loudspeaker.

Ultrasound

Worksheets available No. P3.16a P3.16b

Title Calculating distances Ultrasound questions

Objectives

Key words

Students should be able to:

ultrasound

• recall that sounds in the range 20–20 000 Hz can be detected by the human ear

• recall that electronic systems can be used to

produce ultrasound waves, which have a frequency higher than the upper limit of hearing for humans.

• compare the amplitudes and frequencies of

ultrasounds from diagrams of oscilloscope traces

• explain that ultrasound waves are partially reflected when they meet a boundary between two different media; the time taken for the reflections to reach a detector is a measure of how far away such a boundary is

• recall that ultrasound waves can be used in industry for cleaning and quality control, and in medicine for pre-natal scanning

• H determine the distance between interfaces in

various media from diagrams of oscilloscope traces.

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Type Classwork (reusable) Homework (reusable)

AQA GCSE Extension Units Teacher’s Guide

Foundation 4

Higher 4 4

Lesson ideas Starter

• Use Practical 1 as a starter. Start by asking students

to define amplitude and frequency, and ask them to explain which one determines the pitch of a note.

Learning activities

• Ask students what they know about ultrasound.

Most will have heard of ultrasound scans for pregnant women, and even seen scans from family members. Ask students to suggest how it works; prompt them with ‘echoes’ if necessary. Note that there is a photograph of a fetal scan on page160 of the Student’s Book.

• You could ask students to find out about other

medical applications of ultrasound (such as breaking up kidney stones). © Pearson Education Limited 2007

• AT The ActiveTeach illustrates the use of ultrasound

in fetal scanning and also explains how oscilloscope traces can be used to work out the distance between interfaces.

• H Worksheet P3.16a provides further practice for students in interpreting oscilloscope traces.

Plenary

only hear sounds in a particular range (typically 20 to 20 000 Hz). Start at a frequency higher than 20 000 Hz and gradually reduce the frequency. Ask students to put their hands up when they can hear a sound. You may wish to explain that the highest note that can be heard gets lower with age; demonstrate this by also holding up your own hand when you can first hear a noise. Demonstrate that sound is still being made below 20 Hz by letting students see or feel that the loudspeaker cone is still vibrating. You can also demonstrate that sound is still being made above the range of hearing using a microphone linked to an oscilloscope, but check first that the microphone is sufficiently sensitive in the very high frequency range to produce a reasonable signal on the oscilloscope. 10 minutes

• Ask students to compile a list of five key points on

sound and ultrasound, summarising the content of this topic and the last. Share ideas and compile a class summary.

Additional homework/research ideas

• Find out the hearing ranges of other animals, and

explain what ‘dog whistles’ are and why they work.

Practicals and demonstrations

Make sure the volume is not too high.

1 Demonstrating hearing range Use a signal generator and loudspeaker to make sounds of varying frequencies. Explain that sounds can be made at different frequencies, but that humans can

Apparatus

P3.17

Signal generator; loudspeaker; microphone; oscilloscope; dog whistle.

Electric motors

Worksheets available No. P3.17a P3.17b

Title Make a motor Electric motors

Type Practical (reusable) Homework (reusable)

Foundation 4 4

Higher 4 4

Objectives

Points to note

Students should be able to:

• Students will not be expected to recall Fleming’s Left

• recall that when a conductor carrying an electric current is placed in a magnetic field, it may experience a force

• recall that the size of the force can be increased

by increasing the strength of the magnetic field or increasing the size of the current

• explain that the conductor will not experience a force if it is parallel to the magnetic field

• recall that the direction of the force is reversed if

either the direction of the current or the direction of the magnetic field is reversed

• explain how the motor effect is used in simple devices.

Key words magnetic field, motor effect H commutator

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Hand Rule, or the detail about commutators given in the Student’s Book.

Lesson ideas Starter

• Ask students to make a concept map showing what they can recall about electricity and magnetism. Keep the concept maps for use in the plenary.

Learning activities

• Ask students to make a list of electrical appliances that include motors, and to say what the motor is used for. For example, a CD or DVD player needs a motor to spin the disc.

• You could follow this up by asking students what

they think the essential parts of a motor are. Students could jot down their answers and revisit them later in the lesson to amend or correct as necessary.

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Practicals and demonstrations

• Practical 1 demonstrates the motor effect. You may

wish to show students how to use Fleming’s Left Hand Rule to work out the direction of movement of the wire, but note that students will not be expected to recall this. (The first finger points along the direction of the magnetic field, from the north to the south pole; the second finger points in the direction of conventional current, from + to –, and the thumb points in the direction of movement.)

• Students can build their own simple motors using a kit. See the notes for Practical 2.

1 The motor effect Set up a horseshoe magnet and a simple circuit as shown in diagram A in the Student’s Book; demonstrate what happens when the switch is pressed. Ask students to suggest what will happen if the magnet is turned so the magnetic field goes in the opposite direction, and what will happen if the connections to the cell or power supply are reversed, then demonstrate to check their answers. 10 minutes Apparatus

• AT An animation on the ActiveTeach explains how

Horseshoe magnet; wire; switch; cells or d.c. power supply.

a motor works.

• H

ICT In practice, most electric motors are more complicated than the diagram shown in the book. Overviews of the different types of motor and discussion of how real motors work can be found on the internet. For more information see www. longman.co.uk/AQAScience. More able students may be interested to see the different types of motor, although they will not be required to recall any of the details.

Plenary

2 Make a motor Worksheet P3.17a provides instructions for students to assemble the components of a standard motor kit (sold by most equipment manufacturers). Common sources of difficulty are having the magnets misaligned (they should be attracting each other) and the wires used as brushes not making good contact with the bared ends of the wire from the coil. 20 minutes Low voltages should be used with insulated wires, as many types readily overheat and may melt the insulation. Ensure good ventilation as the plastic insulation gives off fumes when overheated. Warn students not to put their faces too close to the motors as the model commutators may produce sparks.

• Ask students to amend or redraw their concept

maps to concentrate on the parts of it specifically relevant to electromagnetism and motors.

Additional homework/research ideas

• Ask students to make a list of appliances in their

homes that have motors in them, and to identify what the motors are used for.

Apparatus (per group) Motor kit (base, 2 split pins, axle, mounting for coil, insulated wire, small rubber bands, 2 flat magnets, steel yoke, pins); wire strippers; sticky tape; power pack; Worksheet P3.17a.

P3.18

Making electricity

Worksheets available No. P3.18a P3.18b

Title Bigger voltages Electricity from movement

Type Practical (reusable) Homework (reusable)

Objectives Students should be able to:

• recall that if an electrical conductor cuts through

magnetic field lines, an electrical potential difference is induced across the ends of the conductor

• recall that if a magnet is moved into a coil of wire, an

Foundation 4 4

Higher 4 4

• explain that a current is induced in the wire if it is part of a complete circuit

• explain that if the direction of motion, or the

polarity of the magnet, is reversed, the direction of the induced potential difference and the induced current is reversed

electrical potential difference is induced across the ends of the coil, and that this effect also occurs if the magnetic field is stationary and the coil is moved

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• recall that the size of the induced potential difference increases when:



• H If you have discussed Fleming’s Left Hand Rule

for the motor effect with students, you could now introduce the Right Hand Rule for induction. Note that students will not be required to recall this rule.

a the speed of the movement increases

b the strength of the magnetic field increases c the number of turns on the coil increases

Plenary

d the area of the coil is greater.

• Ask students to add to the concept maps they made

Key words

Practicals and demonstrations

electromagnetic induction, induce

Points to note

• It is the relative motion between magnetic field

and conductor that results in an induced voltage – it does not matter whether it is the magnetic field or the conductor that is moving. In components such as transformers (in Topic P3.20), the changing strength of the magnetic field induces a current without any physical movement.

at the end of the last topic.

1 Making electricity Demonstrate (or allow students to test) a number of different ways of moving a magnet relative to a coil of wire, and ask students to note the direction of the induced potential difference. A demonstration may be better if you do not have enough moving-coil meters that will register a voltage with the coils and magnets available. Situations that could be demonstrated are:

• the north pole of a magnet entering a coil • the magnet stationary inside the coil • the north pole leaving the coil • the magnet stationary outside the coil • the south pole of a magnet entering a coil • the south pole leaving a coil • a coil moving towards the north pole of a magnet • a coil stationary on the magnet • a coil moving away from the north pole of a magnet • a coil moving towards the south pole of a magnet • a coil moving away from the south pole of a

• The main energy transformations involved

in generating electricity were looked at in Key Stage 3, and again in Module P1a of this course. This topic looks at how generators work.

Lesson ideas Starter

• Ask students to jot down all the different ways in

which they used electricity during the previous day. Ask them to split their list into things that rely on batteries, and things that use mains electricity. They should include things that they use only indirectly (central heating pumps, washing machines, etc.). Then ask them what they know about how electricity is generated.

Learning activities

• Use Practical 1 to allow students to discover some basic points about inducing voltages.

• AT The ActiveTeach includes an animation that

illustrates the effects of reversing the polarity on the induced voltage; it also demonstrates that it does not matter whether the magnet or the coil is moved. This could be used in place of Practical 1.

• Practical 2 demonstrates that rotational movement

between a coil and a magnetic field can also induce a voltage. This demonstration helps to set the scene for the work on generators in the next topic.

magnet. 10–15 minutes

Apparatus (per group) Coil of wire wound on a cardboard or plastic tube – 100 turns of closely wound 0.1 mm insulated wire; strong bar magnet; moving-coil meter or galvanometer; connecting wires. 2 Rotation and induced voltage Demonstrate that rotation also induces an alternating voltage by placing a strong magnet on a turntable. Suspend a coil above the magnet, connected to a centre-zero galvanometer. Spin the magnet and observe the pointer on the galvanometer changing direction continuously as the magnet rotates. If possible, the coil could be connected to an oscilloscope to show students the way the voltage varies with time in a more visual manner. G

• Practical 3 offers an opportunity for students to vary

G

different factors and discover their effects on the induced voltage. This practical could be used as the basis for a coursework investigation for training or assessment.

S

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N

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10 minutes

a can be taken to be 10 m/s2 and s is the distance fallen) and asked to work out the actual speeds of the magnet when it enters the coil.

Apparatus Coil of wire wound on a cardboard or plastic tube – 100 turns of closely wound 0.1 mm insulated wire; strong horseshoe magnet or ceramic bar magnets (bar magnets are likely to be cheaper); demonstration centre-zero galvanometer or ‘Edspot’ galvanometer; connecting wires.



Optional: CRO. 3 Bigger potential differences Worksheet P3.18a leads students through a series of simple practical activities to discover the factors that can increase the size of the induced voltage. Alternatively, ask students to plan their own investigations into the factors that affect the induced voltage, based on the prompt in the Student’s Book. In this case you may wish students to make their own coils with different numbers of turns. When investigating the effect of speed of movement, students could just move the magnet faster by hand. However, a more quantitative approach is to drop a magnet through the coil from different heights – the longer the drop, the faster the magnet will be moving when it enters the coil. This can be done by fitting a long cardboard tube inside the coil of wire to act as a guide, and standing the apparatus on foam to absorb the impact if the magnet hits the bench. The magnet should be attached to a length of cotton thread. The height from which the magnet is dropped can be measured by measuring the length of cotton pulled up out of the top of the tube. Note that the speed at which the magnet enters the coil does not vary linearly with height, and the magnet will continue to accelerate while falling More able students can be given the equation v2=2as (where

P3.19

Note that the ‘number of turns’ on the coil is cotton thread turns per unit length – not just a coil with cardboard tube more turns because it magnet is longer, so care must be taken in providing suitably wound coils. coil The old style school magnets made with steel are usually very weak and are often foam unsatisfactory. Small ceramic magnets and the very strong neodymium–iron–boron discs stuck to a wooden dowel provide a suitable way of varying the field strength. The core to the coil should be soft iron rather than steel, but either will have an effect.

20–40 minutes Apparatus (per group) 2 coils with different numbers of coils per unit length labelled with the number of turns (or a reel of suitable insulated wire and a cardboard tube to wrap it around); 2 magnets of different strengths; iron core material (a bundle of thick iron nails will work); wooden core material (pencils should work); cardboard tube wide enough to take the magnets but narrow enough to fit inside the coils; clamp and stand; cotton thread; sticky tape; foam; connecting wires; moving-coil voltmeter; paperclips; Worksheet P3.18a.

Generators

Worksheets available No. P3.19a P3.19b

Title Generator diagrams Generator designs

Type Classwork (write-on) Homework (reusable)

Foundation

Higher 4 4

Objectives

Points to note

Students should be able to:

• Students are not required to recall the details of

• explain from a diagram how an a.c. generator works, including the purpose of the slip rings and brushes.

Key words alternating current, brush, slip ring

generators in power stations.

Lesson ideas Starter

• Ask students to spend a few minutes jotting down

what they know about direct and alternating current (covered in Topic P2.25 in Additional Science), then ask for points to compile a summary list on the board.

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Learning activities

Additional homework/research ideas

• Practical 1 demonstrates the difference between a.c. • Ask students to make a list of the different ways in and d.c. This demonstration was suggested in Topic P2.25, but is worth repeating here to remind students of earlier work.

• Students should be able to see that a.c. is easier to

produce as it is produced by rotating generators. Students may also ask why a.c. is easier to transmit – this is at least in part because transformers can be used with a.c. but not d.c. (see the next topic), so the voltage can be easily changed from that produced by the generators to the higher voltages used in transmission lines and then back to the low voltages needed in households or by other users.

• AT The ActiveTeach animation explains how a generator works.

Plenary

• Worksheet P3.19a provides unlabelled diagrams that students can use to make their own summaries of how generators work.

•

Practicals and demonstrations 1 Oscilloscope demonstration Connect an oscilloscope to a small generator or bicycle dynamo. Have the various gains set to produce an alternating wave that shows the output, and ask students to suggest what the trace is showing. This should remind them of work on alternating current in Unit P2. Follow this up by asking them what they think the oscilloscope will show if a cell is connected across the oscilloscope terminals, then demonstrate. Note that a cell must be used, rather than the d.c. output of a power supply, as the latter is often rectified and smoothed a.c., and so will not show a straight line. 5 minutes Apparatus

Alternatively, students could continue to add to the concept maps they started in Topic P3.17.

P3.20

which a generator can be turned to generate mains electricity (e.g. steam turbines, wind turbines, etc.).

Oscilloscope; generator or dynamo; cell or battery in holder; connecting wires.

Transformers

Worksheets available No. P3.20a P3.20b

Title Transformers and energy Transformer calculations

Type Classwork (reusable) Homework (reusable)

Foundation 4 4

Higher 4 4

Objectives

Key words

Students should be able to:

step-down transformer, step-up transformer, transformer

• describe the basic structure of the transformer • recall that an alternating current in the primary

coil produces a changing magnetic field in the iron core and hence in the secondary coil, and that this induces an alternating potential difference across the ends of the secondary coil

• explain that in a step-up transformer the potential

difference across the secondary coil is greater than the potential difference across the primary coil

• explain that in a step-down transformer the

potential difference across the secondary coil is less than the potential difference across the primary coil

• determine which type of transformer should be used for a particular application

• describe the uses of step-up and step-down transformers in the National Grid

• H recall and use the equation for calculating the

Points to note

• Many power cables of the kind shown in

photograph A in the Student’s Book include diodes to convert the current from a.c. to d.c. in addition to a transformer.

Lesson ideas Starter

• Help students to recall previous work on induction by asking them to complete a sentence starting ‘Electromagnetic induction …’. They should be encouraged to complete the sentence in several different ways, working alone or in groups, before sharing ideas. This is also a chance to correct any misconceptions that show up in their responses.

potential differences in a transformer.

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Learning activities

• AT The video on the ActiveTeach shows X talking

about using mains power to recharge the yacht’s batteries, and to power the electrical equipment on the yacht when it is moored in a marina. It points out the need to convert the 230 V a.c. mains supply into a lower-voltage d.c. supply for the equipment to use. [Note that students may have already seen this video when studying Unit P2.]

• Emphasise that current does not flow through the

iron core. If you have demonstrated a transformer (Practical 1) point out that the coils are made from insulated wire, so there is no way of electricity getting into the core.

• Students could investigate for themselves the effects

Practicals and demonstrations 1 Transformer demonstration A demountable transformer (called a ‘dissectible’ transformer in some equipment catalogues) is best, as students can then see that there are no electrical connections between the two coils, or between the coils and the core. What demonstrations are possible will depend on the type of transformer you have available, but could include:

• using the transformer to convert mains voltage to •

of changing the number of coils on the primary and secondary coils in a ‘home-made’ transformer. Encourage them to compare their findings with the theoretical voltages calculated using the equation.

• AT The ActiveTeach includes a spreadsheet that will help students to work out which kind of transformer is needed for a particular application.

• Some students may think that if a transformer

doubles the voltage you will get twice the energy/ power. This is not the case as the current halves when the voltage doubles. Similarly, a step-down transformer produces a lower voltage but a higher current. There are also energy losses due to heating, so in all cases the useful energy obtained from a transformer is less than the energy put in. This is looked at in more detail on Worksheet P3.20a. It may be best to work through the sheet with some groups, although more able students should be able to work through it alone or in small groups.

Plenary

• Ask students to write down three key points about

electricity generation. Give them a few minutes, then ask for suggestions and compile an agreed class list of four or five points.

Additional homework/research ideas

• Ask students to list all the transformers they can find

at home, and note the output voltages (note that most of these will mention d.c., so you may wish to discuss the fact that the ‘boxes’ in the cables or plugs include components to convert a.c. to d.c.). Students could also be asked to suggest suitable ratios of primary to secondary coils for all the transformers they find.

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12 V, and connecting it to a torch bulb (explaining that the mains voltage would have blown the bulb) removing the top of the core (if this is in a Ushape with a separate bar across the top) or separating the two halves (if it is two U-shaped pieces) when the supply to the primary coil is switched off. Attempt this again with the supply on, and show that the parts of the core cannot be separated, demonstrating that there is a strong magnetic field in the core. adding a ‘home-made’ secondary coil to the core, and using this to power a torch bulb. The advantage of this is that the coil can be very loosely wound, demonstrating again that there is no electrical connection between the coil and the core.

Beware of creating a step-up transformer by connecting the equipment the wrong way round. Apparatus Demountable transformer; torch bulb; voltmeters. 2 Make a transformer The ‘Westminster’ electromagnetic kit contains C-cores that can be used as transformer cores. Students can make their own transformers by winding coils onto the core and investigating the effect of different numbers of turns of wire in the primary and secondary coils. Students should use laboratory power supplies that can deliver the current needed at low voltages, and must never attempt to connect their transformers to the mains supply. Ensure that the voltages/currents used do not overheat the insulation on the wires, which can melt and/or give off fumes if overheated. Warn students to switch off immediately if this happens and stand back. Keep the room well ventilated. Apparatus (per group) Power supply; 2 C-cores and clamp; insulated wire; 2 voltmeters; connecting wires and crocodile clips; mounted bulb.

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P3.00

Answers

P3.00 Investigating space

2 Students should have drawn a ray diagram showing how the person can see from the top of their head to their feet, like this:

Student’s Book 1 a and b Student’s list could include words such as light, luminous, dark, shadow, eclipse, reflection, refraction, colour, lens, mirror, with definitions of each. 2 Concept maps should include key words such as: sound, vibration, air, medium, vacuum, loud, quiet, amplitude, wave, wavelength, frequency, pitch, high, low. The key words should be correctly linked.

mirror 1.7m

Student’s Book

a 0.85 m (i.e. half the height of the person). Students could arrive at this answer by drawing a scale diagram, or by reasoning that the two rays shown reflecting from the mirror form symmetrical isosceles triangles, and the points at which they reflect are half way from the eyes to the feet, and halfway from the eyes to the top of the head, so the total length of mirror between the two extreme rays shown is half the height of the person.

1 a A line at right angles to the mirror at the point where a ray of light hits it.

b The top of the mirror needs to be level with the person’s eyes.

b The angle between the normal and a ray of light reflected from a mirror.

c No, the same reasoning would apply.

3 The bullet points should include ideas about sources of electricity, conductors and insulators, the need for a complete circuit, energy transformations by components such as bulbs or motors, measurement of current and voltage, and resistance.

P3.10 Plane mirrors

c The picture of something that you can see in a mirror. d Flat. 2 Rays of light pass through / come from a real image, but only appear to come from a virtual image. 3 a 8 cm tall.

Worksheet P3.10b 1 Ray drawn so that the angle of reflection is equal to the angle of incidence. 2 Labels correctly placed. 3 Same size – the image appears to be the same size as the object. Upright – the image is the same way up as the object.

b 10 cm. 4 a draw dotted version of light bulb here

Virtual – rays of light appear to come from the image, they do not actually pass through the image. 4 a Area of underside of car found by drawing rays of light that reflect from the mirror. b Further under the car, just behind the front wheels.

b Answers will vary, but should include the following: plane mirror, normal, angle of incidence, angle of reflection, incident ray, reflected ray, virtual image.

Worksheet P3.10a 1 Ray drawn from bottom of tree reflecting off both mirrors, and the final rays extended to show where the image appears to be. © Pearson Education Limited 2007

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Answers

P3.11 Curved mirrors

3 a Correctly drawn ray diagram using the measurements given in the question.

Student’s Book 1 Similarities: both are virtual and upright.

mirror object

Differences: The image in a plane mirror is the same size as the object, the image in a convex mirror is diminished. The image in a plane mirror is the same distance behind the mirror as the object is in front, this is not necessarily the case for a convex mirror. 2 a See cars coming from around a corner.

F

image

b It gives a wider field of view. 3 a All mirrors can produce virtual images. b A concave mirror does not always produce a virtual image, as the nature of the image depends on the distance of the object from the mirror. 4 a Correctly drawn ray diagram with focal points marked, showing an image that is real, inverted, magnified and further from the mirror than the object.

F 2F

b Answers will vary, depending on exactly where the object has been placed. 5 The aim is to see a magnified upright virtual image in the mirror, so you would have to hold your face less than one focal length from the mirror.

b 5 cm image, so the magnification is 2.5 times. c Real, the rays of light pass through the image. 4 For a 10 cm focal length, the magnification is 0.66. For a 5 cm focal length the magnification is approximately 0.23, so the image is bigger for the longer focal length. 5 Students will need to draw a series of ray diagrams to help them to answer this question. As the object moves towards the 2F point (20 cm) the image gets bigger and further from the mirror. When the object reaches 2F, the image is the same size as the object and at the same position as the object. As the object moves from 2F towards F it continues to get bigger and further from the mirror. At F there is no image (the rays do not converge), and then the image becomes virtual and magnified, getting smaller and closer to the mirror as the object approaches the mirror.

P3.12 Refraction

6 Concept maps should include all the information on the Student’s Book pages

Student’s Book

Worksheet P3.11b

1 The change of speed and direction that occurs when light passes from one material to another.

1 a Plane, so the driver can see how far behind other vehicles are. b It allows a wider field of view. c It makes a vehicle seen in it seem further away, so the driver could misjudge where the vehicle is. 2 a Image A is magnified, upright, virtual. Image B is diminished, upright and virtual. b A is a concave mirror, and B is a convex mirror, because of the way they have reflected the rays.

2 The greater the change of angle, the greater the difference in speed. As light slows down when it enters water or glass, it must slow down more when it goes into glass than when it goes into water, so light must travel more slowly in glass than in water. 3 a Violet. b It bends more than red light, so it must have slowed down more. 4 a The spreading out of the different colours in white light when it passes through a prism. b The different colours in white light are slowed down by different amounts, so they bend by different angles.

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Answers

5 Windows have two parallel interfaces between air and glass, so the dispersion effects caused when the light goes into the glass are counteracted when the light leaves the glass again.

3 writing on paper

glass b

6 a Diagram of light passing through a glass block, with normals and angles correctly labelled.

angle of incidence

angle of refraction

normal

writing on paper

glass block

normal

angle of refraction angle of incidence

b Diagram of light passing through a prism, with suitable explanatory labels. Light bends towards the normal as it enters the glass. Violet light is bent more than red light

Light bends away from the normal as it leaves the glass. Violet light is bent more than red light The colours in white light have spread out to form a spectrum

4 Diagram similar to that in Q3, showing the apparent depth of the water.

Worksheet P3.12b 1 Diagram correctly labelled. 2 a From air to glass, as the change in speed is greater. b Diagram showing light refracting away from the normal as it leaves the glass. 3 a The normals. b X marked at the two points where light is entering glass.

Worksheet P3.12a

c Y marked at the two points where light is leaving glass.

1

d

water coin



coin is invisible

you can see the coin

2 eye

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4 Students’ drawings may vary slightly, but the key point is that each ray of light is bent towards the normal as it enters the prism, and bent away from the normal where it leaves.

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P3.13 Lenses

2 a B – between 1 and 2 focal lengths from the lens. b 6/4=1.5.

Student’s Book

3 a Correctly drawn scale diagram.

1 The rays of light do not actually pass through the image, they only appear to come from it.

b Virtual, as the rays of light do not pass through the lens.

2 Correctly drawn diagram with focal points marked and rays drawn accurately to show an image that is real, inverted, magnified, and located beyond 2F.

c Student’s diagrams should give a magnification of around 2. 4 a Converging. b Diverging.

F 2F

2F

F

3 Virtual. 4 Magnification=image size/object size. 5 a An object placed beyond 2F will form a real, diminished image. 6 Beyond 2F the image is real, inverted and diminished, and is between F and 2F on the far side of the lens. The image gets bigger as the object gets closer to the lens, until at 2F it is the same size as the object. The image continues to get bigger as the object moves towards F. Once the object is closer than one focal length to the lens, the image becomes vertical, upright and magnified. The image gets bigger as the object gets closer to the lens. 7 The advert should summarise the key points from this topic.

Worksheet P3.13a 1 Magnified, inverted, virtual. 2 a Stars and galaxies do not really have a top and bottom (or similar answer). b The light from stars is very faint, and would be swamped by brighter light from the surroundings.

A person with short sight needs lenses to make the light rays diverge, so that when they are converged again by the eye they do not meet in front of the retina. Suitable diagrams should accompany the explanations.

P3.14 Cameras Student’s Book 1 Real. 2 a More light can get into the camera through a bigger hole. b Light from one part of the object can reach more than one place on the screen. 3 The focal length should be the same as the length of the camera (i.e. the distance from the pinhole to the screen). 4 Ray diagram similar to the first part of diagram B in the Student’s Book. 5 To allow the camera to focus on objects at different distances. 6 a Make the aperture (opening) smaller, or have the shutter open for a shorter length of time.

3 a The objective lens, as the light rays going through this lens pass through the image it forms.

b If the lighting is very bright the amount of light reaching the film needs to be reduced.

b The eyepiece lens.

7 The explanation should include the need to let enough light in to register on a film, with the resultant need to focus light rays coming through a bigger hole.

Worksheet P3.13b 1 a The rays should diverge, as if all coming from a single point to the left of the lens. b The light rays should converge to a point. c The ray should pass through without changing direction.

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c A person with long sight needs lenses that will make the light from near objects converge more so they meet at the retina.

Worksheet P3.14a 1 a Inverted, smaller than the object, very dim.

d The rays should emerge parallel to the axis.

b Suitable ray diagram showing rays from the top and bottom of the object passing through the pinhole.





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Answers

2 a Three separate images, all the same size (but smaller than the object), inverted and dim. b Light coming through each pinhole forms a separate image. 3 a The image should still be inverted and smaller than the object, but will be brighter and less sharp than before. b Students could explain the larger hole as like lots of small holes run together, each part of which will produce a separate image, resulting in a brighter image (because more light gets into the camera) but one that is less sharp as there are effectively lots of separate images together. The ray diagrams should be similar to the second part of diagram B in the Student’s Book. 4 Converging. The rays of light spreading out from the object have to be brought together to form a sharp image. 5 a Depends on the lenses available and the size of the pinhole camera.

4 An instrument produces a mixture of frequencies, not just one. A trumpet and a violin produce different mixtures of frequencies. 5 Smooth sine wave drawn and amplitude correctly marked. amplitude

0

6 a The peaks would be closer together. b The waves would not be as tall. c There would be a complicated wave shape, not a smooth curve. 7 Suitable waves added to the answer to question 5.

Worksheet P3.15a 1 A and F; B and I; C and G; D and E; H and J; K and L.

b The focal length is similar to the length of the pinhole camera.

2 A and B; C and H; D and L; E and F; G and J; I and K.

6 The hole in a camera needs to be quite large to let in enough light, but a large hole gives a blurred image, so the lens is needed to give a sharp image.

4 C, H, I, K.

3 E, F, G, J. 5 C.

Worksheet P3.14b

6 H, I.

Any sensible clues for the words in the grid. The words are:

Worksheet P3.15b

Across prism; 5 focus; 6 incidence; 10 reflection; 2 14 magnification; 15 lens; 16 converge. Down

1 Sound needs a material to travel through. Space is mostly vacuum, so sound cannot travel in space. 2 Amplitude should be marked as half the total height of the wave (i.e. from the centreline to either a crest or a trough).

plane; 3 spectrum; 4 normal; 7 dispersion; 8 focal 1 length; 9 concave; 11 refraction; 12 virtual; 13 diverge.

3 a 100 Hz.

P3.15 Sound

c 66.6 Hz.

Student’s Book 1 a Both travel as waves, both can be reflected and both can be refracted. b Sound needs a medium to travel through, light does not. Sound can travel through all solids, light can only travel through transparent ones. Accept other answers, such as the different speeds. 2 25 Hz. 3 a Wave drawn that has a higher amplitude and lower frequency than the original.

b 15 000 Hz. 4 a C – it shows the fewest waves in the time represented on the oscilloscope screen, so the frequency is lowest. b B – it shows the most waves, so the frequency is the highest. c C – the amplitude is lowest. 5 a A and D. b They have different waveforms (they are mostly one frequency, but there are also other frequencies present that will make the notes sound different even though they are the same pitch and loudness).

b Wave drawn that has a smaller amplitude and higher frequency than the original.

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P3.16 Ultrasound

3 Reflections from the bottom of the steel, the bottom of the polythene and the bottom of the aluminium.

Student’s Book

4 Thickness=(0.59 cm/ms×8 ms)/2=2.36 cm.

1 Sound too high for humans to hear / sound of frequencies above 20 000 Hz.

5 a 19 ms. b 8 ms.

2 Animals such as bats, or electronic machines.

c 11 ms.

3 a Visible light cannot pass through the skin or body tissues and so cannot be used to form an image of the inside of the body.

d Thickness=(0.27 cm/ms×11 ms)/2=1.485 cm.

b X-rays can cause damage to tissues, so are not used if there is a safer alternative, or if the risk of using them is greater than the possible benefit of having the scan. 4 Ultrasound waves are sent into the body, and are partially reflected each time they pass from one material to another. The probe detects the echoes. It measures the time between the original signal and the echo and a computer then works out where the echo came from and displays all the echo information as an image. 5 It removes dirt gently so it does not damage the object. 6 Ultrasound could be sent through the plate. Some will reflect from the back surface of the plate, and the echo can be detected. The thickness of the plate can be calculated from the time it takes for the echo to return to the probe. 7 a 2 ms. b Distance=speed × time=0.632 cm/ms × 2 ms=1.264 cm. c 0.632 cm. d Time for second echo to return is 5 μs, so the distance is 0.632 cm/ms × 5 ms=3.16 cm. Thickness of plate is half this, so is 1.58 cm. 8 a Any frequency above 20 000 Hz. b Medical scanning, cleaning, quality control. c Measure the time taken for the echo from each boundary to return, and use the speed of sound in the material to calculate the distance the sound has travelled. As an echo travels both ways, the actual distance is half the distance travelled by the sound.

e It took the ultrasound 25 ms to return from the base of the aluminium, with 6 ms of this being taken to travel in the aluminium. Thickness=(0.63 cm/ms×6 ms)/2=1.89 cm.

Worksheet P3.16b 1 a Probe. b Gel. c Computer. d Ultrasound waves. e Screen. 2 The machine sends an ultrasound pulse into the material, and detects the sound reflected from the back surface of the sheet. It uses the time between the pulse and the echo to work out the thickness. 3 Thickness=(0.27 cm/ms × 3.6 ms)/2=0.486 cm. 4 a Too thick. The sound has taken more time to travel than it should. b Thickness=(0.27 cm/ms × 3.8 ms)/2=0.513 cm. Error=0.027 cm. 5 Shorter. If the sheet is thinner, the ultrasound has a shorter distance to travel, so it will not take as long. 6 Thickness=(0.63 cm/ms × 2.2 ms)/2=0.693 cm. 7 There may be a crack within the steel that is reflecting some of the sound. The depth of the crack from the top surface is (0.63 cm/ms × 0.5 ms)/2=0.1575 cm.

P3.17 Electric motors Student’s Book 1 a Any five machines that include motors, such as CD or DVD player, washing machine, computer (for the cooling fan), etc.

Worksheet P3.16a

b Answers depend on the responses in part a.

1 a 7 ms.

2 a The force/movement will be downwards.

b Distance=0.59 cm/ms×7 ms=4.13 cm.

b The force will be bigger.

c 4.13 cm/2=2.065 cm.

c The force will be weaker.

2 a Thickness=(0.27 cm/ms×7.5 ms)/2=1.013 cm. b Thickness=(0.63 cm/ms×5 ms)/2=1.575 cm.

3 Nothing. The wire has to be running across the field lines, not along them. 4 More turns of wire would give a bigger turning force.

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5 a A movement caused when an electric current flows through a wire in a magnetic field. b Use stronger magnets or a bigger current.

4 Advantages: no cost of replacing or recharging batteries, you will never be left without lights because the batteries are flat.

Worksheet P3.17b

Disadvantages: it makes the bicycle harder to ride, the lights will be dim when going uphill (or at any other time the bicycle is moving slowly), the lights will not work at all when stopped at a junction.

1 a Down. The current is flowing in the opposite direction to that in the first diagram.

5 Use a weaker magnet, move the magnet more slowly, have fewer turns on the coil.

b Up. The magnetic field is reversed compared with a (or both field and current are reversed compared with the original diagram, so the two changes cancel each other out).

6 Students’ own answers should include all the key points from the topic.

c It will not move. No current is flowing.

1 a Opposite direction, because the magnet is being moved in the opposite direction.

c Reverse the direction of the current or the direction of the magnetic field.

2 a Magnet. b Cell or battery. c Coil. d Brush. 3 a Provides a magnetic field. b Provides a current in the coil. c Carries the current through the magnetic field. d Makes electrical contact between the coil and the circuit. 4 a The motor would run faster / produce more force, because there are more pieces of wire carrying current in the magnetic field. b The motor would run the other way, as the current would flow in the opposite direction. c The motor would run more slowly / produce less force, as the magnetic field would be weaker.

Worksheet P3.18b b Same direction, as the magnet is reversed but it is also being moved in the opposite direction, so the two changes will cancel each other out. c Opposite direction, as the magnet and coil are moving away from each other instead of towards each other. d There will be no current, as the two objects are moving at the same speed and there is no relative motion between them. 2 a It goes into the coil and then comes out of it again. b It will increase as the magnet starts moving and then decrease as it comes to a stop inside the magnet. It will increase in the opposite direction as the magnet starts to move out, and decrease to zero when the magnet is right out of the coil and stops moving. c

e The motor would run faster / produce more force, because a greater current produces a greater motor effect. f The motor would turn in the opposite direction, because the magnetic field would be pointing the opposite way.

+ Voltage

d The motor would run slower / produce less force, because there are fewer pieces of wire carrying current in the magnetic field.

0

Time

–

P3.19 Generators Student’s Book

P3.18 Making electricity

1 a The induced potential difference (and hence the current) would be less.

Student’s Book

b The induced potential difference would be greater.

1 Electromagnetic induction.

c The induced potential difference would be weaker.

2 Make the wire part of a complete circuit. 3 a Downhill.

2 They would get twisted and eventually would stop the coil turning.

b The bicycle is likely to be going faster when going downhill, so the dynamo would spin faster.

3 a Direct current always flows in the same direction. Alternating current changes direction many times each second.

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b Cells produce d.c. Generators and dynamos produce a.c. 4 Accept any explanation that covers the key points, such as: at b the left-hand part of the coil is moving in one direction relative to the magnetic field, and by the time it has rotated half a turn (at d) it is moving in the opposite direction relative to the field, so at this point the induced current will flow in the opposite direction. 5 a They are cheaper. b To induce a very high potential difference.

Vp Np = Ns Vs 4

230 V=192 12 V Ns

Ns=192×

12V 230V

=10 turns. 5 Vp Np = Vs Ns 1500 20 000 V = 30 000 Vs Vs=20 000 V× 30 000 1500

6 The bullet points should describe all the main features of generators, including the slip rings and brushes.

6 Suitably labelled diagram.

Worksheet P3.19b

Worksheet P3.20a

1 a B, A, D, C.

1 The transformers increase the voltage of the electricity produced. At the same time, the current is reduced, so the overall energy supplied remains the same as it would if the transformers had not been used. A good answer might also comment on energy lost as heat in the transformers.

b B has no core, only one magnet, and only has 50 turns in the coil; A is missing the core and a magnet, but has 100 turns; D has two magnets and 100 turns on the coil, but no iron core; C has 100 turns on the coil, two magnets, and an iron core. 2 Turn it faster, put even more turns of wire on the coil, or use stronger magnets. 3 A power station generator uses electromagnets, has bigger coils with more turns on them and produces a much higher potential difference. Students may mention other differences, such as having more than one coil of wire in the generator, or details of bearings, etc.

P3.20 Transformers Student’s Book 1 a Because alternating current is used in the coil, which means that the direction of the current is continuously changing, and the direction of the magnetic field depends on the direction of the current. b The changing magnetic field will induce a changing potential difference in the secondary coil. 2 Direct current will induce a constant magnetic field, and a changing magnetic field through the secondary coil is needed to induce a current there.

=400 000 V (or 400 kV).

2 a Some energy from the electricity is wasted as heat, and this is the electricity Bill is paying for but not using. b The transformer reduces the voltage, but will also increase the current so the energy supplied is the same (apart from the energy wasted as heat). 3 Statement A is true. The total energy given out / transformed by any machine is equal to the energy it takes in / uses. Statement B is false. The electrical energy supplied by the transformer is slightly less than the energy supplied to it, because some of the energy supplied is converted to heat energy.

Worksheet P3.20b 1 Correctly drawn diagram, with primary and secondary coils and iron core labelled. 2 Vp is the input voltage / the voltage across the primary coil. Vs is the output voltage/the voltage across the secondary coil. Np is the number of turns on the primary coil. Ns is the number of turns on the secondary coil.

3 a Step-down. The laptop needs less than 230 V to charge its battery, so the mains voltage must be reduced.

b Vp is biggest.

b 230 V, because it is connected to the mains supply.

b 163.

3 a Vs is biggest. 4 a 368 V. 5 144 V.

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P3.00 Investigative Skills Assessment (Student’s Book) 1 a Tension. (1 mark) b Continuous. (1 mark) c Length and mass per unit length of wire. (2 marks) d Frequency. (1 mark) e Continuous. (1 mark)

7 Conclusion consistent with student’s own results. (2 marks) 8 Either: yes, with a valid reason, such as having repeated results, or having compared results with other groups, or: no, with explanation that repeating results or comparing results would improve reliability. (1 mark)

2 a There is no check for reliability. (1 mark)

9 Suitable table of results with all relevant data included, (1 mark)

b Accept any answer between 3 and 5. (1 mark)

columns and rows correctly labelled, (1 mark)

3 Accept any answer that explains what proportionality means (in terms of one factor doubling if the other does, or in terms of a straight line on a graph) and that these results do not fit that pattern. (2 marks) (1 mark for a clear, ordered answer)

units present and correct. (1 mark)

4 a 180 N. (1 mark)

11 a Tension. (1 mark)

b Accept any answer between 60 N and 80 N. (1 mark)

b Continuous. (1 mark)

5 a Find the point on the graph corresponding to 247 Hz, and read the tension from the vertical axis. (2 marks)

d Frequency. (1 mark)

b The tension should be 44 N, but allow for the limitations of the scales used on the graph. (1 mark)

P3.00 Investigative Skills Assessment (Copymaster File) Section 1 1 Clear statement of question to be investigated. (2 marks) 2 a Correct independent variable, e.g. speed of movement, number of turns of wire. (1 mark) b Correct independent variable, e.g. potential difference. (1 mark) 3 Explanation of how range was chosen, e.g. did a trial run to see the minimum number of coils needed to produce a detectable potential difference. (1 mark)

10 correct choice of bar chart or graph, (1 mark) suitable scales chosen and labelled, (1 mark) correct plotting. (1 mark) Section 2

c Length and mass per unit length of wire. (2 marks) e Continuous. (1 mark) 12 a There is no check for reliability. (1 mark) b Accept any answer between 3 and 5. (1 mark) 13 Accept any answer that explains what proportionality means (in terms of one factor doubling if the other does, or in terms of a straight line on a graph) and that these results do not fit that pattern. (2 marks) (1 mark for a clear, ordered answer) 14 a 180 N (1 mark) b Accept any answer between 60 N and 80 N (1 mark) 15 a Find the point on the graph corresponding to 247 Hz, and read the tension from the vertical axis. (2 marks) b 44 N. (1 mark)

4 a Voltmeter. (1 mark) b Potential difference (accept voltage). (1 mark) 5 Either: any anomalous results circled, or: correct statement that no results looked anomalous. (1 mark) 6 Either: yes, with a valid reason such as wanting improved reliability / checking anomalous results, or: no, with explanation that plotting a series of results on a graph is a way of checking reliability. (1 mark)

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P3

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P3 Assessment exercises Question Answer 1a At the point where the lines cross.

Extra information

Mark 1

b

A plumb line (or equivalent) and a means of suspending the card.

2

c

She suspended the card she used the plumb line to mark a vertical line and then repeated this process twice more. A suspended card will always hang with its centre of mass below the point of suspension so when it is suspended from two or more different places, the centre of mass must lie where the lines cross. Ravi. His lines all cross at one point, whereas on the other cards the lines form a triangle, so they must have been inaccurate. Random. Any explanation that either rules out a zero error (as no instruments requiring zeroing are involved), or a statement that a systematic error would always be an error in the same direction, which is unlikely in this kind of activity.

1 mark for each point. Accept any sensible apparatus for doing this. 1 mark for each point.

Accept equivalent explanations.

1

d

e

f

2 a b

c

That there may be life on Mars. That they would see other built objects – e.g. buildings, etc.

c

Polar orbit because it could eventually survey/photograph the whole surface of the planet.

4 a b

1 1 mark for name; 1 mark for explanation.

Hydrogen and helium. Fusion reactions inside stars (or in supernova explosions) create other elements.

2

1 1

Total 12 1

Acceleration depends on speed and direction, and its direction is constantly changing. The centripetal force depends on the mass of the object moving in a circle so the notice is to ensure the maximum mass in the carriage is not too big for the strength of the arm to cope with. (Or equivalent explanation.) The arm will need to be stronger because there is a greater force when the radius of the circle is smaller.

3 a b

3

1 1

Accept any equivalent suggestions. 1 mark for each point.

Both needed for the mark.

1 1 Total 5 1 1 2

Total 4 1 1 1 Total 3

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Question Answer Continuous. 5 a A mirror could be made with any radius. The magnification. b

Extra information 1 mark for each point.

c

Accurately drawn base for diagram (i.e. object correct size and distance from the mirror, with focal point marked correctly). Two rays drawn accurately to show location of image (the image should be inverted, and twice the size of the object). 2. The magnification of a particular mirror depends on where the object is located.

1 mark for base; 2 marks for rays

6

A real image can be projected on a screen. A virtual image cannot.

1 mark for each point.

Total 8 2

7 a b

It did not fit the pattern of the other results. It makes it easier to spot results that may be incorrect. When making a calculation based on results, readings can be taken from a line of best fit rather than an individual result, making the final result more reliable. Values from graph substituted correctly final answer=20 A. Any valid calculation or explanation for the choice.

1 mark for each point.

Total 2 1 2

d e

c d

8 a

bi ii

Mark 2 1

Some ultrasound is reflected when it goes into a different medium and the time between sending the sound and receiving the echo can be used to work out how far into the material the echo came from. The bottom one. The first peak is caused by the join between the two pieces of material, and the second is caused by the far side of the bottom piece of material.

3

1 1

1 mark for values, 1 mark for 2 final answer. 1 mark for answer, 1 mark for 2 reasoning. 1 mark for each point.

Total 7 2

1 1

Total 4 45 marks

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P3 Unit test Question Answer Centre of mass marked in the centre of the post. 1 a The centre of mass is on the lines of symmetry in a b symmetrical body. At point P. c Line drawn from P that is perpendicular to the rope. d C. e The perpendicular distance between P and rope is the f greatest. 2 a i ii b i ii iii c d e

3 a

b

c d

170

Extra information Accept equivalent explanations.

1 1 1 1

Io. It is closest to Jupiter. Io is the closest to Jupiter. Accept equivalent explanations. Ganymede has the greatest mass. The greater mass of Ganymede might be offset by its greater distance from Jupiter. The surface appears to be similar to ice-covered oceans on Earth. A hole drilled in the ice should eventually come to liquid water. Any two from: 1 mark for each point. The drill may have gone through a place where there is no ocean beneath. The drill may not be able to go far enough through the ice. There may be no water beneath the ice at all. [5] Planetary nebula. [1] Cloud of dust and gas. [2] Nuclear fusion reactions start. [6] White dwarf. [4] Red giant. [3] Star converts hydrogen to helium. There will be a supernova explosion instead of a red giant. A very large star will then form a black hole. A smaller star will form a neutron star. A ring of dust and gas thrown off by a red giant before it becomes a white dwarf. Radiation pressure balances gravity.

AQA GCSE Extension Science Teacher’s Guide

Mark 1 1

Total 6 1 1 1 1 1 1 1 2

All correct for the mark.

Total 9 1

1 mark for each point.

3

1 1 Total 6

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Answers

Question Answer Two correct construction lines drawn, as shown. 4 a

F

b c d

5 a

b

F

Extra information 1 mark for each correct construction line; 1 mark for lines crossing at top of image; 1 mark for image.

Mark 4

2F

Lines traced to cross at top of image. Image drawn in correct plane and upright. Eye drawn in correct position, as shown above. Correct substitution of 1.2 (±0.1)/2 correct evaluation (0.6 ±0.1). One from: security mirror in shop, mirror allowing view of concealed bend, or any other valid response. Any two from: Turn it faster. Increase magnetic field. More turns on coil. Bigger area of coil. They allow contact between the coil and the rest of the circuit; without the wires becoming tangled

1 mark for each point.

1 2 1

1 mark for each point.

Total 8 2

1 mark for each point.

2

1 mark for each point.

Total 4 1 1 1 1 2

6 a b c d e

Material. Categoric. Amount of refraction. Wavelength of light. More results for each material allows him to compare/ average his results (or spot outliers); so his results will be more reliable.

f i

The beam will be narrower after refraction/the material will refract different wavelengths by different amounts.

1

ii

He would need to check his results are valid for all wavelengths, or a comment about spectacles needing to work for all wavelengths of visible light.

1

Total 8 7 a b

Trace should have a lower amplitude and a lower frequency/longer wavelength Each instrument also produces a number of different frequencies; and the additional frequencies are different with different instruments / which produces different waveforms.

1 mark for each point.

2

1 mark for each point.

2

Total 4 45 marks

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