Key Stage 3 Science. Andy Cooke Jean Martin

Transcription

1 Key Stage 3 Science Andy Cooke Jean Martin

2 Series editors Consultant Authors Andy Cooke Jean Martin Sam Ellis Andy Cooke Sam Ellis David Glover Jean Martin Janet McKechnie Chris Ram Nicky Thomas PUBLISHED BY THE PRESS SYNDICATE OF THE UNIVERSITY OF CAMBRIDGE The Pitt Building, Trumpington Street, Cambridge, United Kingdom CAMBRIDGE UNIVERSITY PRESS The Edinburgh Building, Cambridge CB2 2RU, UK 40 West 20th Street, New York, NY , USA 477 Williamstown Road, Port Melbourne, VIC 3207, Australia Ruiz de Alarcón 13, Madrid, Spain Dock House, The Waterfront, Cape Town 8001, South Africa Cambridge University Press 2004 First published 2004 Printed in Dubai by Oriental Press Typeface Delima MT System QuarkXPress A catalogue record for this book is available from the British Library ISBN X paperback Material in this book was previously published in Spectrum Year 7 Class Book (pp ), Spectrum Year 8 Class Book (pp ) and Spectrum Year 9 Class Book (pp ). Cover design by Blue Pig Design Co Page make-up and illustration by Hardlines Ltd, Charlbury, Oxford NOTICE TO TEACHERS It is illegal to reproduce any part of this work in material form (including photocopying and electronic storage) except under the following circumstances: (i) where you are abiding by a licence granted to your school or institution by the Copyright Licensing Agency; (ii) where no such licence exists, or where you wish to exceed the terms of a licence, and you have gained the written permission of Cambridge University Press; (iii) where you are allowed to reproduce without permission under the provisions of Chapter 3 of the Copyright, Designs and Patents Act 1988.

3 Contents Introduction Page v Unit 7I Energy resources 1 7I.1 Energy and fuels 1 7I.2 Fossil fuels 5 7I.3 Renewable energy resources 8 7I.4 Living things and energy 12 Unit 7J Electrical circuits 15 7J.1 How electrical circuits work 15 7J.2 Inside a circuit 18 7J.3 Energy for the circuit 21 7J.4 Parallel circuits 23 7J.5 Using electricity safely 26 7J.6 Discovering electricity 28 Unit 7K Forces and their effects 30 7K.1 Where we come across forces 30 7K.2 Weight 32 7K.3 Stretching materials 34 7K.4 Floating and sinking 36 7K.5 Friction 39 7K.6 Moving and stopping 42 Unit 7L The Solar System and beyond 45 7L.1 The Earth in space 45 7L.2 The four seasons 48 7L.3 Lights in space 50 7L.4 The Sun and the Moon 52 7L.5 The Solar System 54 7L.6 Beyond the Solar System 56 Unit 8I Heating and cooling 59 8I.1 Measuring how hot things are 59 8I.2 Changing the temperature 61 8I.3 Hot to cold 62 8I.4 Moving the heat energy in liquids and gases 64 8I.5 How energy travels through space 66 8I.6 Keeping warm 67 8I.7 Changing between solid, liquid and gas 68 Unit 8J Magnets and electromagnets 72 8J.1 Magnetic forces 72 8J.2 Magnetic fields 75 8J.3 Making and using magnets 76 8J.4 Making and using electromagnets 78 iii

4 Unit 8K Light 82 8K.1 Where light comes from and how it travels 82 8K.2 Light hitting objects 85 8K.3 Mirrors 87 8K.4 Bending light 89 8K.5 The spectrum 91 8K.6 Colours 93 Unit 8L Sound and hearing 97 8L.1 Making sound 97 8L.2 Travelling sound 101 8L.3 Hearing sound 103 8L.4 Dangerous sound 105 Unit 9I Energy and electricity 109 9I.1 How is energy involved in doing useful things? 109 9I.2 How does electricity transfer energy? 111 9I.3 Paying for and reducing the waste of electricty 113 9I.4 Where do we get electrical energy from? 116 Unit 9J Gravity and space 119 9J.1 What is gravity? 119 9J.2 How have our ideas about the Solar System changed? 122 9J.3 What keeps the planets and satelites in orbit? 125 Unit 9K Speeding up 131 9K.1 Describing how fast something moves 131 9K.2 Working out speed 133 9K.3 Force and speed 136 9K.4 Slowing things down 139 9K.5 Streamlining 141 9K.6 Skydiving and parachutes 144 Unit 9L Pressure and moments 147 9L.1 What is pressure? 147 9L.2 Gases under pressure 150 9L.3 Liquids under pressure 152 9L.4 Turning forces 154 9L.5 Balance and levers 157 Scientific investigations 161 Glossary/Index 169 Acknowledgements 178 iv

5 7I Energy resources In this unit we shall be studying what energy is and how we use it. 7I.1 Energy and fuels Energy is one of the big ideas in science. It is so important that it has its own unit, joules. We measure energy in joules. What energy is Anything that involves energy change can be called work. Nothing can happen without energy making it happen. To do work energy must change in some way. It can: The microwave oven needs energy to cook. The rocket needs energy to take off. move from one place to another this is called energy transfer; change from one type of energy to another this is called transformation. The cheetah needs energy to run. The plant needs energy to grow. KEY WORDS energy joules gravitational potential chemical kinetic heat light elastic potential electrical sound engine Bunsen burner fossil fuel coal mineral oil natural gas non-renewable renewable wind tidal solar wave hydro-electric geothermal biomass 1 What is meant by energy? 2 What must energy do to make things happen? 3 Make a list of six things that you think need energy to make them happen or work. Unit 7I 1

6 There are different types of energy We are surrounded by different types of energy. Once you know what they are, you can spot them everywhere. Gravitational potential energy is stored in things which are high up. A moving object has kinetic energy. DIESEL FUEL Fuels store chemical energy. Heat energy is given out by hot objects. Light energy is given out by luminous objects. Elastic potential energy is stored in things which are squashed or stretched. Electrical energy is the energy carried by electricity. 4 Name the eight types of energy. Sound energy is given out by loudspeakers. 5 List any types of energy that are present in your classroom. Making things happen We know that energy needs to change from one type to another to make things happen. We can show some of these changes using an energy transformation diagram. The picture shows an example: 6 What type of energy does a kettle transform electrical energy into? Electrical energy Heat energy 7 What useful energy does a bulb transform electrical energy into? 2 Unit 7I

7 Useful fuels Fuels have chemical energy stored in them. We burn fuels to release this stored energy as heat. We use the energy to make lots of useful things happen. Most of our electrical energy comes from burning fuels in power stations. This is then transformed into electrical energy by generators. In the science laboratory you will use a Bunsen burner. This burns methane or propane gas to release heat energy. In everyday life we use lots of different fuels to do different jobs. In a car this fuel is usually petrol or diesel. It burns inside the engine. 8 Look at the five pictures showing different fuels being used. Then, list five common fuels. 9 What fuel can be used instead of petrol and diesel? 10 Which fuel was used to light street lights in the 19th century? We burn fuels to do jobs for us. These jobs mainly fall into one of four categories: transport, heating, cooking and making electricity. Oil is used to heat schools. Gas is used to cook. Aircraft use aviation fuel. 11 What are the four main categories of uses for fuels? Coal is used to generate electricity. 12 Which fuels can be used to heat our homes? 13 Name a fuel (other than the one shown in the picture) that can be used in a power station. Unit 7I 3