Cambridge checkpoint science_coursebook_7
- 1. Mary Jones, Diane Fellowes-Freeman and David Sang Coursebook Cambridge Checkpoint Science 7
- 2. cambridge university press Cambridge, New York, Melbourne, Madrid, Cape Town, Singapore, São Paulo, Delhi, Tokyo, Mexico City Cambridge University Press The Edinburgh Building, Cambridge CB2 8RU, UK www.cambridge.org Information on this title: www.cambridge.org/9781107613331 © Cambridge University Press 2012 This publication is in copyright. Subject to statutory exception and to the provisions of relevant collective licensing agreements, no reproduction of any part may take place without the written permission of Cambridge University Press. First published 2012 Printed in India by Replika Press Pvt Ltd A catalogue record for this publication is available from the British Library ISBN 978-1-107-61333-1 Paperback Cambridge University Press has no responsibility for the persistence or accuracy of URLs for external or third-party internet websites referred to in this publication, and does not guarantee that any content on such websites is, or will remain, accurate or appropriate. notice to teachers References to Activities contained in these resources are provided ‘as is’ and information provided is on the understanding that teachers and technicians shall undertake a thorough and appropriate risk assessment before undertaking any of the Activities listed. Cambridge University Press makes no warranties, representations or claims of any kind concerning the Activities. To the extent permitted by law, Cambridge University Press will not be liable for any loss, injury, claim, liability or damage of any kind resulting from the use of the Activities.
- 3. Introduction Welcome to your Cambridge Secondary 1 Science course! This book covers the first year, Stage 7, of the Cambridge Secondary 1 Science curriculum. At the end of the year, your teacher may ask you to take a test called a Progression Test. This book will help you to learn how to be a good scientist, and to do well in the test. The main areas of science The book is divided into three main sections, each one dealing with one of three main areas of science. These are: Biology – the study of living organisms Chemistry – the study of the substances from which the Earth and the rest of the Universe are made Physics – the study of the nature and properties of matter, energy and forces. There are no sharp dividing lines between these three branches of science. You will find many overlaps between them. Learning to be a scientist During your course, you will learn a lot of facts and information. You will also begin to learn to think like a scientist. Scientists collect information and do experiments to try to find out how things work. You will learn how to plan an experiment to try to find out the answer to a question. You will learn how to record your results, and how to use them to make a conclusion. When you see this symbol , it means that the task will help you to develop your scientific enquiry skills. Using your knowledge It’s important to learn facts and scientific ideas as you go through your science course. But it is just as important to be able to use these facts and ideas. When you see this symbol , it means that you are being asked to use your knowledge to work out an answer. You will have to think hard to find the answer for yourself, using the science that you have learnt. (A+I stands for Applications and Implications.)
- 4. Contents Introduction 3 Biology Unit 1 Plants and humans as organisms 1.1 Plant organs 6 1.2 Human organ systems 8 1.3 The human skeleton 10 1.4 Joints 12 1.5 Muscles 14 1.6 Studying the human body 16 End of unit questions 18 Unit 2 Cells and organisms 2.1 Characteristics of living organisms 20 2.2 Micro-organisms 22 2.3 Micro-organisms and decay 24 2.4 Micro-organisms and food 26 2.5 Micro-organisms and disease 28 2.6 Plant cells 30 2.7 Animal cells 32 2.8 Cells, tissues and organs 34 End of unit questions 36 Unit 3 Living things in their environment 3.1 Adaptations 38 3.2 Food chains 40 3.3 Humans and food chains 42 3.4 Pollution 44 3.5 Ozone depletion 46 3.6 Conservation 48 3.7 Energy resources 50 End of unit questions 52 Unit 4 Variation and classification 4.1 What is a species? 54 4.2 Variation in a species 56 4.3 Investigating variation 58 4.4 Classifying plants 60 4.5 Classifying vertebrates 62 4.6 Classifying invertebrates 64 End of unit questions 66 Chemistry Unit 5 States of matter 5.1 States of matter 68 5.2 Particle theory 70 5.3 Changing state 72 5.4 Explaining changes of state 75 End of unit questions 78 Unit 6 Material properties 6.1 Metals 80 6.2 Non-metals 82 6.3 Comparing metals and non-metals 84 6.4 Everyday materials and their properties 86 End of unit questions 88 Unit 7 Material changes 7.1 Acids and alkalis 90 7.2 Is it an acid or an alkali? 92 7.3 The pH scale 94 7.4 Neutralisation 96 7.5 Neutralisation in action 98 7.6 Investigating acids and alkalis 100 End of unit questions 102 Unit 8 The Earth 8.1 Rocks, minerals and soils 104 8.2 Soil 106 8.3 Igneous rocks 108 8.4 Sedimentary rocks 110 8.5 Metamorphic rocks 112 8.6 Weathering 114 8.7 Moving rocks 116 8.8 Fossils 118 8.9 The fossil record 120 8.10 The structure and age of the Earth 122 8.11 The geological timescale 124 End of unit questions 126
- 5. Contents Physics Unit 9 Forces and motion 9.1 Seeing forces 128 9.2 Forces big and small 131 9.3 Weight – the pull of gravity 134 9.4 Friction – an important force 136 9.5 Air resistance 138 9.6 Patterns of falling 140 End of unit questions 142 Unit 10 Energy 10.1 Using energy 144 10.2 Chemical stores of energy 146 10.3 More energy stores 148 10.4 Thermal energy 150 10.5 Kinetic energy 152 10.6 Energy on the move 154 10.7 Energy changing form 156 10.8 Energy is conserved 158 End of unit questions 160 Unit 11 The Earth and beyond 11.1 Day and night 162 11.2 The starry skies 164 11.3 The moving planets 166 11.4 Seeing stars and planets 168 11.5 The Moon and its phases 170 11.6 A revolution in astronomy 172 11.7 400 years of astronomy 174 11.8 Journey into space 176 End of unit questions 178 Reference Laboratory apparatus 180 Units 181 How to measure a length 181 How to measure a temperature 182 How to measure a volume of liquid 182 How to construct a results table 183 How to draw a line graph 184 Glossary and index 185 Acknowledgements 191
- 6. 1 Plants and humans as organisms 1.1 Plant organs This map shows where plants cover the surface of the Earth. The map was made using information collected by a space satellite. Most plants are green. This is because they contain a green pigment (colouring) called chlorophyll. Chlorophyll absorbs (takes in) energy from sunlight. Plants use this energy to make food. All the food that is eaten by animals was originally made by plants. Plants give out oxygen during the daytime. The oxygen in the air, which almost all living things need to stay alive, was all made by plants. rainforest grassland and forest desert ice Questions 1 Look at the map. Explain why some parts of the map are shown in dark green, and some parts are light green. 2 There are very few plants in the brown parts of the map. Suggest why there are not many plants in these places. 3 Find the place where you live on the map. a What does the map tell you about the plants that cover the part of the world where you live? b Do you agree with the information on the map about your part of the world? Explain your answer. 4 Animals can only live on Earth because there are plants on Earth. Explain why. 1.1
- 7. 1 Plants and humans as organisms 1.1 Plant organs The structure of a plant A plant is a living thing. Another word for a living thing is an organism. The parts of an organism are called organs. The diagram shows some of the organs in a flowering plant. Questions 5 Why do you think roots branch out into the soil? You may be able to think of two reasons. 6 Suggest why many leaves are very broad and thin. Summary Activity 1.1 Pressing a plant Your teacher will help you to find a complete, small plant. 1 Wash the roots of your plant carefully. Try to get rid of all the soil, but don’t damage the roots. 2 Carefully place the plant on a sheet of newspaper. Spread it out so that all of its parts are as flat as you can make them. 3 Put another sheet of newspaper over the top of your plant. Put a heavy weight on it to press the plant flat. 4 Leave your plant for at least a week to dry out. 5 Put your plant into your notebook and stick it down with some strips of sticky tape. Label the different organs, and write down what each of them does. Flowers are reproductive organs. They produce seeds, which can grow into new plants. The roots hold the plant firmly in the soil. They absorb water and minerals from the soil. The stem holds the leaves and flowers above the ground. Leaves are the food factories of the plant. They absorb energy from sunlight, and use it to make food.
- 8. 1 Plants and humans as organisms 1.2 Human organ systems We have seen that the different parts of plants are called organs. Animals also have organs. For example, an eye is an organ. The heart is an organ, and so is the brain. The organs in a human work together in teams. A group of organs that work together is called an organ system. Questions 1 Look at the diagram of the digestive system. Write down, in order, the organs that food passes through as it moves through the digestive system. 2 Some of the food you eat is not broken down into tiny particles in the digestive system. Suggest what happens to the food that is not broken down. The digestive system When you eat or drink, food goes into your digestive system. This is a long tube that runs all the way through the body. Food usually takes between one and three days to travel from one end of the tube to the other. Most of the food is broken down into tiny particles inside the digestive system. The breaking down is called digestion. The tiny particles move out of the digestive system, through its walls. They move into the blood. The blood carries them to every part of the body. small intestine liver pancreas rectum large intestine (colon) stomach mouth artery to lungs vein from lungs heart arteries to body veins from body The circulatory system The circulatory system transports substances all over the body. It is made up of tubes called blood vessels. These tubes contain blood. The blood is pumped around the circulatory system by the heart.
- 9. 1 Plants and humans as organisms Summary Summary 1.2 Human organ systems Questions 3 Explain how nerves help the different organs in the body to work together. 4 Why do all cells in the body need oxygen? 5 Describe the function of the lungs. The nervous system The nervous system helps different parts of the body to communicate with one another. Signals travel along nerves from the brain and spinal cord to all the other body organs. Sense organs are also part of the nervous system. For example, your eyes sense light. Signals travel from your eyes to your brain. The respiratory system The respiratory system is where oxygen enters your body and carbon dioxide leaves it. All of your cells need oxygen, so that they can respire. This is how they get their energy. When cells respire, they make carbon dioxide, which is a waste product. Air moves down a series of tubes, until it is deep inside the lungs. This is where oxygen moves into your blood. Carbon dioxide moves out of the blood and into the lungs. The air containing this carbon dioxide moves out of the lungs when you breathe out. brain spinal cord nerves lung bronchus ribs diaphragm trachea (windpipe)
- 10. 1 Plants and humans as organisms 1.3 The human skeleton Your skeleton supports your body and helps it to move. It also protects some of the soft organs inside you. The diagram shows the main bones in the skeleton. Questions 1 List three functions of the skeleton. 2 Look at the diagram of the skeleton. How are the bones in the arms and legs similar? 3 How many ribs does a person have? (Remember that there are the same number on both sides of the body.) 4 As well as supporting the body, some bones protect other organs. Name the bones that protect: brain, heart and lungs. 5 Look at the X-ray of a mink. Do you think a mink has the same bones as a human? What evidence do you have for your answer? cranium This is an X-ray of a mink. vertebral column clavicle rib sternum scapula humerus ulna radius carpals pelvic girdle femur tibia fibula
- 11. 1 Plants and humans as organisms 10 N 9 8 7 6 5 4 3 2 1 0 Summary In this experiment, you will use drinking straws instead of real bones. You will measure the force needed to make the straw bend, rather than break. The diagram shows how you will find the force needed to bend the straw. You will use a forcemeter. You can find out how to use a forcemeter on page 131. It’s easiest to do this in pairs. One of you pulls the forcemeter. The other one notes the reading on the forcemeter when the straw collapses. 1 Copy the results table, ready to fill in as you do your experiment. 2 Collect two identical straws. Keep one full length. Cut one in half. Cut one of the halves into half again. 3 Measure the length of a full-length straw, in cm. Fill in your measurement in the first row of your results table. 4 Find the force needed to make a full- length straw bend. Write your result in your results table. 5 Now repeat steps 3 and 4 with the half- length straw and the one-quarter-length straw. Activity 1.3 Do long bones break more easily than short bones? 1.3 The human skeleton Questions A1 To make this experiment a fair test, you kept everything the same except the length of the straws. Write down three things that you kept the same. A2 What conclusion can you make from your results? straw short nail in wooden support forcemeter pull Press gently on the straw to hold it in place. Pull gently, directly upwards. Read the force when the straw collapses. Length of straw /cm Force needed to bend the straw /N
- 12. 1 Plants and humans as organisms 1.4 Joints Fixed and moveable joints A joint is a place where two bones meet. We have two main types of joints in our bodies: The skull has fixed joints in the cranium. The cranium is made up of several bones firmly joined together. This helps the cranium to protect the brain. The jawbone is joined to the rest of the skull by a moveable joint. This allows the jaw to move up and down and from side to side when you chew, talk or yawn. Hinge joints and ball-and-socket joints Your shoulder joint can move in almost all directions. You can swing your arm round in a complete circle. This is because the shoulder joint is a ball-and-socket joint. A ball on one bone fits into a socket on the other. Your elbow joint is a hinge joint. It can move in only one direction. It moves like a door on a hinge. Questions 1 State one place in the body where you have a fixed joint. Why is it useful to have a fixed joint in this place? 2 Name the bones that form the ball-and-socket joint in your shoulder. 3 Name the bones that form the hinge joint at your elbow. The skull contains both fixed joints and moveable joints. The shoulder is a ball-and-socket joint. The elbow is a hinge joint. shoulder joint elbow joint cranium orbit fixed joint moveable joint jawbone
- 13. 1 Plants and humans as organisms Activity 1.4 Which kind of joint? Summary Try moving each of these joints in your body, and decide whether each one is: a fixed joint a hinge joint a ball-and-socket joint a a finger joint, b the knee joint, c a toe joint, d the hip joint 1.4 Joints Questions 4 Suggest why it is important to reduce friction at moveable joints. 5 Describe where cartilage is found at the elbow joint. Why is the cartilage there? 6 What is the function of synovial fluid? 7 Look at the diagram of the elbow joint. Suggest how the two bones are held together at the elbow joint. Structure of a moveable joint The diagram shows what the elbow joint would look like if you could cut through it. It is important that joints can move easily. When two surfaces move against each other, a force called friction tries to stop them. You can read more about friction on page 136. To reduce friction: the ends of the bones are covered with a very smooth, slippery material called cartilage a thick, slippery fluid called synovial fluid fills the spaces between the two bones. The synovial fluid helps to lubricate the joint, like oil in the moving parts of an engine or bicycle. humerus fat tissue synovial membrane synovial fluid cartilage ulna ligaments (joint capsule)
- 14. 1 Plants and humans as organisms 1.5 Muscles Muscles are organs that help us to move. The diagram shows the two main muscles in the upper arm. The muscles are attached to the bones by tendons. Tendons are very strong, and they do not stretch. Questions 1 Name the bones that the biceps muscle is attached to. 2 Name the bones that the triceps muscle is attached to. 3 ‘Bi’ means ‘two’. ‘Tri’ means three. Look carefully at the diagram, and suggest why the biceps and triceps are given their names. Questions 4 Predict what will happen if the biceps stops contracting, and the triceps contracts. 5 Explain why it is important that tendons do not stretch. How muscles work Muscles can get shorter. This is called contraction. When muscles contract, they produce a pulling force. Look at the diagram of the muscles in the arm. When the biceps muscle contracts, it pulls on the radius and scapula. The pulling force is transmitted to these bones through the strong tendons. The radius is pulled upwards, towards the scapula. The arm bends. two tendons humerus scapula radius ulna You can see the biceps muscle bulging when it makes the arm bend. three tendons biceps muscle triceps muscle
- 15. 1 Plants and humans as organisms Summary 1.5 Muscles Question 6 Explain why the biceps muscle alone cannot make the arm straighten. Antagonistic muscles Muscles can contract and make themselves shorter. However, muscles cannot make themselves get longer. When a muscle is not contracting, we say that it is relaxed. A relaxed muscle does not do anything by itself. But if a force pulls on it, the force can make the relaxed muscle get longer. The top diagram shows what happens when the biceps muscle contracts and the triceps muscle relaxes. The contracting biceps muscle makes the arm bend at the elbow joint. It also pulls the relaxed triceps muscle and makes it longer. The next diagram shows how the arm can be made straight again. To do this, the triceps muscle contracts, and the biceps muscle relaxes. You can see that the biceps and triceps work as a team. When one of them contracts, the other one relaxes. When one of them contracts, it pulls the bones in one direction, and when the other contracts, it pulls the bones in the opposite direction. A pair of muscles that work together like this are called antagonistic muscles. To bend the arm, the biceps contracts (gets shorter) and the triceps relaxes. To straighten the arm, the triceps contracts and the biceps relaxes. The contracting triceps pulls on the tendon, so the ulna moves downwards. pulling force The contracting biceps pulls on the tendon, so the radius moves upwards.