Cambridge Checkpoint Lower Secondary Science 9 Student's Book PDF

Cambridge checkp int THIRD EDITION Lower Secondary Science 9 SAMPLE MATERIAL We are working with Cambridge Assessment...

Cambridge checkp int THIRD EDITION Lower Secondary Science 9 SAMPLE MATERIAL We are working with Cambridge Assessment International Education to gain endorsement for this forthcoming title. Peter D Riley  We are working with Cambridge Assessment Please note this is a sample International Education to gain endorsement and not a full chapter for this forthcoming series. Help students engage with and fully understand topics they are studying with engaging content following the new Cambridge Lower Secondary Science curriculum framework (0893) from 2020. Teacher’s Guide with Boost Student’s Book Boost eBook Workbook subscription £19.50 £13 for 1-year access £7.25 £150 for access until 2026 March 2021 March 2021 June 2021 July 2021 Student’s Book 7 eBook 7 Workbook 7 Teacher’s Guide 7 9781398300187 9781398302136 9781398301399 9781398300750 Student’s Book 8 eBook 8 Workbook 8 Teacher’s Guide 8 9781398302099 9781398302174 9781398301412 9781398300767 Student’s Book 9 eBook 9 Workbook 9 Teacher’s Guide 9 9781398302181 9781398302228 9781398301436 9781398300774 Boost eBooks – interactive, engaging and completely flexible Boost eBooks use the latest research and technologies to provide the very best learning experience for students. They can be downloaded onto any device and used in the classroom, at home or on the move. l Interactive: Packed with features such as notes, links, highlights, bookmarks, formative quizzes, flashcards, videos and interactive revision. l Accessible: Effortlessly support different learning styles with text-to-speech function. l Flexible: Seamlessly switch between the printed page view and interactive view. Practise and consolidate knowledge gained from the Student’s Book with this, write-in workbook full of corresponding learning activities. l Provide guidance for students on successfully covering all learning objectives within the new curriculum framework. l Reinforce students’ understanding of key scientific concepts with varied question types, quizzes and the use of ICT. l Challenge students with extra practice activities to encourage regular self-assessment. Created with teachers and students in schools across the globe, Boost is the next generation in digital learning for schools, bringing quality content and new technology together in one interactive website. The Cambridge Checkpoint Lower Secondary Science Teacher’s Guides include a print handbook and a subscription to Boost, where you will find a range of online resources to support your teaching. l Confidently deliver the new curriculum framework: Expert author guidance on the different approaches to learning, including developing scientific language and the skills required to think and work scientifically. l Develop key concepts and skills: Suggested activities, quizzes and guidance on assessment, as well as ideas for supporting and extending students working at different levels. l Support the use of ESL: Introductions and activities included that have been developed by an ESL specialist to help facilitate the most effective teaching in classrooms with mixed English abilities. l Enrich learning: Audio versions of the glossary to help aid understanding, pronunciation and critical appreciation. To explore the entire series, visit www.hoddereducation.com/cambridge-checkpoint-science We’re here to help! If we can help with questions, and to find out more, please contact us at [email protected]  Cambridge checkp int THIRD EDITION Lower Secondary Science 9 Peter D Riley Photo credits: p.3 t, l © Hans-Joerg Krohn; p.3 t, c © INNA FINKOVA/Alamy Stock Photo; p.3 t, r © Arbalest/ stock.adobe.com; p.5 t © Panther Media GmbH/Alamy Stock Photo; p.5 b © Photo Researchers/Science History Images/Alamy Stock Photo; p.8 t © Martyn F. Chillmaid Every effort has been made to trace all copyright holders, but if any have been inadvertently overlooked, the Publishers will be pleased to make the necessary arrangements at the first opportunity. Although every effort has been made to ensure that website addresses are correct at time of going to press, Hodder Education cannot be held responsible for the content of any website mentioned in this book. It is sometimes possible to find a relocated web page by typing in the address of the home page for a website in the URL window of your browser. Hachette UK’s policy is to use papers that are natural, renewable and recyclable products and made from wood grown in well-managed forests and other controlled sources. The logging and manufacturing processes are expected to conform to the environmental regulations of the country of origin. Orders: please contact Bookpoint Ltd, 130 Park Drive, Milton Park, Abingdon, Oxon OX14 4SE. Telephone: +44 (0)1235 827827. Fax: +44 (0)1235 400401. Email: [email protected] Lines are open from 9 a.m. to 5 p.m., Monday to Saturday, with a 24-hour message answering service. You can also order through our website: www.hoddereducation.com ISBN: 9781398302181 © Peter D Riley 2021 First published in 2021 This edition published in 2021 by Hodder Education, An Hachette UK Company Carmelite House 50 Victoria Embankment London EC4Y 0DZ www.hoddereducation.com Impression number 10 9 8 7 6 5 4 3 2 1 Year 2025 2024 2023 2022 2021 All rights reserved. Apart from any use permitted under UK copyright law, no part of this publication may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying and recording, or held within any information storage and retrieval system, without permission in writing from the publisher or under licence from the Copyright Licensing Agency Limited. Further details of such licences (for reprographic reproduction) may be obtained from the Copyright Licensing Agency Limited, www.cla.co.uk Cover photo © NicoElNino – stock.adobe.com Illustrations by Integra Software Services Pvt. Ltd., Pondicherry, India. Figure 14.1 by Barking Dog Art. Typeset in Integra Software Services Pvt. Ltd., Pondicherry, India. Printed in the UK. A catalogue record for this title is available from the British Library. Contents How to use this book Introducing science Biology Chapter 1 Water and life Chapter 2 Photosynthesis Chapter 3 Genetics Chapter 4 Care in fetal development Chapter 5 Environmental change and extinction Chemistry Chapter 6 The Periodic Table Chapter 7 Bonds and structures Chapter 8 Density Chapter 9 Displacement reactions Chapter 10 Preparing common salts Chapter 11 Rates of reaction Physics Chapter 12 Energy Chapter 13 Waves Chapter 14 Electric circuits Earth and space Chapter 15 The planet Earth Chapter 16 Cycles on Earth Chapter 17 Earth in space Chapter 18 Theories of everything Glossary Index Acknowledgements iii  14 Electric circuits l A simple circuit l Series and parallel circuits l Current l Voltage l Resistance l Buzzers l Batteries Do you remember? l Name a good conductor of electricity. l Name an electrical insulator. l If you make a circuit and it does not conduct electricity, what do you need to check? p Figure 14.1 14_01a Science Stage 9 Student's Book Third Edition DID YOU KNOW? l Draw circuit diagrams that would work based on the components Barkingdogart 14_01b Science Stage 9 Student's Book Third Edition Electricity travels at each student has in front of them. How will they know if the circuit Barkingdogart the speed of light is complete? – about 300 000 l What is the name given to the tiny parts of an atom that make a current kilometers per of electricity? second. l How could you use a bag of lemons to light an LED? 2  14 Electric circuits p Figure 14.2 Complicated wiring p Figure 14.3 Microcircuits on a p Figure 14.4 Circuits on a microchip computer circuit board Electrical circuits can be very complicated as shown by Figures 14.2, 14.3 and 14.4 above. DID YOU KNOW? It does not matter how complicated the electrical circuit is, they all work A bird can sit on a due to the properties and processes of simple circuits that we use in school power line because it science laboratories. This means that a study of simple electrical circuits is not part of a circuit. can lead some people to an interest in electrical engineering, and an If it touched a second involvement in developing the circuits shown in the figures above. power line with its beak and made a circuit, the bird would A simple electrical circuit be electrocuted. Figure 14.5 below shows the simple circuit you studied in Stage 7. See how many of the questions you can answer to check the knowledge of electrical 1 How do you circuits you already have. a close this circuit b open this circuit? 2 What happens cell when the circuit is a closed b opened? 3 Use the symbols in wire Figure 14.6 to make a circuit diagram of switch the simple circuit in Figure 14.5. lamp  Figure 14.5 Figure 14.6 shows the symbols for components in the circuit: cell connecting wire lamp switch  Figure 14.6 3  PHYSICS When two or more cells are joined together they make a battery. The symbols in Figure 14.7 show the arrangement for batteries with two cells, three cells and any number of cells. p Figure 14.7 The circuits symbols for two cells, three cells and any number of cells Series and parallel circuits There are two kinds of electrical circuits – series circuits and parallel circuits. 4 Use the symbols in Figure 14.6 to make a b circuit diagrams of Figures 14.8a and b. series circuit parallel circuit p Figure 14.8a A series circuit and b a parallel circuit In a series circuit, all the components are arranged in a line or a loop, as Figure 14.8a shows. In a parallel circuit, two or more components are wired up side by side, as Figure 14.8b shows. Current When the current flows through a series circuit you can think of it as passing through all the components one after the other. When the current flows through a parallel circuit, it divides where the components are in parallel. The two currents flowing through each part of the parallel circuit is equal to the total current that flows from the cell of the battery (but see ‘Measuring current in series and parallel circuits’ on page 00). 4  14 Electric circuits Science in context The current of electricity most widely used The electricity that we use in our homes, schools and workplaces is not generated by cells like the ones used in this chapter. Most of the electricity we use today is generated by magnets that spin in coils of copper wire in power stations. This development came about in the following way. A scientist living in Denmark, called Hans Christian Ørsted, was working with a battery and wires, as you have done, when he noticed that the magnet in a compass needle moved when electricity passed through a wire close by. He followed this discovery p Fig 14.9 Ørsted demonstrating by making further experiments on an experiment at the university electric currents and magnets, and of Copenhagen published his work in 1820. Later that same year, the French scientist André-Marie Ampére saw a demonstration of Ørsted’s discovery and began developing ideas to explain it. He concluded that there was a relationship between electricity and magnetism that could produce a force. The English scientist, Michael Faraday, studied Ørsted’s and Ampére’s work and discovered that magnetism could also be used to generate electricity. 5 What scientific skill did Ørsted use to make his discovery? 6 How did Ørsted communicate his discovery to other scientists? 7 How did Ørsted’s discovery lead to the building of power stations? p Figure 14.10 Faraday demonstrating an experiment 5  PHYSICS CHALLENGE In Stage 8, you studied the magnetic field around a magnet. Faraday YOURSELF discovered that if you change the magnetic field around a wire, it Power stations generates a current of electricity in the wire. provide electricity for street lights in many Faraday was also a great communicator of science and performed many places across the demonstrations of his work. Faraday’s discovery was developed by world. What is their engineers into the power stations that provide most of the electricity you effect on the planet at use today. night-time? electricity to Use the internet to find high-pressure the turbines turn National Grid steam is directed an electromagnet, images to answer this onto turbines, producing electricity question. Find your high-pressure steam making them turn in the coils location on the planet transformer and compare it with the night-time images. shaft electromagnet Does the study of condensed steam street lights around cooling water the planet help identify human populations? Explain your answer. to cooling tower boiler pump coal, oil or excess steam is cooled gas furnace, and the water is used or nuclear again LET’S TALK reactor What are the benefits of power stations p Figure 14.11 The parts of a power station and street lights around the world? The parts of a power station that use fossil or nuclear fuel generate How may street lights steam. This spins the turbines and an electromagnet, generating affect other living electricity that passes along cables to towns and cities, sending it out to organisms? buildings such as homes, schools, factories and shops. 8 Can you Measuring current remember how The unit for measuring the current flowing through a circuit is the many electrons flow past any point ampere. It is usually shortened to the word amp or amps and its in a circuit in one symbol is A. second when the current is 1 amp? Is it The current flow in the circuit is measured using an ammeter. When it is a 6 million placed in a circuit, the positive (red) terminal must be connected by a wire b 6 million million to the positive terminal of the cell, battery or power supply. It is always c 6 million million connected in series with the component through which the current flow is million to be measured, as Figure 14.12 on the next page shows. Ammeters usually d 6 million million million million? have a very low resistance so that the current passes through them without affecting the rest of the circuit. 6  14 Electric circuits a – b + power supply A – + + – A ammeter p Figure 14.12a An ammeter connected in a circuit and b the circuit diagram showing its symbol Measuring current in series and parallel circuits Sometimes scientists make investigations to check what they have read. In this enquiry you will set up the circuits shown in Figure 14.13, but include a switch to find out about the current flow in them. You will need: a cell, two lamps, four wires, a switch and an ammeter. Investigation a b A A B B C p Figure 14.13 Measuring current in a series and b parallel circuits Set up each circuit in turn and measure the current at the points shown. CHALLENGE Record your measurements. YOURSELF Analysis and evaluation How would you Compare your data with the information in this chapter. measure the current produced by a lemon Conclusion battery? Work out Draw a conclusion from your evaluation and state its limitations. a plan and, if your teacher approves, Suggest how the investigation could be improved to provide more try it. reliable data. 7  PHYSICS Voltage The ability of the cell to drive a current is measured by its voltage. This is indicated by a figure on the side of the cell with the letter ‘V’ after it. The volt, symbol V, is the unit used to measure the difference in electrostatic potential energy (usually just referred to as ‘potential difference’) between two points. The voltage written on the side of the cell refers to the difference in potential between its positive and negative terminals. It is a measure of the electrical energy that the cell can give to the electrons in a circuit. When cells are arranged in series, with the positive terminal of one cell connected to the negative terminal of the next cell, the current-driving ability of the combined battery of cells can be calculated by adding their voltages. For example, two 1.5 V cells in series produce a voltage of 3 V. The two cells together give the electrons in the circuit twice as much electrical energy as each one would provide separately. DID YOU KNOW? A lightning flash only lasts for a few microseconds, but in that time, 1 billion volts and a current of up to 200 000 amperes is generated. p Figure 14.14 The voltage is clearly displayed on the packaging of cells and batteries Measuring voltage The voltage or potential difference between two points in a circuit is measured using a voltmeter. a + – b power supply 9 Compare how an ammeter and a voltmeter are connected into a circuit by looking at V – Figure 14.12 on the + previous page and + – Figure 14.15 on this V voltmeter page. p Figure 14.15a A voltmeter connected in a circuit and b the circuit diagram showing its symbol 8  14 Electric circuits The voltmeter is connected into a circuit with its positive (red) terminal connected to a wire that leads towards the positive terminal of the cell, battery or power supply. The negative (black) terminal must be connected to a wire that leads towards the negative terminal of the source of the current. However, unlike the connection of an ammeter, the wires are attached to either side of the part of the circuit being tested – that is, it is arranged in parallel with this part of the circuit. Voltmeters generally have a very high resistance (see next section), so when connected in parallel they take little current and do not affect the rest of the circuit. Comparing voltages You will need: two cells, a switch, two lamps, nine wires and a voltmeter. Investigation 1 Draw a circuit diagram to show how you would check the voltage of a cell in a circuit with a switch and a lamp. Check it with your teacher and, if approved, try it. 2 Look at the voltage of the cell you are to test. When you make your test, compare your voltage reading with the voltage stated on the cell. What do you find? 3 Draw a circuit diagram with a second lamp arranged in series in your previous circuit. Show how you would check the voltage of the two lamps and the cell in the circuit and, if your teacher approves, try it. What do you find? 4 Draw a circuit diagram with two lamps and two cells arranged in series in your previous circuit. Show how you would check the voltage of the two lamps and the two cells in the circuit and, if your teacher approves, try it. What do you find? 5 Draw a circuit diagram with a cell and two lamps arranged in parallel. Show how you would check the voltage of the two lamps and the cell in the circuit and, if your teacher approves, try it. What do you find? Resistance In Stage 7 of your science course we looked at how electrons push their way through wires and other components in circuits. As the electrons push their way through, the matter in the materials pushes back on them and opposes their movement. This property of a material to oppose the movement of electrons is called resistance. As the electrons push their way through the material and rub against it, the material gets hot, just as if you rub your hands together, they get hot. Some materials like the wires in lamps used in school science experiments get so hot they give out light. 9  PHYSICS We can calculate the resistance of a circuit by measuring the voltage and the current and then using the equation resistance = voltage/current. Investigating resistance with lamps You will need: a cell, five wires, a switch and three lamps. Hypothesis Construct a hypothesis to explain what might happen when a circuit is set up with one lamp, then with another lamp added in series, and then with a third lamp added in series. Prediction Make a prediction based on your hypothesis. Investigation 1 Make circuit diagrams of a a cell, a switch and one lamp b a cell, a switch and two lamps c a cell, a switch and three lamps. 2 Set up each circuit in turn, close the switch and record the result. 3 Use the ammeter and voltmeter to record the resistance of each of these circuits. Analysis and evaluation Compare the data produced by each circuit. Conclusion Compare your evaluation with your hypothesis and prediction and draw a conclusion. How could the investigation be improved? For example, how could using a white or dark card behind the lamps and using a camera help with recording data? 10  14 Electric circuits Summary ✔ There are two kinds of circuit: series and parallel. ✔ In parallel circuits, the current divides between the parts of the circuit that are in parallel. ✔ An ammeter is used to measure the current in a circuit. ✔ The voltage is the difference in potential between two points in a circuit and is also the ability of a cell to drive a current around a circuit. ✔ A voltmeter is used to measure voltage. ✔ Resistance is the property of a material to oppose the movement of electrons. ✔ Resistance can be calculated with the use of the following equation: voltage V resistance = or Ω = current I ✔ Fixed resistors and variable resistors are used to control the flow of an electric current in a circuit. ✔ The buzzer is a component that makes a sound when electricity passes through it. End of chapter questions 1 How are lamps arranged in a a series circuit? b a parallel circuit? 2 What is an ammeter? 3 How do you set up an ammeter in a circuit? 4 What is a voltmeter? 5 How is a voltmeter set up in a circuit? 6 Make a list of the components in each of the three circuits shown in Figure 14.16. p Figure 14.16 7 Draw one example of a series circuit and one example of a parallel circuit. 8 A student measured the voltage in a circuit and found it was 2.0 V, then measured the current and found it was 0.5 A. What was the resistance in the circuit? 9 What is the difference between a fixed and a variable resistor? 11 Cambridge checkp int Lower Secondary Science 9 Help students engage with and fully understand topics they are studying with engaging content following the new Cambridge Lower Secondary Science curriculum framework. l Provide activities to increase students’ subject knowledge and develop the skills necessary to think and work scientifically. l Test students’ comprehension of each topic with questions designed to develop deeper thinking skills. l Embed knowledge and increase students’ vocabulary with whole class and smaller group discussion. For over 25 years we have been This resource is endorsed by Cambridge king for ove or r Assessment International Education trusted by Cambridge schools W 25 ducation Ca around the world to provide m bridge A Provides support as part of a set of resources quality support for teaching and YEARS for the Cambridge Lower Secondary Science al E learning. For this reason we have curriculum framework (0893) from 2020 on e ss WITH nati ss ment Inter been selected by Cambridge Has passed Cambridge International’s rigorous Assessment International Education as an quality-assurance process official publisher of endorsed material for their syllabuses. Developed by subject experts For Cambridge schools worldwide We are working with Cambridge Assessment International Education to gain endorsement for this forthcoming This series includes eBooks series. and teacher support. Visit www.hoddereducation.com/boost to find out more.