Cambridge Primary Science Year 9 Workbook 2nd Edition PDF

Cambridge Lower Secondary Science WORKBOOK 9 Mary Jones, Diane Fellowes-Freeman & Michael Smyth Second edition Digital access  Cambridge Lower Secondary Science WORKBOOK 9...

Cambridge Lower Secondary Science WORKBOOK 9 Mary Jones, Diane Fellowes-Freeman & Michael Smyth Second edition Digital access  Cambridge Lower Secondary Science WORKBOOK 9 Mary Jones, Diane Fellowes-Freeman & Michael Smyth University Printing House, Cambridge CB2 8BS, United Kingdom One Liberty Plaza, 20th Floor, New York, NY 10006, USA 477 Williamstown Road, Port Melbourne, VIC 3207, Australia 314–321, 3rd Floor, Plot 3, Splendor Forum, Jasola District Centre, New Delhi – 110025, India 79 Anson Road, #06–04/06, Singapore 079906 Cambridge University Press is part of the University of Cambridge. It furthers the University’s mission by disseminating knowledge in the pursuit of education, learning and research at the highest international levels of excellence. www.cambridge.org Information on this title: www.cambridge.org/978-1-108-88807-3 © Cambridge University Press 2021 This publication is in copyright. Subject to statutory exception E and to the provisions of relevant collective licensing agreements, M no reproduction of any part may take place without the written permission of Cambridge University Press. CO First edition 2009 Second edition 2014 Third edition 2021 TO 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 Printed in ‘country’ by ‘printer still to be confirmed’ PY A catalogue record for this publication is available from the British Library CO ISBN 978-1-108-88807-3 Coursebook with digital access (2 years) ISBN 978-1-108-93187-8 Digital coursebook (2 years) ISBN 978-1-108-74449-2 Coursebook eBook T Additional resources for this publication at www.cambridge.org/delange IN Cambridge International copyright material in this publication is reproduced PR under license and remains the intellectual property of Cambridge Assessment International Education IM NOTICE TO TEACHERS NOTICE TO TEACHERS IN THE UK The photocopy masters in this publication may be photocopied It is illegal to reproduce any part of this work in material form or distributed [electronically] free of charge for classroom use (including photocopying and electronic storage) except under the within the school or institution that purchased the publication. following circumstances: Worksheets and copies of them remain in the copyright of (i) where you are abiding by a licence granted to your school or Cambridge University Press, and such copies may not be institution by the Copyright Licensing Agency; distributed or used in any way outside the purchasing institution. (ii) where no such licence exists, or where you wish to exceed the Exam-style questions [and sample answers] have been written by terms of a licence, and you have gained the written permission the authors. In examinations, the way marks are awarded may be of Cambridge University Press; different. References to assessment and/or assessment preparation (iii) where you are allowed to reproduce without permission under are the publisher’s interpretation of the syllabus requirements the provisions of Chapter 3 of the Copyright, Designs and and may not fully reflect the approach of Cambridge Assessment Patents Act 1988, which covers, for example, the reproduction International Education. of short passages within certain types of educational anthology and reproduction for the purposes of setting examination questions.  Contents Contents 1 Photosynthesis and the carbon cycle 1.1 Photosynthesis 02 1.2 More about photosynthesis 09 1.3 The carbon cycle 17 1.4 Climate change 20 2 Properties of materials 2.1 Atomic structure and the Periodic Table 24 2.2 Trends in Groups within the Periodic Table 27 2.3 Why elements react to form compounds 33 2.4 Simple and giant structures 37 3 Forces and energy 3.1 Density 42 3.2 Heat and temperature 46 3.3 Conversation of energy 50 3.4 Moving from hot to cold 55 3.5 Ways of transferring thermal energy 58 3.6 Cooling by evaporation 62 4 Maintaining life 4.1 Plants and water 66 4.2 Transpiration 72 4.3 Excretion in humans 75 4.4 Keeping a fetus healthy 77 3 Contents 5 Reactivity 5.1 Reactivity and displacement reactions 83 5.2 Using the reactivity series and displacement reactions 89 5.3 Salts 92 5.4 Other ways of making salts 95 5.5 Rearranging atoms 101 6 Sound and space 6.1 Loudness and pitch of sound 109 6.2 Interference of sound 113 6.3 Formation of the moon 117 6.4 Nebulae 121 6.5 Tectonics 125 7 Genes and inheritance 7.1 Chromosomes, genes and DNA 131 7.2 Gametes and inheritance 133 7.3 Variation 135 7.4 Natural selection 141 8 Rates of reaction 8.1 Measuring rates of reaction 147 8.2 Surface area and the rate of reaction 154 8.3 Temperature and the rate of reaction 158 8.4 Concentration and the rate of reaction 163 9 Electricity 9.1 Parallel circuits 171 9.2 Current and voltage in parallel circuits 174 9.3 Resistance 179 9.4 Practical circuits 184 4  1 Photosynthesis How to use this book and the carbon cycle How to use this book 1.1 Photosynthesis 1.1A How light level affects photosynthesis This workbook provides questions for Focus you to practise what you have learned In this exercise, you decide which variables to keep the same in an 1.2 More about photosynthesis experiment. You put results into a table and make a conclusion. in class. There is a topic to match each Arun does an experiment to investigate whether plants photosynthesise 6 Explain how Sofia’s results support her conclusion. topic in your Learner’s Book. Each topic faster when they have more light. The diagram shows the apparatus he uses. contains the following sections: Focus: these questions help you to master the basics 7 How can Sofia improve her experiment? Tick theA correct Apparatus answer. Apparatus B Apparatus C Use Arun three puts sets of dishes Apparatus A nextfor to each quantity of fertiliser. a window. He puts Use aApparatus B in of different kind a shady watercorner ofeach plant in the same dish. room. He puts Apparatus C in a dark cupboard. Put each dish in a different temperature. 1.2B Testing a variegated leaf for starch 2 Practice In this exercise, you provide explanations using your scientific knowledge. Zara found a plant that had leaves with some green areas and some white areas. Leaves like this are called variegated leaves. Practice: these questions help you to white become more confident in using what you have learned green She decided to test one of the leaves for starch. She made this prediction: The green parts of the leaf will contain starch, but the white parts will not. 1.2 More about photosynthesis 13 1.2C Floating discs experiment Challenge In this task, you will interpret the results of an experiment. You will think about variables, write a conclusion and use your scientific knowledge to explain a set of results. Sofia and Zara do an experiment to investigate photosynthesis. Challenge: these questions will make They cut ten little discs out of a leaf, using a hole punch. Each disc is exactly the same size and is cut from the same leaf. you think very hard They put one disc into water in a small beaker and shine light onto it. Little bubbles appear on the underside of the leaf disc. After a while, the bubbles of gas make the leaf disc float to the surface of the water. Sofia and Zara record the time taken for the leaf disc to float to the surface, then repeat their experiment with four more leaf discs. leaf disc bubbles 1 Name the gas that the leaf disc produced when it photosynthesised. 2 Explain why the bubbles of gas formed on the underside of the leaf, not on the top. 5 3 In what way does the time taken for the leaf disc to rise depend on the bubbles of gas? Explain your answer. 1 Photosynthesis and the carbon cycle 1.1 Photosynthesis 1.1A How light level affects photosynthesis Focus In this exercise, you decide which variables to keep the same in an experiment. You put results into a table and make a conclusion. Arun does an experiment to investigate whether plants photosynthesise faster when they have more light. The diagram shows the apparatus he uses. Apparatus A Apparatus B Apparatus C Arun puts Apparatus A next to a window. He puts Apparatus B in a shady corner of the same room. He puts Apparatus C in a dark cupboard. 2  1.1 Photosynthesis 1 What should Arun keep the same for all three sets of apparatus? Tick (✓) three boxes. the amount of light the type of plant the mass of the plant the number of bubbles the temperature Arun leaves his three sets of apparatus for two days. Then he measures the volume of gas collected in each test tube. This is what he writes down. A 18.3 cm3 B 7.2 cm3 C 0,5 cm3 2 Complete Arun’s results table. Apparatus Amount of light A B C 3 What conclusion can Arun make from his results? Tick (✓) one box. Plants need chlorophyll for photosynthesis. Plants that live in water photosynthesise more slowly than plants that live on land. Plants photosynthesise faster when they have more light. Plants use water for photosynthesis. 3 1 Photosynthesis and the carbon cycle 1.1B The effect of different colours of light on the rate of photosynthesis Practice This exercise gives you practice in recording results, and also thinking about variables in an experiment. Marcus wanted to find out which colour of light would make a plant photosynthesise fastest. The diagram shows the apparatus that he set up. red cellophane blue cellophane water water test tube test tube water plant water plant green cellophane colourless cellophane water water test tube test tube water plant water plant Marcus shone a light onto each tube. He counted the number of bubbles that the water plant gave off in one minute. He did this three times for each piece of pondweed. These are his results. red - 10, 12, 11 blue - 8, 12, 10 green - 4, 5, 6 colourless - 11, 13, 12 4  1.1 Photosynthesis 1 What was the variable that Marcus changed in his experiment? 2 What was the variable that Marcus measured in his experiment? 3 List three variables that Marcus should have kept the same in his experiment. first variable second variable third variable 4 Draw a results table in the space below, and fill in Marcus’s results so that they are easy to understand. Remember to include a column where you can write in the mean value for each set of results. 5 1 Photosynthesis and the carbon cycle 5 Complete the bar chart to show Marcus’s results. red green blue colourless Colour of light 6 Write down a conclusion that Marcus can make from his results. 1.1C Turning an idea into a hypothesis that can be tested Challenge In this challenging task you will choose an idea and then turn it into a hypothesis that can be tested by scientific experiment. Then you will write a plan for the experiment. Here is an idea about water plants and photosynthesis. Idea: Carbon dioxide is one of the raw materials for photosynthesis. We can provide extra carbon dioxide to a water plant by bubbling carbon dioxide gas into the water. This could allow the water plant to photosynthesise faster. 6  1.1 Photosynthesis 1 Use the idea to write down a hypothesis that you could test by doing an experiment. Check your hypothesis with your teacher before you move on to question 2. 2 Use the next two pages to write a plan for an experiment you could do, to test your hypothesis. Try to make your plan really clear and detailed, so that someone else could follow it to do your experiment. Include a labelled diagram of the apparatus you would use. Draw a results chart, with headings. Predict what you think the results might be, giving a reason for your prediction. Remember to state your independent variable, dependent variable, and the variables that you will try to keep the same. 7 1 Photosynthesis and the carbon cycle 8  1.2 More about photosynthesis 1.2 More about photosynthesis 1.2A Duckweed experiment Focus In this exercise, you practise planning experiments, recording results and making conclusions. Sofia does an experiment to find out if extra nitrate fertiliser helps duckweed plants to grow faster. She takes five dishes and puts the same amount of distilled water into each of them. She labels the dishes A, B, C, D and E. She adds one grain of fertiliser to dish B, two grains to dish C, three grains to dish D and four grains to dish E. She puts five duckweed plants into each dish. A B C D E duckweed plants grains of fertiliser 9 1 Photosynthesis and the carbon cycle 1 Write the number of grains of fertiliser that Sofia puts into each dish in the boxes next to each diagram. 2 Which variable does Sofia change in her experiment? Tick (✓) the correct answer. number of duckweed plants volume of water quantity of fertiliser 3 Which variables should Sofia keep the same in her experiment? Tick (✓) all the correct answers. number of duckweed plants quantity of fertiliser light intensity volume of water temperature After two weeks, Sofia counts the number of duckweed plants in each dish. She writes the results in her notebook. A 5 plants B 9 plants C 10 plants D 8 plants E no plants 4 Complete the results chart. Dish Number of grains of fertiliser Number of plants at end of experiment A 0 5 10  1.2 More about photosynthesis 5 Draw a bar chart to display Sofia’s results. Put ‘number of grains of fertiliser’ on the horizontal axis. Put ‘number of plants at end of experiment’ on the vertical axis. Sofia says: From my experiement, I conclude that duckweed plants grow more if they have extra nitrate fertilier. But too much nitrate fertiliser stops them growing. 11 1 Photosynthesis and the carbon cycle 6 Explain how Sofia’s results support her conclusion. 7 How can Sofia improve her experiment? Tick (✓) the correct answer. Use three sets of dishes for each quantity of fertiliser. Use a different kind of water plant in each dish. Put each dish in a different temperature. 1.2B Testing a variegated leaf for starch Practice In this exercise, you provide explanations using your scientific knowledge. Zara found a plant that had leaves with some green areas and some white areas. Leaves like this are called variegated leaves. white green She decided to test one of the leaves for starch. She made this prediction: The green parts of the leaf will contain starch, but the white parts will not. 12  1.2 More about photosynthesis 1 What is the substance that makes leaves green? 2 Explain why Zara’s prediction is likely to be correct. 3 First, Zara put the leaf into boiling water, and left it there for 5 minutes. Explain why she did this. 4 Next, she took the leaf out of the water and put it into some hot alcohol. Explain why she did this. 5 Lastly, Zara dipped the leaf into water and spread it out on a white tile. The leaf looked white. She added iodine solution to the leaf. Some parts of the leaf went orange-brown, and some went blue-black. On the diagram below, shade in the parts of the leaf that would go blue-black, if Zara’s prediction was correct. 6 What substance causes the iodine to turn blue-black? 13 1 Photosynthesis and the carbon cycle 1.2C Floating discs experiment Challenge In this task, you will interpret the results of an experiment. You will think about variables, write a conclusion and use your scientific knowledge to explain a set of results. Sofia and Zara do an experiment to investigate photosynthesis. They cut ten little discs out of a leaf, using a hole punch. Each disc is exactly the same size and is cut from the same leaf. They put one disc into water in a small beaker and shine light onto it. Little bubbles appear on the underside of the leaf disc. After a while, the bubbles of gas make the leaf disc float to the surface of the water. Sofia and Zara record the time taken for the leaf disc to float to the surface, then repeat their experiment with four more leaf discs. leaf disc bubbles 1 Name the gas that the leaf disc produced when it photosynthesised. 2 Explain why the bubbles of gas formed on the underside of the leaf, not on the top. 3 In what way does the time taken for the leaf disc to rise depend on the bubbles of gas? Explain your answer. 14  1.2 More about photosynthesis Sofia and Zara do the investigation again, but this time they put the beaker and the leaf discs in a room with only dim lighting. Here are the girls’ results from both tests. Time taken for leaf disc to rise to the surface, in seconds Conditions Try 1 Try 2 Try 3 Try 4 Try 5 Mean bright light 14 3 12 14 11 dim light 44 66 69 77 71 4 Suggest the hypothesis that the girls were testing. 5 What was the independent variable in the girls’ experiment? 6 Sofia thought that there was one anomalous result in each row of their results table. Draw circles around the two anomalous results in the table. 15 1 Photosynthesis and the carbon cycle 7 Calculate the mean times taken for each row in the results table. Write your answers in the last column. Remember not to include the anomalous results when you calculate the mean. 8 Suggest why the times taken for the five leaf discs to rise in each of the lighting conditions were not all the same. 9 Write a conclusion for the girls’ experiment. 10 Suggest an explanation for the difference between the mean times for the leaf discs to rise in bright light and in dim light 16  1.3 The carbon cycle 1.3 The carbon cycle 1.3 Completing a carbon cycle diagram The diagram shows part of the carbon cycle. carbon dioxide in the air carbohydrates carbon compounds in in decomposers fossil fuels e.g. oil and coal carbohydrates carbohydrates in animals in green plants Focus 1 On the diagram, write these labels next to the correct arrows: R next to three arrows that show respiration P next to one arrow that shows photosynthesis C next to one arrow that shows fossil fuels being formed D next to two arrows that show decomposition F next to one arrow that shows feeding Practice Hydrogencarbonate indicator changes colour according to how much carbon dioxide there is in it. The indicator is purple when there is no carbon dioxide. The indicator is red when there is a low concentration of carbon dioxide. The indicator is yellow when there is a high concentration of carbon dioxide. 17 1 Photosynthesis and the carbon cycle Arun set up four boiling tubes like this: hydrogencarbonate indicator freshwater shrimp water plant A B C D Arun recorded the colour of the indicator in each tube at the start of his experiment. Then he left the tubes in the laboratory for two hours, and recorded the colour again. This is what he wrote down. A red, red B red, yellow C red, purple D red, red 2 Suggest why Arun put a bung in each tube. 3 Describe two variables that Arun kept the same in his experiment. 4 Construct a results table in the space below, and complete it to show Arun’s results. 18  1.3 The carbon cycle 5 Explain Arun’s results. Challenge 6 Use Arun’s results, and the diagram of the carbon cycle, to explain the importance of plants in maintaining a stable concentration of carbon dioxide in the atmosphere. 19 1 Photosynthesis and the carbon cycle 1.4 Climate change 1.4 Interpreting graphs about climate change In this exercise, you look at graphs displaying data collected by NASA (the USA’s National Aeronatutics and Space Adminstration) and NOAA (the USA’s National Oceanic and Atmosphere Adminstration). You will need to study the graphs carefully to answer the questions, and also use your own knowledge about photosynthesis, the carbon cycle and climate change. Focus Here are three graphs about climate change. Graph A +250 +200 +150 Change in sea +100 level in mm +50 0 −50 1880 1900 1920 1940 1960 1980 2000 2020 Year 20  1.4 Climate change Graph B 0.8 mean values for 1979 to 2016 0.6 values in Extent of sea ice in the 2017 to 2018 Bering Sea (in the Arctic) 0.4 in millions of km2 0.2 0.0 Oct Nov Dec Jan Feb Mar Apr May Jun Jul Date Graph C 0.042 0.040 0.038 Percentage carbon dioxide 0.036 concentration in the atmosphere 0.034 0.032 0.030 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 2010 2015 2020 Year 1 Write the letter of the graph that matches each of these statements. There is more carbon dioxide in the atmosphere now than there used to be. Sea level is steadily rising. Sea ice in the Arctic is present for fewer months in the year now, and there is less of it. 21 1 Photosynthesis and the carbon cycle Practice 2 Look at graph A. Describe in words what is shown on the graph. Include some figures in your answer, for example by stating the change in sea level since 1880. 3 Look at graph B. Describe two ways in which the extent of sea ice in the Bering Sea in 2017 to 2018 differed from the mean extent from 1979 to 2016. 1st way 2nd way Challenge 4 Look at graph B again. What extra data would you want to collect, in order to be certain that the extent of sea ice really is changing? Explain your answer. 22  1.4 Climate change 5 Look at graph C. Most scientists think that human activities are contributing to the changes in carbon dioxide concentration shown in the graph. Use your own knowledge to explain why they think this. 6 Look at graph C again. The measurements of carbon dioxide concentration were made in Hawaii, which is in the northern hemisphere. Thinking about plants and photosynthesis, suggest why the line wiggles up and down each year. 23 2 Properties of materials 2 Properties of materials 2.1 Atomic structure and the Periodic Table 2.1 Atomic structure All parts of this exercise will help you to use the Periodic Table to find information about the structure of the atoms of elements. You will need to use the information in the Periodic Table to answer the following questions. metals 1 atomic number 2 H He non-metals hydrogen helium 1 mass number 4 3 4 5 6 7 8 9 10 Li Be B C N O F Ne lithium beryllium boron carbon nitrogen oxygen fluorine neon 7 9 11 12 14 16 19 20 11 12 13 14 15 16 17 18 Na Mg Al Si P S Cl Ar sodium magnesium aluminium silicon phosphorus sulfur chlorine argon 23 24 27 28 31 32 35 40 19 20 K Ca potassium calcium 39 40 Focus The atoms of one element are different from the atoms of all other elements. They have different atomic numbers and mass numbers. 1 What is the atomic number for magnesium? 2 What is the mass number for nitrogen? 24  2.1 Atomic structure and the Periodic Table 3 Which element has the atomic number 13? 4 Which element has the mass number 20? Atoms of different elements have different numbers of protons, neutrons and electrons. The smaller number is the atomic number and the larger number is the mass number. Look at this example: Lithium The atomic number tells Atomic number = 3 you how many protons Mass number = 7 3 there are. Li Number of protons = 3 lithium Number of neutrons = 7 − 3 = 4 7 The mass number tells you how many protons plus Number of electrons = 3 (always the same neutrons there are. as the number of protons) 5 Complete these numbers for a boron atom. Boron Atomic number = Mass number = 5 B boron Number of protons = 11 Number of neutrons = Number of electrons = Practice 6 The element carbon has an atomic number of 6 and a mass number of 12. a How many protons does a carbon atom have? b How many electrons does a carbon atom have? c How many neutrons does a carbon atom have? 25 2 Properties of materials d Draw and label the structure of an atom of carbon. 7 Complete the table. Atomic Mass Electronic Element Protons Neutrons Electrons number number structure beryllium 4 9 4 5 4 2,2 phosphorus 15 31 calcium 20 40 Challenge 8 As you move along the row in the Periodic Table from left to right, and then along to the next row, the atomic number and the mass number change. Look carefully. Describes these changes. The atomic number The mass number 26  2.2 Trends in Groups within the Periodic Table 9 Which two elements have the same mass number? 10 Name an element that is a gas and has the same number of neutrons as protons. 11 Complete the table and identify the element. Element: atomic number mass number number of protons 19 number of neutrons 20 number of electrons electronic structure 2.2 Trends in Groups within the Periodic Table 2.2A Elements in the same group Focus In this exercise you compare the structure of atoms in Group 1. 3 Li lithium 7 Elements in the same group are similar. 11 Na Lithium, sodium and potassium are elements sodium 23 in Group 1. 19 They are all metals. K potassium 39 27 2 Properties of materials 1 What can you say about the number of protons in these three metals, as you look down the group? 2 What can you say about the mass number of these three metals as you look down the group? Lithium has electrons arranged in two shells. It has two electrons in the first (inner) 3p 4n shell, and one in the second, outer shell. This is shown as 2,1. It is called the electronic structure lithium 3 This diagram shows the structure of the sodium atom. Complete these numbers for sodium: Atomic number = Mass number = Number of protons = 11p 12n Number of neutrons = Number of electrons = sodium 4 Write the electronic structure of sodium. 5 What is similar about the structures of an atom of lithium and an atom of sodium? 28  2.2 Trends in Groups within the Periodic Table 6 This diagram shows the structure of the potassium atom. Complete these numbers for potassium: Atomic number = Mass number = Number of protons = 19p 20n Number of neutrons = Number of electrons = potassium 7 Write the electronic structure of potassium 8 Compare the structure of the atoms of these three metals in Group1. What is similar about their structure? 9 What is different about the three atoms? Try to state two differences. 2.2B Trends in groups in the Periodic Table Practice This exercise will help you to identify trends in groups of the Periodic Table. 1 Explain what is meant by a ‘group’ in the Periodic Table. 29 2 Properties of materials 2 This table contains some data about the elements in Group 7 of the Periodic Table. The elements are given in descending order. Atomic Mass Melting Boiling Element Reactivity number number point /°C point /°C fluorine 9 19 −220 −188 most reactive chlorine 17 35 −101 −34 bromine 35 80   −7   59 less reactive iodine 53 astatine 85 a What trends can you see in this group of the Periodic Table? b Iodine is the fourth element in this group. Would you expect the melting point of iodine to be higher or lower than that of bromine? c Would you expect iodine to be a solid, a liquid or a gas at room temperature? Give a reason for your answer. d Would you expect iodine to have a higher or lower boiling point than astatine? Give a reason for your answer. e Would you expect astatine to be more or less reactive than iodine? 30  2.2 Trends in Groups within the Periodic Table 2.2C Comparing trends in Groups 1 and 7 Challenge In this challenge exercise you will use information to compare elements in the same group. Group 1 Element Atomic number Mass number Melting point /°C Boiling point /°C lithium 3 7 180 1360 sodium 11 23 98 900 potassium 19 39 63 777 Group 7 Element Atomic number Mass number Melting point /°C Boiling point /°C fluorine 9 19 −220 −188 chlorine 17 35 −101 −34 bromine 35 80   −7   59 Use the information to answer the questions. 1 As the atomic numbers in Group 1 increase, what happens to the melting point? 2 As the atomic numbers in Group 7 increase, what happens to the melting point? 3 Compare the trends in boiling points in Group 1 and Group 7. 31 2 Properties of materials In Group 1 the least reactive shown in the table is lithium; the most reactive is potassium. In Group 7 the least reactive shown in the table is bromine; the most reactive is fluorine. 4 Describe how reactivity relates to the size of the atoms in each group. In Group 1: In Group 7: 5 The elements that come next in each group, in order of atomic number, are: rubidium in Group 1 iodine in Group 7. Make predictions about the reactivity, melting point and boiling point of rubidium and iodine, compared with the other elements in their group. Rubidium, Group 1 Reactivity: Melting point: Boiling point: Iodine, Group 7 Reactivity: Melting point: Boiling point: 32  2.3 Why elements react to form compounds 2.3 Why elements react to form compounds 2.3A Atoms and ions Focus This exercise will help you to show the difference between an atom and an ion. 1 This diagram shows the structure of a lithium atom. Label the electron shell with the highest energy level. 2 Draw a diagram to show the structure of a lithium ion. 33 2 Properties of materials 3 The symbol for a lithium atom is Li. What is the symbol for a lithium ion? 4 This diagram shows the structure of a fluorine atom. Draw a diagram to show the structure of a fluorine ion. 5 The symbol for a fluorine atom is F. What is the symbol for a fluorine ion? 2.3B Why do ions form? Practice In this exercise you will practice drawing atoms and ions and explain why ions form. 34  2.3 Why elements react to form compounds 1 Using the information here, draw atoms and ions of sodium and chlorine in the spaces below. sodium chlorine atomic number 11 atomic number 17 mass number 23 mass number 35 sodium atom: chlorine atom: sodium ion: chlorine ion: 2 How are the electrons in an atom held in place? 3 Why are ions formed? 35 2 Properties of materials 2.3C Forming ionic compounds. Challenge In this exercise you will draw diagrams to illustrate the formation of ionic compounds. 1 When calcium reacts with chlorine the compound calcium chloride is formed. The formula for calcium chloride is CaCl2. Information you may need: Calcium has an atomic number of 20 and a mass number of 40. Chlorine has an atomic number of 17 and a mass number of 35. a Draw diagrams to show the structures of calcium and chlorine atoms. Make sure you label the calcium and chlorine atoms. b Draw diagrams to show the ions of calcium and chlorine. Make sure you label the calcium and chlorine ions. 36  2.4 Simple and giant structures c Explain why the formula for calcium chloride is CaCl2. You may use diagrams to help you explain. 2.4 Simple and Giant structures 2.4A Ionic or covalent bonds Focus This exercise will help you to distinguish between ionic and covalent substances Look at the diagrams that show the structures of two substances A and B. Substance A Substance B 37 2 Properties of materials 1 What type of bonding do you think Substance A has? Give a reason for your answer. 2 Label Substance B to show where there are strong forces. 3 Which substance has bonds where electrons are shared? 4 Which substance has a lattice structure? 5 A substance when dissolved in water conducts electricity. What type of bonding does it have? 6 Some giant structures are called macromolecules. What type of bonding do they have? 7 Give an example of a macromolecule. 38  2.4 Simple and giant structures 2.4B Properties of ionic and covalent substances Practice In this exercise you will identify properties of substances linked to their structures Look carefully at the table and answer the questions. solid, liquid or Ionic or simple Melting point / Boiling point / Substance gas at room molecule with °C °C temperature? covalent bonds potassium 770 1500 chloride Substance X −182 −161 calcium solid ionic chloride ammonia −77 −34 magnesium 2825 3600 oxide bromine   −7   59 simple molecule with Substance Y    0 100 liquid covalent bonds 1 Calcium chloride is an ionic compound that is solid at room temperature. What does that tell you about its melting and boiling points? 2 Is Substance X a solid, liquid or gas at room temperature? 3 List the substances that are solids at room temperature. 39 2 Properties of materials 4 List the substances, other than Substance Y, that have simple molecules with covalent bonds. 5 Suggest what Substance Y is. Give a reason for your suggestion. 6 Which substance, other than Substance Y, is a liquid at room temperature? 7 Explain why magnesium oxide has high melting and boiling points. 8 Explain why ammonia has low melting and boiling points. 2.4C Giant structures of carbon Challenge In this exercise you will link the structure of diamond and graphite to their properties. Diamond and graphite are both giant structures formed from the element carbon. 40  2.4 Simple and giant structures 1 Which of the diagrams below represents the structure of diamond and which graphite? This structure represents: This structure represents: 2 Graphite is a very soft material. Explain how its structure is related to its properties. 3 Diamond is the hardest material on Earth. Explain how its structure is related to its properties. 41 3 Forces and energy 3.1 Density 3.1A Comparing densities Focus In this exercise you will compare the densities of different substances. 1 Which of these substances has the lowest density? Tick ( ) one box. solid liquid gas 2 Marcus has four blocks, A–D, each made from a different type of wood. All four blocks have the same volume. The masses of the blocks are: A 50 g B 76 g C 32 g D 68 g Which block has the greatest density? Write the letter 42  3.1 Density 3 Zara has four pieces of metal, P–S, each made from a different type of metal. All four pieces have the same mass. The volumes of the pieces are: P  22 cm3      Q  35 cm3      R  19 cm3      S  27 cm3 Which piece of metal has the greatest density? Write the letter 4 Arun has some solid blocks with different densities. State how the density of a solid block should compare with water if the block is to float on water. 3.1B Understanding and calculating density Practice In this exercise you will describe density and calculate some densities. 1 Which of these statements describes density? Tick ( ) one statement. the weight of a substance the volume that a substance occupies the mass of a certain volume of substance the volume of a certain mass of substance 2 Complete the equation for density. density = 43 3 Forces and energy 3 Calculate the density of each of these substances. a A 10 g mass of water that has a volume of 10 cm3. g/cm3 b A 170 g mass of brass that has a volume of 20 cm3. g/cm3 c A 56 g mass of propane that has a volume of 100 cm3. g/cm3 4 A solid cube is made from copper. The lengths of the sides of the cube are 2.0 cm. a Calculate the volume of the cube. cm3 b The mass of the cube is 71.2 g. Calculate the density of the copper. g/cm3 44  3.1 Density 3.1C Density, floating and sinking Challenge In this exercise you will use density to work out whether substances will float or sink. 1 The table shows the densities of four different types of plastic. The plastics are all solids. type of plastic density / g/cm3 polyethylene 0.91 polypropylene 0.94 cellulose acetate 1.28 polyvinyl chloride 1.38 The densities of two liquids are: water 1.0 g/cm3 engine oil 0.92 g/cm3 Name a type of plastic from the table that will a float in both engine oil and in water b sink in engine oil but float in water c sink in both engine oil and in water. 2 Marcus has a model boat with a volume of 250 cm3. Calculate the maximum mass of this boat that will float in water. The density of water is 1.0 g/cm3. g 45 3 Forces and energy 3 A ship is being built using a material called mild steel. Mild steel has a density of 7.9 g/cm3. Seawater has a density of 1.02 g/cm3. Explain how a ship can be made from mild steel and safely float in seawater. 3.2 Heat and temperature 3.2A Heat or temperature Focus In this exercise you will decide whether examples describe heat or temperature. 1 Complete each of the sentences using the word heat or temperature. a 100 °C is the at which water boils. b 25 000 J is the quantity of needed to make cold water warmer. c 22 °C is often described as room 46  3.2 Heat and temperature 2 Sofia has two cups of coffee. The volume of coffee in both cups is the same. One cup of coffee is at 55 °C. The other cup of coffee is at 30 °C. Which statements are true? Tick ( ) two boxes. the temperature of the coffee in each cup is different the temperature of the coffee in each cup is the same the heat in the coffee in each cup is different the heat in the coffee in each cup is the same 3 Zara serves two bowls of soup. In one bowl Zara puts 100 cm3 of soup at 60 °C. In the other bowl Zara puts 200 cm3 of soup at 60 °C. Which statements are true? Tick ( ) two boxes. the temperature of the soup in each bowl is different the temperature of the soup in each bowl is the same the heat in the soup in each bowl is different the heat in the soup in each bowl is the same 3.2B Comparing heat and temperature Practice In this exercise you will describe the difference between heat and temperature. 1 a Write down the unit of temperature b Write down the unit of heat 47 3 Forces and energy 2 Draw straight lines to match the quantity with the correct description. Quantity Description the total energy of particles in a substance heat the maximum energy of particles in a substance temperature the minimum energy of particles in a substance the average energy of particles in a substance 3 Complete the sentences using appropriate (best) words. In a solid, the particles vibrate about positions. When a solid is heated, the particles vibrate When the temperature of a solid decreases, the particles vibrate 4 Two solid blocks are at 20 °C. One block has double the mass of the other block. Explain how the heat and temperature of the blocks compare. Use ideas about particles. heat temperature 48  3.2 Heat and temperature 3.2C Measuring heat and temperature Challenge In this exercise you will think about measuring heat and temperature. 1 Look at the list of equipment. ruler thermometer protractor joule meter volt meter a Name the equipment from the list that can be used to measure the temperature of water when it is being heated. b Name the equipment from the list that can be used to measure the quantity of heat added to water when it is being heated. 2 Marcus uses an electric immersion heater to heat water. Marcus measures the heat supplied to the water and the temperature of the water at regular intervals. His results are in the table. quantity of heat supplied / J temperature of water / oC    0 10 1000 12 2000 14 3000 15 4000 18 5000 20 a Marcus thinks that one of his results is anomalous. i State which result is anomalous. ii Describe what Marcus could do about this result. 49 3 Forces and energy b Use the results in the table to estimate i the quantity of heat supplied when the temperature of the water was 19 °C ii the quantity of heat needed to raise the temperature of the water to 30 °C 3.3 Conservation of energy 3.3A What does conservation of energy mean? Focus In this exercise you think about the meaning of the statement ‘conservation of energy’. 1 Which of these will happen when energy is conserved? Tick ( ) one box. the quantity of energy will increase the quantity of energy will stay the same a quantity of energy can be made a quantity of energy can be destroyed 2 Which of these shows conservation of energy in an electric lamp? Tick ( ) one box. energy input to the lamp equals energy output from the lamp energy input to the lamp is greater than energy output from the lamp energy input to the lamp is less than energy output from the lamp the lamp should be switched off when not being used 50  3.3 Conversation of energy 3 100 J of electrical energy is supplied to a motor. The electrical energy is changed to thermal and kinetic energy in the motor. Write down the total quantity of thermal and kinetic energy changed in the motor. J 4 A car engine changes chemical energy to thermal and kinetic energy. A total of 3500 J of thermal and kinetic energy are changed. Write down the quantity of chemical energy changed in the engine. J 3.3B The law of conservation of energy Practice In this exercise you apply the law of conservation of energy. 1 Write down the law of conservation of energy. 2 An electric lamp changes electrical energy to light and thermal energy. Explain how the law of conservation of energy applies to this electric lamp. 51 3 Forces and energy 3 Sofia takes in more chemical energy from food on days when she is playing sports than on days when she is resting. Use the law of conservation of energy to explain why. 4 An electric motor changes electrical energy into kinetic and thermal energy. 65% of the electrical energy is changed to kinetic energy. Calculate the percentage of electrical energy changed to thermal energy. % 3.3C Calculating energy changes Challenge In this exercise you use the law of conservation of energy to calculate quantities of energy. 52  3.3 Conversation of energy 1 An electric lamp takes in 1000 J of electrical energy. The lamp wastes 850 J of energy. Calculate the quantity of useful energy changed by the lamp. J 2 A motorcycle engine uses 2400 J of chemical energy in fuel. The thermal energy changed is 1000 J. The sound energy changed is 600 J. The remaining energy is changed to kinetic for movement. Calculate the quantity of kinetic energy changed by the engine. J 53 3 Forces and energy 3 A television changes electrical energy into thermal, light and sound energy. 50% of the energy is changed to thermal. 30% of the energy is changed to light. a Calculate the percentage of the energy changed to sound. J b Draw a labelled energy flow diagram for the television in the space below. 54  3.4 Moving from hot to cold 3.4 Moving from hot to cold 3.4A Direction of thermal energy transfer 1 Focus In this exercise you think about the direction of the transfer of thermal energy. 1 Complete the sentence using the appropriate (best) word. Thermal energy is transferred from a place of higher temperature to a place of temperature. 2 Draw an arrow on each of these diagrams to show the direction of thermal energy transfer. a cooking pot at 100 °C flame at 450 °C b air in room electric heater at 15 °C at 250 °C 55 3 Forces and energy c ice pack at 0 °C foot at 37 °C 3.4B Direction of thermal energy transfer 2 Practice In this exercise you think in more detail about thermal energy transfer. 1 Two objects are in contact. The two objects are at different temperatures. Describe the direction of thermal energy transfer between these two objects. 2 The diagram shows three blocks of metal that are in contact with each other. The starting temperature of each block is shown. Draw arrows on the diagram to show the direction of thermal energy transfer between the blocks. 20 °C 10 °C 30 °C 56  3.4 Moving from hot to cold 3 A cup of hot tea is at a temperature of 60 °C. The tea is left in a room that is at 25 °C. Sketch a graph of how the temperature of the tea will change with time. Continue your graph until the temperature of the tea is constant. 70 60 50 40 Temperature / °C 30 20 10 0 Time 3.4C Direction of thermal energy transfer 3 Challenge In this exercise you make predictions about thermal energy transfer. 1 Zara’s body temperature is 37 °C. a Explain why Zara feels cold when the air temperature is 5 °C. b Explain why Zara feels hot when the air temperature is 40 °C. 57 3 Forces and energy 2 Arun fills a glass with water to drink. The temperature of the water is 10 °C. Arun puts ice in the water. The temperature of the ice is −15 °C. Explain what will happen to the temperature of the water when the ice is added. 3 Sofia makes a cup of hot coffee. She adds cold milk to the coffee. Explain what happens to the temperature of the coffee and the temperature of the milk. 3.5 Ways of transferring thermal energy 3.5A Describing thermal energy transfers Focus In this exercise you describe how thermal energy is transferred in different situations. 58  3.5 Ways of transferring thermal energy 1 Complete the sentences using words from the list. Each word can be used more than once. conduction   convection   radiation a Thermal energy is transferred from the Sun to Earth by b Thermal energy is transferred within metals by c When warm air rises through cold air, this is called d Neither nor can occur in a vacuum. 2 Draw straight lines to match the type of thermal energy transfer to the way it works. Type of thermal energy transfer How it works particles vibrate more, take up conduction more space and decrease the density of the substance particles vibrate more, collide with convection particles beside them, making these particles also vibrate more type of wave that does not radiation require particles to transfer thermal energy 59 3 Forces and energy 3.5B Comparing thermal energy transfers Practice In this exercise you make comparisons between the three types of thermal energy transfer. 1 Explain why conduction of heat occurs more easily in solids than in gases. 2 Explain why convection can occur in liquids and gases but not in solids. 3 Explain why radiation can occur in a vacuum while conduction and convection cannot occur in a vacuum. 3.5C Variables affecting thermal energy transfer Challenge In this exercise you consider the variables that affect thermal energy transfers. 60  3.5 Ways of transferring thermal energy Use ideas about conduction, convection or radiation when answering these questions. 1 a Explain why a cooking pot is made from metal. b Explain why the handle of the cooking pot is made from wood. 2 Explain why houses in hot countries are often painted white. 3 Explain why clothing made from wool can help you keep warm in cold weather. 4 A plastic box with shiny silver aluminium foil on the inside can be used to keep food hot. 61 3 Forces and energy Explain how this works. 3.6 Cooling by evaporation 3.6A How evaporation works Focus In this exercise you think about what evaporation is and how it works. 1 Which of these describes evaporation? Tick ( ) one box. when a solid changes to a liquid when a liquid changes to a gas when a liquid changes to a solid when a gas changes to a liquid 2 Which particles cause evaporation? Tick ( ) one box. the particles with the most energy the particles with the least energy Explain your answer. 62  3.6 Cooling by evaporation 3 The boiling point of water is 100 °C. Water can evaporate at Water can only temperatures evaporate at much lower 100 °C than 100 °C Who is correct, Sofia or Zara? Give an example to support your answer. 3.6B Evaporation and cooling 1 Practice In this exercise you think about how evaporation causes cooling. 1 Sweat is produced in the skin. Which of these explains how sweat can cool (lower the temperature of   ) the skin. Tick ( ) one box. Sweat evaporates, removing thermal energy from skin. Sweat evaporates, adding thermal energy to the skin. Sweat is produced at a lower temperature than the skin. Sweat is produced at a higher temperature than the skin. 63 3 Forces and energy 2 A liquid is evaporating. The liquid is not being heated. a Explain what happens to the average energy of the particles in the liquid. b Explain what happens to the temperature of the liquid. 3 Arun has sweat on his face. The air temperature is 25 °C. Arun uses a fan to blow air onto his face. The fan does not change the temperature of the air. Explain why the fan helps Arun to cool (lose heat) faster. 3.6C Evaporation and cooling 2 Challenge In this exercise you think in more detail about how evaporation causes cooling. 1 Perfume evaporates faster than water. Sofia has perfume and water at the same temperature. Sofia puts an equal volume of the perfume and the water separately on her hand. Explain which feels colder. 64  3.6 Cooling by evaporation 2 Humidity is a measure of the quantity of water vapour in air. In conditions of high humidity, evaporation stops. Explain why sweat will not cool (lower the temperature of) the skin in conditions of high humidity. 3 A type of air cooler works by blowing air from the room through a sponge soaked in water. Explain how blowing air through a sponge soaked in water lowers the temperature of the air. 65 4 Maintaining life 4 Maintaining life 4.1 Plants and water 4.1A Water uptake by orange plant seedlings Focus In this exercise, you use a set of results to make conclusions. Scientists investigated root hairs on two varieties of orange plant seedlings, variety A and variety B. They recorded: the mean numbers of root hairs per plant the mean length of the root hairs on each plant. The table shows their results. Orange plant Mean number of root Mean length of root hairs variety hairs per plant on each plant in mm A 920 0.03 B 800 0.02 1 The scientists counted the number of root hairs on 10 plants of variety A. How could they use their results to calculate the mean number of root hairs per plant of variety A? 66  4.1 Plants and water 2 The scientists found that variety A orange plants took up more water in one hour than variety B orange plants. Use the results in the table to explain why. 3 Describe what happens to water, after it has been taken up by a root hair. 4.1B Celery experiment Practice In this exercise, you use a set of results to construct a line graph. You use your graph to make a conclusion. Zara investigates the rate of water movement up a celery stalk. She wants to find out how the temperature of the water affects this. red dye 67 4 Maintaining life Zara takes eight celery stalks. She stands each stalk in a beaker containing a red dye. She puts each beaker into a water bath. Each water bath is kept at a different temperature. After ten minutes, she takes out all of the celery stalks. She cuts each stalk across, every 0.5 cm along. She looks for the red dye in the slices of the stalk. Zara records how far the dye has travelled up each stalk. She writes her results in a table. Temperature in °C Distance the dye travels in cm 0 1.0 10 1.9 20 3.1 30 4.0 40 4.8 50 3.2 60 7.0 70 8.1 1 Which one of Zara’s results is anomalous? (Anomalous means that it does not fit the pattern.) Draw a circle around the anomalous result in the table. 68  4.1 Plants and water 2 Use Zara’s results to construct a line graph on the grid. Put temperature in °C on the horizontal axis. Put distance the dye travels, in cm on the vertical axis. Draw a line of best fit. Do not include the anomalous result. 69 4 Maintaining life 3 What conclusion can Zara make from her experiment? Tick ( ) one box. Plants need more water when the temperature is higher. As temperature increases, the rate of transport of water in celery stalks increases. Celery leaves use water for photosynthesis. 4.1C Interpreting data about water uptake Challenge In this challenge task, you will look at some data collected by researchers who did experiments on wheat plants. You will choose a good way to display the data, and then make a suggestion, based on the data. A team of scientists wanted to compare how much water is taken up by three different varieties of wheat growing in a cold place. They grew seedlings of each of the three varieties of wheat. They provided all of the seedlings with the same volume of water. They placed the seedlings at a temperature of 2 °C. They measured how much water each group of seedlings had taken up after two weeks, and again after six weeks. The table shows the results. Variety of Volume of water taken up per g of wheat plant, in cm3 wheat after 2 weeks at 2 °C after 6 weeks at 2 °C A 78 102 B 64 94 C 72 122 70  4.1 Plants and water 1 Suggest why the scientists measured the volume of water taken up per gram of the wheat plants, rather than the volume taken up by a whole plant. 2 Think about different ways in which you could display these results. Choose one good way and display the results on the grid. 71 4 Maintaining life 3 Compare the volumes of water taken up by the three varieties of wheat after two weeks. 4 Describe how the results after six weeks are different from those after two weeks. 5 Plants need to take up water so that they can photosynthesise and grow well. Suggest which variety of wheat would be the best choice for a farmer in Canada, where the temperatures often fall very low. Explain your choice. 4.2 Transpiration 4.2 How temperature affects water loss This exercise gives you practice in constructing results tables, drawing line graphs and dealing with anomalous results. You’ll also do some calculations and use your knowledge to try to explain patterns in results. Focus Sofia set up an experiment to investigate this hypothesis: Plants lose more water from their leaves when the temperature increases. The diagrams show how Sofia set up her experiment. 72  4.2 Transpiration Plant A kept at 4 °C Plant B kept at 20 °C Plant C kept at 30 °C 863g 893g 842g 1 Look at Sofia’s hypothesis. Explain why she covered the pot and soil of each plant with a plastic bag. 2 Sofia read the mass, in grams, of each plant and pot each day for 8 days. These are the results that she wrote down: Plant A: 863, 854, 845, 837, 829, 822, 814, 807 Plant B: 893, 873, 856, 837, 861, 792, 779, 761 Plant C: 842, 810, 780, 748, 714, 682, 650, 618 Draw a results table, and fill in Sofia’s results. Practice 3 Sofia decided that one of her results was anomalous. Draw a circle around the anomalous result in your results table. 4 Draw line graphs to display Sofia’s results on the grid on the next page. Put time on the horizontal axis, and mass of plant and pot on the vertical axis. You do not need to start at 0 on the y-axis. Draw a separate line for each plant. What should you do about the anomalous result? 73 4 Maintaining life Challenge 5 Sofia calculated the mean loss of mass per day for plant A like this: mass on day 1 = 863 g mass on day 8 = 807 g therefore loss of mass over 7 days was 863 − 807 = 56 g therefore the mean loss of mass per day was 56 ÷ 7 = 8 g per day. 74  4.3 Excretion in humans In the space below, calculate the mean loss of mass per day for plant B and plant C. 6 Use your knowledge of plants and water to suggest an explanation for Sofia’s results. 4.3 Excretion in humans 4.3 Structure and function of the excretory system In this exercise, you check that you know the structure of the excretory system and can describe the functions of the different organs that are part of this system. 75 4 Maintaining life Focus 1 Complete the sentences. Use words from the list. Use each word once. kidneys renal urea urine water The are part of the excretory system. This is also known as the system. In the excretory system, a waste substance called is filtered out of the blood. It dissolves in , forming a liquid called. Practice 2 Complete the diagram of the excretory system. right kidney artery bringing blood to the kidney vein taking blood away from the kidney bladder 3 Add labels to the diagram. You should label four structures. 76  4.4 Keeping a fetus healthy Challenge 4 Describe the function of each of the structures that you have labelled on the diagram. 4.4 Keeping a fetus healthy 4.4A Length of pregnancy Focus In this exercise, you will practise organising data in the best way. You will also think about the meaning of the word ‘correlation’, and practise using data to support an argument. Incidental image to be supplied. 77 4 Maintaining life The table shows the mean mass of an adult female of eight different species of mammal, and the mean time for which pregnancy lasts in that species. Species Mean mass of a female / kg Mean length of pregnancy/ days moose (elk) 550 245 llama 113 330 goat   15 150 wolf   40 64 lion 150 108 rabbit    1 33 elephant 5000 640 chimpanzee   40 227 1 In the table below, rearrange the data so that it is easier to see if there is a relationship between the mean mass of a female and the mean length of pregnancy. Species Mean mass of a female / kg Mean length of pregnancy/ days 78  4.4 Keeping a fetus healthy 2 Is there a correlation between the mean mass of a female and the mean length of pregnancy? Explain your answer and use figures from the table to support it. 4.4B Does caffeine affect birthweight? Practice In this exercise, you will look at some data collected by researchers in Sweden. You will practise using data to make conclusions and think about how an investigation could be improved. A study was carried out in Sweden to investigate the idea that women who drink a lot of coffee during pregnancy might have smaller babies. 1037 pregnant women took part. They each answered a questionnaire about how much coffee they drank. When their babies were born, their birthweights were measured. The results are shown in the table. Mean caffeine intake per day / mg Mean birthweight / g less than 100 3660 100 to 299 3661 300 to 499 3597 500 or more 3694 79 4 Maintaining life 1 Plot these results as a bar chart on the grid. Think carefully about the range for the scale on the vertical axis. Remember that you do not need to begin at 0. 2 What conclusion can you make from these results? Explain your answer and use figures from the table to support it. 3 Suggest two ways in which the researchers could have improved their study. 80  4.4 Keeping a fetus healthy 4.4C Smoking and birthweight Challenge In this exercise, you analyse data about smoking and birthweight. You use the data to draw conclusions and explain how you made these conclusions. Scientists in Japan studied how the birthweight of a baby is affected if the mother smokes while she is pregnant. They interviewed 53 386 mothers whose babies were born between 2004 and 2010 in a large city in Japan. They asked the mothers whether they had smoked during pregnancy. They also recorded the mass of the baby at birth. If the baby’s mass was less than 2500 g at birth, this was recorded as low birthweight. The table shows their results. Mother did not smoke during Mother smoked during pregnancy pregnancy Birth year Percentage of Percentage of Number of Number of babies with low babies with low babies born babies born birthweight birthweight 2004 to 2005 2609 14.0 23 713 9.6 2006 to 2007 2109 14.5 24 955 9.9 Look at the row for 2004 to 2005. 1 How many babies were born in total in 2004 to 2005? 2 Did most mothers smoke during pregnancy in 2004 to 2005? Use the numbers in the table to explain your answer. 81 4 Maintaining life 3 Did smoking during pregnancy increase the risk of a baby having low birthweight? Use the numbers in the table to explain your answer. Now look at the next row as well – the row for 2006 to 2007. 4 Look at the number of babies born. Is there any evidence that fewer women smoked during pregnancy in 2006 to 2007, than in 2004 to 2005? Use the numbers in the table to explain your answer. 5 Do you think that the results in the table prove that smoking during pregnancy is harmful to a fetus? Explain your answer. 82  1.1 Characteristics of living things 5 Reactivity 5.1 Reactivity and displacement reactions 5.1A Using the reactivity series Focus In this exercise you use the information from the reactivity series to make some predictions. The diagram shows the reactivity series of metals. most reactive Potassium, K Sodium, Na Calcium, Ca Magnesium, Mg Aluminium, Al Zinc, Zn Iron, Fe Lead, Pb Copper, Cu Silver, Ag Gold, Au least reactive 83 5 Reactivity 1 Sodium burns brightly when heated, and forms an oxide. Does magnesium react more vigorously or less vigorously than sodium? 2 Copper reacts very slowly when heated. Suggest how silver reacts when heated. 3 Lead reacts very slowly with dilute acid. How do you expect iron to react with dilute acid, compared with lead? 4 If an iron nail is put in a solution of copper sulfate, there is a reaction. This is the word equation: copper sulfate + iron iron sulfate + copper Iron is more reactive than copper, so it ‘pushes out’ or displaces the copper from the sulfate. 5 If you place a copper nail in a solution of iron sulfate, will there be a displacement reaction? Explain your answer. 6 Suggest a metal that cannot displace copper in the solution of copper sulfate. 7 Metal X displaces lead in a solution of lead chloride. Metal X does not displace zinc in a solution of zinc chloride. Suggest what metal X could be. 84  5.1 Reactivity and displacement reactions 8 Look at possible reactions described below. Write yes next to those that will happen and no next to those that will not. a zinc and copper sulfate, to give copper b lead and magnesium chloride, to give magnesium c copper and aluminium chloride, to give aluminium d zinc and iron chloride, to give iron e iron and lead chloride, to give lead 9 Write the word equation of the reaction between magnesium and zinc chloride. + + 5.1B Displacement reactions Practice In this exercise you will practice interpreting information and writing word equations. 1 More reactive metals can displace less reactive ones from solutions of salts. The table below shows the results of an experiment that uses displacement reactions. Iron Copper Zinc Magnesium Copper sulfate reaction reaction reaction Zinc sulfate no reaction no reaction reaction Magnesium sulfate no reaction no reaction no reaction a The table shows that zinc displaces the copper in copper sulfate. What does this tell you about the reactivity of zinc and copper? b Write the word equation for the reaction between zinc and copper sulfate. 85 5 Reactivity c The table shows there is no reaction between magnesium sulfate and zinc. What does this tell you about the reactivity of these two metals? d Use the table to work out whether iron is more or less reactive than copper. Then, work out whether magnesium is more or less reactive than iron. Write these metals in order of reactivity, starting with the most reactive, based on the information in the table. 2 Sofia has been given the task of identifying a metal. She knows that the metal is one of zinc, iron, copper or silver. She has been given a number of small pieces of the metal and also some solutions of copper sulfate, zinc sulfate, iron sulfate and silver nitrate. a Explain how she could use these solutions to identify the metal. b Explain how you could use displacement reactions to distinguish between iron and zinc. You may use any solutions you choose. 86  5.1 Reactivity and displacement reactions 5.1C Displacing metals. Challenge In this exercise you will discuss the reactivity of metals and predict which displacement reactions will take place. Arun has six metals A, B, C, D, E and F. He also has six test tubes of a solution of a salt of metal A, six test tubes of a solution of a salt of metal B, and so on. He adds a small piece of each metal to six tubes , one of each of the salt solutions. The bar chart shows the number of displacement reactions that take place. 5 4 number of displacement 3 reactions taking place 2 1 0 A B C D E F metal 1 Which of the metals A, B, C, D, E, F is most reactive? Explain your choice. 2 Complete the table using Arun’s results. Use a tick to show where a reaction happened and a cross where a reaction has not happened. Hint: Start filling in the table for the most reactive metal first, then the next most reactive and so on. 87 5 Reactivity Metal A B C D E F A B Metal salt C D E F 3 Metal C is copper and metal D is zinc. Suggest what the other metals might be. Give reasons for your choices. 4 Complete the following word equations. If there is no reaction between the metal and the salt, write no reaction. a copper sulfate + iron b magnesium chloride + zinc c aluminium sulfate + magnesium d lead chloride + silver e zinc chloride + iron 5 Explain why it is not possible for you to carry out displacement reactions using the metal potassium. 88  5.2 Using the reactivity series and displacement reactions 5.2 Using the reactivity series and displacement reactions 5.2 Using displacement reactions Focus This exercise will give you practice in using information from displacement reactions to identify an unknown metal. 1 A metal displaces the iron from a solution of iron sulfate and the copper from a solution of copper sulfate. This metal does not displace the magnesium from a solution of magnesium sulfate. a What does this tell you about the reactivity of the unknown metal? b This unknown metal could be one of two metals. Which two? c What displacement reaction could you carry out to tell which of the two metals it is? Explain how this would help you to identify which of the two metals it is. Practice In this exercise you will practice describing and explaining the use of displacement reactions. 2 The most common ore of lead is lead sulfide. To extract the lead, the ore is first heated in air to produce lead oxide. The lead oxide is then heated with carbon to extract the lead. 89 5 Reactivity a Explain why carbon can be used to extract lead from lead oxide. b Write the word equation for the reaction that takes place when lead oxide is heated with carbon. c Copper is less reactive than lead. Predict whether carbon can be used to extract copper from copper oxide. d Aluminium is much more reactive than many metals. The main ore of aluminium is bauxite. Bauxite is purified to make aluminium oxide. Explain why it is not possible to extract aluminium metal from aluminium oxide using carbon. Challenge In this exercise you will explain how displacement reactions are used in practical ways. 3 a Explain how the displacement of iron from iron oxide is used to weld rails together. b Why is this method used and not ordinary welding? 90  5.2 Using the reactivity series and displacement reactions c Write the word equation for this reaction. 4 Iron is produced from its ore, iron oxide, by using a displacement reaction. This is done in a blast furnace. a Which element is used to displace iron? b Describe briefly how this process is carried out. c Write the word equation for this reaction. d Suggest where the element used in this reaction fits in the reactivity series. 91 5 Reactivity 5.3 Salts 5.3A Which acid is used to make which salt? Focus In this exercise you identify which salt is used to produce a salt. Then you identify a salt from its formula. 1 Link the name of the acid with its formula, and with the name of the salt it produces. Draw lines to link the boxes. Use a ruler. Acid Formula Salt hydrochloric acid HNO3 sulfates sulfuric acid HCl nitrates nitric acid H2SO4 chlorides 2 The following compounds are all salts of magnesium. For each one, state the acid that has been used to make the salt. magnesium chloride magnesium sulfate magnesium nitrate 3 Write the name of the salt next to its formula. NaCl CuSO4 CuCl2 KNO3 92  5.3 Salts 4 Citric acid is found in fruit. What are salts of this acid called? 5.3B Making salts Practice In this exercise you will explain how some salts are made and practice some word equations. 1 Explain how you could make the salt zinc nitrate using zinc metal. 2 Write the word equation for this reaction. 3 Explain why you could not make silver sulfate by that method. 4 Explain why you could not make potassium sulfate by that method. 5 Copper sulfate is made by mixing copper oxide with sulfuric acid and gently heating it. a Why is it important that the acid mixture does not boil? b Write the word equation for the reaction. 93 5 Reactivity 6 Write the word equations for the following reactions: a magnesium and nitric acid b copper oxide and nitric acid c zinc and hydrochloric acid d zinc and sulfuric acid 5.3C Practical steps for making salts Challenge In this exercise you will describe in detail the practical steps needed to produce a salt using an oxide and acid. 1 Why is copper chloride not made by reacting copper with dilute sulfuric acid? 2 Describe the three steps involved in producing crystals of the salt copper chloride. For each step, describe the method and include the safety precautions needed. Use diagrams if that will help your answer. 94  5.4 Other ways of making salts 5.4 Other ways of making salts 5.4A Preparing copper chloride Focus In this exercise you explain the steps in the formation of a salt. You also consider