Cambridge IGCSE Sciences - Co-ordinated (Double) 0654 — 2015 May/June Paper 3 · Variant 1

This document consists of 31 printed pages and 1 blank page. DC (AC/JG) 97590/4 © UCLES 2015 [Turn over Cambridge International Examinations Cambridge International General Certificate of Secondary Education * 7 9 5 4 2 3 8 5 3 7 * CO-ORDINATED SCIENCES 0654/31 Paper 3 (Extended) May/June 2015 2 hours Candidates answer on the Question Paper. No Additional Materials are required. READ THESE INSTRUCTIONS FIRST Write your Centre number, candidate number and name on all the work you hand in. Write in dark blue or black pen. You may use an HB pencil for any diagrams, graphs, tables or rough working. Do not use staples, paper clips, glue or correction fluid. DO NOT WRITE IN ANY BARCODES. Answer all questions. Electronic calculators may be used. You may lose marks if you do not show your working or if you do not use appropriate units. A copy of the Periodic Table is printed on page 32. At the end of the examination, fasten all your work securely together. The number of marks is given in brackets [ ] at the end of each question or part question.

2 0654/31/M/J/15 © UCLES 2015 1 (a) Fig. 1.1 shows a wind-powered generator used to power an Arctic research station. Fig. 1.1 During one 24-hour period, the average power output of the wind-powered generator is 20 kW. Calculate the energy output of the generator in joules over the 24-hour period. Show your working. energy = … J [2] (b) In the Arctic, harmful ultraviolet radiation is able to reach the surface of the Earth. The scientists at the research station are exposed to this ultraviolet radiation. Ultraviolet radiation is ionising radiation. (i) State one danger to human beings of being exposed to large quantities of ultraviolet radiation. … [1] (ii) Ultraviolet radiation is part of the electromagnetic spectrum. Name one other radiation which is part of the electromagnetic spectrum and state a use for this radiation. radiation … use … [1]

3 0654/31/M/J/15 © UCLES 2015 [Turn over (c) Sometimes the scientists pull a flat sledge across the ice and snow carrying some of their equipment. Fig. 1.2 shows a scientist pulling a loaded sledge across the ice. Fig. 1.2 The scientist pulls the sledge at a constant speed of 0.8 m / s. The mass of the loaded sledge is 30 kg. Calculate the kinetic energy of the sledge. State the formula that you use and show your working. formula working kinetic energy = … J [2] (d) The scientist carries a nylon tent. As he walks, the nylon material gains a static charge. Explain what happens to cause the nylon to become charged. … … … … [2]

4 0654/31/M/J/15 © UCLES 2015 (e) The scientists are investigating polar bears which live in the cold Arctic region. Polar bears have black skin covered in thick white fur. Explain why white fur keeps a polar bear warmer than black fur. … … [1] (f) If the scientists run into difficulties when they are on the ice, they ask for help by launching a rocket (flare). Observers see the rocket explode with a flash of light and hear a loud bang. This is shown in Fig. 1.3. observers path of rocket (flare) rocket (flare) exploding Fig. 1.3 Explain why the flash of light is seen before hearing the bang. … … [1]

5 0654/31/M/J/15 © UCLES 2015 [Turn over 2 Fig. 2.1 shows apparatus a student uses to study the change in temperature when some metallic zinc is added to copper sulfate solution. The student checks that the temperature of the copper sulfate solution is steady and then adds powdered zinc. Data from the experiment are shown in the graph below the apparatus. temperature time 0 X zinc added insulated beaker copper sulfate solution zinc temperature sensor Fig. 2.1 (a) (i) State the word that is used to describe a chemical reaction that causes an increase in temperature. … [1] (ii) Suggest why the temperature after X in Fig. 2.1 rises to a maximum and then decreases. … … … [2]

6 0654/31/M/J/15 © UCLES 2015 (iii) Predict and explain the temperature changes, if any, when the student carries out a second experiment in which he adds powdered copper to a zinc sulfate solution. … … … … [3] (b) Hand warmers are used by people who may be out of doors in cold weather. Fig. 2.2 shows one type of hand warmer. permeable (porous) container mixture inside contains damp iron filings Fig. 2.2 When the hand warmer is exposed to the air, the air diffuses through the permeable (porous) container and causes a chemical reaction that releases thermal energy (heat). During the reaction that occurs inside the hand warmer, iron is oxidised by oxygen gas to iron oxide, Fe2O3. Suggest a balanced symbol equation for this oxidation reaction. … [2]

7 0654/31/M/J/15 © UCLES 2015 [Turn over (c) Hand warmers like the one in Fig. 2.2 may release thermal energy for up to seven hours. The total surface area of the iron filings used in the hand warmer affects the rate of oxidation. A scientist compares two hand warmers, F and G. hand warmer F mixture contains small grains of iron filings hand warmer G mixture contains larger grains of iron filings The only difference between these hand warmers is that the size of the grains of iron in F is smaller than those in G. (i) Predict and explain which hand warmer, F or G, releases thermal energy for the longer time period. hand warmer … explanation … … … … [3] (ii) State and explain whether the chemical potential energy of the contents of the hand warmer increases, decreases or remains unchanged when it is used. … … … [2]

8 0654/31/M/J/15 © UCLES 2015 3 Fig. 3.1 shows apparatus that can be used to compare the composition of inspired and expired air. limewater test-tube A test-tube B air entering the apparatus air leaving the apparatus tube Q tube R tube P Fig. 3.1 (a) A person breathes slowly in and out of the apparatus at tube P for half a minute, as shown in Fig. 3.1. (i) On Fig. 3.1, draw two arrows to show the directions of air flow in tubes Q and R while the person is breathing in and out through the apparatus. [1] (ii) As the person breathes in and out, the composition of the air flowing into the apparatus through tube P is different from the air leaving the apparatus through tube P. State two of these differences for the air leaving the apparatus. 1 … 2 … [2]

9 0654/31/M/J/15 © UCLES 2015 [Turn over (iii) Describe what you would expect to observe in the limewater in test-tube A and in test-tube B after half a minute. test-tube A … test-tube B … [2] (iv) Assume that the change that you predicted in (a)(iii) occurs. State what could then be concluded from this experiment. … …[1] (b) Suggest and explain how the results of this experiment would be different if the person breathing through the apparatus had just finished some vigorous exercise. difference … … explanation … … … [2]

10 0654/31/M/J/15 © UCLES 2015 4 Table 4.1 shows information about five materials, H to L. Table 4.1 name chemical formula H argon Ar I aspirin (pain killer) C9H8O4 J hydrogen H2 K oxygen O2 L sea water – (a) (i) State and explain which of the materials, H to L, are elements. … … … [2] (ii) Explain why a chemical formula can be written for water but cannot be written for sea water. … … [1] (iii) Aspirin is a white solid compound at room temperature. Describe, without practical details, one way in which the purity of a sample of aspirin could be checked. … … … [2]

11 0654/31/M/J/15 © UCLES 2015 [Turn over (b) Fig. 4.1 shows an incomplete diagram of the electron arrangement in an atom of argon, proton number 18. electron Fig. 4.1 (i) Complete Fig. 4.1 by adding the missing electrons. [2] (ii) Most of the argon atoms in the Earth’s atmosphere have a nucleon number of 40 (Ar-40). Most of the argon atoms in space have a nucleon number of 36 (Ar-36). Explain why both types of atoms are argon but can have different nucleon numbers. … … … [2]

12 0654/31/M/J/15 © UCLES 2015 5 (a) Fig. 5.1 shows a torch (flashlight) shining at a plane mirror. Fig. 5.1 (i) A ray of light reflects off the mirror. Use a ruler to complete the diagram to show the ray of light reflecting off the mirror. [2] (ii) Label the angle of incidence on your diagram in Fig. 5.1. [1]

13 0654/31/M/J/15 © UCLES 2015 [Turn over (b) Some large torches have two lamps. These lamps can be connected to the battery in series or in parallel. (i) Complete the circuit diagrams in Fig. 5.2 to show a series circuit and a parallel circuit for a torch containing two lamps. Each circuit must contain a switch which switches both lamps on and off at the same time. series parallel Fig. 5.2 [3] (ii) Each lamp in the torch has a resistance of 5 Ω. Calculate the combined resistance of two lamps when placed in parallel. State the formula that you use and show your working. formula working resistance = … Ω [2]

14 0654/31/M/J/15 © UCLES 2015 6 For healthy growth, plants must absorb magnesium ions from the soil. If a plant cannot absorb enough magnesium, its leaves lose their green colour. Later, the plant grows more slowly. (a) (i) Explain why a lack of magnesium causes plants to lose their green colour. … … [1] (ii) Explain why, later, the plant grows more slowly. … … … [2] (b) Two groups of wheat plants of the same variety were grown in two different fields, field A and field B. The two fields were next to each other, and with the same conditions except for the amount of fertiliser added to the soil. • Field A had regularly been treated with a nitrogen-containing fertiliser over the previous five years. • Field B had not been treated with any fertiliser during this time. In each field, the height of the wheat plants was measured over a period of 120 days, and the final wheat yield was also measured. Fig. 6.1 shows the results. 0 20 40 60 time / days 80 100 120 80 60 40 20 0 mean height of plants / cm field A final yield 650 g / m2 field B final yield 360 g / m2 Fig. 6.1

15 0654/31/M/J/15 © UCLES 2015 [Turn over (i) Compare the change in heights of the wheat plants in field B with those in field A for the first 20 days, … … next 100 days. … … … [3] (ii) Suggest why adding fertiliser to field A resulted in a higher final yield. … … … [2] (c) Describe how fertiliser from farms can damage the environment in nearby rivers or lakes. … … … … … [3]

16 0654/31/M/J/15 © UCLES 2015 7 Natural gas is a mixture of hydrocarbons usually found near deposits of petroleum (crude oil). Biogas is a gaseous mixture produced by the decomposition of organic material such as plants and animal waste. The three charts, A, B and C, in Fig. 7.1 show the compositions of three gaseous mixtures, air, natural gas and biogas. methane 95% methane 95% methane 95% nitrogen 78% oxygen 21% nitrogen 8% methane 60% oxygen 21% carbon dioxide 25% other gases 5% other gases 1% other gases 7% A B C Fig. 7.1 (a) (i) Deduce which chart, A, B or C, shows the composition of biogas. chart … explanation … … … [2] (ii) Name two compounds that are formed when the main compound in natural gas burns completely in air. 1 … 2 … [2]

17 0654/31/M/J/15 © UCLES 2015 [Turn over (b) Fig. 7.2 shows a simplified diagram of waste gases from a car engine passing over a catalyst. Mixtures of hydrocarbons, such as diesel, are used as car fuel. The waste gases from car engines contain many substances that cause air pollution. catalyst waste gases air and hydrocarbon fuel are drawn into the engine Fig. 7.2 Chemical reactions on the catalyst remove nitrous oxide, N2O, and carbon monoxide, CO, from the waste gases. (i) State the meaning of the term catalyst. … … … [2] (ii) Use information from Fig. 7.2 to suggest how nitrous oxide and carbon monoxide are formed inside the car’s engine. nitrous oxide … … … carbon monoxide … … … [4]

18 0654/31/M/J/15 © UCLES 2015 8 (a) Fig. 8.1 shows a pea seed cut in half. Fig. 8.1 Many plant seeds, such as peas, beans and rice, are used as foods for humans. Suggest why plant seeds like these contain more energy than foods, such as lettuce or cabbage, that have come from other parts of plants. … … … [2] (b) Fig. 8.2 shows an apple cut in half lengthways. seed outer part of apple Fig. 8.2 Apple seeds taste bitter when chewed. The chewed seeds are poisonous if eaten in large quantities. However, the outer part of the apple is not poisonous. (i) Explain why it is important for dispersal of the apple seeds that the outer part of the apple is not poisonous. … … [1]

19 0654/31/M/J/15 © UCLES 2015 [Turn over (ii) Suggest why having bitter-tasting seeds helps the survival of apple trees. … … … [2] (c) Fig. 8.3 shows a fruit from another plant. Fig. 8.3 (i) Suggest how the seeds of this plant are dispersed. … … [1] (ii) Explain why seed dispersal is important for a plant. … … … [2]

20 0654/31/M/J/15 © UCLES 2015 9 (a) A cook places a metal saucepan containing water onto a hot-plate on an electric cooker. The saucepan and water are shown in Fig. 9.1. heat water metal saucepan hot-plate Fig. 9.1 (i) Thermal energy can be transferred by conduction, convection and radiation. The thermal energy is transferred through the metal saucepan by conduction. Describe this process in terms of particles. … … … [2] (ii) Fig. 9.2 is a scale diagram showing the energy transformations involved in heating the water. electrical power input = 2.0 kW useful power heating water = 0.80 kW wasted power = 1.2 kW Fig. 9.2

21 0654/31/M/J/15 © UCLES 2015 [Turn over Calculate the efficiency of heating water in this way. Show your working and give your answer as a percentage. efficiency = …% [2] (b) While water is heated, a small amount of water evaporates. When the temperature of the water reaches 100 °C, the water boils. State two ways in which boiling differs from evaporation. 1 … … 2 … … [2] (c) When the water starts to boil, the cook knows that the water is bubbling because he can hear the sound of the bubbling. Sound waves move through the air as a series of compressions and rarefactions. State the difference between a compression and a rarefaction. … … … [1]

22 0654/31/M/J/15 © UCLES 2015 (d) Fig. 9.3 shows three different ways in which particles may be arranged in substances. A B C Fig. 9.3 State which diagram best represents the way particles are arranged in the liquid water in the saucepan. Explain your answer. diagram … explanation … … [1] (e) The saucepan and water have a weight of 20 N. The surface of the base in contact with the cooker is 300 cm2. Calculate the pressure in N / m2 exerted by the saucepan and water on the surface of the cooker. State the formula that you use and show your working. formula working pressure = … N / m2 [3]

23 0654/31/M/J/15 © UCLES 2015 [Turn over 10 Fig. 10.1 shows the structure of the human eye as seen in horizontal section. V Z Y X W Fig. 10.1 (a) Name the parts of the eye labelled V and W. V … W … [2] (b) Fig. 10.2 shows an eye as seen from the front. Label Fig. 10.2 to show which parts correspond to the structures labelled X, Y and Z in Fig. 10.1. One has been done for you. Z Fig. 10.2 [2]

24 0654/31/M/J/15 © UCLES 2015 (c) Complete the rest of Table 10.1 to show what happens when the eye changes its focus from a distant object to a near object. Table 10.1 structure change when starting to focus on a near object ciliary muscles suspensory ligaments lens – shape lens – focal length decreased [3] (d) Older people often find it difficult to focus on near objects, although they are still able to focus well on distant objects. Suggest and explain a reason for this. … … … [2]

25 0654/31/M/J/15 © UCLES 2015 [Turn over 11 Fig. 11.1 shows two electrolysis reactions in beakers A and B. Gases are produced at three of the four electrodes. In one of the beakers, the electrolyte is aqueous copper chloride and in the other the electrolyte is dilute sulfuric acid. beaker A beaker B d.c. power supply d.c. power supply + – + – P Q R S Fig. 11.1 (a) (i) State and explain in which beaker, A or B, the electrolysis of copper chloride is taking place. beaker … explanation … … [1] (ii) Name the gaseous element produced on the surface of electrode Q in beaker A. Explain your answer. gas … explanation … … [2] (iii) Name the gas produced on the surface of electrode P in beaker A. … [1]

26 0654/31/M/J/15 © UCLES 2015 (b) Fig. 11.2 shows the electrolysis of copper sulfate solution using copper electrodes. d.c. power supply + – copper cathode copper anode aqueous copper sulfate Fig. 11.2 During this electrolysis reaction the masses of the electrodes slowly change. Table 11.1 shows the mass of the cathode at the start and end of the process. Table 11.1 cathode mass at the start / g cathode mass at the end / g 177.42 178.38 (i) Calculate the number of moles of copper deposited on the cathode during the electrolysis. The relative atomic mass of copper is 64. Show your working. number of moles of copper = … [2] (ii) State and explain what happens to the mass of the anode during the electrolysis. … … … [2]

27 0654/31/M/J/15 © UCLES 2015 [Turn over 12 (a) Give an example of a fossil fuel. … [1] (b) Fossil fuels are non-renewable. Explain what is meant by non-renewable. … … [1] (c) Many governments are making efforts to reduce the use of fossil fuels. Suggest two ways in which the use of fossil fuels can be reduced. 1 … 2 … [2]

28 0654/31/M/J/15 © UCLES 2015 13 (a) Fig. 13.1 shows a fishing boat using ultrasound waves to detect a shoal of fish, 120 m below the surface. shoal of fish 120 m transmitted waves reflected waves transmitter / receiver Fig. 13.1 (i) The speed of ultrasound waves in water is 1500 m / s. Short pulses of ultrasound are sent out from the boat and the echo from the fish is detected by the boat. Calculate the time taken between the ultrasound waves being emitted and the detection of the echo. State the formula that you use and show your working. formula working time = … s [2]

29 0654/31/M/J/15 © UCLES 2015 [Turn over (ii) The frequency of the ultrasound waves used to detect fish is 45 000 Hz. Calculate the wavelength of the ultrasound waves. State the formula that you use and show your working. formula working wave length = … m [2] (iii) State the approximate human range of audible frequencies. from … Hz to …Hz [1] (iv) State why humans cannot hear ultrasound waves. … … [1]

30 0654/31/M/J/15 © UCLES 2015 (b) The power of ocean waves can be used as a source of energy. Fig. 13.2 shows a model of a device which could generate electricity from waves. A magnet is able to move inside a coil. The coil is fixed to the concrete block on the sea floor. N S concrete block sea floor float surface of sea support cable coil cable to land Fig. 13.2 (i) Describe how this device generates an e.m.f. … … … … … [3] (ii) Suggest two changes which could be made to the device to increase the e.m.f. produced. 1 … … 2 … … [2]

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32 0654/31/M/J/15 © UCLES 2015 Group The Periodic Table of the Elements 140 Ce Cerium 58 141 Pr Praseodymium 59 144 Nd Neodymium 60 Pm Promethium 61 150 Sm Samarium 62 152 Eu Europium 63 157 Gd Gadolinium 64 159 Tb Terbium 65 162 Dy Dysprosium 66 165 Ho Holmium 67 167 Er Erbium 68 169 Tm Thulium 69 173 Yb Ytterbium 70 175 Lu Lutetium 71 232 Th Thorium 90 Pa Protactinium 91 238 231 147 237 244 243 247 247 251 252 257 258 259 260 U Uranium 92 Np Neptunium 93 Pu Plutonium 94 Am Americium 95 Cm Curium 96 Bk Berkelium 97 Cf Californium 98 Es Einsteinium 99 Fm Fermium 100 Md Mendelevium 101 No Nobelium 102 Lr Lawrencium 103 1 H Hydrogen 1 7 Li Lithium 3 23 Na Sodium 11 24 Mg Magnesium 12 40 Ca Calcium 20 45 Sc Scandium 21 48 Ti Titanium 22 51 V Vanadium 23 52 Cr Chromium 24 55 Mn Manganese 25 56 Fe Iron 26 59 Co Cobalt 27 59 Ni Nickel 28 64 Cu Copper 29 65 Zn Zinc 30 70 Ga Gallium 31 27 Al Aluminium 13 11 B Boron 5 12 C Carbon 6 14 N Nitrogen 7 16 O Oxygen 8 19 F Fluorine 9 28 Si Silicon 14 31 P Phosphorus 15 32 S Sulfur 16 35.5 Cl Chlorine 17 40 Ar Argon 18 20 Ne Neon 10 4 He Helium 2 73 Ge Germanium 32 75 As Arsenic 33 79 Se Selenium 34 80 Br Bromine 35 84 Kr Krypton 36 39 K Potassium 19 88 Sr Strontium 38 89 Y Yttrium 39 91 Zr Zirconium 40 93 Nb Niobium 41 96 Mo Molybdenum 42 Tc Technetium 43 101 Ru Ruthenium 44 103 Rh Rhodium 45 106 Pd Palladium 46 108 Ag Silver 47 112 Cd Cadmium 48 115 In Indium 49 119 Sn Tin 50 122 Sb Antimony 51 128 Te Tellurium 52 127 I Iodine 53 131 Xe Xenon 54 137 Ba Barium 56 139 La Lanthanum 57 * 178 Hf Hafnium 72 181 Ta Tantalum 73 184 W Tungsten 74 186 Re Rhenium 75 190 Os Osmium 76 192 Ir Iridium 77 195 Pt Platinum 78 197 Au Gold 79 201 Hg Mercury 80 204 Tl Thallium 81 207 Pb Lead 82 209 209 210 222 Bi Bismuth 83 Po Polonium 84 At Astatine 85 Rn Radon 86 Fr Francium 87 227 Ac Actinium 89 † 9 Be Beryllium 4 I II III IV V VI VII 0 85 Rb Rubidium 37 133 Cs Caesium 55 226 223 Ra Radium 88 a X b a = relative atomic mass X = atomic symbol b = atomic (proton) number Key DATA SHEET * 58–71 Lanthanoid series † 90–103 Actinoid series The volume of one mole of any gas is 24dm3 at room temperature and pressure (r.t.p.). To avoid the issue of disclosure of answer-related information to candidates, all copyright acknowledgements are reproduced online in the Cambridge International Examinations Copyright Acknowledgements Booklet. This is produced for each series of examinations and is freely available to download at www.cie.org.uk after the live examination series.

® IGCSE is the registered trademark of Cambridge International Examinations. CAMBRIDGE INTERNATIONAL EXAMINATIONS Cambridge International General Certificate of Secondary Education MARK SCHEME for the May/June 2015 series 0654 CO-ORDINATED SCIENCES 0654/31 Paper 3 (Extended Theory), maximum raw mark 120 This mark scheme is published as an aid to teachers and candidates, to indicate the requirements of the examination. It shows the basis on which Examiners were instructed to award marks. It does not indicate the details of the discussions that took place at an Examiners’ meeting before marking began, which would have considered the acceptability of alternative answers. Mark schemes should be read in conjunction with the question paper and the Principal Examiner Report for Teachers. Cambridge will not enter into discussions about these mark schemes. Cambridge is publishing the mark schemes for the May/June 2015 series for most Cambridge IGCSE®, Cambridge International A and AS Level components and some Cambridge O Level components.

Page 2 Mark Scheme Syllabus Paper Cambridge IGCSE – May/June 2015 0654 31 © Cambridge International Examinations 2015 1 (a) Use of (energy =) power × time ; = 24 × 60 × 60 × 20 000 = 1.73 × 109 (J) ; [2] (b) (i) cancer / mutation / damage to DNA / damage to cells / sunburn ; [1] (ii) radiation and correct use ; [both required for mark] [1] (c) (KE =) ½mv2 ; = ½ × 30 × 0.8 × 0.8 = 9.6 (J) ; [2] (d) friction ; transfer of electrons / charged particles ; [2] (e) black surfaces emit more thermal energy / heat energy than white surfaces ; [1] (f) light travels faster than sound, etc. ; [1] [Total: 10] 2 (a) (i) exothermic ; [1] (ii) the idea that thermal energy given out until (one of) the reactants is used up / thermal energy is only released while reaction occurs ; the idea that when reactants used up / reaction stops, the mixture cools / starts to return to room temperature / energy leaves beaker / temperature increases until reactants used up ; [2] (iii) no temperature change ; because no reaction occurs ; because copper is less reactive than zinc ; [3] (b) 4Fe + 3O2 → 2Fe2O3 all formulae ; and then look for balanced ; [2]

Page 3 Mark Scheme Syllabus Paper Cambridge IGCSE – May/June 2015 0654 31 © Cambridge International Examinations 2015 (c) (i) (G) no mark G / larger grains have smaller surface area ; smaller surface area causes lower speed of reaction / longer reaction time / time to use up reactants ; lower speed of reaction causes longer reaction time / time to use up reactants ; extra detail, e.g. correct collision theory ideas ; [max 3] (ii) decreases ; (chemical potential) energy is transferred (out of the mixture) as thermal energy / heat ; [2] [Total: 13] 3 (a) (i) arrows on Q and R, both pointing to the right ; [1] (ii) less CO2 leaving the apparatus ; more oxygen leaving the apparatus ; cooler ; [max 2] (iii) A – no change ; B – goes cloudy / milky ; [2] (iv) more CO2 in expired air ; [1] (b) faster change / more cloudy (in tube B) ; because more respiration / more CO2 in expired air ; [2] [Total: 8] 4 (a) (i) H J and K / argon hydrogen oxygen ; only one type of atom / in Periodic Table / cannot be simplified ; [2] (ii) it is a mixture / owtte ; [1] (iii) measure the melting point ; compare with published value / should be same as published value ; OR chromatography ; compare with pure sample ; [2]

Page 4 Mark Scheme Syllabus Paper Cambridge IGCSE – May/June 2015 0654 31 © Cambridge International Examinations 2015 (b) (i) total of 18 electrons ; arranged 2,8,8 ; [2] (ii) both (argon) atoms have 18 / same number of protons ; Ar – 36 has 18 neutrons (per atom) and Ar – 40 has 22 neutrons (per atom) / different numbers of neutrons (per atom) ; [2] [Total: 9] 5 (a) (i) ray of light reflecting off mirror ; at approx. correct angle ; [2] (ii) angle of incidence correctly labelled ; [1] (b) (i) correct series circuit ; correct parallel circuit ; switch in correct place and all symbols correct ; [3] (ii) 1 / RT = 1 / R1 + 1 / R2 (or RT = R1R2 ) / relevant working ; R1 + R2 2.5 (Ω) ; [2] [Total: 8] 6 (a) (i) needed for chlorophyll ; [1] (ii) chlorophyll needed for photosynthesis ; (so) less photosynthesis ; (so) less sugar / energy for growth ; [max 2] (b) (i) first 20 days: the same ; [1] next 100 days: do not grow as high in Field B ; grow slower in Field B ; approx. straight line instead of curve ; final (mean) difference of 35 cm ; [max 2] [max 3] (ii) supplies extra nitrate; for making protein ; [2] (c) washed (out of soil) into river / lake ; eutrophication ; increased growth of algae / surface plants ; blocks light to plants (deeper down) ; algae / plants, die ; bacteria feed on them / population increases ; bacteria, etc. use oxygen ; lack of oxygen kills fish ; [max 3] [Total: 11]

Page 5 Mark Scheme Syllabus Paper Cambridge IGCSE – May/June 2015 0654 31 © Cambridge International Examinations 2015 7 (a) (i) (C) no mark A is natural gas ; B is air ; products of decomposition (of organic material) are CH4 / CO2 ; [max 2] (ii) carbon dioxide ; water ; [2] (b) (i) ref. to increasing the speed of a reaction ; remaining unchanged itself ; [2] (ii) air (taken into the engine) contains nitrogen and oxygen ; nitrous oxide formed from (direct) combination / reaction of nitrogen and oxygen ; (very) hot (and pressurised) in engine so (direct) combination / reaction possible ; carbon monoxide from reaction between the fuel / hydrocarbons and oxygen ; reference to incomplete combustion ; [max 4] [Total: 10] 8 (a) contain starch / carbohydrate / oil / fat / contain chemical energy ; stored there (by the plant) ; for later development / until they can photosynthesise ; [max 2] (b) (i) (animals disperse the seeds) when they eat (the outer part) of the apple ; [1] (ii) stops animals eating / chewing the seeds ; which would damage / kill the embryo / seed would not grow into plant ; unchewed seeds can pass through intestines / in faeces / not digested ; [max 2] (c) (i) wind ; [1] (ii) colonising new areas ; reduces overcrowding / competition ; [2] [Total: 8]

Page 6 Mark Scheme Syllabus Paper Cambridge IGCSE – May/June 2015 0654 31 © Cambridge International Examinations 2015 9 (a) (i) particles gain thermal energy and vibrate faster / more ; this vibration passes through the metal saucepan ; [2] (ii) (efficiency =) useful energy output / energy input ; (or working) = 40 (%) ; [2] (b) evaporation can occur at any temperature / boiling only happens at the boiling point ; evaporation happens only at the surface / boiling occurs throughout the liquid ; during boiling all / most molecules have enough energy to leave / evaporation lets only the molecules with the highest kinetic energy out ; evaporation can occur using the internal energy of the system / boiling requires a(n external) source of heat ; evaporation produces cooling / boiling does not produce cooling ; evaporation is a slow process / boiling is a rapid process ; [max 2] (c) compressions are regions where the particles in air are close together / rarefactions are regions where the particles in air are spread out ; compressions are regions with air at higher pressure than normal / rarefactions are regions with air at lower pressure than normal ; [max 1] (d) (B) no mark because particles are closely packed and randomly arranged ; [1] (e) (pressure =) force / area ; = 20 / 0.03 ; (evidence of cm2 to m2 conversion) = 667 / 670 (N / m2) ; [3] [Total: 11] 10 (a) V = lens ; W = retina ; [2] (b) ;; [2] Y X

Page 7 Mark Scheme Syllabus Paper Cambridge IGCSE – May/June 2015 0654 31 © Cambridge International Examinations 2015 (c) structure change when starting to focus on a near object ciliary muscles contract ; suspensory ligaments less taut / AW ; (accept: relax) lens – shape thicker / fatter ; lens – focal length decreased [3] (d) weaker ciliary muscles / AW ; so cannot make lens thick enough ; OR loss of lens elasticity ; so cannot become thick enough ; [max 2] [Total: 9] 11 (a) (i) (B) no mark the idea that the electrolysis of copper chloride does not produce gas at the cathode / R / negative / does not produce two gases / produces gas only at the anode / S / positive / produces copper (a solid) and chlorine (a gas) ; [1] (ii) oxygen ; oxygen is evolved from the anode / positive electrode (when dilute sulfuric acid is electrolysed) ; [2] (iii) hydrogen ; [1] (b) (i) mass of copper deposited = 178.38 – 177.42 = 0.96 (g) ; moles of copper = 0.96 ÷ 64 = 0.015 ; [2] (ii) anode mass decreases ; anode dissolves / atoms break away as ions / Cu → Cu2+ + 2e- ; [max 2] [Total: 8]

Page 8 Mark Scheme Syllabus Paper Cambridge IGCSE – May/June 2015 0654 31 © Cambridge International Examinations 2015 12 (a) coal / petroleum / natural gas ; [1] (b) cannot be replaced once used ; [1] (c) (one named) alternative energy sources ; insulation ; low-energy appliances / equipment ; more public transport / less use of cars ; less use of / recycling of plastics ; AVP ; [max 2] [Total: 4] 13 (a) (i) (time =) distance / speed ; = 240 / 1500 = 0.16 (s) ; [2] (ii) (wavelength =) velocity / frequency ; = 1500 / 45 000 = 0.033 (m) ; [2] (iii) 20 Hz to 20 000 Hz ; [1] (iv) ultrasound waves have a frequency above 20 000 Hz ; [1] (b) (i) float moves up and down ; makes magnet move in coil ; magnetic field in coil is changing / cut ; induces emf ; [max 3] (ii) stronger magnet ; more turns ; [2] [Total: 11]