Cambridge IGCSE Science - Combined 0653 — 2015 Oct/Nov Paper 3 · Variant 3

This document consists of 28 printed pages. DC (NH/FD) 104364/3 © UCLES 2015 [Turn over * 0 7 7 1 7 7 0 7 0 7 * COMBINED SCIENCE 0653/33 Paper 3 (Extended) October/November 2015 1 hour 15 minutes 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 a HB pencil for any diagrams or graphs. 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 28. 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. Cambridge International Examinations Cambridge International General Certificate of Secondary Education

2 0653/33/O/N/15 © UCLES 2015 1 (a) Use words from the list to complete the sentences about the human gas exchange system. Each word can be used once, more than once, or not at all. arteries capillaries into large long out of small veins The alveoli have a … surface area for the diffusion of oxygen … the blood. There is a good supply of blood flowing in … close to the alveoli which provides a short diffusion pathway for gases. [3] (b) Some people suffer from asthma which affects the bronchioles of the gas exchange system. Fig. 1.1 shows a cross section of a healthy bronchiole, and a bronchiole of a person with asthma. wall of bronchiole airway healthy bronchiole bronchiole of a person with asthma airway mucus wall of bronchiole Fig. 1.1 The airflow towards the alveoli is reduced if a person has asthma. Describe two features visible in Fig. 1.1 which could reduce the airflow to the alveoli. 1 … 2 …[2] (c) A study is carried out to compare the breathing of people with asthma with the breathing of healthy people. The volumes of air inhaled in one minute are measured and an average is calculated. Both groups of people are tested while resting. Results average volume inhaled by a healthy person = 5.8 dm3 / minute average volume inhaled by a person with asthma = 12.5 dm3 / minute

3 0653/33/O/N/15 © UCLES 2015 [Turn over (i) Calculate the average percentage of extra air the person with asthma inhales per minute compared with a healthy person. Show your working. answer = …% [2] (ii) The person with asthma needs to breathe a greater volume of air per minute by breathing more quickly and more deeply. The same changes occur to the breathing of all people when they exercise. Explain why these breathing changes are needed during exercise. … … … …[2] (d) The tar in tobacco smoke affects the gas exchange system. Two of these effects are listed below. cilia become paralysed more mucus is produced Choose one of the effects above and explain why it is especially harmful for a person with asthma to smoke. State which change you are choosing. change … explanation … … … …[2]

4 0653/33/O/N/15 © UCLES 2015 2 Fig. 2.1 shows the apparatus used to investigate the temperature changes which occur during some chemical processes. temperature sensor connected to computer insulated cup water Fig. 2.1 The temperature sensor is placed in the water and the computer starts to log data. After 10 seconds some solid silver nitrate is added to the water in the cup. The mixture is stirred until the solid dissolves. After another 40 seconds a length of copper wire is placed in the solution. Fig. 2.2 shows the computer display of temperature change for the first 100 seconds. 0 0 5 10 15 20 25 30 35 temperature / °C 40 10 20 30 40 50 60 70 80 90 100 time / s silver nitrate placed in water copper placed in solution Fig. 2.2 (a) Describe the energy change taking place as the silver nitrate dissolves. …[1]

5 0653/33/O/N/15 © UCLES 2015 [Turn over (b) The experiment shown in Fig. 2.2 is experiment 1. The procedure is repeated, using twice the mass of silver nitrate in the same volume of pure water. This is experiment 2. The same length of copper wire is added at 50 seconds. Fig. 2.3 shows part of the computer display with the results of both experiments. 0 0 5 10 15 20 25 30 35 temperature / °C 40 10 20 30 40 50 60 70 80 90 100 time / s experiment 1 experiment 2 Fig. 2.3 (i) Complete the graph for experiment 2 on Fig. 2.3 to show the change in temperature as copper reacts. [1] (ii) Explain, in terms of the collision of particles, how increasing concentration affects the rate of reaction. … … …[2]

6 0653/33/O/N/15 © UCLES 2015 (c) Fig. 2.4 shows the appearance of the contents of the cup at the end of the experiment. copper wire crystals of silver pale blue solution Fig. 2.4 Crystals of metallic silver coat the copper wire and the liquid is now a pale blue solution. (i) Use the words atoms and ions to complete the sentences which explain what happens during the reaction. Each word may be used once or more than once. Copper … in the wire become copper … in the solution. Silver … in the solution become silver … in the crystals. [1] (ii) Table 2.1 shows a list of metals in order of reactivity. Table 2.1 potassium sodium calcium magnesium zinc iron copper Write silver in its correct position in the list in Table 2.1. [1] (iii) Suggest how the reactivity of a metal depends on how easily its atoms change into ions in a chemical reaction. … … …[1]

7 0653/33/O/N/15 © UCLES 2015 [Turn over Please turn over for Question 3.

8 0653/33/O/N/15 © UCLES 2015 3 Fig. 3.1 shows a girl on a skateboard track which ends in a shallow pool of water. A B C D shallow pool of water Fig. 3.1 (a) Name the force that causes the girl to move down the skateboard track from A to B. …[1] (b) State the main energy transfer as the girl travels from A to B. from … energy to … energy [1]

9 0653/33/O/N/15 © UCLES 2015 [Turn over (c) Fig. 3.2 shows a speed/time graph of the girl as she travels. 10 8 6 4 2 0 0 1 2 3 4 5 6 time/s speed m/s A B C D Fig. 3.2 (i) Describe the motion of the girl between points A and B, … B and C. …[2] (ii) Use Fig. 3.2 to calculate the distance travelled by the girl between points A and C. Show your working. distance = … m [2]

10 0653/33/O/N/15 © UCLES 2015 (d) The girl crouches low on the skateboard to minimise air resistance. When she enters the shallow pool of water, the water resistance stops her quickly. Explain, in terms of the particle theory of matter, why water resistance is more effective than air resistance at stopping the skateboarder. You may wish to draw diagrams to help your explanation. … … … … … …[3]

11 0653/33/O/N/15 © UCLES 2015 [Turn over Please turn over for Question 4.

12 0653/33/O/N/15 © UCLES 2015 4 (a) Vitamins are needed in small quantities as part of a balanced diet. One vitamin is vitamin C. (i) State what is meant by the term balanced diet. … … …[1] (ii) State why we need vitamin C in our diet. … …[1] (b) A student does an experiment to find if temperature affects the vitamin C content of a citrus fruit juice. The fruit juice is freshly made and then 10 cm3 samples of the juice are stored for four days at the temperatures shown in the table. At the start, a 10 cm3 volume of fruit juice contains 5 mg of vitamin C. Table 4.1 shows the average mass of vitamin C in each 10 cm3 sample of juice at the end of the four days. Table 4.1 temperature / °C mass of vitamin C / mg in 10 cm3 of juice 4 (in refrigerator) 4.9 20 3.8 30 3.5 40 2.8 50 1.4 (i) Describe the effect of increasing temperature on the vitamin C content of the juice. … …[1] (ii) Suggest an explanation for the effect you described in (b)(i). … …[1]

13 0653/33/O/N/15 © UCLES 2015 [Turn over (iii) When the experiment was repeated in different parts of the world, the initial masses of vitamin C in the 10 cm3 samples were found to be very different. Suggest and explain a reason for this observation. … … … …[2] (c) Many new mothers feed their babies on formula milk which is made up with warm water and given to the baby from a bottle. Using the information in Table 4.1 suggest why boiling water should not be used to make up formula milk. … … …[1] (d) A new mother was deciding whether to bottle-feed her baby. Explain one advantage and one disadvantage of bottle feeding. advantage … … disadvantage … …[2]

14 0653/33/O/N/15 © UCLES 2015 5 (a) Fig. 5.1 shows Period 3 of the Periodic Table. A B Na 23 11 Sodium Mg 24 12 Magnesium Al 27 13 Aluminium Si 28 14 Silicon P 31 15 Phosphorus S 32 16 Sulfur Cl 35.5 17 Chlorine Ar 40 18 Argon Fig. 5.1 Draw an arrow in box A to show the direction of increasing metallic character of the elements across the period. Draw an arrow in box B to show the direction of increasing number of outer shell electrons in atoms of the elements across the period. [1] (b) (i) Table 5.1 shows some observations made after a piece of sodium is dropped into water containing some full-range indicator (Universal Indicator). Complete Table 5.1 to explain each observation. Table 5.1 observation explanation bubbles of gas indicator changes from green to purple [2]

15 0653/33/O/N/15 © UCLES 2015 [Turn over (ii) Fig. 5.2 shows part of Group I of the Periodic Table. Li Group I 7 3 Lithium Na 23 11 Sodium K 39 19 Potassium Rb 85 37 Rubidium Fig. 5.2 Predict one way in which the reaction between rubidium and water differs from the reaction between sodium and water. Explain your answer. difference … explanation … … …[2]

16 0653/33/O/N/15 © UCLES 2015 (iii) Fig. 5.3 shows the outer electron shell in a sodium atom. Complete the diagram of the outer shell of a rubidium atom to suggest how many electrons there are in the outer shell of a rubidium atom. Na Rb Fig. 5.3 Describe how you used the Periodic Table to make this suggestion. … … …[2]

17 0653/33/O/N/15 © UCLES 2015 [Turn over Please turn over for Question 6.

18 0653/33/O/N/15 © UCLES 2015 6 Electric power can be generated using the energy of waves on the sea. Fig. 6.1 shows a group of small wave energy converters which are anchored to the sea floor below. floating tube containing wave energy converter waves Fig. 6.1 Inside each floating tube there are several generators that convert the wave movement energy into electrical energy. (a) (i) A total of 10 waves passed one end of a container in 20 seconds. Calculate the frequency of the waves. Show your working and state the unit of your answer. frequency = … unit … [2] (ii) Each floating container is 30 m long. In Fig. 6.1 each sea wave takes 10 seconds to pass along each floating container from end to end. Calculate the speed of the waves across the sea. speed = …m/s [1]

19 0653/33/O/N/15 © UCLES 2015 [Turn over (iii) Use your answers to (a)(i) and (ii) to calculate the wavelength of the waves. State the formula that you use and show your working. formula working wavelength = … m [2] (b) The amplitude of the waves on one day was 0.5 m. State the vertical distance that each container will move through as a wave passes. distance = … m [1] (c) The generators are controlled by radio signals. A radio signal is sent from a control centre 100 km away. Fig. 6.2 shows an incomplete diagram of the electromagnetic spectrum. gamma radiation visible light Fig. 6.2 Write an R in the box for the part of the spectrum where radio waves are found. [1]

20 0653/33/O/N/15 © UCLES 2015 (d) Fig. 6.3 shows a tidal energy turbine, which is placed on the sea-bed. The flow of the tide turns the turbine. air turbine sea Fig. 6.3 Engineers believe wave generators and tidal generators will be important for supplying electrical energy in the future. (i) Give one advantage, other than cost, that tidal generators have over wave generators for the supply of electrical energy. … …[1] (ii) The water flow through a tidal generator delivers energy at 500 kW. The electrical output from this turbine is 150 kW. Calculate the efficiency of the tidal turbine. State the formula that you use and show your working. formula working efficiency = … % [1]

21 0653/33/O/N/15 © UCLES 2015 [Turn over 7 Fig. 7.1 shows what happens to most of the solar radiation reaching the Earth. (DUWK DWPRVSKHUH 6XQ LQFRPLQJVRODUUDGLDWLRQ PRVWUDGLDWLRQLVDEVRUEHG E\WKH(DUWKҋVVXUIDFHDQG ZDUPVLW LQIUDUHGUDGLDWLRQHPLWWHG IURPWKH(DUWKҋVVXUIDFH VRPHRIWKHLQIUDUHGSDVVHV RXWRIWKHDWPRVSKHUH VRPHRIWKHLQIUDUHGLVDEVRUEHG E\JUHHQKRXVHJDVPROHFXOHV LQWKHDWPRVSKHUH      Fig. 7.1 Use Fig. 7.1 to (a) Describe the role of the atmosphere in keeping the Earth warm. … … …[2] (b) Name two greenhouse gases. … and … [1] (c) Describe two ways in which human activities cause the concentrations of these greenhouse gases to increase. 1 … … 2 … …[2] (d) State one measure that can be taken to reduce the levels of greenhouse gases in the atmosphere. … …[1]

22 0653/33/O/N/15 © UCLES 2015 8 A student extracts some copper from a sample of green copper carbonate, CuCO3. (a) He adds dilute hydrochloric acid to the copper carbonate until it is all dissolved. A blue solution of copper chloride, CuCl2, is formed. Fig. 8.1 shows that bubbles of gas appear. copper carbonate dilute hydrochloric acid Fig. 8.1 (i) The word equation for the reaction is: hydrochloric acid + copper carbonate copper chloride + carbon dioxide + water Write the balanced chemical equation for this reaction. …[2]

23 0653/33/O/N/15 © UCLES 2015 [Turn over (ii) The student checks that the gas is carbon dioxide. When the reaction is complete, he collects some of the gas in a pipette. Fig. 8.2 shows how he collects the gas and then passes it through a solution X. solution ; reaction mixture gas gas pipette Fig. 8.2 State the name of solution X and describe the effect of carbon dioxide on its appearance. name … effect … …[2]

24 0653/33/O/N/15 © UCLES 2015 (b) The student places the copper chloride solution that he has made into the electrolysis cell shown in Fig. 8.3. power supply + – anode carbon electrodes cathode copper chloride solution Fig. 8.3 (i) Complete Fig. 8.3 by labelling each electrode to show the product formed. [2] (ii) The electrolyte contains copper ions and chloride ions. Describe the direction of movement of these particles when the switch in the circuit is closed. copper ions (Cu2+) … chloride ions (Cl–) …[2]

25 0653/33/O/N/15 © UCLES 2015 [Turn over (c) Another compound of copper and chlorine exists, with a different formula. It contains copper ions which have only one positive charge, Cu+. (i) Deduce the formula of the copper chloride compound containing the ion Cu+. Explain your answer. formula … explanation … … …[2] (ii) Copper is a transition metal. The ability to form more than one compound with another element is typical of transition metals. State another property which is typical of transition metals but not of other metals. …[1] (d) Carbon is an element that forms different compounds with the element hydrogen. Draw the structures of molecules of the carbon compounds methane and ethene in the boxes. methane + & ethene + & [2]

26 0653/33/O/N/15 © UCLES 2015 9 (a) Fig. 9.1 shows two oppositely charged metal plates. Fig. 9.1 The two oppositely charged plates are free to move. State what will happen. Give a reason for your answer. … … …[2] (b) (i) Complete the following sentence: An electric field is a region in which an electric charge experiences a … . [1] (ii) Fig. 9.2 shows an electron entering the electric field between two oppositely charged plates. e– Fig. 9.2 An electron carries a negative charge. On Fig. 9.2 draw a line to show the path the electron might take after it enters the electric field. [1]

27 0653/33/O/N/15 © UCLES 2015 (c) Fig. 9.3 shows a circuit diagram for an electric heater, supplied with 12 V from a car battery. 12 V heater Fig. 9.3 (i) The heater circuit is changed to include a second identical heater and a lamp to show when the heaters are switched on. The heaters must be connected in parallel to work. Complete the circuit diagram below to include both heaters and the lamp connected so that the circuit works when the switch is closed. 12 V [3] (ii) The heater transfers t hermal energy to some water. This causes convection in the water. Explain why the thermal energy causes convection in the water. … … …[2]

28 0653/33/O/N/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 October/November 2015 series 0653 COMBINED SCIENCE 0653/33 Paper 3 (Extended Theory), maximum raw mark 80 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 October/November 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 – October/November 2015 0653 33 © Cambridge International Examinations 2015 1 (a) large ; into ; capillaries ; [3] (b) smaller airway diameter ; presence of mucus obstructing flow ; [2] (c) (i) 12.5 – 5.8 = 6.7 (dm3 / min) ; 5.8 6.7 × 100 = 115(%) or 116(%) ; or 5.8 12.5 = 215 ; 215 – 100 = 115 (%) ; [max 2] (ii) to get more oxygen (into the blood) / remove more carbon dioxide ; for respiration ; [2] (d) (cilia become paralysed) mucus cannot be shifted upwards ; airways become even more restricted / more mucus for bacteria to breed in / bacteria / tar will not be removed from the lungs / increases risk of bronchitis ; or (more mucus is produced) airway becomes even more restricted / blocked ; more mucus for bacteria to breed in / remain in lungs / increases chances of chest infections / reduces oxygen supply for the body ; [max 2] [Total: 11] 2 (a) thermal energy to chemical energy ; [1] (b) (i) steeper gradient than solid line ; [1] (ii) increasing concentration increases rate of reaction ; increased frequency of collisions ; [2] (c) (i) atoms ions ions atoms ; (must be in this order) [1] (ii) silver written below copper ; [1] (iii) the atoms of more reactive metals become ions more readily than those of less reactive metals ; [1] [Total: 7]

Page 3 Mark Scheme Syllabus Paper Cambridge IGCSE – October/November 2015 0653 33 © Cambridge International Examinations 2015 3 (a) weight / gravitational force (accept gravity) ; [1] (b) (gravitational) potential (energy) to kinetic (energy) ; [1] (c) (i) accelerating ; constant speed ; [2] (ii) area under graph between A and C or (½ × 2 × 9) + (2 × 9) or ½(2+4) × 9 ; = 27 (m) ; [2] (d) particles far apart in air / gas, but close together / touching in water / liquid (accept diagrammatic description) ; stopping the skateboarder requires loss of KE ; more work done / loses more KE / more difficult to push water particles aside than pushing air particles aside / owtte / diagrams ; harder to push water molecules apart because of the forces between them / more particles ; [max 3] [Total: 9] 4 (a) (i) contains the correct proportions of nutrients for an individual ; [1] (ii) to prevent scurvy / AVP ; [1] (b) (i) as temperature increases the amount of vitamin C decreases ; [1] (ii) rate / amount of decomposition / breakdown / disappearance increases with temperature ; [1] (iii) temperature will vary in different parts of the world ; this will affect the amount of vitamin C (in fruit before the experiment) ; OR amount of water given / contained in1 fruit may vary ; this could affect concentration of the fruit juice ; OR different variety of orange / fruits vary genetically ; (naturally) contains different amounts of vitamin C ; AVPs ;; [max 2] (c) boiling water destroy some / all of the vitamin C ; [1] (d) (advantage) convenient if you need to leave the baby / mother may not have enough milk / AVP ; (disadvantage) does not contain antibodies / any reference to bonding / AVP ; [2] [Total: 9]

Page 4 Mark Scheme Syllabus Paper Cambridge IGCSE – October/November 2015 0653 33 © Cambridge International Examinations 2015 A B 5 (a) [1] (b) (i) observation explanation (bubbles of gas) hydrogen ; (changes from green to purple) alkaline solution ; [2] (ii) more vigorous reaction / hydrogen produced faster / greater temperature rise ; alkali metals become more reactive down the group ; (accept correct references to ease of ionisation of metal atoms) [2] (iii) one electron in shell ; all Group I elements have 1 electron in outer shell ; [2] [Total: 7] 6 (a) (i) ( 20 10 =) 0.5 ; Hz / hertz ; [2] (ii) ( 10 30 ) = 3 (m / s) [1] (iii) v = fλ (in any form) / 0.5 3 ; = 6 (m) ; (allow ecf from (i) and / or (ii) ) [2] (b) 2 × amplitude (0.5) = 1 (m) ; [1] (c) R placed in right-hand end box ; [1] (d) (i) tidal energy more predictable / nearer to land so easier access / installation / any other reasonable suggestion based on access to the energy involved or easier technology / ORA ; [1]

Page 5 Mark Scheme Syllabus Paper Cambridge IGCSE – October/November 2015 0653 33 © Cambridge International Examinations 2015 (ii) (efficiency = input energy output energy useful ) = 500 150 × 100 = 30(%) ; [1] [Total: 9] 7 (a) allows solar radiation to reach the Earth’s surface ; contains greenhouse gas molecules / example ; (greenhouse gases in the atmosphere) absorb infra-red radiation (that is emitted from the Earth’s surface) ; infra-red radiation is then (re-)emitted by the greenhouse gases into the atmosphere / back to the Earth’s surface ; [max 2] (b) two from: carbon dioxide / methane / water vapour ; [1] (c) two from: (increased) use of fossil fuels / example; (increased) deforestation ; (increased) keeping of cows / growing rice ; AVP ; [max 2] (d) reduced use of fossil fuels / removal of carbon dioxide from exhaust / promote the use of public transport ; reduced deforestation ; reduced agricultural practices that cause methane to be produced ; plant more trees ; use more renewable energy sources ; AVP ; [max 1] [Total: 6] 8 (a) (i) 2HCl + (CuCO3) → (CuCl2) + CO2 + H2O formulae ; balanced ; [2] (ii) limewater ; turns milky / cloudy etc. ; [2] (b) (i) copper (deposit on cathode) ; chlorine (gas at anode) ; [2] (ii) (copper ions): move towards cathode / negative (electrode) ; (chloride ions): move towards anode / positive (electrode) ; [2]

Page 6 Mark Scheme Syllabus Paper Cambridge IGCSE – October/November 2015 0653 33 © Cambridge International Examinations 2015 (c) (i) CuCl ; reference to the need for charge balance ; [2] (ii) high density / high melting point / form coloured compounds / act as catalysts ; [max 1] (d) correct structure of methane molecule ; correct structure of ethane molecule ; [2] [Total: 13] 9 (a) (i) move towards each other ; unlike charges attract ; [2] (b) (i) force ; [1] (ii) any path heading towards the upper positive plate ; [1] (c) (i) complete circuit with 2 extra components included in series and / or in parallel ; two heaters in parallel ; lamp in series in main circuit ; [3] (ii) water expands / volume increases / particles get further apart water becomes less dense ; (less dense) / warm water rises (above denser colder water) / owtte ; [2] [Total: 9]