Cambridge IGCSE Sciences - Co-ordinated (Double) 0654 — 2015 Oct/Nov Paper 2 · Variant 3

This document consists of 30 printed pages and 2 blank pages. DC (AC/CGW) 102950/4 © UCLES 2015 [Turn over Cambridge International Examinations Cambridge International General Certificate of Secondary Education * 5 7 4 8 1 1 9 7 8 8 * CO-ORDINATED SCIENCES 0654/23 Paper 2 (Core) October/November 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 0654/23/O/N/15 © UCLES 2015 1 Table 1.1 shows the composition of 100 cm3 cow’s milk and goat’s milk. Table 1.1 amount per 100 cm3 cow’s milk goat’s milk energy (kJ) 290 320 fat (g) 3.4 3.9 protein (g) 3.4 3.5 carbohydrate (g) 4.9 4.7 calcium (mg) 110 120 iron (mg) 0.020 0.010 vitamin C (mg) 1.50 1.48 vitamin D (mg) 0.001 0.001 (a) Using the information in Table 1.1, (i) name two substances that are present in goat’s milk at higher concentrations than in cow’s milk, 1 … 2 … [2] (ii) name one mineral ion that is present in cow’s milk at higher concentration than in goat’s milk, … [1] (iii) suggest why goat’s milk provides more energy per 100 cm3 than cow’s milk. … … [1]

3 0654/23/O/N/15 © UCLES 2015 [Turn over (b) (i) A healthy adult has to consume 90 mg of vitamin C per day to meet their dietary vitamin C requirement. An adult could get all their daily vitamin C requirement from drinking cow’s milk. Use the information in Table 1.1 to calculate how much cow’s milk would be needed. … mg vitamin C is present in 100 cm3 cow’s milk so, … mg vitamin C is present in 1 litre (1000 cm3) milk so, 90 mg vitamin C is present in … litres of milk. milk required = … litres per day [2] (ii) Use your answer to state whether cow’s milk is a good dietary source of vitamin C. Explain your answer. … … [1] (iii) State the deficiency symptoms that result from a diet that does not contain enough vitamin C. … … … [2] (c) (i) Milk contains no dietary fibre (roughage). State the importance of fibre in the diet. … … [1] (ii) Name a food that is a good source of dietary fibre. … [1]

4 0654/23/O/N/15 © UCLES 2015 BLANK PAGE

5 0654/23/O/N/15 © UCLES 2015 [Turn over 2 Fig. 2.1 shows apparatus a student uses to investigate the reaction between dilute hydrochloric acid and sodium hydroxide solution. beaker pH sensor sodium hydroxide solution tap allows acid to be added slowly pH meter dilute hydrochloric acid 13 pH Fig. 2.1 (a) (i) Suggest one advantage of using an electronic pH meter to measure pH rather than using a coloured indicator such as litmus solution. … … [1] (ii) Name the type of chemical reaction which occurs between dilute acids and alkalis (bases). … [1] (iii) Complete the general word equation for the reaction between acids and bases. acid base + + [2]

6 0654/23/O/N/15 © UCLES 2015 (b) The student places 20.0 cm3 of sodium hydroxide solution into the beaker. He then adds hydrochloric acid carefully, in stages, and records the pH of the mixture after each addition. Fig. 2.2 shows a graph of the results. 0 1 2 3 4 5 6 0 10 20 30 40 volume of acid added / cm3 50 60 70 80 pH of reaction mixture 7 8 9 10 11 12 13 14 Fig. 2.2 (i) Describe how the pH of the mixture changes • as the first 35 cm3 of acid are added, … … • as the next 10 cm3 of acid are added. … … [2]

7 0654/23/O/N/15 © UCLES 2015 [Turn over (ii) Use the graph to find the volume of acid that reacted with the alkali to produce an exactly neutral solution. Show your working on the graph. volume of acid = … cm3 [2] (iii) Explain how the student can use his results to produce an exactly neutral mixture using the same acid and alkali as he used in his first experiment. … … … [2] (iv) Predict what would be observed if the student heated the neutral mixture he makes in (b) (iii) until the water in the mixture has evaporated. … … [1]

8 0654/23/O/N/15 © UCLES 2015 3 (a) A boy, sitting on a beach, is exposed to many forms of electromagnetic radiation. (i) Fig. 3.1 shows an incomplete electromagnetic spectrum. On Fig. 3.1 write the names infra-red, radio waves, ultraviolet and X-rays in their correct positions. gamma radiation visible light microwaves Fig. 3.1 [2] (ii) The boy is using his mobile phone (cell phone). Name the part of the electromagnetic spectrum used for mobile phone communications. … [1] (b) Someone has left some broken glass on the beach. The curved glass acts like a lens focussing the Sun’s rays onto a piece of paper and setting it alight. Fig. 3.2 shows a lens focussing the rays of light. Fig. 3.2 is drawn to actual size. paper centre of lens Fig. 3.2 (i) On Fig. 3.2 use a label line and the letter P to label the principal focus of the lens. [1] (ii) Measure, in millimetres, the focal length of the lens in Fig. 3.2. focal length = … mm [1]

9 0654/23/O/N/15 © UCLES 2015 [Turn over (c) A scuba diver is swimming in the sea near the beach. Fig. 3.3 shows a scuba diver. Fig. 3.3 The scuba diver can breathe underwater because she carries a cylinder of air on her back. Air is a mixture of gases. The molecules of gas in the cylinder move randomly. Describe how the gas molecules exert a pressure on the wall of the cylinder. … … … … [2] (d) Fig. 3.4 shows a penguin walking on a beach. Fig. 3.4 The boy wants to calculate the pressure exerted by the penguin through its feet onto the beach. State the two quantities which the boy needs to know to calculate the pressure. … and … [2]

10 0654/23/O/N/15 © UCLES 2015 (e) Fig. 3.5 shows three different ways in which particles may be arranged in substances. A B C Fig. 3.5 Water in the sea is a liquid. State which diagram from Fig. 3.5 best represents the way particles are arranged in liquid water. Explain your answer. diagram … explanation … … [1]

11 0654/23/O/N/15 © UCLES 2015 [Turn over 4 Magnesium is a metal found in Group II of the Periodic Table. (a) When burning magnesium is placed into a gas jar filled with carbon dioxide, it continues to burn as shown in Fig. 4.1. clouds of grey smoke gas jar carbon dioxide magnesium burning Fig. 4.1 The clouds of grey smoke formed in this reaction are a mixture of magnesium oxide and carbon. (i) Construct the word equation for the reaction between magnesium and carbon dioxide. + + [1] (ii) Explain why the reaction in (a) (i) can be described as reduction and oxidation (redox). … … … [2]

12 0654/23/O/N/15 © UCLES 2015 (b) Magnesium is produced by the electrolysis of magnesium chloride. Fig. 4.2 shows a simplified diagram of the process. ï d.c. power supply molten magnesium chloride + Fig. 4.2 (i) On Fig. 4.2 label the anode. [1] (ii) Electrolysis of magnesium chloride separates the elements that are bonded together. Magnesium is formed at the cathode. State the name and chemical formula of the substance produced at the anode. name … formula … [2]

13 0654/23/O/N/15 © UCLES 2015 [Turn over (c) Lead is less reactive than magnesium. Lead can be separated from lead oxide by heating it with substance Z. Fig. 4.3 shows a drop of limewater suspended on a glass rod held above a heated mixture of lead oxide and substance Z. glass rod strong heat drop of limewater mixture of lead oxide and substance Z Fig. 4.3 During the reaction, a gas is given off that turns the drop of limewater cloudy. (i) Name substance Z and the gas that is given off. substance Z … gas …[2] (ii) Suggest one way of showing that the reaction has produced some metallic lead. … … [1]

14 0654/23/O/N/15 © UCLES 2015 5 Fig. 5.1 shows a strawberry plant. stem growing along the ground strawberry X Y new plant developing Fig. 5.1 (a) A stem of the strawberry plant is growing along the ground, with a new plant developing at the end of this stem. (i) Name the type of reproduction shown by this process. … [1] (ii) Explain why the new plant will produce exactly the same type of strawberries as the parent plant. … … [1] (b) The strawberry plant has leaves and flowers. State the main function of (i) the leaves, … … [1] (ii) the flowers. … … [1]

15 0654/23/O/N/15 © UCLES 2015 [Turn over (c) Using Fig. 5.1, name (i) the part of the flower labelled X, … [1] (ii) the leaf-like structure above the strawberry, labelled Y. … [1] (d) Fig. 5.2 shows an insect called a strawberry blossom weevil. Fig. 5.2 The strawberry blossom weevil destroys some of the strawberry flowers. Explain why these blossom weevils will reduce the amount of fruit produced by a strawberry plant. … … [1]

16 0654/23/O/N/15 © UCLES 2015 6 (a) A motorcyclist begins a journey on a motorcycle. The motorcycle starts from rest and stops at a road junction after 80 seconds. The motorcycle then moves off again and completes the journey. Fig. 6.1 shows a speed / time graph for the journey. 20 0 10 20 30 5 25 15 40 0 60 80 time / s speed m / s 100 120 140 160 A D E H B C F G Fig. 6.1 (i) The motorcyclist travels at 9 m / s four times during the journey. On Fig. 6.1, indicate with a cross (X), the four times when the motorcyclist has a speed of 9 m / s. [1] (ii) State how long it takes the motorcyclist to reach 9 m / s for the first time. … s [1] (iii) State for how long the motorcyclist travels at a constant speed of 18 m / s. … s [1] (iv) Using the letters, A to H on Fig. 6.1, state a section of the graph showing the motorcycle slowing down. Explain your answer. part of journey … explanation … … [2]

17 0654/23/O/N/15 © UCLES 2015 [Turn over (b) One of the lamps on the motorcycle is a simple filament lamp. A simple filament lamp is shown in Fig. 6.2. glass bulb nitrogen gas metal filament metal support metal base glass support Fig. 6.2 The hot lamp loses thermal energy by conduction, convection and radiation. (i) Thermal energy is transferred through the metal base by conduction. Describe the process of conduction. … … … [2] (ii) Describe how thermal energy is transferred between the hot metal filament and the glass bulb by convection. … … … [2] (iii) The lamp loses energy by emitting visible light and infra-red radiations. These are both part of the electromagnetic spectrum but they have different wavelengths and frequencies. State the meaning of the terms wavelength and frequency. wavelength … … … frequency … … [3]

18 0654/23/O/N/15 © UCLES 2015 (c) (i) The lamp has a resistance of 4 Ω. The motorcycle battery has a potential difference of 12 V. Calculate the current in the lamp. State the formula that you use and show your working. formula working current = … A [2] (ii) Two of these lamps are connected together in a series circuit. Each lamp has a resistance of 4 Ω. Calculate the combined resistance of the two lamps in series . … Ω [1]

19 0654/23/O/N/15 © UCLES 2015 [Turn over 7 Part of a plant shoot was cut, and then placed in a beaker of coloured water, as shown in Fig. 7.1. leaf coloured water stem Fig. 7.1 After two hours, the shoot was removed. Fig. 7.2 shows what the shoot looked like. leaf areas stained by the coloured water stem Fig. 7.2 (a) Name the main tissue that has been stained by the coloured water. … [1]

20 0654/23/O/N/15 © UCLES 2015 (b) The movement of the coloured water is caused by transpiration. Describe the process of transpiration. You should use these terms in your explanation. evaporation mesophyll stomata vapour … … … … … … [4] (c) Suggest how the result shown in Fig. 7.2 on page 19, would have been different if the cut shoot had been left for the two hours in more humid conditions. … … [1]

21 0654/23/O/N/15 © UCLES 2015 [Turn over 8 Gasoline (petrol) is a mixture of hydrocarbons used as car fuel. (a) Complete the sentence using words chosen from the list. You may use each word once, more than once, or not at all. biogas catalytic coal cracking distillation fractional peat petroleum Gasoline is separated from the raw material known as … using the process of … … [2] (b) Waste gases produced by the burning of gasoline in car engines are released into the air. gasoline and air waste gases (i) Name two gaseous compounds that are produced by the complete combustion of the hydrocarbons in gasoline. 1 … 2 … [2] (ii) Explain why the exhaust gases from cars should never be allowed to build up in a garage or other confined space where there are people. … … … [2]

22 0654/23/O/N/15 © UCLES 2015 (c) (i) Describe how a solution of bromine is used to test whether a hydrocarbon is saturated or unsaturated. … … … [2] (ii) Complete the diagram below to show the molecular structure of one molecule of ethene. C C [2]

23 0654/23/O/N/15 © UCLES 2015 [Turn over 9 (a) Fig. 9.1 shows two forces acting on a submarine as it travels at constant speed. driving force water resistance Fig. 9.1 Explain why you know that the driving force and water resistance are equal and opposite. … … [1] (b) Some submarines use periscopes to view ships on the surface of the sea when the submarine is submerged. A simple periscope is shown in Fig. 9.2. prism object periscope observer looking at object Fig. 9.2 By drawing a ray of light from the object to the observer’s eye on Fig. 9.2, show what happens to light from an object as it passes through the periscope. [3] (c) A nuclear-powered submarine contains a small nuclear reactor. Radiation is released from the reactor during nuclear fission in the reactor. The reactor has to be shielded to protect the crew from this radiation. (i) Suggest a material which could be used to shield a nuclear reactor to stop β-radiation escaping. … [1] (ii) Suggest an instrument that could be used to check the radiation level outside the shielding of the reactor. … [1]

24 0654/23/O/N/15 © UCLES 2015 10 Fig. 10.1 shows an okapi. Okapis are rare animals. Their habitat is in the forests of central Africa. Fig. 10.1 Okapis are threatened with extinction. The two main causes of this are hunting and the cutting down of trees by humans. (a) (i) State the term for the cutting down of large numbers of trees by humans. … [1] (ii) Suggest two reasons why humans cut down large numbers of trees in the forests of central Africa. 1 … 2 … [2] (b) Suggest two ways in which the extinction of the okapi could be prevented. 1 … 2 … [2] (c) Fig. 10.2 shows a food chain that includes the okapi. tree leaves okapi leopard Fig. 10.2 If the okapi becomes extinct, explain how this would affect (i) the trees in the forest, … … [1] (ii) the leopards. … … [1]

25 0654/23/O/N/15 © UCLES 2015 [Turn over 11 (a) Table 11.1 shows some data about the elements in the second period of the Periodic Table. The numbers in the second row of Table 11.1 refer to a particular property, X, of the atoms of the elements. Table 11.1 symbol Li Be B C N O F Ne melting point / °C 181 1283 2027 3727 –210 –219 –220 –248 atomic property X 3 4 5 6 7 8 9 10 (i) State the name of the element shown in Table 11.1 that has the lowest melting point. … [1] (ii) Suggest the identity of atomic property X. … [1] (iii) An atom of fluorine, F, has a nucleon (mass) number of 19. State the composition of the nucleus of this fluorine atom. … … [2] (b) Sodium in Group I of the Periodic Table reacts with chlorine in Group VII to form crystals of an ionic compound. (i) Name the ionic compound formed when sodium reacts with chlorine. … [1] (ii) Describe how the structure of a sodium atom is changed when it is converted into a sodium ion. … … [1] (iii) Explain, in terms of protons and electrons, why a chlorine atom is electrically neutral but a chloride ion has a negative electrical charge. … … … … [2]

26 0654/23/O/N/15 © UCLES 2015 (c) Fig. 11.1 shows solution C and three reagents. solution C barium chloride silver nitrate sulfuric acid Fig. 11.1 A student wants to find out whether solution C contains chloride ions. State which one of the reagents she should add to solution C. Describe the result if chloride ions are present. reagent … result … [2]

27 0654/23/O/N/15 © UCLES 2015 [Turn over 12 (a) An astronaut is planning to travel to Mars in a spaceship powered by a rocket. The weight of the spaceship including fuel and cargo at take off is 30 000 000 N. When the spaceship blasts off from Earth, it has a thrust force of 35 000 000 N. (i) Calculate the resultant upward force. … N [1] (ii) Explain why the thrust force must be greater than the weight of the spaceship. … … [1] (iii) During a spaceship voyage, there are many energy transformations. Use words from the list to complete the sentences. You may use each word once, more than once or not at all. chemical gravitational kinetic light strain thermal During the launch, the rocket burns fuel containing … energy. This energy is transformed to … energy as the fuel is burned. As the spaceship moves faster it gains … energy. [2]

28 0654/23/O/N/15 © UCLES 2015 (b) The astronaut remains in communication with Earth on his journey to Mars, using radio waves. (i) State one reason why it is impossible to use sound waves for communication between the astronaut and Earth. … … [1] (ii) When Mars is 225 000 000 km from Earth a radio signal takes 750 s to travel between Mars and Earth. Calculate the speed of radio waves. State the formula that you use and show your working. formula working speed = … km / s [2] (c) Astronauts have greater exposure to ionising radiation than people who remain on Earth. The ionising radiation is cosmic radiation from outer space. This is one source of background radiation on Earth. (i) State what is meant by the term background radiation. … … [1] (ii) State one other source of background radiation on Earth. … [1]

29 0654/23/O/N/15 © UCLES 2015 [Turn over 13 (a) Fig. 13.1 shows how the volume of air in a person’s lungs changed over a two minute period. During this time, the person carried out a brief period of exercise. 4 3 2 volume of air in lungs / litres 1 0 0 1 period of exercise 2 time / minutes Fig. 13.1 (i) Using the information in Fig. 13.1, state two ways in which this person’s breathing changed when they carried out the exercise. 1 … 2 … [2] (ii) Suggest two ways in which the air this person breathes out will be different in composition from the air they breathe in. 1 … 2 … [2]

30 0654/23/O/N/15 © UCLES 2015 (b) During the period of exercise, the person releases adrenaline. (i) Suggest two effects that the adrenaline would have on the person exercising. 1 … 2 … [2] (ii) Adrenaline is a hormone. Define the term hormone. … … … … [3]

31 0654/23/O/N/15 © UCLES 2015 BLANK PAGE

32 0654/23/O/N/15 © UCLES 2015 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. 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.).

® 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 0654 CO-ORDINATED SCIENCES 0654/23 Paper 2 (Core 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 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 0654 23 © Cambridge International Examinations 2015 1 (a) (i) fat ; protein ; calcium ; [max 2] (ii) iron ; [1] (iii) has more fat ; [1] (b) (i) (1.50) 15 ; 6 ; [2] (ii) no, because large amount is needed to meet vitamin C requirement ; [1] (iii) bleeding gums ; poor skin / bruising ; scurvy ; [max 2] (c) (i) prevents constipation / promotes peristalsis ; [1] (ii) (named) cereal grain / fruit / vegetable ; [1] [Total: 11] 2 (a) (i) idea of greater precision / accuracy ; [1] (ii) neutralisation ; [1] (iii) salt ; water ; [2] (b) (i) (first 35 cm3) decreased slowly / decreased from pH 13 to 12 ; (next 10 cm3) decreased rapidly / more quickly / decreased from pH12 to 2 ; [2] (ii) 40 (cm3) ; evidence of finding the volume at pH = 7 ; [2] (iii) take same amount / 20.0 cm3 of alkali ; add 40 cm3 of the acid (allow ecf from (ii)) ; [2] (iv) white solid / solid sodium chloride ; [1] [Total: 11]

Page 3 Mark Scheme Syllabus Paper Cambridge IGCSE – October/November 2015 0654 23 © Cambridge International Examinations 2015 3 (a) (i) (gamma) X-rays ultraviolet (visible) infra-red (microwaves) radio waves (all four correct 2 marks, any two correct 1 mark) ;; [2] (ii) microwaves ; [1] (b) (i) label line at base of fire / label line where both rays meet ; [1] (ii) 55 (mm) ± 1 mm ; [1] (c) particles constantly in motion ; collide with walls of container ; force of collisions exerts a pressure ; [max 2] (d) weight (of penguin) ; (surface) area of foot / feet ; [2] (e) diagram B (no mark) particles are touching and randomly arranged ; (if A or C – 0 marks even with correct explanation) [1] [Total: 10] 4 (a) (i) magnesium + carbon dioxide → magnesium oxide + carbon ; [1] (ii) oxidation is gain of oxygen and reduction is removal of oxygen ; magnesium gains oxygen and is oxidised ; carbon dioxide loses oxygen and is reduced ; [max 2] (b) (i) anode clearly labelled ; [1] (ii) chlorine ; Cl 2 ; [2] (c) (i) carbon ; carbon dioxide ; [2] (ii) test the electrical conductivity of the product / lead will conduct electricity ; [1] [Total: 9]

Page 4 Mark Scheme Syllabus Paper Cambridge IGCSE – October/November 2015 0654 23 © Cambridge International Examinations 2015 5 (a) (i) asexual ; [1] (ii) no gametes / fertilisation involved ; genetically identical ; [max 1] (b) (i) photosynthesis ; [1] (ii) sexual reproduction ; [1] (c) (i) anther / stamen ; [1] (ii) sepal ; [1] (d) because the fruits develop from the flowers ; [1] [Total: 7] 6 (a) (i) crosses (X) marked on graph at 13–14 s, 71 s, 105 s and 150 s ; [1] (ii) 13–14 (s) ; [1] (iii) 20 (s) ; [1] (iv) C–D or G–H ; graph goes down ; [2] (b) (i) thermal energy produces increased particle vibration ; particle vibration is passed on from particle to particle ; metals are good thermal conductors ; [max 2] (ii) gas around filament heats up / gas expands ; gas rises / gas less dense ; [2] (iii) wavelength: distance between two waves ; but distance between two peaks / two troughs / two identical points on consecutive waves ; frequency: number of waves produced per second / number of waves passing a fixed point per second ; [3] (c) (i) (current) = resistance voltage ; = 4 12 = 3 (A) ; [2] (ii) 8 (Ω) ; [1] [Total: 15]

Page 5 Mark Scheme Syllabus Paper Cambridge IGCSE – October/November 2015 0654 23 © Cambridge International Examinations 2015 7 (a) xylem ; [1] (b) evaporation of water ; from surfaces of mesophyll cells ; followed by loss of water vapour ; by diffusion ; out through stomata ; [max 4] (c) (i) (coloured) water does not move as far ; [1] [Total: 6] 8 (a) petroleum ; fractional distillation ; [2] (b) (i) carbon dioxide ; water ; [2] (ii) reference to carbon monoxide / incomplete combustion ; which are toxic / which could poison people ; [2] (c) (i) hydrocarbon will decolourise bromine ; if it is unsaturated ; [2] (ii) ; [2] carbon – carbon double bond ; 4 × H and all else correct ; [Total: 10] 9 (a) no resultant force because constant speed ; [1] (b) three straight lines ; horizontal lines from boat and into eye ; internal reflection shown at both prisms ; [3] (c) (i) lead / concrete / aluminium ; [1] (ii) geiger counter / GM tube, etc. ; [1] [Total: 6]

Page 6 Mark Scheme Syllabus Paper Cambridge IGCSE – October/November 2015 0654 23 © Cambridge International Examinations 2015 10 (a) (i) deforestation ; [1] (ii) logging ; building of roads / towns / factories ; farming ; fuel ; [max 2] (b) control of hunting / nature reserve / conservation area ; (captive) breeding programmes ; alternatives to timber / control of deforestation / replanting ; AVP ; [max 2] (c) (i) grow / photosynthesise more (because not eaten by okapis) ; [1] (ii) have less food / must find alternative food sources ; (accept: more competition for food / migration) [1] [Total: 7] 11 (a) (i) neon ; [1] (ii) proton / atomic number / number of electrons ; [1] (iii) 9 protons ; 10 neutrons ; [2] (b) (i) sodium chloride ; [1] (ii) reference to loss of electron(s) / loss of outer shell ; [1] (iii) balance of charge / protons and electrons in the atom ; excess of electrons in the ion / gains electrons ; [2] (c) silver nitrate ; white precipitate ; [2] [Total: 10] 12 (a) (i) 5 000 000 (N) ; [1] (ii) need positive resultant, for upward motion / acceleration ; [1] (iii) chemical, thermal (heat), kinetic ;; (all three for 2 marks, any two for 1 mark) [2]

Page 7 Mark Scheme Syllabus Paper Cambridge IGCSE – October/November 2015 0654 23 © Cambridge International Examinations 2015 (b) (i) sound waves cannot travel through space / vacuum or sound waves need a medium ; [1] (ii) speed = time distance ; = 750 000 000 225 = 300 000 (km / s) ; [2] (c) (i) ionising radiation that humans are exposed to / radiation that is always there ; [1] (ii) rocks ; [1] [Total: 9] 13 (a) (i) increased rate of breathing ; increased depth of breathing / volume of breaths ; [2] (ii) less oxygen / O2 ; (reject: no oxygen) more carbon dioxide / CO2 ; more water vapour ; warmer ; [max 2] (b) (i) increased heart / pulse rate ; increased blood glucose ; AVP ; [max 2] (ii) chemical / substance produced by a gland ; carried in the blood ; alters the activity of target organ(s) ; destroyed by the liver ; [max 3] [Total: 9]