Cambridge IGCSE Sciences - Co-ordinated (Double) 0654 — 2011 Oct/Nov Paper 3 · Variant 3

This document consists of 27 printed pages and 1 blank page. IB11 11_0654_33/4RP © UCLES 2011 [Turn over *3777145801* For Examiner's Use 1 2 3 4 5 6 7 8 9 Total UNIVERSITY OF CAMBRIDGE INTERNATIONAL EXAMINATIONS International General Certificate of Secondary Education CO-ORDINATED SCIENCES 0654/33 Paper 3 (Extended) October/November 2011 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 a soft pencil for any diagrams, graphs, tables or rough working. Do not use staples, paper clips, highlighters, glue or correction fluid. DO NOT WRITE IN ANY BARCODES. Answer all questions. 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. www.XtremePapers.com

2 © UCLES 2011 0654/33/O/N/11 For Examiner's Use 1 (a) Fig. 1.1 shows a flowering plant, and two cells from the plant. cell A cell B Fig. 1.1 (i) On Fig. 1.1, draw a line from each cell to a part of the plant in which it could be found. [2] (ii) State one difference between the contents of cell A and cell B, and explain the reasons for this difference. difference explanation [3] (b) A grower has a rare variety of orchid with unusual flowers. She decides to produce new plants from this orchid using tissue culture. Explain why it is better for the grower to use tissue culture to produce new plants, rather than sowing seeds she has collected from the orchid plant. [3]

3 © UCLES 2011 0654/33/O/N/11 [Turn over For Examiner's Use (c) Genetic engineering has been used to produce a new variety of maize (corn) plants. This was done by introducing a gene into the maize cells that causes the plant to produce a toxin. The toxin only kills insects that eat parts of the plant. (i) Suggest one possible advantage to a farmer of growing this type of maize. [1] (ii) Suggest one possible problem that could be caused by growing this type of maize. [1]

4 © UCLES 2011 0654/33/O/N/11 For Examiner's Use 2 Melamine resin and PTFE are important plastics which have many uses in the home and industry. Wool consists of fibres which are made of protein molecules. (a) All of the above substances are made of polymer molecules. Explain the general meaning of the term polymer. [2] (b) Fig. 2.1 shows the displayed formula of the monomer that reacts to produce PTFE. F C F F C F Fig. 2.1 (i) Fig. 2.2 shows the outer shell electrons in a carbon atom and a fluorine atom. F C Fig. 2.2 Complete the bonding diagram below to show how the outer electrons are arranged in the molecule whose displayed formula is shown in Fig. 2.1. C F F F F C [2]

5 © UCLES 2011 0654/33/O/N/11 [Turn over For Examiner's Use (ii) Explain why the molecule shown in Fig. 2.1 is not an example of a hydrocarbon. [1] (iii) Draw the displayed formula of a small section of a PTFE molecule. The section that you draw must show eight fluorine atoms. [3] (c) Melamine resin and PTFE behave differently when they are heated. PTFE becomes softer and may melt, but melamine resin does not melt even when it is heated strongly. Explain this difference in terms of forces between molecules. You may draw some simple diagrams if it helps you to answer this question. [3]

6 © UCLES 2011 0654/33/O/N/11 For Examiner's Use (d) Fig. 2.3 shows a magnified section of a wool fibre. The fibre has been washed using hot, temporarily hard water. The fibre is covered with tiny crystals of limescale. fibre tiny crystals of limescale Fig. 2.3 (i) Complete the symbolic equation which represents the chemical reaction which causes limescale to form. Ca(HCO3)2 [1] (ii) Ion exchange resins are polymers with positive ions attached to the polymer chains. Describe and explain briefly how the process of ion exchange can be used to soften hard water. [3]

7 © UCLES 2011 0654/33/O/N/11 [Turn over For Examiner's Use 3 A car is being driven on a journey. (a) (i) State the two quantities needed to find the momentum of the car. and [1] (ii) The car turns a corner without changing speed. Explain why the momentum of the car has changed. [2]

8 © UCLES 2011 0654/33/O/N/11 For Examiner's Use (b) Fig 3.1 shows a speed–time graph for part of the car’s journey, during which the brakes are used. speed m / s 0 1 2 3 4 5 6 30 20 10 0 time / s Fig. 3.1 (i) Mark with an X the point on the graph at which the brakes are applied. [1] (ii) Calculate the deceleration of the car. Show your working. [2] (iii) Calculate the distance travelled by the car during deceleration. Show your working. [2]

9 © UCLES 2011 0654/33/O/N/11 [Turn over For Examiner's Use (c) Fig 3.2 shows the circuit diagram of the parallel circuit used to supply electrical energy to two identical headlamps in the car. Fig 3.2 The current through the filament of one headlamp is 2.4 A. The potential difference across each of the headlamps is 12 V. (i) Calculate the resistance of the headlamp filament whilst in use. State the formula that you use and show your working. formula used working [2] (ii) Calculate the total resistance of the two headlamps in parallel. State the formula that you use and show your working. formula used working [3]

10 © UCLES 2011 0654/33/O/N/11 For Examiner's Use 4 (a) (i) Caffeine is a compound contained in coffee. Many people who consume caffeine during the day find that they have difficulty in getting to sleep at night. Explain why it is correct to refer to caffeine as a drug. [1] (ii) Some drugs are analgesics. Why might a person need to take an analgesic? [1] (b) Some coffee drinks are sold in self-heating cans. Fig. 4.1 shows a cross-sectional diagram of one design of self-heating can. calcium oxide thin metal sheet water coffee drink pin Fig. 4.1

11 © UCLES 2011 0654/33/O/N/11 [Turn over For Examiner's Use Fig. 4.2 shows the can after it has been turned upside down and the pin pushed through the thin metal sheet. This allows the water to fall into the calcium oxide. pin pushed down heat energy transferred to coffee drink Fig. 4.2 The reaction between calcium oxide and water is highly exothermic and produces the ionic compound calcium hydroxide, Ca(OH)2. (i) In an internet video to explain how the can works, it is stated that the water mixes with ‘limestone’. State why this information is incorrect. [1] (ii) Use the position of calcium in the Periodic Table to explain why the electrical charge of a calcium ion is +2. [3]

12 © UCLES 2011 0654/33/O/N/11 For Examiner's Use (iii) Deduce the electrical charge of the hydroxide ion. Show how you obtained your answer. [2] (c) The balanced equation for the reaction between calcium oxide and water is shown below. CaO + H2O Ca(OH)2 This shows that one mole of calcium oxide reacts with one mole of water. (i) A self-heating can is designed to contain 224 g of calcium oxide. Calculate the number of moles of calcium oxide in 224 g of the compound. Show your working. [2]

13 © UCLES 2011 0654/33/O/N/11 [Turn over For Examiner's Use (ii) Calculate the mass of water which is needed to react with 224 g of calcium oxide. Show your working. [2]

14 © UCLES 2011 0654/33/O/N/11 For Examiner's Use 5 Cichlid fish live in lakes in east Africa. Fig. 5.1 shows a cichlid fish. Fig. 5.1 (a) State two features, visible on Fig. 5.1, which are characteristic of fish. 1 2 [1] (b) Most fish have external fertilisation. (i) Explain what is meant by external fertilisation. [2] (ii) Explain why animals that live entirely on land cannot use external fertilisation. [1]

15 © UCLES 2011 0654/33/O/N/11 [Turn over For Examiner's Use (c) Wild cichlid fish are unusual because they care for their eggs and young. The mother keeps the fertilised eggs in her mouth until they hatch. After the young fish have hatched, she takes them back into her mouth when danger threatens. This behaviour is caused by the fish's genes, and is inherited. Suggest how natural selection in an east African lake could have led to the evolution of this behaviour. [3]

16 © UCLES 2011 0654/33/O/N/11 For Examiner's Use (d) Cichlid fish that have been bred in captivity can be bought as pets. Breeders take the young away from the captive mothers after they have hatched because these mothers often eat their young. Research was carried out into the behaviour of mothers in two groups of cichlid fish. • Group A had been bred from a population of fish that had been kept in captivity for more than 30 years. • Group B had recently been caught in the wild. The researchers used 4 female fish from each group. They allowed each fish to breed as normal with male fish from the same group. They left the young fish with their mothers. All the fish were kept in the same conditions. Table 5.1 shows the results. Table 5.1 group A group B number of mothers 4 4 number of mothers that ate their young by 1 day after hatching 3 0 (i) Explain how these results suggest that the difference in behaviour between the group A and group B fish was caused by their genes, and not by their environment. [2]

17 © UCLES 2011 0654/33/O/N/11 [Turn over For Examiner's Use (ii) The researchers also measured the testosterone levels in the mother fish in both groups. Fig. 5.2 shows the results. while eggs were developing 1 day after hatching 40 30 20 10 0 average testosterone concentration in mother’s body / arbitrary units bred in captivity recently caught in the wild Fig. 5.2 Describe the differences in testosterone concentrations in the two groups of mother fish. [2] (iii) These results do not prove that high testosterone levels in population A caused the mothers to eat their young. Outline two reasons why this statement is correct. 1 2 [2]

18 © UCLES 2011 0654/33/O/N/11 For Examiner's Use 6 An orchestra is playing in a theatre. (a) A musician is playing the cymbals. cymbals (i) Describe how the sound travels through the air from the cymbals to the ear of a man in the audience. [2] (ii) The man in the audience thought that the sound from the cymbals was loud because of its high frequency. He was wrong. Explain why the man was wrong. [2] (b) The theatre has an internal volume of 50 000 m3. The air inside it has a density of 1.3 kg / m3. (i) Show that the mass of the air in the theatre is 65 000 kg. State the formula that you use and show your working. formula used working [2]

19 © UCLES 2011 0654/33/O/N/11 [Turn over For Examiner's Use (ii) The air is heated by 10 °C. The specific heat capacity of air is 1000 J / kg °C. Calculate the energy needed to heat up the air in the theatre. State the formula that you use and show your working. formula used working [3] (c) Coloured light is shone onto the stage. Red light has a wave speed of 3 x 108 m / s (300 000 000 m / s) and a wavelength of 7.5 x 10–7 m (0.000 000 75 m). (i) Explain what is meant by the term wavelength. [1] (ii) Calculate the frequency of red light. State the formula that you use and show your working. formula used working [3]

20 © UCLES 2011 0654/33/O/N/11 For Examiner's Use 7 (a) Table 7.1 shows the electron arrangements of atoms of five elements, P to T. Table 7.1 atom 1st shell 2nd shell 3rd shell 4th shell P 2 1 Q 2 8 1 R 2 8 2 S 2 8 8 1 T 2 8 8 2 (i) Explain how the electron arrangements show that all of the elements, P to T, are metals. [1] (ii) An atom of element P has a nucleon (mass) number of 7. State the number of neutrons in this atom. [1]

21 © UCLES 2011 0654/33/O/N/11 [Turn over For Examiner's Use (b) Fig. 7.1 shows an electrochemical cell which was made by a student in a school laboratory. volts + – magnesium iron electrolyte 2.0 V Fig. 7.1 (i) The student was asked to choose one of the liquids shown below as the electrolyte in her cell. dilute sulfuric acid hexane sodium chloride solution She correctly chose sodium chloride solution. Explain briefly why the other two liquids would not have been suitable. [2]

22 © UCLES 2011 0654/33/O/N/11 For Examiner's Use (ii) The student used her cell to investigate the relative reactivity of four metals, magnesium, iron and two unknown metals, X and Y. The student had learned that the more reactive metal always becomes the negative electrode. The results of experiments involving all four metals are shown in Table 7.2. Table 7.2 experiment negative electrode positive electrode cell voltage / volts 1 magnesium iron 2.0 2 magnesium X 2.7 3 magnesium Y 1.6 Use the results in Table 7.2 to place the four metals in order of reactivity. most reactive least reactive [2]

23 © UCLES 2011 0654/33/O/N/11 [Turn over BLANK PAGE Please turn over for Question 8.

24 © UCLES 2011 0654/33/O/N/11 For Examiner's Use 8 (a) Fig. 8.1 shows a section through a part of a person's lungs where gas exchange takes place. blood vessel X Y Fig. 8.1 (i) Name the structure labelled X. [1] (ii) Name the type of blood vessel that is shown in Fig. 8.1. [1] (iii) State what is shown by arrow Y, and explain why this process takes place. [3] (b) Describe how blood travels from the heart to the lungs. Your description should include the role of the heart in this process. [3]

25 © UCLES 2011 0654/33/O/N/11 [Turn over For Examiner's Use (c) Describe and explain how the actions of the intercostal muscles and diaphragm muscles cause inhalation (breathing in) to take place. [3]

26 © UCLES 2011 0654/33/O/N/11 For Examiner's Use 9 (a) The bar chart in Fig 9.1 shows the electrical power rating of two kettles. A B 3000 2000 1000 0 kettle power / watts Fig. 9.1 Kettle A takes 10 minutes to boil some water. Predict how long kettle B will take to boil the same mass of water. [1] (b) Kettle A has a label underneath it. Fig. 9.2 shows some of the information on this label. voltage 250 V power 1000 W Fig. 9.2 (i) Calculate the maximum current through the kettle. State the formula that you use and show your working. formula used working [2]

27 © UCLES 2011 0654/33/O/N/11 For Examiner's Use (ii) This current passes through the kettle for 2 minutes. Calculate the charge which passes through the kettle in this time. State the formula that you use and show your working. formula used working [2] (c) Use the idea of convection to explain why a kettle has the heating element at the bottom. [2]

28 Permission to reproduce items where third-party owned material protected by copyright is included has been sought and cleared where possible. Every reasonable effort has been made by the publisher (UCLES) to trace copyright holders, but if any items requiring clearance have unwittingly been included, the publisher will be pleased to make amends at the earliest possible opportunity. University of Cambridge International Examinations is part of the Cambridge Assessment Group. Cambridge Assessment is the brand name of University of Cambridge Local Examinations Syndicate (UCLES), which is itself a department of the University of Cambridge. © UCLES 2011 0654/33/O/N/11 Group 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 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 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 Ra Radium 88 The volume of one mole of any gas is 24 dm3 at room temperature and pressure (r.t.p.). a X b a = relative atomic mass X = atomic symbol b = proton (atomic) number Key *58-71 Lanthanoid series 90-103 Actinoid series DATA SHEET The Periodic Table of the Elements

UNIVERSITY OF CAMBRIDGE INTERNATIONAL EXAMINATIONS International General Certificate of Secondary Education MARK SCHEME for the October/November 2011 question paper for the guidance of teachers 0654 CO-ORDINATED SCIENCES 0654/33 Paper 3 (Extended Theory), maximum raw mark 100 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 must be read in conjunction with the question papers and the report on the examination. • Cambridge will not enter into discussions or correspondence in connection with these mark schemes. Cambridge is publishing the mark schemes for the October/November 2011 question papers for most IGCSE, GCE Advanced Level and Advanced Subsidiary Level syllabuses and some Ordinary Level syllabuses. www.XtremePapers.com

Page 2 Mark Scheme: Teachers’ version Syllabus Paper IGCSE – October/November 2011 0654 33 © University of Cambridge International Examinations 2011 1 (a) (i) line from cell A to leaf ; line from cell B to root ; [2] (ii) cell A has chloroplasts / chlorophyll ; for photosynthesis ; cell B does not because it, is underground / gets no light ; [3] (b) tissue culture is asexual reproduction / producing seeds is sexual reproduction ; tissue culture produces identical plants ; plants grown from seeds show variation ; ref. genetically identical (for tissue culture) or genetically different plants (for seeds) ; seeds may not germinate / mature plants produced more quickly using tissue culture ; [max 3] (c) (i) higher yields / no need to spray, pesticides / insecticides ; [1] (ii) may harm beneficial or harmless insects that eat parts of the plant (e.g. butterflies or bees that eat nectar or pollen) / may affect ecosystem because fewer insects for other animals to eat / people may not like the idea of eating this maize / may make it difficult for farmers in developing countries to compete with those in developed countries ; [1] [Total: 10] 2 (a) (i) (long) chain (molecule) ; made of repeating units / monomers ; [2] (b) (i) bonding pairs ; non-bonding pairs ; [2] (ii) no hydrogen / hydrocarbons contain carbon and hydrogen (only) ; [1] (iii) four C and 8 F ; all single bonds ; indication that chain continues ; [3]

Page 3 Mark Scheme: Teachers’ version Syllabus Paper IGCSE – October/November 2011 0654 33 © University of Cambridge International Examinations 2011 (c) PTFE only weak attractive forces between molecules ; molecules move past each other easily when heated ; melamine molecules have cross-links / strong bonds holding molecules together ; molecules locked in place / do not move past each other when heated ; [max 3] (d) (i) → CaCO3 + CO2 + H2O ; [1] (ii) (hard) water passed through resin / beads / support / column ; calcium / magnesium, ions stick to resin ; sodium ions detach from resin / replace Ca2+ / Mg2+ ; [3] [Total: 15] 3 (a) (i) mass and velocity ; [1] (ii) velocity / momentum are vector quantities ; direction has changed ; [2] (b) (i) X at 2 seconds ; [1] (ii) (deceleration =) change in speed / time (or gradient) OR 15 / 3 OR rise ÷ run ; = 5 m / s2 ; [2] (iii) area under graph ; 22.5 m ; [2] (c) (i) (resistance =) voltage / current ; = 12 / 2.4 = 5 Ω ; [2] (ii) 1 / R = 1 / R1 + 1 / R2 ; = 1 / 5 + 1 / 5 ; (R = 5 / 2 =) 2.5 Ω ; [3] [Total: 13] 4 (a) (i) changes the way the body works / owtte ; [1] (ii) pain relief ; [1] (b) (i) limestone is, calcium carbonate / not calcium oxide ; [1] (ii) calcium is in Group 2 / atoms have two outer electrons ; these / two / outer, electrons lost (when calcium ion forms) ; ion has two more positive charges (protons) than negative charges (electrons) ; [3] (iii) single negative ; working to show need for charge balance ; [2]

Page 4 Mark Scheme: Teachers’ version Syllabus Paper IGCSE – October/November 2011 0654 33 © University of Cambridge International Examinations 2011 (c) (i) (use of moles = mass ÷ molar mass) Mr calcium oxide = 56 ; 224 ÷ 56 = 4 ; [2] (ii) (look for direct proportion from equation with or without reference to moles, e.g.) 56 g of CaO react with 18 g water ; 224 g CaO will react with 18 × 224 ÷ 56 = 72 g ; OR 1 mole of CaO reacts with 1 mole of H2O / 4 moles CaO react with 4 moles H2O ; mass of 4 moles water = 18 × 4 = 72 g ; [max 2] [Total: 12] 5 (a) any two of: scales / fins / operculum ; [1] (b) (i) joining of male and female, gamete / sex cells / nuclei ; outside the female's body ; [2] (ii) sperm / male gamete / male sex cell, would not be able to swim ; OR gametes / sex cells / eggs / sperm / zygote, would dry out ; [max 1] (c) (accept reverse argument throughout for fish that do not have this behaviour) idea that this behaviour, increases chance of survival / gives an advantage ; young of fish who does this more likely to breed ; and (more likely to) pass on genes for this behaviour to their offspring ; [3] (d) (i) both sets of fish kept in the same conditions / environment is the same for both sets of fish (so not environment) ; populations A and B genetically different ; [2] (ii) more testosterone in population A (mothers) ; detail, for example: both before and after eggs hatched / figures quoted / difference quoted ; [2] (iii) numbers too small (to draw any firm conclusions) ; idea that results only show correlation, not cause ; [2] [Total: 13]

Page 5 Mark Scheme: Teachers’ version Syllabus Paper IGCSE – October/November 2011 0654 33 © University of Cambridge International Examinations 2011 6 (a) (i) air particles ; vibrate ; compressions and rarefactions ; series of compressions and rarefactions ; [2] (ii) frequency = pitch ; loudness = amplitude ; [2] (b) (i) (mass =) density × volume ; = 1.3 × 50 000 = 65 000 kg ; [2] (ii) (E =) mass × specific heat capacity × change in temperature ; = 65 000 × 1000 × 10 ; = 650 000 000 J / 6.5 × 105 kJ ; [3] (c) (i) distance between identical points on successive waves ; [1] (ii) v = f × λ ; f = 300 000 000/0.000 000 75 ; = 400 000 000 000 000 Hz / 4 × 1014 Hz / 400 THz ; [3] [Total: 13] 7 (a) (i) outer electrons show group number / all in Groups 1 or 2 / all in groups on left of Periodic Table ; [1] (ii) 4 ; [1] (b) (i) hexane, cannot be electrolyte / is covalent / contains no ions / cannot conduct ; (sulfuric) acid, reacts with / dissolves, the, electrodes / metal ; [2] (ii) magnesium ; Y iron X ; [2] (magnesium shown as most reactive then other three correct) [Total: 6] 8 (a) (i) alveolus / air sac ; [1] (ii) capillary ; [1] (iii) carbon dioxide movement ; diffusion ; more CO2 in blood vessel than in alveolus / there is a diffusion gradient ; because respiration (in body cells) produces CO2 ; [max 3]

Page 6 Mark Scheme: Teachers’ version Syllabus Paper IGCSE – October/November 2011 0654 33 © University of Cambridge International Examinations 2011 (b) from right ventricle ; heart / right ventricle / cardiac muscle, contracts ; (heart) produces pressure ; blood travels along pulmonary artery ; [max 3] (c) both sets of muscles contract ; increase volume of, thorax / chest (cavity) / lungs ; decrease pressure (in thorax / chest (cavity) / lungs) ; air moves in down pressure gradient ; [max 3] [Total: 11] 9 (a) 5 minutes ; [1] (b) (i) (current =) power / voltage ; (current =) 1000 / 250 = 4 A ; [2] (ii) charge = current × time ; = 4 × 120 = 480 C ; [2] (c) hot water rises / cold water sinks ; (because) hot water is less dense / cold water is more dense ; [2] [Total: 7]