Cambridge IGCSE Sciences - Co-ordinated (Double) 0654 — 2025 Feb/March Paper 6 · Variant 2

1 A student investigates the loss of thermal energy from a large animal and from a small animal using a boiling tube and a test-tube to represent the animals. The boiling tube is larger than the test-tube. (a) Procedure The student: • almost fills the boiling tube with hot water • places a thermometer in the hot water • waits 30 seconds and then records in Table 1.1 the temperature of the water for time = 0 • records in Table 1.1, the temperature of the water every minute for 5 minutes. Repeats the procedure using the test-tube instead of the boiling tube. Fig. 1.1 shows the thermometer readings for each tube at time = 4 minutes. Record in Table 1.1 these values to the nearest 0.5 °C. °C °C 60 50 50 40 40 30 boiling tube test-tube Fig. 1.1 Table 1.1 temperature of water in temperature of water in time / minutes boiling tube / °C test-tube / °C 0 80.0 77.5 1 66.0 54.0 2 57.5 46.5 3 52.0 42.0 4 5 46.0 36.5 [2] (b) (i) You are going to plot both sets of data in Table 1.1 on the same grid. On the grid: • plot temperature of water in the boiling tube (vertical axis) against time • draw the curve of best fit and label this curve L • plot temperature of water (vertical axis) against time for the test-tube • draw the curve of best fit and label this curve S. [5] (ii) Use your graph to estimate the temperature of the water in the boiling tube at 1.5 minutes. Show your working on the graph. temperature = .................................................... °C [2] (c) (i) Calculate the decrease in temperature for the water in each tube between the start and at 5 minutes. boiling tube .......................................................... °C test-tube .......................................................... °C [1] (ii) Use your results to suggest how the rate of loss of thermal energy from a large animal compares to the rate of loss of thermal energy from a small animal. ........................................................................................................................................... ..................................................................................................................................... [1] (d) (i) Explain why repeating the procedure increases confidence in the results. ........................................................................................................................................... ..................................................................................................................................... [1] (ii) Suggest why it is important to wait 30 seconds before taking the first thermometer reading. ........................................................................................................................................... ..................................................................................................................................... [1] (iii) Suggest why it is important to stir the water before taking each temperature reading. ........................................................................................................................................... ..................................................................................................................................... [1] [Total: 14]

Mark scheme: Question Answer Marks 1(a) 48.5 ; 2 38.0 ; 1(b)(i) axes right way round and labelled with quantity and unit ; 5 e.g.: y-axis temperature/T and °C and x axis time/t and minutes/min(s) sensible linear scale and plots cover at least half the grid ; plots correct for boiling tube  half small square ; plots correct for test tube  half small square ; curve of best fit for each test-tube and labelled ; 1 (b)(ii) correct reading from graph ; 2 graph marked with 2 lines one from each axis ; 1(c)(i) 34 and 41 ; 1 1(c)(ii) larger animals lose heat at a lower rate / more slowly / 1 smaller animals lose heat at a larger rate / more quickly ; 1(d)(i) exclude anomalies/ reduce random error ; 1 1(d)(ii) record the highest temperature ; 1 1(d)(iii) ensure temperature even throughout ; 1

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2 (a) A student has two leaves A and B, on a white tile. The leaves are from the same species of plant. The green chlorophyll is removed from each leaf. (i) The student puts a few drops of iodine solution to cover the upper surface of each leaf. • The iodine solution on leaf A changes colour. • The iodine solution on leaf B does not change colour. State the colours the student observes. leaf A ........................................................................ leaf B ........................................................................ [2] (ii) State a conclusion for the observations in (a)(i). leaf A ........................................................................ leaf B ........................................................................ [1] (iii) Leaf A is from a plant grown in the light for 2 days. Leaf B is from a plant grown in the dark for 2 days. Explain your conclusion in (a)(ii). ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ..................................................................................................................................... [1] (b) (i) Suggest why chlorophyll is removed from each leaf. ........................................................................................................................................... ..................................................................................................................................... [1] (ii) Describe how chlorophyll is removed from a leaf. ........................................................................................................................................... ..................................................................................................................................... [1] [Total: 6]

Mark scheme: 2(a)(i) A: blue-black ; 2 B: brown ; 2(a)(ii) starch present in A 1 and no starch present in B ; 2(a)(iii) light needed for starch production ORA ; 1 2(b)(i) colour would mask test result / to see colour of iodine solution more clearly ; 1 2(b)(ii) hot water then hot ethanol then water rinse ; 1

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3 A student identifies solid J and some of the ions present in solid K and in aqueous L and aqueous M. Solid K and aqueous L contain the same cation. (a) J is a shiny grey solid. J is kept in a sealed container because it reacts with water vapour in the air and gives off a gas. The student adds J to water. The student observes: • J moving up and down in the water • bubbling • J getting smaller • a colourless solution forming • a gas forming which pops with a lighted splint. (i) Identify the gas formed. ..................................................................................................................................... [1] (ii) J is an element. State the type of element. ..................................................................................................................................... [1] The solution formed in 3(a) is also used in 3(b)(i), 3(c), and 3(d). (b) (i) Procedure The student: • pours some of the solution formed in (a) into a boiling tube of carbon dioxide gas • puts a stopper in the boiling tube and shakes the tube. The student sees a white precipitate form in the solution. Identify the solution. ..................................................................................................................................... [1] (ii) The student separates the solid precipitate from the solution. Draw a labelled diagram of the assembled apparatus the student uses. Label the precipitate and the solution. [2] (c) Procedure The student: • pours some aqueous L and some of the solution formed in (a) into separate test-tubes • adds aqueous sodium hydroxide dropwise to each test-tube until it is in excess. In both solutions the student observes a white precipitate that does not dissolve in excess aqueous sodium hydroxide. Identify the cation present in aqueous L and identify solid J. cation in aqueous L .................................................................................................................. solid J ....................................................................................................................................... [1] (d) Procedure The student: • puts solid K into a boiling tube and connects a delivery tube to the boiling tube • heats K and bubbles the gas formed into some of the solution formed in (a). The student sees a white precipitate form in the solution. (i) Identify the anion present in solid K. ..................................................................................................................................... [1] (ii) Draw a labelled diagram of the assembled apparatus the student uses. [2] (e) Flame tests are often used to identify metal ions. State two reasons why a flame test is done using a blue Bunsen burner flame rather than a yellow one. reason 1 .................................................................................................................................... ................................................................................................................................................... reason 2 .................................................................................................................................... ................................................................................................................................................... [2] (f) The student tests aqueous M for the presence of chloride ions. They add dilute hydrochloric acid, HCl (aq), and aqueous silver nitrate to aqueous M. The student observes a white precipitate. A teacher tells the student that the test they have used does not confirm the identity of the chloride ion. Explain why the test the student uses does not prove that chloride ions are present in aqueous M. State an improvement to the test to confirm the presence of chloride ions. explanation ............................................................................................................................... ................................................................................................................................................... improvement ............................................................................................................................. ................................................................................................................................................... [2] [Total: 13]

Mark scheme: 3(a)(i) hydrogen / H2 ; 1 3(a)(ii) metal ; 1 3(b)(i) limewater / (aqueous) calcium hydroxide ; 1 3(b)(ii) filter funnel and filter paper with a ‘v’ and receiving vessel ; 2 3 correct labels – precipitate, solution and 1 other(filter paper/(filter funnel) ; 3(c) calcium ion / Ca2+ 1 and J is calcium / Ca ; 3(d)(i) carbonate ; 1 3(d)(ii) boiling tube, delivery tube and receiving vessel (expect test-tube) ; 2 heat(Bunsen burner) and stopper in boiling tube with no stopper in receiving vessel and delivery tube lengths correct and liquid (limewater) in receiving vessel (expect test-tube) ; 3(e) blue flame is hotter ; 2 doesn’t mask colour of metal ion in flame ; 3(f) hydrochloric acid contains chloride ions ; 2 use nitric acid ;

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4 When ammonium sulfate is heated with sodium hydroxide, it reacts to form ammonia gas. Ammonia gas is not collected over water because it is soluble in water. Plan an investigation to find the relationship between the mass of ammonium sulfate used and the volume of ammonia gas made. You are provided with: • aqueous sodium hydroxide • ammonium sulfate powder. You may use any common laboratory apparatus. Include in your plan: • the apparatus you will need and an explanation of any safety precautions • a brief description of the method • the measurements you will make and how you make them as valid as possible • the variables you will control • how you will process your results to draw a conclusion. You may include a labelled diagram if you wish. You may include a results table if you wish, you are not required to enter any readings in the table. .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .................................................................................................................................................... [7]

Mark scheme: 4 apparatus and safety 7 syringe and volume / amount gas measured in the method ; balance and mass / amount solid measured in the method ; method of heating and airtight apparatus ; goggles to protect eyes from sodium hydroxide / gloves to protect skin / hands from burning / hot apparatus ; method add ammonium sulfate to aqueous sodium hydroxide and collect gas given off (as the reaction finishes) for at least 2 masses / amounts of ammonium sulfate; measurements and validity volume of ammonia ; mass of ammonium sulfate ; do each mass / amount more than once to identify / exclude anomalies ; five different masses / amounts ; control volume of sodium hydroxide ; concentration of sodium hydroxide ; temperature ; processing for conclusion plot graph of volume against mass ; straight line – linear relationship / straight line through origin – proportional / increasing diagonal line as T increases then volume increases ; when mass increases does volume increase, decrease or stay the same ;

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5 A student investigates how the stability of a plastic bottle depends on the height of the water in the bottle. Fig. 5.1 shows the apparatus the student uses and where the student pushes the bottle. lid push bottle water h Fig. 5.1 (a) (i) Fig. 5.1 shows the height h of the water in the bottle. Record h in cm to the nearest 0.1 cm. h = ......................................................... cm Fig. 5.1 is drawn to a scale of one-fifth full size. Calculate the actual height H of the water in the bottle. Record this value of H in Table 5.1. Table 5.1 height of water in the bottle H angle θ / cm / ° 10 61 15 66 20 70 25 72 [2] (ii) Procedure The student: • gently pushes sideways at the top of the bottle until they find the point where it just starts to fall over without pushing any more • measures the angle θ. The angle θ is the angle between the bottle and the table. The student repeats the procedure for another 4 values of H. Table 5.1 shows the results the student obtains. Fig. 5.2 shows the bottle as it just starts to fall over. θ Fig. 5.2 Measure the angle θ in Fig. 5.2. Record this value in Table 5.1. [1] (b) Describe in detail, the relationship between the height H of water in the bottle and angle θ. ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ............................................................................................................................................. [2] (c) It is difficult to hold the bottle in the exact position when it starts to fall over and measure the angle θ at the same time. Suggest how to overcome this difficulty. Do not include using another person in your answer. ................................................................................................................................................... ............................................................................................................................................. [1] (d) Another student repeats the procedure using the same apparatus. The bottle falls over at an angle θ of 64 °. Estimate the height H of water in the bottle. Use the results in Table 5.1. height ................................................... cm [1] [Total: 7]

Mark scheme: 5(a)(i) h = 1.2 ; 2 H = 6 ; 5(a)(ii) 51 () in table ; 1 5(b) as H increases increases ; 2 the increases in get smaller as H increases; 5(c) video the experiment and play back in slow motion or pause / clamp in position once bottle starts to fall/ do the experiment 1 near a wall and mark position on the wall / place a solid object in front as it starts to fall ; 5(d) 13 ; 1

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6 A student determines the density of modelling clay using two different methods. The student is provided with a cuboid made of modelling clay. (a) Method 1 (i) The modelling clay is shown in Fig. 6.1. h l w Fig. 6.1 Record the dimensions l, w and h of the cuboid in cm to the nearest 0.1 cm. l = ......................................................... cm w = ......................................................... cm h = ......................................................... cm [2] (ii) Calculate the volume V1 of the modelling clay. Use the equation shown. V1 = l × w × h Give your answer to three significant figures. V1 = .................................................. cm3 [2] (iii) The student measures the mass of the modelling clay. The reading on the balance is shown in Fig. 6.2. balance 63.46 Fig. 6.2 Record the mass m of the modelling clay to the nearest 0.1 g. m = ...................................................... g [1] (iv) Calculate the density ρ1 of the modelling clay. Use the equation shown. m ρ1 = V1 ρ1 = .............................................. g / cm3 [1] (b) Describe one reason why your measurements of the dimensions in (a)(i) are not accurate. ................................................................................................................................................... ............................................................................................................................................. [1] (c) Method 2 (i) Another student finds the volume of the same piece of modelling clay by displacing water in a measuring cylinder. The student shapes the modelling clay so that it fits into the measuring cylinder. The student puts the modelling clay into the water so that it is completely below the surface of the water. Fig. 6.3 shows the readings on the measuring cylinder. cm3 cm3 55 95 50 90 45 85 40 80 35 75 volume of water V2 volume of water and modelling clay V3 Fig. 6.3 Record V2 and V3 to the nearest cm3. V2 = ........................................................ cm3 V3 = ........................................................ cm3 [1] (ii) Calculate the volume Vc of the modelling clay. Use the equation shown. Vc = V3 – V2 Vc = ........................................................ cm3 [1] (iii) Calculate the density ρ2 of the modelling clay. Use the value of m from (a)(iii). ρ2 = .................................................... g / cm3 [1]

Mark scheme: 6(a)(i) l = 5.5 and w = 3.3 and h = 2.6 ;; 2 3 correct = 2 marks, 1 correct = 1 mark 6(a)(ii) 47.19 ; 2 47.2 ; 6(a)(iii) 63.5 ; 1 6(a)(iv) 1.3(45…) ; 1 6(b) sides may not be uniform AW ; 1 6(c)(i) 41 and 87 ; 1 6(c)(ii) 46 ; 1 6(c)(iii) 1.4 / 1.38 ; 1 6(d)(i) mass of water would not be included in the mass of the modelling clay ; 1 6(d)(ii) calculation showing 10% of one of the values and its use with conclusion ; 1 6(d)(iii) density increases 1 and because of dividing by a smaller V/ density is inversely proportional to volume ;

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