Cambridge IGCSE Sciences - Co-ordinated (Double) 0654 — 2021 May/June Paper 5 · Variant 1

1 You are going to investigate the movement of coloured water in a celery stem. (a) Procedure • Take the piece of celery and cut it approximately in half as shown in Fig. 1.1. celery stem cut here white tile Fig. 1.1 • Place one half with the freshly cut end in the coloured water as shown in Fig. 1.2. Leave for at least five minutes. Continue with the question while you are waiting. coloured cut end water Fig. 1.2 (i) In the box provided, make an enlarged detailed pencil drawing of the cut end of the celery from the white tile. It may help you to use the hand lens. [3] (ii) Procedure • After five minutes, remove the piece of celery from the coloured water and blot it dry. • Cut a 2 mm slice from the end that was in the coloured water. • Place this slice on the white tile with the newly cut surface facing upwards. • Examine this upper surface using the hand lens. On your drawing from (a)(i), use a label line to label with an X one of the areas that is now stained. [1] (iii) The stained areas are xylem tissue. State what can be concluded about the function of the xylem tissue. ..................................................................................................................................... [1] (b) A student measures and records the movement of coloured water into a celery stem over five hours. Their results are shown in Table 1.1. Table 1.1 time taken / hours distance moved / mm 0 0 1 21 2 39 3 60 4 82 5 97 (i) On the grid provided, plot a graph of distance moved (vertical axis) against time taken. [3] (ii) Draw the best-fit straight line. [1] (iii) Use your graph to determine the distance moved by the coloured water after 1.5 hours. Indicate on your graph how you arrived at your answer. distance moved = .................................................. mm [2] (iv) Describe the relationship between the distance moved by the coloured water and the time taken. ........................................................................................................................................... ..................................................................................................................................... [1] [Total: 12]

Mark scheme: 1(a)(i) clear and continuous outline with single line, correct shape ; greater than half the box ; detail – crinkly outer edge and circles ; 3 1(a)(ii) line to circle labelled X ; 1 1(a)(iii) transport of water / red colour ; 1 1(b)(i) axes correct way round and labelled with quantity and units ; sensible linear scale chosen so points cover at least half of the grid ; plots correct ± half small square ; 3 1(b)(ii) best fit line ; 1 1(b)(iii) correct reading from graph ; marking on graph ; 2 1(b)(iv) as time increases distance increases ; 1

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2 You are going to test some celery for its nutrient content. (a) Procedure • Pour about 1 cm depth of celery puree into each of three test-tubes. • To one test-tube add an equal amount of Benedict’s solution, shake well and place in the hot water-bath provided for about three minutes. Continue with the procedure while you are waiting. • To the second test-tube add an equal amount of biuret solution. • To the third test-tube add a few drops of iodine solution. (i) Observe and record in Table 2.1 the final colour in each test-tube. Table 2.1 food test final colour observed conclusion Benedict’s solution biuret solution iodine solution [3] (ii) Complete Table 2.1 by writing a conclusion for each of the three tests. [3] (b) (i) A student tests the celery for the presence of fat. State the two substances needed for the fat test. .............................................................. and ............................................................... [1] (ii) Explain why there should be no flames in the laboratory when doing this test. ..................................................................................................................................... [1] [Total: 8]

Mark scheme: 2(a)(i) observation yellow / green / orange / red ; blue ; brown / orange ; 3 2(a)(ii) conclusion contains reducing sugar does not contain protein does not contain starch 3 2(b)(i) water and ethanol / alcohol 1 2(b)(ii) alcohol / ethanol is flammable 1

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3 In this investigation you are going to design a test to distinguish between sodium hydrogencarbonate and sodium carbonate. (a) Procedure • Place 1 cm depth of aqueous sodium hydrogencarbonate into each of four test-tubes. • Place a wooden splint into the first test-tube and leave it soaking until needed. • Add a few drops of methyl orange indicator to the second test-tube and record your observation in Table 3.1. • Add 1 cm depth of dilute hydrochloric acid to the third test-tube and test the gas given off. Record in Table 3.1 your observation, the gas test used and the identity of the gas. • Add 1 cm depth of aqueous magnesium chloride to the fourth test-tube. Record your observation in Table 3.1. • Place the splint from the first test-tube into the top of a blue Bunsen burner flame. Record in Table 3.1 the first colour seen. Repeat the procedure using aqueous sodium carbonate instead of aqueous sodium hydrogencarbonate. Table 3.1 aqueous aqueous sodium hydrogencarbonate sodium carbonate colour with methyl orange observation when dilute hydrochloric acid added test for the gas given off identity of gas observation when aqueous magnesium chloride added flame test colour [6] (b) A colourless solution is either sodium hydrogencarbonate or sodium carbonate. Use the results in Table 3.1 to describe a test to identify the solution as either sodium hydrogencarbonate or sodium carbonate. ................................................................................................................................................... ................................................................................................................................................... ............................................................................................................................................. [1] [Total: 7]

Mark scheme: 3(a) (methyl orange) yellow in both boxes ; (HCl) bubbles in both boxes; limewater and carbon dioxide both boxes ; (MgCl2) colourless / no reaction ; white ppt ; (flame test) both yellow / orange ; 3(b) add aqueous magnesium chloride (and white ppt with Na2CO3 and not NaHCO3) ; 1

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4 You are going to investigate the effect of surface area on the rate of a reaction. Marble chips react with dilute hydrochloric acid to make carbon dioxide gas. You will use three forms of marble chips. Each form has a different surface area. large marble chips small surface area small marble chips powdered marble chips large surface area (a) Procedure • Place about 6 cm depth of dilute hydrochloric acid into a boiling tube (large test-tube). • Set up the apparatus shown in Fig. 4.1. • Add three large marble chips to the acid and quickly replace the bung. • Start the timer immediately. • Stop the timer when the test-tube is filled with gas. • If it takes longer than three minutes then record the time as >180 s. • Record the time in Table 4.1. • Pour the contents of the boiling tube into the waste container. test-tube boiling tube water dilute hydrochloric water acid Fig. 4.1 Repeat the procedure using seven small marble chips. Repeat the procedure using two spatulas of powdered marble chips. You will need to be very quick replacing the bung. Table 4.1 time to fill one test-tube with gas / s large marble chips small marble chips powdered marble chips [3] (b) State the relationship between surface area and rate of reaction. ................................................................................................................................................... ............................................................................................................................................. [1] (c) Suggest a different method of collecting and measuring the gas produced. Name the apparatus and explain how the rate of reaction is measured. ................................................................................................................................................... ................................................................................................................................................... ............................................................................................................................................. [2] [Total: 6]

Mark scheme: 4(a) time for one result ; times for all 3 ; order large > small > powdered ; 4(b) as surface area increases rate increases ; 1 4(c) (gas) syringe ; volume in a certain time / time for a certain volume ; 2

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5 Pure water has a fixed boiling temperature of 100 °C. When an impurity such as salt is added to water the boiling temperature increases. Plan an experiment to find out if the amount of salt added to water is proportional to the increase in boiling temperature of the water. You may use any common laboratory apparatus and samples of water and salt. You will not be doing this experiment. Include in your plan: • the apparatus needed • a brief description of the method, explaining any safety precautions • the measurements you will make, including how to make them as accurate as possible • the variables you will control • how you will process your results and use them to draw a conclusion. You may include a labelled diagram if you wish. You may also include a table that can be used to record results if you wish. You are not required to include any results. .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .................................................................................................................................................... [7] [Total: 7]

Mark scheme: 5 At least 1 mark must come from each section apparatus container and thermometer; balance; method water into container and boil (to record bpt of pure water) ; add salt and (heat to) boil; minimum 5 amounts; safety goggles / gloves and boiling water and (burn / hurt) skin / hands / eyes ; repeat; measurements ; boiling point of pure water ; boiling point of water and salt ; mass of salt added / stated mass added ; control and process volume of water ; calculate average ; processing to use results to draw conclusions draw graph of mass / amount salt against boiling point ; pattern shown in graph described / as mass increases look for pattern in boiling temperature ;

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6 You are going to investigate how the potential difference V across a lamp and the power P of the lamp change as the length l of a resistance wire in series with the lamp changes. The circuit shown in Fig. 6.1 has been set up for you. power source A V l S sliding contact 0 100 X Y resistance wire metre rule Fig. 6.1 (a) Procedure • Close the switch. • Place the sliding contact S on the resistance wire at a distance l = 15.0 cm from X. (i) Record in Table 6.1: • the current I flowing through the lamp • the potential difference V across the lamp. Open the switch. Table 6.1 length l current I potential difference V power P / cm / A / V / ........ 15.0 30.0 45.0 60.0 [2] (ii) Repeat the procedure in (a) for values of l = 30.0 cm, 45.0 cm and 60.0 cm. Record in Table 6.1 the current I and the potential difference V for each length. [3] (b) (i) Calculate the power P of the lamp for each length of wire. Use the equation shown. P = V × I Record in Table 6.1 your values of P to an appropriate number of significant figures. [2] (ii) Complete the column heading in Table 6.1 by giving the unit for power. [1] (iii) State what you observe, when doing the experiment, which shows that the power P of the lamp decreases as the length l of resistance wire increases. ........................................................................................................................................... ..................................................................................................................................... [1] (c) A student suggests that the potential difference V across the lamp is proportional to the length l of resistance wire in the circuit. State if your values in Table 6.1 support this suggestion. Justify your statement by referring to the values. statement .................................................................................................................................. justification ................................................................................................................................ ................................................................................................................................................... [1] [Total: 10]

Mark scheme: 6(a)(i) V value recorded ; 6(a)(ii) I values < 1 A and to at least 2 decimal places ; V values < 2.5 V and to at least 1 decimal place ; V values decreasing ; 3 6(b)(i) all P values correct; values to consistent significant figures/dp ; 2 6(b)(ii) W / watt ; 1 6(b)(iii) lamp gets dimmer (as l increases) ; 1 6(c) (expect no / disagree) justification matches comment and refers to results ; e.g. l / V values not constant. / V decreases as l increases / V doesn’t double as l doubles 1

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7 You are going to use a spring to measure the mass and density of a stone. A spring has been set up in a clamp for you, as shown in Fig. 7.1. spring Fig. 7.1 (a) (i) Measure and record the length l 0 of the unstretched spring in centimetres to the nearest millimetre. Do not include the loops at the ends of the spring. l 0 = ................................................... cm [1] (ii) Use a double-headed arrow ( ) to show on Fig. 7.1 the length l 0 that you measured. [1] (b) (i) Procedure • Suspend a mass m of 200 g on the spring. • Measure the new length l M of the spring in centimetres to the nearest millimetre. l M = ................................................... cm [1] (ii) Calculate the extension e of the spring. Use the equation shown. e = (l M – l 0) e = ................................................... cm [1] (c) Procedure • Remove the 200 g mass from the spring. • Attach the stone provided to the spring. (i) Measure the new length lA of the spring. lA = ......................................................... cm Calculate the extension eA of the spring caused by the stone. Use the equation shown. eA = (lA – l 0) eA = ..........................................................cm [1] (ii) Calculate the mass m of the stone. Use the equation shown. 200 × eA m = e m = ...................................................... g [1] (d) Procedure • Place the beaker of water under the stone. • Slowly lower the clamp until the stone is just completely immersed in the water, as shown in Fig. 7.2. spring stone beaker water Fig. 7.2 Measure the new length lW of the spring. l W = ......................................................... cm Calculate the extension eW of the spring. Use the equation shown. eW = (l W – l 0) eW = ......................................................... cm [1] (e) Use your answers to (c)(i) and (d) to calculate the density d of the stone. Use the equation shown. eA d = (eA – eW) density d of stone = .............................................. g / cm3 [1] (f) (i) It is important to avoid a line-of-sight (parallax) error when measuring the length of the spring. Describe how you avoided this error. ........................................................................................................................................... ..................................................................................................................................... [1] (ii) To obtain a more accurate length, suggest one other precaution or improvement to the procedure that can be made. ........................................................................................................................................... ..................................................................................................................................... [1] [Total: 10]

Mark scheme: 7(a)(i) l 0 recorded to the nearest millimetre ; 1 7(a)(ii) spring with no loops at the ends, carefully marked ; 1 7(b)(i) l Μ in millimetres and > l 0; 1 7(b)(ii) e correct from candidates’ values ; 1 7(c)(i) l Α present and eΑ correct ; 1 7(c)(ii) m correct and correctly rounded ; 1 Question Answer Marks 7(d) l Ω present and < l Α and eω correct ; 1 7(e) 2.5 < d < 3.5 ; 1 7(f)(i) view perpendicularly to scale / rule close to spring / use a fiducial aid ; 1 7(f)(ii) repeat measurements (and average) / clamp the rule vertically ; 1

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