Cambridge IGCSE Sciences - Co-ordinated (Double) 0654 — 2024 May/June Paper 6 · Variant 1

1 Fig. 1.1 is a photograph of a slice of an orange shown actual size. A B Fig. 1.1 (a) In the box, make a large, detailed, pencil drawing of the slice of the orange shown in Fig. 1.1. [3] (b) (i) Draw a line to join points A and B on Fig. 1.1. Record the length of this line AB in millimetres to the nearest millimetre. length of line AB on Fig. 1.1 = .................................................. mm [1] (ii) Draw the line AB on your drawing in (a). Record the length of this line in millimetres to the nearest millimetre. length of line AB on your drawing = .................................................. mm [1] (iii) Calculate the magnification m of your drawing. Use your measurements in (b)(i) and (b)(ii) and the equation shown. length of line AB on your drawing m = length of line AB on Fig. 1.1 Record your value to two significant figures. magnification m = ......................................................... [2] (c) Fig. 1.2 is a photograph of a slice of a kiwi fruit shown actual size. Fig. 1.2 State two visible differences between the slice of orange shown in Fig. 1.1 and the slice of kiwi fruit shown in Fig. 1.2. difference 1 ............................................................................................................................... ................................................................................................................................................... difference 2 ............................................................................................................................... ................................................................................................................................................... [2] (d) Suggest how the mean diameter of the kiwi fruit is determined. ................................................................................................................................................... ............................................................................................................................................. [1] [Total: 10]

Mark scheme: 1(a) quality – clear and continuous lines ; size – circular and at least half the box used and must fit inside the box ; detail – skin and minimum 6 segments ; 3 1(b)(i) line drawn and 65; 1 1(b)(ii) line drawn and measurements to nearest mm ; 1 1(b)(iii) correct calculation ; 2 significant figures ; 2 1(c) any two from: size / orange is larger / kiwi is smaller ; shape / orange is round and kiwi is oval ; seeds / presence of seeds / number of seeds / orange has fewer/no seeds / kiwi has (more) seeds ; skin / orange has thicker skin / kiwi has thinner skin ; segments / orange has segments / kiwi doesn’t have segments ; core / orange has larger core / kiwi has smaller core / kiwi has flesh in the centre ; 2 1(d) add measurements from several places and divide by the number of measurements taken ; 1

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2 A student compares the vitamin C concentration of orange juice with three other fruit juices, D, E and F. DCPIP is a blue solution that decolourises (goes colourless) when vitamin C is added to it. DCPIP is used as an indicator for vitamin C concentration as shown in Fig. 2.1. few drops of vitamin C needed to high vitamin C concentration decolourise DCPIP many drops of vitamin C needed to low vitamin C concentration decolourise DCPIP Fig. 2.1 (a) Procedure The student: • places two drops of DCPIP into a well of a spotting tile • adds drops of orange juice to the well of DCPIP • records how many drops of orange juice are needed to decolourise the DCPIP. The student repeats the procedure with the other fruit juices. (i) Name a piece of equipment suitable for putting the DCPIP in the well. ..................................................................................................................................... [1] (ii) Suggest a suitable colour for the spotting tile. Explain your answer. colour ................................................................................................................................ explanation ........................................................................................................................ ........................................................................................................................................... [1] (iii) Fig. 2.2 shows part of the student’s notebook. number of drops orange juice IIIII IIIII IIIII II juice D IIII juice E IIIII IIII juice F IIIII IIIII IIII Fig. 2.2 Draw a table for the student’s results shown in Fig. 2.2. Record the student’s results in your table. [3] (iv) Use the student’s results and Fig. 2.1 to place the juices in order of their vitamin C concentration. highest vitamin C ............................................... ............................................... ............................................... lowest vitamin C ............................................... [1] (b) (i) Explain why repeating the procedure allows the student to have more confidence in their results. ........................................................................................................................................... ..................................................................................................................................... [1] (ii) Counting the number of drops is one source of error in this procedure. Explain why this is a source of error. Suggest one improvement. Do not include repeating the procedure. explanation ........................................................................................................................ ........................................................................................................................................... improvement ..................................................................................................................... ........................................................................................................................................... [2] (c) Scurvy is a disease caused by a lack of vitamin C in the diet. A student does not drink orange juice or fruit juices D, E and F. Suggest why the student does not get scurvy. ................................................................................................................................................... ............................................................................................................................................. [1] [Total: 10]

Mark scheme: 2(a)(i) dropping pipette ; 1 2(a)(ii) white and can see colour change ; 1 2(a)(iii) headings: juice and (number of) drops ; juice labels and results separated ; orange = 17 and D = 4 and E = 9 and F = 14 ; 3 2(a)(iv) D E F orange (least) ; 1 2(b)(i) Identifies / exclude anomalies ; 1 2(b)(ii) drop size varies / losing count ; measure volume / do on a larger scale ; 2 2(c) other sources in diet ; 1

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3 A student investigates the reaction between magnesium and aqueous copper sulfate. More reactive metals displace less reactive metals from solutions of their salts. magnesium + copper sulfate magnesium sulfate + copper The unit M is used to measure the concentration of a solution. The higher the value of M, the more concentrated the solution. A 1 M solution is two times more concentrated than a 0.5 M solution. (a) Procedure The student: • places a polystyrene cup into a beaker • uses a measuring cylinder to add 25 cm3 of 1.00 M aqueous copper sulfate to the polystyrene cup as shown in Fig. 3.1 polystyrene cup aqueous copper sulfate beaker Fig. 3.1 • places a thermometer into the polystyrene cup and records in Table 3.1 the temperature of the aqueous copper sulfate to the nearest 0.5 °C • adds magnesium powder to the aqueous copper sulfate in the cup • stirs the mixture and records in Table 3.1 the highest temperature reached to the nearest 0.5 °C. The student repeats the procedure using the concentrations of aqueous copper sulfate shown in Table 3.1. Table 3.1 concentration initial temperature highest temperature of temperature increase of aqueous of aqueous the mixture ΔT copper sulfate copper sulfate / °C / °C / M / °C 1.00 21.5 85.5 64.0 0.75 22.0 0.50 22.5 54.0 31.5 0.25 21.0 0.00 21.5 21.5 0.0 Fig. 3.2 shows the thermometer readings for the highest temperatures for 0.75 M aqueous copper sulfate and 0.25 M aqueous copper sulfate. °C °C 80 40 70 30 0.75 M aqueous copper sulfate 0.25 M aqueous copper sulfate Fig. 3.2 Record in Table 3.1 these temperatures to the nearest 0.5 °C. [2] (b) The student observes that the mixture left at the end of the reaction is a colourless solution with pieces of grey solid and pink solid. (i) Explain how this observation shows that the magnesium powder is in excess. ........................................................................................................................................... ..................................................................................................................................... [1] (ii) Suggest the identity of the pink solid. ..................................................................................................................................... [1] (c) (i) Explain why the polystyrene cup is placed in the beaker. ........................................................................................................................................... ..................................................................................................................................... [1] (ii) State the name of a piece of apparatus suitable for measuring the 25 cm3 of aqueous copper sulfate more accurately than the measuring cylinder. ..................................................................................................................................... [1] (d) (i) Calculate the temperature increase ΔT for 0.75 M aqueous copper sulfate and 0.25 M aqueous copper sulfate. Record these values in Table 3.1. [1] (ii) On the grid, plot a graph of temperature increase ΔT (vertical axis) against concentration of aqueous copper sulfate. [3] (iii) Draw the best-fit straight line. [1] (iv) A teacher says that the temperature increase is proportional to the concentration of aqueous copper sulfate. Suggest if this is supported by the student’s data. Explain your answer. ........................................................................................................................................... ..................................................................................................................................... [1] (v) Use your graph to estimate the temperature increase ΔT when 0.35 M aqueous copper sulfate is used in the procedure. ΔT = .................................................... °C [1] (e) Suggest one improvement to the procedure which will give more confidence in the values of ΔT. Do not include repeating the procedure. Explain your answer. improvement ............................................................................................................................. ................................................................................................................................................... explanation ............................................................................................................................... ................................................................................................................................................... [1] [Total: 14]

Mark scheme: 3(a) 70.0 ; 38.5 ; 2 3(b)(i) grey solid left unreacted at the end of the reaction ; 1 3(b)(ii) copper ; 1 3(c)(i) for stability / not easily knocked over / thermometer doesn’t overbalance it ; 1 3(c)(ii) volumetric / graduated pipette / burette ; 1 3(d)(i) 48(.0) and 17.5 ; 1 3(d)(ii) axes correct orientation and labelled with quantity and unit ; sensible linear scales with plotted points covering ⩾ ½ grid and all points able to be plotted ; points plotted correctly  ½ small square ; 3 3(d)(iii) best fit straight line through origin ; 1 3(d)(iv) yes as straight line through origin / as concentration doubles so temperature change doubles / ratio of concentration ÷ T is constant ; 1 3(d)(v) value from graph ; 1 3(e) any one from: insulate/use lid AND less heat loss ; find the mass of magnesium AND so only variable is copper sulfate concentration/so mass is controlled ; 1

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4 A student identifies a solution labelled H. (a) The student puts solution H into five test-tubes and does the tests in Table 4.1. The student identifies H as aqueous potassium chloride. Complete Table 4.1 with the student’s observations. Table 4.1 test observation add dilute nitric acid followed by a few drops of aqueous silver nitrate add dilute nitric acid followed by aqueous barium nitrate flame test add aqueous ammonia add aqueous sodium hydroxide [5] (b) Explain why a flame test uses a blue Bunsen burner flame instead of a yellow one. ................................................................................................................................................... ............................................................................................................................................. [1] [Total: 6]

Mark scheme: 4(a) white precipitate ; colourless solution / no reaction / no precipitate ; lilac ; colourless solution / no reaction / no precipitate ; colourless solution / no reaction / no precipitate ; 4(b) yellow masks the colour of the flame test ; 1

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5 A student investigates how the resistance R of a lamp changes as the current I flowing through the lamp changes. The student assembles the circuit shown in Fig. 5.1. A l S P Q resistance wire metre rule Fig. 5.1 (a) Procedure The student: • connects a voltmeter to measure the potential difference across the lamp • closes the switch • places the sliding contact S on the resistance wire at a distance l = 20.0 cm from end P • records in Table 5.1 the current I in the lamp and the potential difference V across the lamp • opens the switch. (i) Using the correct circuit symbol, add a voltmeter to Fig. 5.1 to measure the potential difference across the lamp. [2] (ii) The ammeter and voltmeter readings are shown in Fig. 5.2. 0.5 1 2 A V 0 1 0 3 Fig. 5.2 Record in Table 5.1 the current I in the lamp and the potential difference V across the lamp. Table 5.1 length of resistance current I potential difference V resistance R wire l / cm / A / V / Ω 20.0 9.5 40.0 0.17 1.4 2.8 60.0 0.15 1.2 80.0 0.13 1.0 7.7 [2] (b) The student repeats the procedure in (a) for values of l = 40.0 cm, 60.0 cm and 80.0 cm. Suggest why the student opens the switch after taking each pair of readings of the current I and the potential difference V. ................................................................................................................................................... ............................................................................................................................................. [1] (c) (i) Calculate the resistance R of the lamp when l = 60.0 cm. Use the equation shown. V R = I Record your value of R in Table 5.1. [1] (ii) One of the values of resistance R in Table 5.1 is incorrect. State which value of R is incorrect. Suggest the error the student makes to get this value. value ..................................... error ................................................................................................................................... ........................................................................................................................................... [2] (d) (i) Describe how the resistance R of the lamp changes as the length l of resistance wire changes. ..................................................................................................................................... [1] (ii) Describe how the resistance R of the lamp changes as the current I flowing through the lamp changes. ..................................................................................................................................... [1] (e) A student suggests that the resistance R of the lamp is proportional to the potential difference V across it. State if the values of R and V in Table 5.1 support the student’s suggestion. Use values from Table 5.1 to explain your answer. ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ............................................................................................................................................. [2] (f) As the length l of the resistance wire increases, the brightness of the lamp decreases. A student finds that when l is greater than 80.0 cm, the lamp does not glow. Suggest how the student checks that the lamp is not broken. ................................................................................................................................................... ............................................................................................................................................. [1] [Total: 13]

Mark scheme: 5(a)(i) correct voltmeter symbol ; correct parallel connection ; 2 5(a)(ii) 0.19 (A) ; 1.8 (V) ; 2 5(b) so that the cell does not run down / wire does not overheat ; 1 5(c)(i) 8.0 () ; 1 5(c)(ii) 2.8 ; digits have been transposed / should be 8.2 ; 2 5(d)(i) R decreases as length increases ; 1 5(d)(ii) R decreases as current decreases ; 1 Question Answer Marks 5(e) no and R / V is not constant / equivalent ; table values used to confirm statement ; 2 5(f) check that the ammeter gives a reading / shorten the wire and check the reading or check if the bulb lights ; 1

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6 A student investigates the cooling of hot water in a beaker. Plan an experiment to investigate the relationship between the thickness of the cardboard insulation wrapped around a beaker and the rate of cooling of hot water in the beaker. You are provided with: • a supply of hot water • a beaker • a measuring cylinder • thin sheets of cardboard. You may use any other common laboratory apparatus. In your plan include: • any other apparatus needed • a brief description of the method, including what you will measure and how you will make sure your measurements are accurate • the variables you will control • a results table to record your measurements (you are not required to enter any readings in the table) • how you will process your results to draw a conclusion. You may include a labelled diagram if you wish. .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .................................................................................................................................................... [7]

Mark scheme: 6 One mark from each section and any two others additional apparatus: stop-watch and its use ; thermometer and its use ; ruler and its use ; method: wrap cardboard round beaker and add hot water and measure a temperature for at least 2 thicknesses of cardboard ; measurement and table: measure the thickness of the cardboard ; measure initial temperature of water ; measure the time for a specific temperature decrease / (final) temperature in a specific time ; repeat for 5 different thicknesses of cardboard ; repeat for each thickness and remove/identify anomalies ; table columns thickness / sheets (of insulation) and temperature or time ; control variables: mass / volume / amount of hot water ; same initial hot-water temperature ; same room temperature ; same size / thickness/material of beaker ; processing and conclusion: calculates rate of cooling by taking temp change ÷ time ; graph with rate vs number sheets / thickness ; see if increasing thickness increases or decreases the rate of cooling / describe relationship from shape of graph ; 7

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