Cambridge IGCSE Sciences - Co-ordinated (Double) 0654 — 2020 May/June Paper 5 · Variant 1

1 You are provided with a flower. Remove two of the petals and discard them. (a) (i) In the box, make an enlarged, detailed pencil drawing of the flower. Include the internal parts of the flower. [3] (ii) On your drawing, label an anther, a petal and a stigma. [3] (b) You are going to calculate the magnification of your drawing. (i) Draw a straight line across your drawing from one edge of your drawing to the other. Measure the length of this line in millimetres to the nearest millimetre. length of line = ................................................... mm [1] (ii) Measure this length on the real flower in millimetres to the nearest millimetre. length on real flower = ................................................. mm [1] (iii) Calculate the magnification m of your drawing. Use the equation shown. length of line m = length on real flower Give your answer to two significant figures. m = ......................................................... [2] [Total: 10]

Mark scheme: 1(a)(i) clear and continuous outline; uses at least half of the box; detail including petals, filament and style; 3 1(a)(ii) anther correctly labelled; petal correctly labelled; stigma correctly labelled; 3 1(b)(i) correct measurement; 1 1(b)(ii) value recorded in mm; 1 1(b)(iii) correct calculation with correct rounding; to 2 sf; 2

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2 You are provided with a sample of nectar and a sample of pollen from a flower. The pollen is a suspension in water. (a) Procedure • Pour about 1 cm depth of the sample of nectar into a test-tube. • Add an equal volume of Benedict’s solution. • Place in a hot water-bath for a few minutes. • You may continue with the rest of the procedure while you are waiting. • Pour about 1 cm depth of the sample of nectar into a clean test-tube. • Add an equal volume of biuret solution. • Pour about 1 cm depth of the sample of nectar into a clean test-tube. • Add a few drops of iodine solution. Record in Table 2.1 the final colour observed in each test-tube. Table 2.1 final colour with final colour with final colour with sample Benedict’s solution biuret solution iodine solution nectar pollen [2] (b) Repeat the procedure in (a) using the pollen instead of the nectar. [2] (c) Use your results in Table 2.1 to state the nutrients present in the nectar and pollen samples. nectar contains ......................................................................................................................... pollen contains .......................................................................................................................... [2] (d) Describe how you would test the nectar for the presence of fat. method ...................................................................................................................................... ................................................................................................................................................... observation for a positive result ................................................................................................ [2] (e) A student investigates the nutrient concentration in some nectar and pollen samples using Benedict’s solution. Benedict’s solution will give a range of colours depending on the concentration of the nutrient. State two variables which the student needs to control. variable 1 .................................................................................................................................. variable 2 .................................................................................................................................. [2] [Total: 10]

Mark scheme: 2(a) nectar yellow / green / orange / red ; blue and .... …..orange / brown ; 2 2(b) pollen blue and ……. purple ; …..orange / brown ; 2 2(c) nectar contains reducing sugar; pollen contains protein; 2 2(d) add ethanol (shake and pour solution into) water; white emulsion; 2 2(e) any two from: volume of Benedict’s solution; mass / volume / amount / concentration of food; time in water bath/left in water bath for same time; temperature of water bath; max 2

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3 In this investigation you are going to identify five solutions, J, K, L, M and N. The names of the aqueous solutions are shown. aqueous ammonia acidified aqueous barium nitrate aqueous copper(II) chloride aqueous sodium hydroxide aqueous zinc sulfate You are going to do four experiments to identify which of these solutions are solutions J, K, L, M and N. (a) Experiment 1 • Place 1 cm depth of K in a test-tube. • Add M slowly drop by drop until there is no further change. • Record your observations. ................................................................................................................................................... ............................................................................................................................................. [1] (b) Experiment 2 • Place 1 cm depth of K in a test-tube. • Add L slowly drop by drop until there is no further change. • Record your observations. ................................................................................................................................................... ............................................................................................................................................. [1] (c) Experiment 3 • Place 1 cm depth of J in a test-tube. • Add L slowly drop by drop until there is no further change. • Record your observations. ................................................................................................................................................... ............................................................................................................................................. [1] (d) Experiment 4 • Place 1 cm depth of N in a test-tube. • Add J slowly drop by drop until there is no further change. • Record your observations. ................................................................................................................................................... ............................................................................................................................................. [1] (e) K is a blue solution. All the other solutions are colourless. (i) Name solution K. ..................................................................................................................................... [1] (ii) Use the observations from experiment 1 to name solution M. ..................................................................................................................................... [1] (iii) Use the observations from experiment 2 to name solution L. ..................................................................................................................................... [1] (iv) Use the observations from experiments 3 and 4 to name solutions J and N. Explain how you arrived at your answers. J ........................................................................................................................................ N ........................................................................................................................................ explanation ........................................................................................................................ ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... [2] [Total: 9]

Mark scheme: 3(a) (light) blue precipitate that in excess gives a dark(er) blue solution ; 1 3(b) (light) blue precipitate ; 1 3(c) white precipitate that redissolves in excess ; 1 3(d) white precipitate 1 3(e)(i) K is (aqueous) copper(II) chloride ; 1 3(e)(ii) M is (aqueous) ammonia ; 1 3(e)(iii) L is (aqueous) sodium hydroxide ; 1 3(e)(iv) J is (aqueous) zinc sulfate and N is (aqueous) barium nitrate ; any one from: zinc ions react with aqueous sodium hydroxide to give a white ppt that redissolves to give a colourless solution (so J is zinc sulfate) ; (zinc) sulfates react with barium nitrate to give a white precipitate (so N is barium nitrate) ; max 2

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4 You are going to investigate the temperature change that occurs when dilute hydrochloric acid is neutralised by aqueous sodium hydroxide. (a) Procedure • Measure 5 cm3 of dilute hydrochloric acid using a 25 cm3 measuring cylinder. • Measure 10 cm3 of aqueous sodium hydroxide using a 10 cm3 measuring cylinder and pour into a glass beaker. • Measure and record in Table 4.1 the temperature of this aqueous sodium hydroxide to the nearest 0.5 °C. • Pour the 5 cm3 dilute hydrochloric acid into the 10 cm3 aqueous sodium hydroxide and stir the mixture with the thermometer. • Record in Table 4.1 the highest temperature reached, to the nearest 0.5 °C. • Rinse the beaker. Repeat the procedure using the volumes of dilute hydrochloric acid and aqueous sodium hydroxide shown in Table 4.1. Table 4.1 temperature of volume of highest volume of dilute aqueous sodium temperature aqueous sodium temperature of hydrochloric acid hydroxide in change, ∆T hydroxide mixture in beaker / cm3 beaker / °C / cm3 / °C / °C 5 10 10 10 15 10 20 10 25 10 [3] (b) Calculate the temperature changes, ∆T. Record your values in Table 4.1. [1] (c) Identify the dependent variable in this investigation. ............................................................................................................................................. [1] (d) (i) Plot a graph of the temperature change, ∆T, against the volume of dilute hydrochloric acid, on the grid provided. 0 5 10 15 20 25 30 volume of dilute hydrochloric acid / cm3 [2] (ii) Draw the best-fit curve. [1] (e) During the experiment the liquid in the beaker loses thermal energy to the surroundings. (i) State the effect this will have on the results of the experiment. ........................................................................................................................................... ..................................................................................................................................... [1] (ii) Suggest one way of reducing the loss of thermal energy in this experiment. ........................................................................................................................................... ..................................................................................................................................... [1] (f) Give one advantage of using a 10 cm3 measuring cylinder to measure the volume of aqueous sodium hydroxide, rather than a 25 cm3 measuring cylinder. ............................................................................................................................................. [1] [Total: 11]

Mark scheme: 4(a) all ten temperature readings recorded : all temperature readings recorded to the nearest 0.5°C ; temperature rise for result for 10 cm3 of hydrochloric acid added to be within 10% of the supervisor’s result ; 3 4(b) all temperature changes correctly recorded ; 1 4(c) highest temperature (of mixture in beaker); 1 4(d)(i) y-axis labelled temperature change / °C and an appropriate linear scale where the plotted points use at least half of the y-axis ; all points plotted correctly ± half a small square ; 2 4(d)(ii) curve of best fit ; 1 4(e)(i) highest temperature will be lower / temperature rise will be lower ; 1 4(e)(ii) insulate the beaker / use a plastic beaker / use a lid ; 1 4(f) smaller percentage uncertainty / smaller error ; 1

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5 You are going to determine the density of the material from which a metre rule is made. You are provided with a metre rule. 100.0 cm w w t t side view not to scale metre rule Fig. 5.1 (a) (i) Fig. 5.1 shows the width w and thickness t of a metre rule. Measure the width w and thickness t of your metre rule, each to the nearest 0.1 cm. w = ......................................................... cm t = ......................................................... cm [2] (ii) State which of your measurements, w or t, is the more accurate. Give a reason for your answer. measurement ........................... reason ............................................................................................................................... ........................................................................................................................................... [1] (b) Calculate the volume V of the metre rule. Use the equation shown. V = 100 × w × t V = .................................................. cm3 [1] (c) (i) Procedure • Place the pivot directly under the 65.0 cm mark on the metre rule, so that the distance d = 65.0 cm, as shown in Fig. 5.2. • Place load m on the metre rule. • Adjust the position of load m until the rule is as close to being balanced as possible. metre rule m d = 65.0 cm x 65 0 100 pivot Fig. 5.2 Measure the distance x1 from the centre of load m to the pivot to the nearest 0.1 cm. x1 = ................................................... cm [1] (ii) Describe how you identified the position of the centre of load m. ........................................................................................................................................... ..................................................................................................................................... [1] (iii) Repeat the procedure in (c)(i) for d = 70.0 cm. Measure the distance x2 from the centre of load m to the pivot. x2 = ................................................... cm [2] (d) Use your results for (c)(i) and (c)(iii) to calculate the mass M of the metre rule. Use the equation shown. M = 5.7 (x1 + x2) M = ...................................................... g [2] (e) The value of M obtained in (d) is approximate. State one practical difficulty involved in doing this experiment that makes the measured values of x1 and x2 subject to experimental error. ................................................................................................................................................... (f) Use your answers to (b) and (d) to calculate the density ρ of the material from which the rule is made. Use the equation shown. M ρ = V Give the unit for your answer. ρ = ............................................................... unit = ......................................................... [2] [Total: 13]

Mark scheme: 5(a)(i) w and t recorded and w > t ; both recorded to the nearest mm; 2 5(a)(ii) w and larger than t / t very small / rule measures to 1 mm so greater effect of error on smaller distance; 1 5(b) correct answer with candidate’s values correctly rounded; 1 5(c)(i) x1 present; 1 5(c)(ii) note reading on either side of mass and find the mean value / AW; 1 5(c)(iii) x2 present ; larger than x1 ; 2 5(d) M calculation correct; value within 10% of Supervisor’s value; 2 5(e) difficulty in obtaining an exact balance/difficulty in placing the centre of the mass over the correct mark on the rule / AVP; 1 5(f) density correct from candidate’s values and rounded correctly; g / cm3 ; 2

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6 The rate of cooling of water in a beaker depends upon the volume of water in the beaker. Plan an experiment to investigate how the rate of cooling of hot water depends upon the volume of the water. The apparatus available is listed. thermometer stop-watch beaker measuring cylinder supply of hot water You are not required to do this experiment. In your answer you should: • explain briefly how you would do the experiment • state the key variables you would control • draw a table with column headings to show how you would present your results (you are not required to enter any readings in the table) • explain how you would use your results to reach a conclusion. .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .................................................................................................................................................... [7] [Total: 7] NOTES FOR USE IN QUALITATIVE ANALYSIS Tests for anions anion test test result carbonate (CO32–) add dilute acid effervescence, carbon dioxide produced chloride (Cl –) acidify with dilute nitric acid, then white ppt. [in solution] add aqueous silver nitrate bromide (Br–) acidify with dilute nitric acid, then cream ppt. [in solution] add aqueous silver nitrate nitrate (NO3–) add aqueous sodium hydroxide then ammonia produced [in solution] aluminium foil; warm carefully sulfate (SO42–) acidify, then add aqueous barium white ppt. [in solution] nitrate Tests for aqueous cations cation effect of aqueous sodium hydroxide effect of aqueous ammonia ammonium (NH4+) ammonia produced on warming – calcium (Ca2+) white ppt., insoluble in excess no ppt., or very slight white ppt. copper (Cu2+) light blue ppt., insoluble in excess light blue ppt., soluble in excess, giving a dark blue solution iron(II) (Fe2+) green ppt., insoluble in excess green ppt., insoluble in excess iron(III) (Fe3+) red-brown ppt., insoluble in excess red-brown ppt., insoluble in excess zinc (Zn2+) white ppt., soluble in excess giving a white ppt., soluble in excess, giving a colourless solution colourless solution Tests for gases Flame tests for metal ions gas test and test result metal ion flame colour ammonia (NH3) turns damp, red litmus paper blue lithium (Li+) red carbon dioxide (CO2) turns limewater milky sodium (Na+) yellow chlorine (Cl 2) bleaches damp litmus paper potassium (K+) lilac hydrogen (H2) ‘pops’ with a lighted splint copper(II) (Cu2+) blue-green oxygen (O2) relights a glowing splint

Mark scheme: 6 one mark from each section and any two others (if one section is omitted then max 6 etc.) method time hot water (in beaker) cooling; repeat for different volume(s)of water; number and range of volumes at least 5 volumes ; at least 100 cm3 difference between the largest and smallest volume ; key variables initial temperature of the hot water; temperature of the surroundings / room temperature; size / shape of beaker; time of cooling / same temperature drop; table headings: volume, temperature / time; and all correct units present; conclusion compare temperature drops in equal times–largest drop gives greatest rate; compare times for the same temperature drops–least time gives greatest rate; calculate the rate of temperature fall each time and compare; plot graphs of temperature against time and compare gradients/steeper gradient cools faster ;

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