Cambridge IGCSE Sciences - Co-ordinated (Double) 0654 — 2018 Oct/Nov Paper 5 · Variant 1

1 You are going to investigate a leaf. (a) In the box, make a large detailed pencil drawing of the leaf. [3] (b) (i) Measure the longest length of the leaf, not including any stalk. Record this length, in millimetres, to the nearest millimetre. length of leaf ................................................... mm [1] (ii) Draw a straight line to show this longest length on your drawing. Measure and record the length of this line, in millimetres, to the nearest millimetre. length of line on drawing ................................................... mm [1] (iii) Use your measurements from (b)(i) and (b)(ii) to calculate the magnification of your drawing. magnification = .......................................................... [1] (c) (i) Describe, in detail, the method used to test the leaf for the presence of starch. Include the observation for a positive result. method .............................................................................................................................. ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... observation for a positive result ........................................................................................ ........................................................................................................................................... [4] (ii) Describe and explain one safety precaution, not including safety glasses, tying back hair or wearing gloves, that should be taken when carrying out this procedure. safety precaution ............................................................................................................... explanation ........................................................................................................................ [2] (d) Leaves have stomata in the upper and lower surfaces. These can be seen using a light microscope. A teacher says that all plants have more stomata on the lower surface of their leaves. Plan an investigation to find out if the teacher is correct. ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ...............................................................................................................................................[3]

Mark scheme: 1(a) continuous outline; detail e.g. vein; length of leaf drawn 70 mm or more; 3 1(b)(i) value entered to nearest mm; 1 1(b)(ii) measurement from drawing correct; 1 1(b)(iii) correct calculation of magnification; 1 1(c)(i) (place in) hot (liquid); alcohol; iodine (solution); blue-black; 4 1(c)(ii) water bath / not naked flame; because alcohol/ethanol is flammable; OR cut away from hand ; to avoid cuts; OR wash hands / avoid contact; to remove iodine / iodine stains / iodine solution is irritant / iodine solution is harmful; 2 1(d) count number on upper and lower epidermis/surface; repeat for same species; then use different species; 3

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2 You are going to investigate the temperature changes when solid H reacts with solution J. (a) (i) Using the thermometer, measure the temperature T of solution J. Record, in Table 2.1, this value to the nearest 0.5 °C in the appropriate space for time = 0 min. [1] Table 2.1 time / min temperature T / °C 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 (ii) Procedure • Place all of solid H into a plastic cup supported in a beaker. • Measure 25 cm3 solution J using the measuring cylinder. • Add the measured volume of solution J to the solid H in the plastic cup. • Start the stopclock. • Stir the mixture thoroughly. • Continue stirring and measure the temperature of the mixture every half minute for four minutes. • Record, in Table 2.1, the values to the nearest 0.5 °C. • After the final reading, record in Table 2.2 the appearance of the solid and the solution. Table 2.2 observations solid H solution J before the reaction grey blue after the reaction [4] (b) (i) Use the data in Table 2.1 to estimate the maximum rise in temperature ΔT of the mixture during the reaction. ΔT ..................................................... °C [1] (ii) Explain why the value in (b)(i) is only an estimate. ........................................................................................................................................... .......................................................................................................................................[1] (iii) Suggest how you could improve the procedure in (a)(ii) to achieve a more accurate value of the rise in temperature for this experiment without changing the apparatus or chemicals. ........................................................................................................................................... .......................................................................................................................................[1] (c) (i) Calculate the heat energy E released in this reaction using the equation shown. E = volume of solution J × 4.2 × ΔT Give your answer to 2 significant figures. E = ............................................... joules [2] (ii) Your value of E in (c)(i) is less than the actual amount of energy released by the reaction. Suggest an improvement to the apparatus (not the chemicals) that would result in a higher value of E. Explain why your improvement would result in a higher value of E. improvement ..................................................................................................................... ........................................................................................................................................... explanation ........................................................................................................................ ........................................................................................................................................... [2] (d) (i) Place 1 cm depth of unused solution J in a test-tube and slowly add ammonia solution until in excess. Record your observations. ........................................................................................................................................... .......................................................................................................................................[1] (ii) Using your observation from (d)(i) and one other piece of evidence, identify the cation in solution J. State the other piece of evidence that you have used. cation in J is .............................................. other piece of evidence is ................................................................................................. ........................................................................................................................................... [2]

Mark scheme: 2(a)(i) 1 2(a)(ii) all readings entered; maximum by 2.0 min / SV time plus 0.5 min AND only one maximum; observations solid H solution J (after the reaction) brown / darker grey / black; colourless / paler blue / grey; 4 2(b)(i) correct rise in temperature; 1 2(b)(ii) temperature could have been higher between readings; 1 2(b)(iii) take readings more frequently (than every 0.5 min) / plot a graph and draw best-fit line; 1 2(c)(i) use 25 × 4.2 × (b)(i); correct answer to 2sf; 2 2(c)(ii) insulation around cup / lid; less heat lost to surroundings; 2 2(d)(i) (light) blue ppt. AND dark blue solution; 1 2(d)(ii) copper (ion) / Cu2+ / copper(II); brown solid in (a)(ii) / J is a blue solution / copper is displaced in first reaction; 2

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3 You are going to measure the acceleration of free fall g using a spring. (a) Measure and record the unstretched length l 0 of the spring to the nearest millimetre. Do not include the loops at the end of the spring in your measurement. l 0 = ................................................... mm [1] (b) Attach the spring to the clamp as shown in Fig. 3.1. clamp spring mass bench Fig. 3.1 Procedure • Suspend a 200 g mass on the spring. • Measure the stretched length l 1 of the spring. • Record your value in Table 3.1 on page 8. • Calculate the extension e of the spring produced by the mass. Use the equation shown. e = l 1 − l 0 • Record your value in Table 3.1 on page 8. [1] Table 3.1 stretched time t taken for extension 2 mass m / g length 20 oscillations period T / s T / s2 e / mm l 1 / mm / s 200 300 400 500 (c) Pull the mass down a small distance and release it. The mass oscillates up and down. The period T of the oscillations is the time taken for one oscillation. One oscillation is one complete up-motion and one complete down-motion of the mass, as shown in Fig. 3.2. up highest position one oscillation rest position lowest position down Fig. 3.2 (i) Measure the time t taken for 20 oscillations. Record this time in Table 3.1. [1] (ii) Repeat the procedure in (b) and the measurement in (c)(i) for masses of 300 g, 400 g and 500 g. [1] (iii) Use your answers from (c)(i) and (c)(ii) to calculate the period T (the time for one oscillation) for each of the masses. Record, in Table 3.1, your values of T. [1] (iv) Calculate the values of T 2. Record, in Table 3.1, your answers to two significant figures. [1] (d) (i) On the grid provided, plot a graph of T 2 (vertical axis) against e. Start your axes at (0,0). [3] (ii) Draw the best-fit straight line. [1] (iii) Calculate the gradient of your line. Show all working and indicate on your graph the values you chose to enable an accurate value of the gradient to be calculated. gradient = ...........................................................[2] (iv) Use your answer to (d)(iii) and the equation shown, to determine a value for the acceleration of free fall g. 0.0395 g = gradient g = ................................................. m / s2 [1]

Mark scheme: 3(a) 1 3(b) l1 recorded for m = 200 g AND l1 > l0 AND e correctly calculated; 1 3(c)(i) t value recorded in the table for m = 200; 1 3(c)(ii) all t values present AND increasing; 1 3(c)(iii) all T values correct for t values present; 1 3(c)(iv) all T2 values correct for T values present; 1 3(d)(i) axes labelled with units; suitable choice of scales with ⩾ half the grid used AND starting at (0,0) ; at least 3 plots correct to half a small square; 3 3(d)(ii) good best-fit straight line judgement; 1 3(d)(iii) indication on graph of how data were obtained AND more than half the line used; correct calculation; 2 3(d)(iv) correct calculation of g; 1 3(e) view perpendicularly to rule / scale / AVP; 1 3(f) yes – close enough / within 10% / both close to 10; 1

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