Cambridge IGCSE Science - Combined 0653 — 2017 May/June Paper 5 · Variant 2

1 You are provided with a flower. Carefully remove 2 petals. (a) In the box below, make a large pencil drawing of the flower. This should show all the flower parts including some petals. [4] (b) You are going to calculate the magnification of your drawing. (i) Draw a straight line across your drawing from one edge to the other. Measure the length of this line in millimetres to the nearest millimetre. length = .................................................... mm Measure the same length of the same part on the real flower in millimetres to the nearest millimetre. length = .................................................... mm [2] (ii) Use your two measurements to calculate the magnification of your drawing. Show your working in the space below. magnification = ...............................................[1] (c) Flowers contain nectar. Plan an investigation using two different flowers to find out which nectar contains more reducing sugar. You should include details of how you will carry out the test and what observations will allow you to conclude which nectar contains more reducing sugar. ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ...............................................................................................................................................[3]

Mark scheme: 1(a) quality drawing in pencil using at least half the space ; male parts, anther and filament drawn ; female parts, stigma and ovary drawn ; petals drawn ; 4 1(b)(i) line drawn edge to edge ; correct measurement of drawing and sensible flower measurement ; 2 1(b)(ii) correct calculation ; 1 1(c) benedict’s solution; heat; orange / red indicates more sugar or yellow / green indicates less sugar ; 3

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2 You are going to investigate how the temperature of a reactant affects the rate of reaction between calcium carbonate and hydrochloric acid. You are provided with marble chips (calcium carbonate) and hydrochloric acid. (a) Set up the apparatus provided as shown in Fig. 2.1. To obtain an inverted 100 cm3 measuring cylinder full of water: • fill the measuring cylinder with water • place your finger or hand firmly over the open end of the cylinder so no water can run out • invert and place this end under the water in the water container • remove your hand and clamp the cylinder in place (note that a small amount of air in the measuring cylinder will not be a problem in this experiment) • push the tubing of the delivery tube up into the cylinder a little way. delivery tube clamp 100 cm3 measuring cylinder large test-tube water water container Fig. 2.1 (i) experiment 1 • Disconnect the large test-tube and use a measuring cylinder to place 20 cm3 of hydrochloric acid into it. • Measure the temperature of the acid in the large test-tube and record in Table 2.1 the temperature to the nearest half degree for experiment 1. • Add ten marble chips to the acid. • Connect the delivery tube to the large test-tube making sure that the tube goes up into the measuring cylinder as in Fig. 2.1. • Start the stopclock. • When one minute is shown on the stopclock read the volume V1 of gas collected in the measuring cylinder. • Record in Table 2.1 this volume V1 for experiment 1. • When two minutes is shown on the stopclock read the volume V2 of gas collected in the measuring cylinder. • Record in Table 2.1 this volume V2 for experiment 1. [2] Table 2.1 experiment temperature of volume of gas volume of gas volume of gas acid / °C after one minute after two minutes produced in V1 / cm3 V2 / cm3 second minute V / cm3 1 2 3 (ii) experiment 2 • Pour the contents of the large test-tube into the beaker labelled waste. • Rinse out the large test-tube with water. • Refill the inverted measuring cylinder with water and replace the tube as in Fig. 2.1. • Remove some water from the water container if it is close to overflowing. • Using a measuring cylinder, place 20 cm3 of hydrochloric acid into the large test-tube. • Place the large test-tube containing the acid in a beaker of hot water. • When the temperature of the acid in the large test-tube is about 10 °C above the temperature for experiment 1, record in Table 2.1 this temperature to the nearest half degree for experiment 2. • Immediately remove the large test-tube from the beaker of hot water and add ten unused marble chips to the acid. • Connect the delivery tube to the large test-tube making sure that the tube goes up into the measuring cylinder as in Fig. 2.1. • Start the stopclock. • When one minute is shown on the stopclock read the volume V1 of gas collected in the measuring cylinder. • Record in Table 2.1 this volume V1 for experiment 2. • When two minutes is shown on the stopclock read the volume V2 of gas collected in the measuring cylinder. • Record in Table 2.1 this volume V2 for experiment 2. [2] (iii) experiment 3 Repeat (a)(ii), increasing the temperature of the acid by a further 10 °C. You may need to replace the hot water in the beaker. [2] (b) (i) For each experiment calculate the volume V of gas produced during the second minute. Record your values in Table 2.1. [1] (ii) Use your data to describe the relationship between the temperature of the acid and the rate of the reaction. ........................................................................................................................................... .......................................................................................................................................[1] (c) Suggest an alternative method for measuring the rate of reaction between marble chips and acid. You may draw a labelled diagram but you must state what is being measured. ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ...............................................................................................................................................[2] Please turn over for Question 3.

Mark scheme: 2(a)(i) temperature recorded and within 5 °C of supervisor’s value ; both volumes recorded and V2 > V1 ; 2 2(a)(ii) temperature recorded for experiment 2 and 8–12 °C above the temperature for experiment 1; both volumes recorded and both greater than those in (a)(i) ; 2 2(a)(iii) temperatures for experiment 3 recorded and to nearest half degree ; V1 and V2 for experiment 3 greater than V1 and V2 for experiment 2 ; 2 2(b)(i) all values of V correct ; 1 2(b)(ii) the higher the temperature the higher the rate of the reaction ; 1 Question Answer Marks 2(c) bubble into water ; count bubbles in a certain time / time for certain number of bubbles ; or connect delivery tube to a gas syringe ; measure volume in a certain time / time for a certain volume ; or place reaction flask on a balance ; measure mass (decrease) in a certain time / time for certain drop in mass ; 2

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3 You are going to find the density of water. You are provided with a test-tube, a balance, a measuring cylinder and a beaker containing water. (a) (i) Use the balance to measure the mass m of the test-tube to the nearest 0.1 g. m = ................................................... g [1] (ii) Pour approximately 65 cm3 of water from the beaker into the measuring cylinder. Record the volume V1 of water on the scale of the measuring cylinder. V1 = ............................................... cm3 [1] (iii) Slowly and carefully lower the test-tube into the measuring cylinder until it floats, approximately vertically, as shown in Fig. 3.1. The test-tube should not touch the bottom of the measuring cylinder. Fig. 3.1 Record the new volume V2 of water on the scale of the measuring cylinder. V2 = ............................................... cm3 [2] (iv) Use your volume values from (a)(ii) and (a)(iii) to calculate the volume V3 of water displaced by the test-tube. V3 = ............................................... cm3 [1] (v) Calculate the density d of the water using your values from (a)(i) and (a)(iv), using the equation below. Include the unit in your answer. m d = V3 d = ............................................... unit ............................ [2] (b) (i) Suggest two possible sources of inaccuracy in this experiment. 1. ....................................................................................................................................... 2. ....................................................................................................................................... [2] (ii) State and explain the effect that one of the sources of inaccuracy you gave in (b)(i) would have on the calculated value of d. ........................................................................................................................................... ........................................................................................................................................... .......................................................................................................................................[1]

Mark scheme: 3(a)(i) m present and to 0.1 g ; 1 3(a)(ii) V1 present and 65 ± 5 (cm3) ; 1 3(a)(iii) V2 present ; V2 > V1 ; 2 3(a)(iv) calculation correct ; 1 3(a)(v) calculation correct and 2 / 3 sig fig ; g / cm3 ; 2 3(b)(i) any 2 from ; not reading to bottom of meniscus not reading perpendicular to scale of measuring cylinder / not eye level test tube touching the side of cylinder / how the test-tube floats zero error on balance max 2 3(b)(ii) state effect on V or m and hence effect on d2 ; 1

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