Cambridge IGCSE Science - Combined 0653 — 2015 Oct/Nov Paper 6 · Variant 2

This document consists of 19 printed pages and 1 blank page. IB15 11_0653_62/FP © UCLES 2015 [Turn over *5868575649* Cambridge International Examinations Cambridge International General Certificate of Secondary Education COMBINED SCIENCE 0653/62 Paper 6 Alternative to Practical October/November 2015 1 hour Candidates answer on the Question Paper. No Additional Materials are required. READ THESE INSTRUCTIONS FIRST Write your Centre number, candidate number and name on all the work you hand in. Write in dark blue or black pen. You may use an HB pencil for any diagrams or graphs. Do not use staples, paper clips, glue or correction fluid. DO NOT WRITE IN ANY BARCODES. Answer all questions. Electronic calculators may be used. You may lose marks if you do not show your working or if you do not use appropriate units. At the end of the examination, fasten all your work securely together. The number of marks is given in brackets [ ] at the end of each question or part question.

2 © UCLES 2015 0653/62/O/N/15 1 A student carries out some tests to determine the food groups present in rice and milk. (a) (i) Complete the second row of Table 1.1 to show which food group each test is able to identify. [3] (b) Milk gives a positive result with Benedict’s reagent and biuret reagent. Rice gives a positive result with biuret reagent and iodine solution. Complete Table 1.1 to show the colours observed for these positive results. [3] Table 1.1 reagent Benedict’s biuret iodine food group identified colour with milk at end of test orange colour with rice at end of test blue (c) (i) Describe how you could carry out the test for the presence of fats in a food. [2] (ii) State what is observed if the result of the test in (c)(i) is positive. [1] (iii) Suggest why the test you have described in (c)(i) may be difficult to carry out on the milk. [1]

3 © UCLES 2015 0653/62/O/N/15 [Turn over 2 The teacher gives a student samples of a calcium salt. The student will carry out four experiments. (a) Fig. 2.1 shows the apparatus for experiment 1. Read the instructions for the experiment which are shown below the diagram. heat strongly hard-glass test-tube calcium salt Fig. 2.1 Place a sample of the calcium salt in a hard-glass test-tube. Heat the test-tube strongly. Test the gas that evolved to see if it will burn in air. Experiment 1 Describe how the student can find out if the gas will burn in air. test result [1]

4 © UCLES 2015 0653/62/O/N/15 (b) Fig. 2.2 shows the apparatus for experiment 2. Read the instructions for the experiment which are shown below in the diagram. hydrochloric acid calcium salt limewater Fig. 2.2 To the calcium salt add dilute hydrochloric acid. Test the gas evolved using limewater. Experiment 2 (i) Draw a diagram to show how the student can test the gas coming out of the test-tube using limewater. State the positive result for this test. result [2] (ii) Name the gas that gives the positive result in (b)(i). [1] (c) Experiment 2 gives a positive result with limewater. Name this calcium salt. [1]

5 © UCLES 2015 0653/62/O/N/15 [Turn over (d) Fig. 2.3 shows the apparatus for experiment 3. Read the instructions for the experiment which are shown below the diagram. heat gently dilute nitric acid calcium salt Fig. 2.3 Add dilute nitric acid to a fresh sample of the calcium salt. Warm the test-tube gently. Test the gas that evolves to see if it is acidic. Experiment 3 (i) Describe how the student can test if the gas is acidic. test result [2] (ii) Explain why the test-tube must be warmed gently rather than heated strongly. [1]

6 © UCLES 2015 0653/62/O/N/15 (e) The teacher gives the student two acids of the same concentration, acid Y and acid Z. Fig. 2.4 shows the apparatus for experiment 4. Read the instructions for the experiment which are shown below the diagram. acid Y acid Z calcium salt Fig. 2.4 Add equal volumes of the two acids to the same masses of calcium salt. Compare the speeds of the two reactions. Experiment 4 Suggest how the student can use the gas produced by each reaction to compare the speeds of the reactions. You may draw a diagram to illustrate your answer. [2]

7 © UCLES 2015 0653/62/O/N/15 [Turn over 3 A student is investigating different components in a circuit. He sets up the apparatus shown in Fig. 3.1. He then carries out an experiment to measure the resistance of the power supply. A V power supply X resistance wire ruler crocodile clip d Fig. 3.1 Procedure • Connect the crocodile clip to the resistance wire at a distance d = 15 cm from point X. • Close the switch. • Read the ammeter and voltmeter and then immediately open the switch. • Record the readings in Table 3.1. • Repeat this procedure for the other distances from point X shown in Table 3.1.

8 © UCLES 2015 0653/62/O/N/15 (a) Fig. 3.2 shows the ammeter and voltmeter readings for the distances d = 25 and d = 40 cm. Read the meters to a suitable number of decimal places and record the readings in Table 3.1. V 1.0 2.0 0 A 0.5 1 0 V 1.0 2.0 0 A 0.5 1 0 d = 25 cm d = 25 cm d = 40 cm d = 40 cm Fig. 3.2 [3] Table 3.1 distance d / cm current I / amps potential difference V / volts 15 0.97 0.9 20 0.81 1.0 25 40 60 0.34 1.3 100 0.22 1.4

9 © UCLES 2015 0653/62/O/N/15 [Turn over (b) (i) On the grid provided, plot a graph of V against I. Draw the best-fit straight line. [2] potential difference V / V 0 0.2 0.4 0.6 0.8 current I / A 1.0 0.1 0.3 0.5 0.7 0.9 1.1 1.2 2.4 2.2 2.0 1.8 1.6 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0 (ii) Calculate the gradient of your line. Show all working and indicate on your graph the values you chose to enable the gradient to be calculated. gradient = [2] (iii) The positive value of the gradient of the graph is equal to the resistance of the power supply. Write the positive value of the gradient to an appropriate number of significant figures. resistance of power supply = Ω [1]

10 © UCLES 2015 0653/62/O/N/15 (c) (i) Suggest a reason why distance d must not be less than 15 cm. [1] (ii) Suggest a reason why the student must open the switch immediately after taking each reading. [1]

11 © UCLES 2015 0653/62/O/N/15 [Turn over 4 In a flower, ripe stigmas produce a fluid containing sugar. The sugar stimulates pollen grains that land on a stigma to grow pollen tubes. These pollen tubes allow the nucleus from the pollen to travel to the egg (ovum) in the ovary so that fertilisation can take place. Pollen tubes can be observed using a light microscope. Fig. 4.1 shows a photograph of some of these pollen tubes. pollen tube pollen grain X Y Z 0.2 mm Fig. 4.1 (a) Measure and record the total length of the pollen tube as indicated by the line X-Y-Z on Fig. 4.1. With the help of the scale bar on the side of Fig. 4.1, calculate the actual length of the pollen tube. Show your working. Total length of pollen tube on image (X-Y-Z) = mm [2] Actual length of X-Y-Z = mm [2]

12 © UCLES 2015 0653/62/O/N/15 (b) A student investigates the effect of different strength sugar solutions on the growth of pollen tubes. • He places a drop of sugar solution on a microscope slide and adds pollen grains to it. • He leaves the slide in a warm place for an hour and then looks at the slide using the microscope. • He counts the number of pollen grains that he can see and then calculates the percentage that have pollen tubes. His results are shown in Table 4.1. Table 4.1 concentration of sugar solution (mol / dm3) % of pollen grains with pollen tubes experiment 1 experiment 2 experiment 3 average 0 0 0 0 0 0.25 36 28 32 0.50 72 68 76 0.75 49 41 45 1 10 7 13 Complete the last column of Table 4.1. [1]

13 © UCLES 2015 0653/62/O/N/15 [Turn over (c) (i) Use Table 4.1 to plot on the grid below a graph of average percentage of pollen grains with tubes (vertical axis) against sugar concentration. Draw a best-fit curve. [4] (ii) Use your graph to suggest the best concentration of sugar for pollen tube growth. [1]

14 © UCLES 2015 0653/62/O/N/15 5 A group of students investigate some of the chemical and physical properties of iron, Fe. Chemical properties One student places iron nails into test-tubes, as shown in Fig. 5.1, and leaves them for one week. test-tube 3 test-tube 2 test-tube 1 tap water tap water boiled water iron nail iron nail layer of wax painted iron nail Fig. 5.1 (a) (i) State how the appearance of the nail in test-tube 1 changes after one week. [1] (ii) Describe the appearance of the nail in test-tube 2 after one week. [1] (iii) Explain why there is no change to the nail in test-tube 3 after one week. [1] (b) Another student adds hydrochloric acid to iron filings. He notices that bubbles of gas are formed. (i) He carries out a test that confirms the gas is hydrogen. Describe the test he uses and the observation. test observation [1]

15 © UCLES 2015 0653/62/O/N/15 [Turn over (ii) The iron dissolves, making a light green solution. The student thinks that the green solution contains iron(II) ions. Explain how he proves the presence of iron(II) ions in the green solution. [1] (iii) The student takes some of the green solution and adds a colourless oxidising agent. The mixture changes colour. The teacher says that the iron(II) ions have been changed to iron(III) ions. State the colour of the mixture containing iron(III) ions. [1] (iv) Explain how the student proves the presence of iron(III) ions in this mixture. [1]

16 © UCLES 2015 0653/62/O/N/15 (c) Physical properties A student uses the apparatus in Fig. 5.2 to investigate how a thick metal wire changes shape when a force is applied to it. thick wire slotted masses rule Fig. 5.2 Describe a procedure, using this apparatus, that the student can carry out to compare a wire made of iron with a wire made of steel (an alloy of iron). Explain how you can ensure that this is a fair comparison. [3]

17 © UCLES 2015 0653/62/O/N/15 [Turn over 6 A student has samples of three different liquids, A, B and C. He carries out an experiment to compare the densities of these liquids. The apparatus he uses is shown in Fig. 6.1. liquid A mark on test-tube water is slowly added water Fig. 6.1 Method • He makes a mark on a test-tube. • He holds the test-tube upright in the beaker and slowly adds water to it, drop by drop, until it floats in the beaker of liquid A and the mark on the test-tube is level with the surface of liquid A. • He pours the water from the test-tube into a measuring cylinder and records the volume in Table 6.1. • He repeats the experiment using liquids B and C.

18 © UCLES 2015 0653/62/O/N/15 (a) Name the piece of apparatus that the student could use to add water, drop by drop, to the test-tube in Fig. 6.1. [1] (b) The liquid which requires the greatest volume of water in the test-tube is the most dense. Fig. 6.2 shows the volume of water contained in each test-tube when it floats in liquids A, B and C. 20 15 10 5 20 15 10 5 20 15 10 5 liquid A liquid B liquid C Fig. 6.2 (i) Record, in Table 6.1, each volume of water to the nearest 0.5 cm3. Table 6.1 liquid A liquid B liquid C volume of water / cm3 [3] (ii) Use the results from Table 6.1 to place the liquids A, B, and C in order of density. most dense least dense [1]

19 © UCLES 2015 0653/62/O/N/15 (c) The teacher tells the student that one of the three liquids is water. Suggest one chemical test and one physical test that the student can use to identify the water. chemical test physical test [2] (d) Another student uses two pieces of apparatus to measure two properties of the sample of liquid A which he can use to calculate the density of liquid A. (i) Suggest the names of two pieces of apparatus that he uses and the property measured by each by completing the sentences. The student uses a to measure the of the sample of liquid A. The student uses a to measure the of the sample of liquid A. [2] (ii) State how the student uses the two measurements to calculate the density of liquid A. [1]

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® IGCSE is the registered trademark of Cambridge International Examinations. CAMBRIDGE INTERNATIONAL EXAMINATIONS Cambridge International General Certificate of Secondary Education MARK SCHEME for the October/November 2015 series 0653 COMBINED SCIENCE 0653/62 Paper 6 (Alternative to Practical), maximum raw mark 60 This mark scheme is published as an aid to teachers and candidates, to indicate the requirements of the examination. It shows the basis on which Examiners were instructed to award marks. It does not indicate the details of the discussions that took place at an Examiners’ meeting before marking began, which would have considered the acceptability of alternative answers. Mark schemes should be read in conjunction with the question paper and the Principal Examiner Report for Teachers. Cambridge will not enter into discussions about these mark schemes. Cambridge is publishing the mark schemes for the October/November 2015 series for most Cambridge IGCSE®, Cambridge International A and AS Level components and some Cambridge O Level components.

Page 2 Mark Scheme Syllabus Paper Cambridge IGCSE – October/November 2015 0653 62 © Cambridge International Examinations 2015 1 (a) Benedict’s: (reducing) sugar ; biuret: protein ; iodine: starch ; [3] (b) Benedict’s biuret iodine green / yellow / orange / red ; purple / lilac (orange) (blue) purple / lilac (both) ; blue-black / black ; [3] (c) (i) dissolve in / mix with ethanol ; [2] add water ; (ii) cloudy / milky / white emulsion ; [1] (iii) milk is white / milky / cannot see the result / AW ; [1] [Total: 10] 2 (a) apply a lighted splint / flame AND gas ignites / a flame is seen ; [1] (b) (i) suitable diagram of CO2 passing into limewater ; white ppt. ./ white / milky ; [2] (ii) carbon dioxide ; [1] (c) calcium carbonate / calcium hydrogencarbonate ; [1] (d) (i) litmus paper / pH paper / universal indicator (in the vapour) ; blue to red (blue can be line above) ; OR full range indicator / universal indicator / pH indicator ; red / orange / yellow ; [max 2] (ii) to avoid ejection of hot acid / to avoid vapour of nitric acid / to avoid acid touching the paper ; [1] (e) connect a gas syringe to the tube / collect in measuring cylinder over water / counting bubbles (in water) ; find the volume of gas evolved in a fixed time / time taken to give out a certain volume of gas / number of bubbles in a fixed time / time taken for a certain number of bubbles ; [2] [Total: 10]

Page 3 Mark Scheme Syllabus Paper Cambridge IGCSE – October/November 2015 0653 62 © Cambridge International Examinations 2015 3 (a) d = 25 cm: 0.69 (amps) ; d = 40 cm: 0.48 (amps) ; 1.1 and 1.2 both required (volts, for d = 25 and 40 cm respectively) ; [3] (b) (i) points correctly plotted ± ½ small square (allow one error) ; straight line drawn ; [2] (ii) indication on graph of how data obtained AND at least half of line used ; correct calculation for triangle method using data from graph ; [2] (iii) 0.67 or 0.7 ; [1] (c) (i) the ammeter reading will be off the scale / current greater than 1A / the ammeter may be damaged ; [max 1] (ii) the wire will heat up / (so that) the resistance (of the wire) will be changed ; [1] [Total: 10] 4 (a) (i) 39 ± 2 (mm) ;; [2] (OR (for max 1): 39 ± 4 (mm) or 3.9 ± 0.2 / (cm)) (ii) shows measurement of the scale bar in working 20 mm ± 1 mm ; answer = 0.4 (mm) ; [2] (b) 32 72 45 10 (all four numbers to be correct) ; [1] (c) (i) axes labelled with units; suitable linear scale; at least 4 plots correct ± half small square; best-fit line peaking at or above 0.5 mol / dm3 ; [4] (ii) read from peak of graph ± half small square ; [1] [Total: 10] 5 (a) (i) rusty ; [1] (ii) the nail has not rusted / no change ; [1] (iii) the paint excludes air / oxygen / water / cannot react with air / oxygen / water / prevents oxidation ; [1]

Page 4 Mark Scheme Syllabus Paper Cambridge IGCSE – October/November 2015 0653 62 © Cambridge International Examinations 2015 (b) (i) lighted splint AND pops ; [1] (ii) (add aqueous) ammonia / sodium hydroxide AND green precipitate ; [1] (iii) yellow / orange / brown / red-brown ; [1] (iv) (add aqueous ammonia / sodium hydroxide and) orange / red-brown / brown precipitate ; [1] (c) hang mass from iron wire AND steel wire ; measure deflection / bend / distance with the ruler; use wires of same thickness / same length ; [3] [Total: 10] 6 (a) (teat) pipette / dropper ; [1] (b) (i) A: 16.5 ; B: 8.0 ; C: 11.5 ; [3] (ii) A C B ; [1] (c) (anhydrous) copper sulfate / cobalt chloride ; boiling / freezing point / melting point ; [2] (d) (i) measuring cylinder (to measure) volume ; balance / scale(s) (to measure) mass ; [2] (ii) the mass is divided by the volume / volume mass ; [1] [Total: 10]