Cambridge IGCSE Science - Combined 0653 — 2012 May/June Paper 5 · Variant 3

This document consists of 10 printed pages and 2 blank pages. IB12 06_0653_53/FP © UCLES 2012 [Turn over *0594931566* For Examiner's Use 1 2 3 Total UNIVERSITY OF CAMBRIDGE INTERNATIONAL EXAMINATIONS International General Certificate of Secondary Education COMBINED SCIENCE 0653/53 Paper 5 Practical Test May/June 2012 1 hour 30 minutes Candidates answer on the Question Paper. Additional Materials: As listed in Instructions to Supervisors. 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 a pencil for any diagrams, graphs or rough working. Do not use staples, paper clips, highlighters, glue or correction fluid. DO NOT WRITE IN ANY BARCODES. Answer all questions. Chemistry practical notes for this paper are printed on page 12. 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. www.XtremePapers.com

2 © UCLES 2012 0653/53/M/J/12 For Examiner's Use 1 You are going to test the effect of light on the chemical composition of leaves. You are provided with two leaves from two separate plants of the same species. Leaf A has been removed from a plant that has been in strong light for a period of 24 hours. Leaf B has been removed from a plant that has been kept in the dark for 48 hours. • Half fill a 250 cm3 beaker with water. Heat the water with a Bunsen burner until it is boiling. • Turn off the Bunsen burner. • Pick up leaf A with a pair of tweezers (forceps) and hold it in the hot water for 15 seconds. • Using the tweezers place the leaf into the bottom of the large test-tube labelled A. • Repeat the above procedure for leaf B, but place the leaf into the bottom of the large test-tube labelled B. • Cover the leaves with alcohol and place the tubes A and B, into the beaker of hot water (water bath) for 5 minutes. The Bunsen burner must not be lit. • Carefully remove both tubes from the water bath and pour off the alcohol into the waste beaker. (a) (i) Describe the colour of the alcohol that you have poured off from the tubes. Suggest what substance from the leaf has dissolved in the alcohol to produce the colour you have described. colour substance [2] (ii) ● Remove the leaves from the tubes with tweezers and hold them in the water bath for 2 to 3 seconds. • Place the leaves into the separate petri dishes (or onto the white tiles) labelled A and B. Use the tweezers to lay them flat and cover both leaves with iodine solution. Leave for about 2 minutes. • Wash off the excess iodine solution with cold water. Pour any excess liquid into the waste beaker. • Observe and record the colour of the leaves in Table 1.1. • The colour of each leaf suggests a substance that may be present or absent in it. Use your observation to make a conclusion about each leaf. Record your conclusion in Table 1.1.

3 © UCLES 2012 0653/53/M/J/12 [Turn over For Examiner's Use Table 1.1 leaf A leaf B colour of leaf after 2 minutes conclusion [3] (b) (i) Explain why leaves A and B were placed in boiling water before being placed in alcohol. [1] (ii) Why must the Bunsen burner be turned off before the tubes containing leaves and alcohol are immersed in the water bath? [1] (iii) Explain how light has caused the difference in colour, shown by the iodine test, between leaves A and B. [3]

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5 © UCLES 2012 0653/53/M/J/12 [Turn over For Examiner's Use 2 (a) You are going to find the cross-sectional area of a piece of resistance wire using the apparatus in Fig. 2.1 and Fig. 2.2. A V resistor switch 6 V + – Fig. 2.1 (i) ● Construct the circuit shown in Fig. 2.1. You will be connecting the crocodile clips to the resistance wire. ● Connect one crocodile clip at the 0 cm point on the rule, with most of the length of the wire pointing along the rule. This will become the point X shown on Fig. 2.2. X X Y Y 0 100 80 60 40 20 wire under test metre rule X Y A V resistor switch l 6 V + – Fig. 2.2 ● Complete the circuit by pressing the other crocodile clip firmly on to the resistance wire at point Y shown in Fig. 2.2. Make sure that the length, l, between point X and point Y is 20 cm. • Close the switch and read the current, I, on the ammeter and the potential difference, V, on the voltmeter. Record these readings in Table 2.1. [1] • Open the switch.

6 © UCLES 2012 0653/53/M/J/12 For Examiner's Use Table 2.1 length of wire, l / cm potential difference, V / volts current, I / amps resistance, R / ohms 20 40 60 80 100 (ii) Repeat the procedure described in (i), adjusting point Y so that the length, l, is 40 cm. Close the switch and read the current, I, on the ammeter and the potential difference, V, on the voltmeter. Record these readings in Table 2.1. [1] Open the switch. (iii) Repeat (i) for l = 60 cm, 80 cm and 100 cm. For each length, l, record the current, I, and the potential difference, V, in Table 2.1. [2] Open the switch. (iv) Calculate the resistance, R, of each length of the resistance wire and enter the values in Table 2.1. Use the formula below. resistance, V I R = [1]

7 © UCLES 2012 0653/53/M/J/12 [Turn over For Examiner's Use (b) (i) Plot a graph of resistance, R, (vertical axis) against length of wire, l. Draw a straight line of best fit. Your line should pass through the origin, (0,0). 16 14 12 10 8 6 4 2 0 0 20 40 length, l / cm resistance, R / ohms 60 80 100 [2] (ii) Find the gradient of the line and show clearly your working either on the graph or below. gradient = [2]

8 © UCLES 2012 0653/53/M/J/12 For Examiner's Use (iii) Calculate the cross-sectional area, C, of the resistance wire using the formula given below. 0.000 049 gradient C = C = cm2 [1]

9 © UCLES 2012 0653/53/M/J/12 [Turn over BLANK PAGE Please turn over for Question 3.

10 © UCLES 2012 0653/53/M/J/12 For Examiner's Use 3 Solid mixture A contains one cation and two anions. Use the following tests to identify them. (a) (i) ● Place the mixture A in a 100 cm3 beaker and add about 30 cm3 of distilled or deionised water. • Stir the mixture well. • Filter the mixture into the large test-tube for use in (b)(i) and (b)(ii). Keep the residue in the filter paper for use in (a)(ii). • Describe the colour of the residue and the filtrate. residue filtrate [2] (ii) Scrape a little of the residue (about one-tenth) from (a)(i) into a clean test-tube. Slowly add dilute hydrochloric acid using a teat pipette (or dropper), 1 cm3 at a time, until it has all dissolved. Record all your observations and make a conclusion about the anion present in the residue. Keep this solution for (a)(iii). observations conclusion [2] (iii) To the solution from (a)(ii) add aqueous sodium hydroxide using a teat pipette, 1 cm3 at a time, until there is no further change. Record your observations and conclusion about the cation in the residue from (a)(i). observations conclusion [2]

11 © UCLES 2012 0653/53/M/J/12 For Examiner's Use (b) (i) Place about 2 cm3 of the filtrate from (a)(i) into a clean test-tube. Add 5 drops of aqueous silver nitrate. Record your observations and conclusion. observations conclusion [2] (ii) Place about 2 cm3 of the filtrate from (a)(i) into a clean test-tube. Add about 1 cm3 of aqueous barium chloride. Record your observations and conclusion. observations conclusion [2]

12 Permission to reproduce items where third-party owned material protected by copyright is included has been sought and cleared where possible. Every reasonable effort has been made by the publisher (UCLES) to trace copyright holders, but if any items requiring clearance have unwittingly been included, the publisher will be pleased to make amends at the earliest possible opportunity. University of Cambridge International Examinations is part of the Cambridge Assessment Group. Cambridge Assessment is the brand name of University of Cambridge Local Examinations Syndicate (UCLES), which is itself a department of the University of Cambridge. © UCLES 2012 0653/53/M/J/12 CHEMISTRY PRACTICAL NOTES Test for anions anion test test result carbonate (CO3 2-) add dilute acid effervescence, carbon dioxide produced chloride (Cl -) [in solution] acidify with dilute nitric acid, then add aqueous silver nitrate white ppt. nitrate (NO3 -) [in solution] add aqueous sodium hydroxide then aluminium foil; warm carefully ammonia produced sulfate (SO4 2-) [in solution] acidify then add aqueous barium chloride or aqueous barium nitrate white ppt. Test for aqueous cations cation effect of aqueous sodium hydroxide effect of aqueous ammonia ammonium (NH4 +) ammonia produced on warming - copper(II) (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 colourless solution white ppt., soluble in excess giving a colourless solution Test for gases gas test and test results ammonia (NH3) turns damp red litmus paper blue carbon dioxide (CO2) turns limewater milky chlorine (Cl2) bleaches damp litmus paper hydrogen (H2) “pops” with a lighted splint oxygen (O2) relights a glowing splint

UNIVERSITY OF CAMBRIDGE INTERNATIONAL EXAMINATIONS International General Certificate of Secondary Education MARK SCHEME for the May/June 2012 question paper for the guidance of teachers 0653 COMBINED SCIENCE 0653/53 Paper 5, (Practical Test), maximum raw mark 30 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 must be read in conjunction with the question papers and the report on the examination. • Cambridge will not enter into discussions or correspondence in connection with these mark schemes. Cambridge is publishing the mark schemes for the May/June 2012 question papers for most IGCSE, GCE Advanced Level and Advanced Subsidiary Level syllabuses and some Ordinary Level syllabuses. www.XtremePapers.com

Page 2 Mark Scheme: Teachers’ version Syllabus Paper IGCSE – May/June 2012 0653 53 © University of Cambridge International Examinations 2012 1 (a) (i) green ; chlorophyll ; [2] (ii) A: blue-black / black / blue / violet ; B: brown / orange / yellow ; starch present in A AND starch absent in B ; [3] (b) (i) to soften leaf / to kill leaf ; [1] (ii) to prevent alcohol from igniting ; [1] (iii) photosynthesis occurred in leaf A ; due to light ; making starch / making glucose ; (or reverse argument for leaf B) [3] [Total: 10] 2 (a) (i) V and I reading for 20 cm, AND V and I same order of magnitude as supervisor, AND V greater than I ; [1] (ii) V and I reading for 40 cm, AND V greater than I ; [1] (iii) V and I readings for 60, 80 and 100 cm ; V increases and I decreases down the table ; [2] (iv) all R values calculated for 5 or 4 sets of readings to same number of decimal places ; [1] (b) (i) points: 4 points plotted correctly within ½ square ; line: best straight line passing through (0,0) within ½ square ; [2] (ii) working shown on graph or below graph ; gradient calculated correctly ; [2] (iii) cross-sectional area, C calculated correctly to 2 significant figures ; [1] [Total: 10]

Page 3 Mark Scheme: Teachers’ version Syllabus Paper IGCSE – May/June 2012 0653 53 © University of Cambridge International Examinations 2012 3 (a) (i) residue: green ; filtrate: colourless ; [2] (ii) observations: bubbles / fizzes / effervesces ; conclusion: carbonate / − 2 3 CO ; [2] (iii) observation: blue ppt ; conclusion: copper / Cu2+ / Cu(II) ; [2] (b) (i) observation: white ppt ; conclusion: chloride / − l C ; [2] (ii) observation: no change ; conclusion: not sulfate / not − 2 4 SO ; [2] [Total: 10]