Cambridge A Level Physical Science 8780 — 2011 Oct/Nov Paper 4 · Variant 1

This document consists of 11 printed pages and 1 blank page. DC (CW/CGW) 36356/3 © UCLES 2011 [Turn over UNIVERSITY OF CAMBRIDGE INTERNATIONAL EXAMINATIONS General Certificate of Education Advanced Subsidiary Level * 5 8 9 8 2 4 7 0 6 2 * PHYSICAL SCIENCE 8780/04 Paper 4 Advanced Practical Skills October/November 2011 1 hour 30 minutes Candidates answer on the Question Paper. Additional Materials: As listed in the Confidential Instructions READ THESE INSTRUCTIONS FIRST Write your Centre number, candidate number and name on all the work you hand in. Give details of the practical session and laboratory where appropriate, in the boxes provided. 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 both questions. You will be allowed to work with the apparatus for a maximum of 45 minutes for each question. You are advised to show all working in calculations. Use of a Data Booklet is unnecessary. Qualitative Analysis Notes are printed on pages 11 and 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. For Examiner’s Use 1 2 Total Session Laboratory

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3 8780/04/O/N/11 © UCLES 2011 [Turn over For Examiner’s Use 1 You are going to investigate the deflection h of a cantilevered hacksaw blade. You are provided with the apparatus shown in Fig. 1.1. bench G-clamp blocks of wood mass M hacksaw blade 50 cm rule h l Fig. 1.1 (a) (i) Measure and record the length l and deflection h. l = … h = … (ii) Estimate the absolute uncertainty in your value of h. uncertainty = … [1]

4 8780/04/O/N/11 © UCLES 2011 For Examiner’s Use (b) You are going to measure h at five further values of l between 25.0 and 10.0 cm. (i) Construct a table in which to record all six sets of measurements of l and h. Include a column for values of l 2. (ii) Record your first values of l and h from part (a) in the table. (iii) Loosen the clamp to slide the ruler and hacksaw blade to a new position. Retighten the clamp. Measure and record the new values of l and h. Repeat until six sets of measurements are completed. (iv) Calculate and record values for l 2. [6] (c) (i) On the grid provided, plot your values of h on the y-axis against l 2 on the x-axis. (ii) Decide whether the best-fit line is a curve or a straight line. Draw the best-fit line. (iii) Calculate the gradient of the graph when l 2 = 225 cm2. Show your working. gradient = …

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6 8780/04/O/N/11 © UCLES 2011 For Examiner’s Use (d) (i) Describe one significant source of error or limitation of the procedure in this experiment. … … … (ii) Suggest one improvement that could be made to the experiment and explain why your suggestion would improve the accuracy of the final answer. You may suggest the use of other apparatus or different procedures. … … … … (iii) A student suggests that the deflection h is directly proportional to l 2. Discuss whether your results support this hypothesis. … … … … [3] [Total: 15]

7 8780/04/O/N/11 © UCLES 2011 [Turn over For Examiner’s Use 2 You are provided with an acid Y and two samples of a solid X, labelled A and B. Solid X is a hydrated metal salt. Carry out the following tests to enable you to identify acid Y and both the ions present in solid X. Record your observations in the spaces provided. (a) Strongly heat sample A of solid X. Test any gas evolved both with a glowing splint and with limewater. Record your observations for each gas test. Describe the appearance of the solid during and after heating. glowing splint … limewater … appearance of solid … …[2]

8 8780/04/O/N/11 © UCLES 2011 For Examiner’s Use (b) When solid X reacts with acid Y, the temperature of the mixture changes. Follow the instructions below to add a known mass of solid X to an excess of acid Y, and measure the change in temperature. (i) Use the measuring cylinder to transfer 50 cm3 of acid Y into the polystyrene cup. (ii) Stir the acid with the thermometer and measure its temperature to 0.1 °C. Record this temperature in Table 2.1. (iii) Record the mass of sample B of solid X in Table 2.1. Carefully add all of the sample B into the cup. Add only a little at a time to prevent excess frothing. (iv) When all of sample B has been added, stir the mixture and measure the highest temperature reached. Record this in Table 2.1. (v) The mixture in the cup is solution Z. Label it and retain it for use in parts (c) and (d). (vi) Calculate the temperature change ΔT, and record it in Table 2.1. Table 2.1 mass of solid X / g initial temperature / °C final temperature / °C temperature change ΔT / °C [2] (c) (i) Place about 1 cm depth of solution Z into a clean test-tube. Add five drops of aqueous barium nitrate. Record your observations. … (ii) Place about 1 cm depth of solution Z into a clean test-tube. Add five drops of aqueous silver nitrate. Record your observations. … [1]

9 8780/04/O/N/11 © UCLES 2011 [Turn over For Examiner’s Use (d) (i) Put ten drops of solution Z into a clean test-tube. Add a few drops of aqueous ammonia and shake. Repeat until no further changes are seen. Record your observations. … … … (ii) Put ten drops of solution Z into a clean test-tube. Add a few drops of sodium hydroxide and shake. Repeat until no further changes are seen. Record your observations. … … … [3] (e) Identify acid Y and two ions in solid X. acid Y = … ions in X = … and …[2] (f) (i) Calculate the value for the enthalpy change Q for the reaction in part (b), using Q = m c ΔT. Assume that the mass m of solution Z is 50 g and that the solution has a specific heat capacity c of 4.2 J g–1 K–1. Q = …

10 8780/04/O/N/11 © UCLES 2011 For Examiner’s Use (ii) Use the mass of solid X from Table 2.1 and your answer from part (f)(i) to calculate the enthalpy change when 1 mole of solid X reacts with excess acid Y. [Relative formula mass of X = 341] enthalpy change = … kJ mol–1 [3] (g) (i) State one significant source of error in the experiment in part (b). … … … (ii) Explain how the value of the enthalpy change calculated in (f)(ii) is affected by this source of error. … … … (iii) Suggest an improvement to reduce the effect of this source of error. … … … [2] [Total: 15]

11 8780/04/O/N/11 © UCLES 2011 [Turn over Qualitative Analysis Notes Key: [ppt. = precipitate] 1 Reactions of aqueous cations reaction with NaOH(aq) NH3(aq) aluminium, Al3+(aq) white ppt. soluble in excess white ppt. insoluble in excess ammonium, NH4 +(aq) no ppt. ammonia produced on heating barium, Ba2+(aq) no ppt. (if reagents are pure) no ppt. calcium, Ca2+(aq) white ppt. with high [Ca2+(aq)] no ppt. chromium(III), Cr3+(aq) grey-green ppt. soluble in excess giving dark green solution grey-green ppt. insoluble in excess copper(II), Cu2+(aq) pale blue ppt. insoluble in excess blue ppt. soluble in excess giving dark blue solution iron(II), Fe2+(aq) green ppt. turning brown on contact with air insoluble in excess green ppt. turning brown on contact with air insoluble in excess iron(III), Fe3+(aq) red-brown ppt. insoluble in excess red-brown ppt. insoluble in excess lead(II), Pb2+(aq) white ppt. soluble in excess white ppt. insoluble in excess magnesium, Mg2+(aq) white ppt. insoluble in excess white ppt. insoluble in excess manganese(II), Mn2+(aq) off-white ppt. rapidly turning brown on contact with air insoluble in excess off-white ppt. rapidly turning brown on contact with air insoluble in excess zinc, Zn2+(aq) white ppt. soluble in excess white ppt. soluble in excess [Lead(II) ions can be distinguished from aluminium ions by the insolubility of lead(II) chloride.]

12 8780/04/O/N/11 © UCLES 2011 2 Reactions of anions ion reaction carbonate, CO3 2– CO2 liberated by dilute acids chromate(VI), CrO4 2– (aq) yellow solution turns orange with H+(aq); gives yellow ppt. with Ba2+(aq); gives bright yellow ppt. with Pb2+(aq) chloride, Cl– (aq) gives white ppt. with Ag+(aq) (soluble in NH3(aq)); gives white ppt. with Pb2+(aq) bromide, Br– (aq) gives pale cream ppt. with Ag+(aq) (partially soluble in NH3(aq)); gives white ppt. with Pb2+(aq) iodide, I– (aq) gives yellow ppt. with Ag+(aq) (insoluble In NH3(aq)); gives yellow ppt. with Pb2+(aq) nitrate, NO3 – (aq) NH3 liberated on heating with OH–(aq) and Al foil nitrite, NO2 – (aq) NH3 liberated on heating with OH–(aq) and Al foil, NO liberated by dilute acids (colourless NO → (pale) brown NO2 in air) sulfate, SO4 2– (aq) gives white ppt. with Ba2+(aq) or with Pb2+ (insoluble in excess dilute strong acid) sulfite, SO3 2– (aq) SO2 liberated with dilute acids; gives white ppt. with Ba2+(aq) (soluble in excess dilute strong acid) 3 Tests for gases gas test and test result ammonia, NH3 turns damp red litmus paper blue carbon dioxide, CO2 gives a white ppt. with limewater (ppt. dissolves with excess CO2) chlorine, Cl2 bleaches damp litmus paper hydrogen, H2 “pops” with a lighted splint oxygen, O2 relights a glowing splint sulfur dioxide, SO2 turns acidified aqueous potassium dichromate(VI) (aq) from orange to green 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.

UNIVERSITY OF CAMBRIDGE INTERNATIONAL EXAMINATIONS GCE Advanced Subsidiary Level MARK SCHEME for the October/November 2011 question paper for the guidance of teachers 8780 PHYSICAL SCIENCE 8780/04 Paper 4, 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 October/November 2011 question papers for most IGCSE, GCE Advanced Level and Advanced Subsidiary Level syllabuses and some Ordinary Level syllabuses.

Page 2 Mark Scheme: Teachers’ version Syllabus Paper GCE AS LEVEL – October/November 2011 8780 04 © University of Cambridge International Examinations 2011 1 MMO (a) (ii) 0.1 cm or 0.2 cm [1] (b) 6 different sets of readings [1] range: at least from 25.0 – 10.0 cm, no gaps greater than 3.5 cm unless skewed for ℓ 2 [1] quality: h increases consistently as ℓ increases (check from graph) [1] PDO (b) all columns headed, ℓ/cm, h/cm, ℓ 2/cm2 [1] all raw data in a column to same precision [1] the calculated column correct and ℓ2 to same number, or 1 more, significant figures as ℓ [1] ACE (c) (i) axes labelled, sensible scales chosen (at least half graph paper used and no awkward scales) [1] 6 points plotted correctly [1] (ii) best-fit straight line or curve for candidate’s data [1] (iii) attempt to measure gradient using at least ½ range of data and dy/dx / tangent drawn if necessary [1] correct calculation of gradient [1] (d) (i) suitable limitation: e.g. parallax error in reading h or oscillation [1] (ii) suitable improvement, e.g. clamping ruler, repeat AND calculate average [1] (iii) suitable argument, consistent with graph [1] (acceptable answers: no because it’s a curve; no because the straight line does not go through the origin; yes because it’s a straight line through the origin) [Total: 15]

Page 3 Mark Scheme: Teachers’ version Syllabus Paper GCE AS LEVEL – October/November 2011 8780 04 © University of Cambridge International Examinations 2011 2 (a) MMO/PDO goes out/does not relight AND cloudy/milky/chalky/white precipitate [1] yellow when hot/during heating AND white when cold/cools down [1] (b) MMO/PDO two temperature readings to 0.1/0.05 0C [1] accuracy mark [1] (compare m/∆T with Supervisor’s) (c) MMO/PDO white precipitate AND no reaction/no precipitate [1] (d) MMO/PDO white precipitate with ammonia [1] white precipitate with sodium hydroxide [1] dissolves in excess in BOTH [1] (e) ACE sulfuric [1] zinc AND carbonate [1] (these conclusions must be consistent with the observations recorded) (f) ACE correct calculation of Q [1] correct use of mass and molar mass [1] correct use of units [1] (g) ACE suitable source of error / valid improvement [1] explanation of how it affects enthalpy change [1] [Total: 15]