Cambridge A Level Physical Science 8780 — 2014 Oct/Nov Paper 4 · Variant 1

This document consists of 13 printed pages and 3 blank pages. DC (CW/KN) 84453/8 © UCLES 2014 [Turn over Cambridge International Examinations Cambridge International Advanced Subsidiary Level * 9 1 1 9 8 2 8 6 1 4 * PHYSICAL SCIENCE 8780/04 Paper 4 Advanced Practical Skills October/November 2014 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 or graphs. Do not use staples, paper clips, 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. Electronic calculators may be used. You are advised to show all working in calculations. Use of a Data Booklet is unnecessary. Qualitative Analysis Notes are printed on pages 13 and 14. 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/14 © UCLES 2014 [Turn over 1 In this experiment you will investigate the variation of current from a power supply with resistance in the external circuit. You are provided with a selection of networks of eight different resistance values. Each of the networks should be made up of a combination of resistors of identical resistance. However, it is suspected that one of the resistors has a different resistance. (a) Set up the circuit shown in Fig. 1.1. Connect the 5 Ω network between X and Y. A power supply + – Y X Fig. 1.1 Record the value of the current I through the ammeter. … A

4 8780/04/O/N/14 © UCLES 2014 (b) (i) Construct a suitable table to record the resistance R of each of the eight resistor networks and the corresponding current I. You should include a column in which to record the values of 1 I . (ii) Record, in the table, your first values of I and R from part (a). (iii) Change the resistor network and measure the new current I. Record the new values for R and I in your table. Repeat until all eight sets of readings are taken. Remove each resistor network from the circuit immediately after taking each reading. (iv) Calculate and record the value of 1 I for each measurement of I. (c) (i) On the grid provided, plot your values of 1 I on the y-axis and R on the x-axis. Draw the straight line of best fit. (ii) Calculate the gradient of the graph. Show your working. gradient = … (iii) Use your graph to determine the value of I when R is zero. I … A

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6 8780/04/O/N/14 © UCLES 2014 (d) The relationship between I and R is of the form 1 I = R E + k where E and k are constants. Determine the value of the emf of the power supply E. Give the unit. E = … unit … (e) (i) From your graph, identify the network that contains a resistor of a different resistance from the others. (ii) Test the resistors in this network to find the resistor which has a different resistance from the others. Draw this network and label the resistor which has the different resistance with the letter W. (iii) Determine the resistance of resistor W. Briefly explain how you obtained this value. resistance = … Ω explanation … … … [Total: 15]

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8 8780/04/O/N/14 © UCLES 2014 2 You are provided with solution P, which contains iron ions, another cation and one anion. (a) Test portions of solution P for the presence of chloride and sulfate ions. Use no more than a total of 5 cm3 for these two tests. Retain the remainder of solution P for further tests. Record the tests and your observations in the table below. test observations

9 8780/04/O/N/14 © UCLES 2014 [Turn over (b) Carry out the tests described below. Record all observations. test observations (i) Transfer 1 cm depth of solution P into a clean test-tube. Add 5 drops of aqueous sodium hydroxide. Add a further 1 cm depth of aqueous sodium hydroxide. Pour freshly boiled (very hot) water into a 500 cm3 beaker until it is about one quarter full. Place the test-tube in this beaker for at least 2 minutes. Test for any gas evolved. (ii) Transfer 1 cm depth of solution P into a clean test-tube. Add 1 cm depth of solution Z. Retain the remainder of solution P for use in (b)(iii).

10 8780/04/O/N/14 © UCLES 2014 test observations (iii) To the flask containing the remaining solution P add 20 cm3 of hydrochloric acid. Then add 10 cm3 of hydrogen peroxide. This is solution Q. (iv) Transfer 1 cm depth of solution Q into a clean test-tube. Add 5 drops of aqueous sodium hydroxide. Add a further 1 cm depth of aqueous sodium hydroxide. (v) Transfer 1 cm depth of solution Q into a clean test-tube. Add 1 cm depth of solution Z and leave to stand for 30 seconds. Retain the remainder of solution Q for use in (b)(vi).

11 8780/04/O/N/14 © UCLES 2014 [Turn over test observations (vi) To the flask containing the remaining solution Q add 3 pieces of granulated zinc. Empty the 500 cm3 beaker and refill with freshly boiled (very hot) water until it is about one quarter full. Place the flask in this beaker for about 3 minutes. Do not test the gas evolved. The flask now contains solution R. (vii) Transfer 1 cm depth of solution R into a clean test-tube. Add 5 drops of aqueous sodium hydroxide. Add a further 1 cm depth of aqueous sodium hydroxide. (viii) Transfer 1 cm depth of solution R into a clean test-tube. Add 1 cm depth of solution Z.

12 8780/04/O/N/14 © UCLES 2014 (c) conclusions (i) Identify the three ions present in solution P. In each case give evidence to support your conclusion. … … … … … … (ii) Suggest the role played by hydrogen peroxide in (b)(iii) and the role played by zinc in (b)(vi). In each case give evidence to support your suggestion. role of hydrogen peroxide … evidence … … … role of zinc … evidence … … … (iii) State and explain what is happening to the iron ions in (b)(i). … … … [Total: 15]

13 8780/04/O/N/14 © UCLES 2014 [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 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

14 8780/04/O/N/14 © UCLES 2014 2 Reactions of anions ion reaction carbonate, CO3 2– CO2 liberated by dilute acids chloride, Cl – (aq) gives white ppt. with Ag+(aq) (soluble in NH3(aq)) bromide, Br – (aq) gives pale cream ppt. with Ag+(aq) (partially soluble in NH3(aq)) iodide, I – (aq) gives yellow ppt. with Ag+(aq) (insoluble in NH3(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) sulfi te, 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, Cl 2 bleaches damp litmus paper hydrogen, H2 “pops” with a lighted splint oxygen, O2 relights a glowing splint sulfur dioxide, SO2 turns acidifi ed aqueous potassium manganate(VII) from purple to colour- less

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® IGCSE is the registered trademark of Cambridge International Examinations. CAMBRIDGE INTERNATIONAL EXAMINATIONS Cambridge International Advanced Subsidiary Level MARK SCHEME for the October/November 2014 series 8780 PHYSICAL SCIENCE 8780/04 Paper 4 (Advanced Practical Skills), 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 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 2014 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 International AS Level – October/November 2014 8780 04 © Cambridge International Examinations 2014 1 (a) current reading (no mark) (b) (i) table headings with correct units: R / Ω; I / A; 1 / I / A–1 [1] accept brackets instead of / accept words instead of symbols (ii) record first values of R and I in table (no mark) (iii) 8 sets of readings recorded in table [1] all readings of I made to nearest 0.01 A and consistent [1] significant figures for 1 / I to the same number as for I and consistent [1] accept one more significant figure for 1 / I than given for I from graph: 6 points (not R = 25 Ω) within 1 / I = 0.2 of line [1] (iv) calculation of 1 / I correct for each measurement of I [1] [6] (c) (i) graph: both axes labelled with sensible scales and at least ½ grid used [1] do not accept awkward scales – 3, 7, etc. at least 7 points plotted to within ± ½ small square [1] best straight line drawn [1] (ii) correct substitution into gradient formula and triangle used over at least ½ drawn line [1] (iii) correct read-off of intercept and reciprocal [1] [5] (d) use of E = 1 / gradient [1] [1] expect 5.4 V to 6.5 V unit required (accept A Ω) accept a method using readings from the graph substituted in the equation (e)(i)(ii) correct identification of odd resistor network [1] (iii) correct value of odd resistor [1] explanation of how sections of network were tested to identify odd resistor [1] [3] OR by calculation [Total: 15]

Page 3 Mark Scheme Syllabus Paper Cambridge International AS Level – October/November 2014 8780 04 © Cambridge International Examinations 2014 2 (a) silver nitrate and no / very faint precipitate [1] do not allow addition of aqueous ammonia before the silver nitrate barium nitrate/chloride and white precipitate [1] [2] accept a named soluble lead salt for the reagent (b) (i) green/greenish precipitate [1] *turns brown (on heating / standing) [1] correct test for ammonia with litmus or indicator paper [1] (ii) dark blue precipitate / colouration / solution [1] (iii) solution turns brown / browny-yellow / yellow [1] (iv) brown / dark brown / brown-red precipitate [1] (v) turns blue / dark blue [1] (vi) solution turns yellow / yellow green [1] (vii) greenish/green precipitate [1] *turns brown (on heating / standing) [1] (viii) blue precipitate/colouration/solution [1] [7] *this mark can be awarded in EITHER (b)(i) or (b)(vii) but NOT both MAXIMUM 7 MARKS FOR PART (b) (c) (i) iron(II) with correct evidence [1] ammonium with correct evidence [1] sulfate with correct evidence [1] (ii) hydrogen peroxide is an oxidising agent with correct evidence [1] zinc is a reducing agent with correct evidence [1] allow one mark if BOTH oxidising and reducing agents identified with no or incomplete evidence (iii) (iron(II) changes to iron(III) by) air oxidation [1] [6] [Total: 15]