Cambridge A Level Physical Science 8780 — 2016 Oct/Nov Paper 4 · Variant 1

This document consists of 10 printed pages and 2 blank pages. DC (NH/CGW) 119530/5 © UCLES 2016 [Turn over * 2 6 7 2 5 9 0 3 9 6 * PHYSICAL SCIENCE 8780/04 Paper 4 Advanced Practical Skills October/November 2016 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 9 and 10. 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. Cambridge International Examinations Cambridge International Advanced Subsidiary Level For Examiner’s Use 1 2 Total Session Laboratory

2 8780/04/O/N/16 © UCLES 2016 1 In this experiment you will investigate how the period T of a pendulum changes as the distance d between two points is varied. The period T is the time for one complete oscillation of the pendulum. You have been provided with the apparatus shown in Fig. 1.1. You have also been provided with a metre rule and a stopwatch. rod stand stand bob rod d Fig. 1.1 You will determine the time t for 20 complete oscillations of the pendulum for six different values of distance d. (a) Construct a suitable table in the space below to record all your results for d and t. Include columns for d 2, T and T 4. [1]

3 8780/04/O/N/16 © UCLES 2016 [Turn over (b) (i) Adjust the position of the stands so that d is approximately 35 cm. (ii) Record the value of d to the nearest 0.1 cm in your table in (a). Calculate d 2 and record it in your table. [1] (iii) Pull the bob a short distance towards you and release it. This will set the bob swinging with small oscillations. Measure the time t for 20 complete oscillations and record this in your table. Record t to the nearest 0.1 s. Calculate T and T 4 and record these in your table. [1] (c) Repeat (b)(ii) and (b)(iii) with five different values of d up t o about 90 cm. Record all results in your table. [5] (d) On the grid below, plot a graph of T 4 on the y-axis against d 2 on the x-axis. Start your axes at (0,0). Draw the best-fit line. [4]

4 8780/04/O/N/16 © UCLES 2016 (e) (i) Use your graph to determine the gradient of the line. Show clearly how you determined the gradient. gradient = … [1] (ii) Use your graph to determine the value of T when d is zero. T = …s [2] [Total: 15]

5 8780/04/O/N/16 © UCLES 2016 [Turn over 2 (a) You are provided with a solution of sodium carbonate, Na2CO3. (i) Carry out the following procedure and record your observations in the table below. procedure observations Use a 25 cm3 measuring cylinder to transfer 25 cm3 of the sodium carbonate solution into the beaker labelled Q. Use a different measuring cylinder to add 75 cm3 of 1.00 mol dm–3 sulfuric acid to the beaker labelled Q. Stir the mixture with the glass rod. The beaker now contains solution Q. (ii) The equation for the reaction between sodium carbonate and sulfuric acid is shown. Na2CO3 + H2SO4 → Na2SO4 + CO2 + H2O Use this equation to explain one of your observations recorded in (a)(i). … … … [1]

6 8780/04/O/N/16 © UCLES 2016 (b) (i) Solution Q contains an excess of sulfuric acid. You are going to carry out titrations to find the concentration of sulfuric acid in solution Q. • Fill a clean burette with solution Q. • Use the pipette to transfer 25.0 cm3 of 0.500 mol dm–3 sodium hydroxide to a clean conical flask. • Add a few drops of methyl orange indicator to the flask. • The end-point is the formation of the first permanent orange/red colour. • Carry out sufficient titrations to obtain consistent results. Record below, in a suitable form, all your burette readings and the volume of solution Q added in each titration. Record your results to a suitable level of precision. [4]

7 8780/04/O/N/16 © UCLES 2016 [Turn over (ii) From your titration results, obtain an average volume of solution Q added. Show clearly how you obtained this volume. average volume of solution Q added = … cm3 [1] (c) (i) Suggest a significant source of error in making solution Q. … … [1] (ii) Suggest and explain one way of reducing this source of error. … … … … [1] (d) (i) The equation for the reaction between sulfuric acid and sodium hydroxide is shown. H2SO4 + 2NaOH → Na2SO4 + 2H2O Calculate the concentration of sulfuric acid in solution Q. Show your working and give your answer to an appropriate number of significant figures. concentration = … mol dm–3 [3] (ii) Calculate the amount, in moles, of sulfuric acid in 100 cm3 of solution Q. amount of sulfuric acid = …mol [1]

8 8780/04/O/N/16 © UCLES 2016 (iii) Calculate the amount, in moles, of sulfuric acid that reacted with 25.0 cm3 of the sodium carbonate solution. [75 cm3 of 1.00 mol dm–3 sulfuric acid contains 0.075 moles of sulfuric acid.] amount of sulfuric acid = …mol [1] (iv) Use your answer to (d)(iii) to calculate the mass of Na2CO3 in 25.0 cm3 of the sodium carbonate solution. [Na, 23.0; C, 12.0; O, 16.0] mass of Na2CO3 = …g [2] [Total: 15]

9 8780/04/O/N/16 © UCLES 2016 [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

10 8780/04/O/N/16 © UCLES 2016 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

11 8780/04/O/N/16 © UCLES 2016 BLANK PAGE

12 8780/04/O/N/16 © UCLES 2016 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. To avoid the issue of disclosure of answer-related information to candidates, all copyright acknowledgements are reproduced online in the Cambridge International Examinations Copyright Acknowledgements Booklet. This is produced for each series of examinations and is freely available to download at www.cie.org.uk after the live examination series. 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. BLANK PAGE

® IGCSE is the registered trademark of Cambridge International Examinations. This document consists of 3 printed pages. © UCLES 2016 [Turn over Cambridge International Examinations Cambridge International Advanced Subsidiary Level PHYSICAL SCIENCE 8780/04 Paper 4 Advanced Paper October/November 2016 MARK SCHEME Maximum Mark: 30 Published 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 2016 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 2016 8780 04 © UCLES 2016 1 (a) table with headings and all units [1] (b) (ii) value of d between 30 cm and 40 cm [1] (iii) (initial T =) t / 20 [1] (c) 6 recordings of d and t [1] minimum 5 values of d approximately evenly spaced and maximum value between 85 to 95 cm [1] minimum 5 sets of reading for d and t and all readings recorded to 0.1cm and 0.1 s [1] all calculated d 2 and T 4 calculated correctly from d and T values [1] all calculated d 2 and T 4 to consistent number of significant figures and consistent number of significant figures with d and T values [1] (d) axes labelled and sensible linear scales [1] all accurately plotted within ±½ small square and minimum 5 points plotted [1] best-fit line [1] quality of measurements [1] (e) (i) method for determining gradient shown [1] (ii) correct T 4 value from intercept from graph on y-axis [1] correct T from intercept [1] [Total: 15] 2 (a)(i),(ii) bubbles / fizz / effervescence and carbon dioxide formed [1] or colourless solution and all ions/named ions colourless or gets hot and exothermic reaction (b) (i) suitable recording of readings with units [1] all readings to 0.00 or 0.05 cm3 [1] 2 concordant readings within 0.1 [2] 2 concordant readings within 0.2, scores 1 mark

Page 3 Mark Scheme Syllabus Paper Cambridge International AS Level – October/November 2016 8780 04 © UCLES 2016 (ii) calculation of average using concordant volumes [1] (c) (i) measuring cylinder used to measure solutions in (a) [1] (ii) use a pipette and / or a burette for greater precision [1] (d) (i) moles of NaOH = 0.0125 [1] moles H2SO4 = 0.00625 [1] divides nH2SO4 by average titre [1] (ii) divides nH2SO4 by 10 [1] (iii) moles of reacted acid = 0.075 – answer to (d)(ii) [1] (iv) Mr = 106 [1] nNaCO3 = 106 × answer to (d)(iii) [1] [Total: 15]