Cambridge A Level Physical Science 8780 — 2015 Oct/Nov Paper 4 · Variant 1

This document consists of 11 printed pages and 1 blank page. DC (NH/FD) 104147/4 © UCLES 2015 [Turn over * 0 9 5 5 1 0 8 9 1 8 * PHYSICAL SCIENCE 8780/04 Paper 4 Advanced Practical Skills October/November 2015 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 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. Cambridge International Examinations Cambridge International Advanced Subsidiary Level For Examiner’s Use 1 2 Total Session Laboratory

2 8780/04/O/N/15 © UCLES 2015 1 When a marble is dropped into sand it makes a crater in the sand. In this experiment you will measure the diameter of the craters made when a marble is dropped from known heights into sand. (a) Measure and record the diameter d of the marble. d = … cm [1] (b) The apparatus shown in Fig. 1.1 is set up for you. Do not alter or adjust this apparatus. You are also given a 30 cm ruler, a set square and some additional sand to top up the tray if necessary. Use the 30 cm ruler to level the sand between each set of readings. clamp marble metre rule clamp stand clamp bench tray K sand level with top of tray Fig. 1.1 (i) Hold the marble above the sand so that the bottom of the marble is approximately level with the 65 cm mark on the metre rule. Record the height h1, the distance from the bottom of the marble to the sand. Record all the measurements taken to show how you determined h1. h1 = …[1]

3 8780/04/O/N/15 © UCLES 2015 [Turn over (ii) Drop the marble into the sand. The sand will have a profile similar to that shown in Fig. 1.2. marble sand [ Fig. 1.2 (iii) Measure and record the diameter x1 of the crater. x1 = … cm (iv) Carefully remove the marble and use the 30 cm ruler to level the sand with the top edge of the tray. (v) Drop the marble from the same height h1 twice more and find the average diameter of the crater xAV1 using all three readings. Record all your results and show your working. xAV1 = … cm [1] (vi) Subtract the diameter of the marble d from the average diameter of the crater xAV1. This quantity is y1, where y1 = xAV1 − d. y1 = … cm (c) Repeat the steps in (b), dropping the marble from height h2, where h2 is between 25 cm and 35 cm. h2 = …cm xAV2 = …cm y2 = … cm [2]

4 8780/04/O/N/15 © UCLES 2015 (d) Describe the steps you took to ensure that your readings for h and x were as accurate as possible. (i) height h … … … …[1] (ii) diameter of the crater x … … … …[1] (e) Table 1.1 shows the uncertainties in some of the quantities measured. Table 1.1 diameter of marble d / cm height h / cm diameter of crater x / cm y = (x – d) / cm uncertainty ± 0.1 ± 0.2 (i) Estimate the uncertainty in measuring height h. Record your estimate in Table 1.1. [1] (ii) Calculate the uncertainty in y. Record your answer in Table 1.1. [1] (iii) Calculate the percentage uncertainty in y. percentage uncertainty in y = …% [1]

5 8780/04/O/N/15 © UCLES 2015 [Turn over (f) It is suggested that y2 = Kh, where K is a constant. Use the uncertainties in Table 1.1 to show whether or not your results support this suggestion. … …[4] (g) Describe how you would verify that y2 is proportional to h. … … …[1] [Total: 15]

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7 8780/04/O/N/15 © UCLES 2015 [Turn over 2 You are to investigate the energy change when 2.00 mol dm–3 sodium hydroxide is reacted with dilute sulfuric acid. The experiment you will perform is known as a thermometric titration. (a) Place a polystyrene cup into the 250 cm3 beaker to prevent it from falling over. (i) Use the pipette and pipette filler to transfer 25.0 cm3 of sodium hydroxide solution into the polystyrene cup. Stir the solution with the thermometer. Measure and record the temperature T of the solution. T …°C (ii) You will be adding portions of sulfuric acid to the sodium hydroxide solution. Construct a table to record 12 sets of readings of the total volume of acid VT added and the temperature T of the solution. Record the information from (a)(i) in your table. [3] (iii) Fill the burette with dilute sulfuric acid. (iv) Add about 4 cm3 of the acid to the sodium hydroxide solution. Stir thoroughly with the thermometer and measure the temperature. Record in your table, to an appropriate level of precision, the total volume of acid added and the temperature. (v) Add a further ten portions of sulfuric acid until a total of about 44 cm3 has been added. Measure the temperature of the solution after each addition. Record all the readings in your table to an appropriate level of precision.

8 8780/04/O/N/15 © UCLES 2015 (b) (i) Plot a graph of temperature T (y-axis) against the total volume of sulfuric acid added VT (x-axis) on the grid provided. Use the points you have plotted to draw two best-fit curves. Draw a best-fit curve for the points as the temperature rises. Draw a second best-fit curve for the points as the temperature falls. Extend the curves until they cross each other. The point where the curves cross is the neutral point of the titration. [3] (ii) Use your graph to determine 1. the volume of sulfuric acid VN needed to exactly neutralise 25.0 cm3 of the sodium hydroxide solution, VN = …cm3 [1] 2. the temperature rise ΔT caused by the reaction. ΔT = …°C [1] (iii) Use your answer to (b)(ii)1 to calculate the concentration of the sulfuric acid. concentration of sulfuric acid …mol dm–3 [1] (c) The enthalpy change for the reaction shown below is known as the enthalpy change of neutralisation ΔHN. H+(aq) + OH–(aq) → H2O(l) ΔHN is the enthalpy change when one mole of hydroxide ions, OH–, exactly neutralises one mole of H+ ions.

9 8780/04/O/N/15 © UCLES 2015 [Turn over Question 2 continues on the next page

10 8780/04/O/N/15 © UCLES 2015 (i) Use the formula below to calculate the thermal energy change q for your thermometric titration. q = mcΔT Assume that the density of the reaction mixture is 1.00 g cm–3 and that its specific heat capacity c is 4.18 J g–1 °C–1. q = … J [2] (ii) Use your answers to (b)(iii) and (c)(i) to calculate a value for the energy change of neutralisation, ΔHN. ΔHN … kJ mol–1 [2] (d) (i) Suggest the main source of error in your thermometric titration experiment. … … (ii) Suggest what effect the main source of error would have on ΔT. … … … (iii) Suggest what effect the main source of error would have on ΔHN. … … … [2] [Total: 15]

11 8780/04/O/N/15 © UCLES 2015 [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

12 8780/04/O/N/15 © UCLES 2015 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 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.

® IGCSE is the registered trademark of Cambridge International Examinations. CAMBRIDGE INTERNATIONAL EXAMINATIONS Cambridge International Advanced Subsidiary Level MARK SCHEME for the October/November 2015 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 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 International AS Level – October/November 2015 8780 04 © Cambridge International Examinations 2015 1 (a) supervisor’s result ± 1 mm and recorded to 1 decimal place [1] [1] (b) (i) evidence that the sand level and the reading on metre rule of bottom of the ball are taken and h = 65.0 cm – depth of sand cm [1] [1] (v) three total readings recorded and average calculated correctly [1] [1] (c) height: (h) between 25( cm) and 35 (cm) and x average is smaller than in (b)(v) (and ˃ d) [1] quality: both sets of results within a range ± 0.5 cm [1] [2] (d) (i) idea of use of set square / use of horizontal edge / use of a perpendicular edge [1] [1] (ii) idea of use of splints or very close to sand OR idea of multiple measurements of diameter from a single drop and take average [1] [1] (e) (i) inclusive range: [1] [1] (±) 0.2 to 0.5 (cm) (ii) (±) 0.3 (cm) [1] [1] (iii) (±) value in (e)(ii) divided by value for either y1 or y2 × 100 or divided by average of y1 and y2 × 100 and correct calculation [1] [1]

Page 3 Mark Scheme Syllabus Paper Cambridge International AS Level – October/November 2015 8780 04 © Cambridge International Examinations 2015 (f) calculation of one value of K from values of y and h [1] calculation of a second value of K [1] sensible attempt to use absolute uncertainty in either K value [1] suitable conclusion (comparing the two experiments) using (uncertainty) values i.e. two K values overlap [1] [4] Alternative method: calculation of one value of K from values of y and h (1) substitution of K to find y2 OR [y2]2 OR h2 (1) sensible attempt to use absolute uncertainty in either y or h (1) suitable conclusion (comparing the two experiments) using (uncertainty) values i.e. two K values overlap (1) (g) take more sets of readings and calculate or compare K (for each) OR plot a graph of y 2 against h [1] [1] 2 (a) (ii) suitable table with correct headings and units with headings [1] 12 sets of results with approximately even spacing between volumes [1] appropriate precision and consistency in readings [1] [3] (b) (i) sensible linear scales on BOTH axes and at least half grid used and axes labelled [1] correct plotting [1] two (intersecting) curves of best fit [1] [3] (ii) reading of volume from graph intersection [1] reading of temperature from graph intersection minus the starting temperature [1] [2] (iii) (correct calculation of concentration of sulfuric acid) ratio of 25 cm3 divided by volume of H2SO4 from graph [1] [1]

Page 4 Mark Scheme Syllabus Paper Cambridge International AS Level – October/November 2015 8780 04 © Cambridge International Examinations 2015 (c) (i) use of correct combined mass and correct temperature [1] correct calculation of q [1] [2] (ii) number of moles of NaOH or sulfuric acid [1] correct calculation of energy change for 1 mol [1] [2] (d) (i) inaccurate volume measurement of sodium hydroxide / energy transferred to the surroundings [1] [1] (ii),(iii) correct suggestion for effect on ∆T OR correct suggestion for effect on ∆HN [1] [1]