Cambridge IGCSE Physical Science 0652 — 2019 Oct/Nov Paper 5 · Variant 1

1 You are going to investigate the thermal energy produced when a neutralisation reaction occurs. (a) • Use a measuring cylinder to measure 25 cm3 aqueous hydrochloric acid and place it into a small beaker. • Measure the temperature of the 25 cm3 aqueous hydrochloric acid to the nearest 0.5 °C and record this value at time 0 seconds in Table 1.1. • Rinse the measuring cylinder with distilled water and use it to measure 25 cm3 aqueous sodium hydroxide. • Add the 25 cm3 aqueous sodium hydroxide to the hydrochloric acid in the beaker, start the stopclock and stir the mixture. • Measure the temperature of the mixture in the beaker every 30 seconds for 5 minutes. Record the temperatures to the nearest 0.5 °C in Table 1.1. [3] Table 1.1 time / s temperature / °C 0 30 60 90 120 150 180 210 240 270 300 (b) (i) Plot a graph of temperature (vertical axis) against time on the grid provided. [3] (ii) • Draw the best-fit straight line for the increasing temperatures. • Draw the best-fit straight line for the decreasing temperatures. • Extend both lines until they cross. This is the actual highest temperature reached in the reaction. Record this highest temperature. highest temperature reached = .................................................... °C [2] (c) The temperature rise of the reaction is the highest temperature reached minus the temperature at time 0 seconds. The thermal energy produced by this reaction can be calculated by the equation: thermal energy produced = 50 × 4.2 × temperature rise Calculate the thermal energy produced in this reaction. thermal energy produced = ...................................................... J [1] (d) The calculated amount of thermal energy produced in your experiment is much lower than the expected value. Suggest two different reasons why your value for the thermal energy produced is lower than the expected value. For each reason, suggest how the experiment can be changed to improve the accuracy. The changes must be possible using apparatus found in a school or college laboratory. reason 1 .................................................................................................................................... ................................................................................................................................................... improvement 1 .......................................................................................................................... ................................................................................................................................................... reason 2 .................................................................................................................................... ................................................................................................................................................... improvement 2 .......................................................................................................................... ................................................................................................................................................... [2] (e) In this experiment, the amount of sodium hydroxide exactly neutralises the amount of hydrochloric acid. Neither of the reagents is in excess. The equation for the reaction is: HCl + NaOH NaCl + H2O A student repeats the experiment but replaces the hydrochloric acid with 25 cm3 of sulfuric acid, which has the same concentration as the hydrochloric acid. The equation for this reaction is: H2SO4 + 2NaOH Na2SO4 + 2H2O Suggest a value for the amount of thermal energy produced in this reaction, based on your result in (c). Explain your suggestion. thermal energy produced = ................................... J explanation ............................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... [2] [Total: 13] Question 2 begins over the page

Mark scheme: 1(a) 11 temperatures recorded ; All temperatures to nearest 0.5 °C ; Temperatures increase and decrease ; 3 1(b)(i) both axes labelled and linear ; plotted points cover ⩾ ½ grid space ; all points plotted correctly ± ½ small square ; 3 1(b)(ii) two best-fit lines, drawn with a ruler ; highest temperature recorded ± ½ small square from any 2 lines that cross ; 2 1(c) correct calculation from their highest temperature ; 1 1(d) any two: reason 1: measuring cylinder used improvement: use a burette / pipette / syringe ; reason 2: heat loss improvement: use a lid / lag or insulate it / use a polystyrene cup ; reason 3: thermometer not accurate enough improvement: use a data logger / thermometer with a better resolution ; 2 1(e) same as 1(c) ; same amount / 25 cm3 NaOH / H2SO4 in excess / there are 2 H's in sulfuric acid ; 2

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2 You are given two substances, solid compound A and solution B. You are going to perform a series of tests to identify A and B. (a) Record the appearance of solid A. • Add 20 cm3 distilled water and stir well. Record the appearance of the solution of A. appearance of solid A ............................................................................................................... appearance of the solution of A ................................................................................................ [1] (b) • Put 2 cm depth of the solution of A into each of 4 test-tubes. • To the first test-tube, add a few drops of nitric acid followed by a few drops of aqueous silver nitrate. • To the second test-tube, add a few drops of nitric acid followed by a few drops of aqueous barium nitrate. • To the third test-tube, add aqueous sodium hydroxide until it is in excess. • To the fourth test-tube, add a wooden splint and leave to soak for use in (b)(ii). (i) Record the observations for the first three tests in Table 2.1. Table 2.1 test observation nitric acid and aqueous silver nitrate nitric acid and aqueous barium nitrate aqueous sodium hydroxide [2] (ii) • Place the wooden splint from the fourth test-tube into a blue flame. Record the immediate flame colour. flame colour ................................................................................................................. [1] (iii) Suggest the name of compound A. ............................................................................. [1] (c) • Put 2 cm depth of solution B into a test-tube. • Add the solution of A until it is in excess. Record your observations and identify solution B. observations ............................................................................................................................. ................................................................................................................................................... ................................................................................................................................................... identity of solution B ................................................................................................................. [2] [Total: 7]

Mark scheme: 2(a) white / grey(solid) and blue (solution) ; 1 2(b)(i) no change / no ppt / stays blue and white ppt ; (pale) blue ppt ; 2 2(b)(ii) blue-green ; 1 2(b)(iii) copper sulfate ; 1 2(c) (dark blue solution and (pale)) blue ppt (on excess) ; ammonia (solution) ; 2

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3 You are going to calculate the density of soft modelling clay. You will use two different methods to find its volume. (a) Finding the mass • Flatten the soft modelling clay to make a disc shape which is approximately 5 cm in diameter. • Set up the metre rule and pivot as shown in Fig. 3.1. • Place the pivot under the 50.0 cm mark on the rule. • Place the soft modelling clay on the rule so that its centre is at the 10.0 cm mark on the rule. • Place the 50.0 g mass on the metre rule and adjust its position so that the rule is as close to being balanced as possible. soft modelling 50.0 g mass clay 50.0 cm mark metre rule 0 cm 100 cm 10.0 cm P Fig. 3.1 (i) Determine and record the position P of the centre of the 50.0 g mass on the ruler. P = ................................................... cm [1] (ii) Calculate the mass m of the soft modelling clay. Use the equation: m = 1.25(P–50.0) m = ...................................................... g [1] (iii) It is difficult to obtain an accurate value of the mass of the modelling clay using this method. State one difficulty in this method. ........................................................................................................................................... ........................................................................................................................................... ..................................................................................................................................... [1] (b) Finding the volume – method 1 • Roll the soft modelling clay into a ball. • Use the wooden blocks to help you measure the diameter of the ball. • Measure the diameter d1 of the ball. (i) Record d1. d1 = ................................................... cm [1] (ii) Draw a labelled diagram to show how you used the wooden blocks to help you measure the diameter of the soft modelling clay ball. [1] (iii) • Measure the diameter in two more places on the ball. Record these measurements as d2 and d3. Use your value of d1 from part (b)(i) and the values of d2 and d3 to calculate dav, the average of the three diameter measurements d1, d2 and d3. d2 = ......................................................... cm d3 = ......................................................... cm dav = ......................................................... cm [1] (iv) Calculate the volume V1 of the soft modelling clay. Use the equation: V1 = 0.52dav3 Give your answer to a suitable number of significant figures. V1 = .................................................. cm3 [2] (v) Use your values from (a)(ii) and (b)(iv) to calculate the density ρ1 of the modelling clay. Use the equation: m ρ1 = V1 ρ1 = .............................................. g / cm3 [1] (c) Finding the volume – method 2 • Check that the measuring cylinder provided contains 50.0 cm3 of water. • Gently submerge the soft modelling clay into the water inside the measuring cylinder. (i) Record the new volume V2 shown by the measuring cylinder. V2 = .................................................. cm3 [1] (ii) Calculate volume V3 of the soft modelling clay. Use the equation: V3 = V2 – 50 V3 = .................................................. cm3 [1] (iii) Use your answers from (a)(ii) and (c)(ii) to calculate another density value ρ2 of the soft modelling clay. Use the equation: m ρ2 = V3 ρ2 = .............................................. g / cm3 [1] (d) Suggest which method of measuring the volume of the soft modelling clay is more accurate. Explain your answer. method ...................................................................................................................................... explanation ............................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... [1] [Total: 13]

Mark scheme: 3(a)(i) sensible value for P (likely to be 80.0 cm) 1 3(a)(ii) calculation correct 1 3(a)(iii) any one: difficult to ensure rule is perfectly balanced : centre of soft modelling clay may not be exactly on 10 cm mark ; cannot see / read the marks on the rule ; centre of mass of rule not at 50 cm mark ; difficult to find centre of 50 g mass ; difficult to keep pivot under the 50 cm mark / the pivot slips ; 1 3(b)(i) sensible value for d1 (likely to be 3.2 cm) ; 1 3(b)(ii) diagram showing wooden blocks touching either side of soft modelling clay ball (and metre rule against blocks) ; 1 3(b)(iii) (sensible values for d2 and d3) calculation correct – must use all 3 values ; 1 3(b)(iv) calculation correct ; to 2 / 3 sig figs ; 1 1 3(b)(v) calculation correct ; 1 3(c)(i) sensible value for V3 (likely to be 70 cm3) ; 1 3(c)(ii) calculation correct ; 1 3(c)(iii) calculation correct ; 1 3(d) method 1: measuring cylinder only measures to the nearest ½ cm3 is not very accurate ; method 2: calculation in method 1 assumes a perfect sphere / shape / difficulty in balancing / difficulty in locating position of centres of the masses ; 1

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4 A student investigates how the length of a pendulum affects its period. The period of a pendulum is the time it takes for one complete (to and fro) oscillation as shown in Fig. 4.1. 1 complete oscillation is the time taken for the bob to swing from A to B and back to A again. pendulum bob A B 1 complete oscillation Fig. 4.1 Plan an experiment to investigate the relationship between the length l of a pendulum and its period T as shown in Fig. 4.2. l pendulum bob Fig. 4.2 You can assume you have access to school or college laboratory equipment. Your plan should include: • any additional apparatus needed • a brief description of the method, including number and range of pendulum lengths to use • the measurements you will make • the variables to control • the precautions you will take to ensure that the results are as accurate as possible • the table you will draw to record your results, with column headings (you are not required to enter any readings into the table). 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Mark scheme: 4 1 mark from each ‘MP’ section and any two other marking points from any section. 1 MP section missing – 6 max 2 MP sections missing – 5 max etc. MP1 apparatus stopwatch / clock / timer and rule(r) / measuring tape ; MP2 method measure length (of pendulum) ; measure time for 1 (or more complete) swings / measure the period ; for different lengths ; MP3 control variables same bob / mass of bob / volume of bob ; same angle of swing / displace bob the same distance ; MP4 precautions for accuracy time (5 / 10 (or more) oscillations and divide / take an average ; ruler close to pendulum / string when measuring ; view reading / ruler at eye level / perpendicular (to scale) ; repeat each reading ; use of a fiducial aid explained ; MP5 table table with headings of length and time / period / number of swings ; with units cm / m and s / sec(s) / seconds ; 7

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