Cambridge IGCSE Physical Science 0652 — 2024 Oct/Nov Paper 6 · Variant 1

1 A student investigates the neutralisation of the alkali aqueous sodium hydroxide by dilute hydrochloric acid. When methyl orange is added to aqueous sodium hydroxide it turns yellow. As dilute hydrochloric acid is added to the aqueous sodium hydroxide, the aqueous sodium hydroxide has just been neutralised when a permanent pink colour appears. M is a unit of concentration. The higher the value of M the higher the concentration. 2 M is two times more concentrated than 1 M. (a) Procedure The student: • puts 1.00 M dilute hydrochloric acid into a burette • records in Table 1.1 the initial reading on the burette to the nearest 0.05 cm3 • uses a measuring cylinder to measure 25 cm3 of 0.10 M aqueous sodium hydroxide and pours it into a clean conical flask • adds 5 drops of methyl orange indicator to the conical flask • slowly adds dilute hydrochloric acid to the sodium hydroxide in the conical flask with swirling until the pink colour of the indicator does not disappear • records in Table 1.1 this final reading on the burette. The apparatus is shown in Fig. 1.1. 45 46 47 48 49 50 burette conical flask hydrochloric acid sodium hydroxide and methyl orange indicator Fig. 1.1 The student repeats the procedure with 0.20 M, 0.40 M and 0.60 M aqueous sodium hydroxide instead of 0.10 M and uses the 1.00 M dilute hydrochloric acid in the burette. Table 1.1 concentration of aqueous sodium hydroxide 0.10 M 0.20 M 0.40 M 0.60 M initial reading of dilute hydrochloric acid 11.55 15.75 22.10 32.55 in burette / cm3 final reading of dilute hydrochloric acid 14.05 47.55 in burette / cm3 ............... ............... volume of dilute hydrochloric acid added 2.50 to the aqueous sodium hydroxide / cm3 ............... ............... ............... (i) The readings on the burette, when 0.20 M aqueous sodium hydroxide and 0.40 M aqueous sodium hydroxide are used, are shown in Fig. 1.2. cm3 cm3 31 20 32 21 33 22 0.20 M 0.40 M Fig. 1.2 Record in Table 1.1 these values to the nearest 0.05 cm3. [2] (ii) State the name of a piece of apparatus suitable for measuring the 25 cm3 of aqueous sodium hydroxide more accurately. ..................................................................................................................................... [1] (b) (i) Calculate the volume of dilute hydrochloric acid added for each concentration of aqueous sodium hydroxide. Record these values in Table 1.1. [2] (ii) Suggest one improvement to the procedure to give more confidence in the volume of dilute hydrochloric acid added. Explain why this improves the procedure. improvement ..................................................................................................................... ........................................................................................................................................... explanation ........................................................................................................................ ........................................................................................................................................... [2] (c) (i) On the grid, plot the data points of volume of dilute hydrochloric acid added (vertical axis) against concentration of aqueous sodium hydroxide. Start the axes at the origin (0,0). [3] (ii) Draw the best‑fit straight line. Extend the line until it crosses an axis. [2] (iii) State the relationship between concentration of aqueous sodium hydroxide and volume of dilute hydrochloric acid added. ........................................................................................................................................... ..................................................................................................................................... [1] (iv) Use your graph to predict the volume of 1.00 M dilute hydrochloric acid needed to exactly neutralise 25 cm3 of 0.50 M aqueous sodium hydroxide. Show on your graph how you arrived at your answer. volume of dilute hydrochloric acid = .................................................. cm3 [1] (v) Another student repeats this procedure but uses 2.00 M dilute hydrochloric acid in the burette instead of 1.00 M dilute hydrochloric acid. Draw a line on the grid to show the results the student gets. Label this line E. [2] [Total: 16]

Mark scheme: Question Answer Marks 1(a)(i) 20.70 ; 2 32.15 ; 1(a)(ii) (volumetric) pipette ; 1 1(b)(i) 4.95 and 10.05 ; 2 15.00 ; 1(b)(ii) repeat (and average) ; 2 can exclude / identify anomalies ; 1(c)(i) axes correct orientation and labelled with quantity and unit ; 3 suitable linear scales starting from the origin with the plotted points covering ⩾ ½ grid ; points plotted correctly ; 1(c)(ii) best-fit straight line ; 2 extended to an axis ; 1(c)(iii) concentration (of aqueous sodium hydroxide) is proportional to volume (of dilute hydrochloric acid added) ; 1 OR as concentration (of aqueous sodium hydroxide) increases the volume (of dilute hydrochloric acid added) increases ; 1(c)(iv) volume from graph and lines on graph to show volume ; 1 1(c)(v) line under the existing line ; 2 half the values ;

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2 A student investigates the solution made when dilute hydrochloric acid exactly neutralises aqueous sodium hydroxide. Procedure The student: • does a flame test on the solution • does a chloride test on the solution • identifies the solution as aqueous sodium chloride. (a) Describe how to do a flame test on the aqueous sodium chloride. State the colour of the flame the student observes. procedure for flame test ............................................................................................................ ................................................................................................................................................... ................................................................................................................................................... colour of flame .......................................................................................................................... [2] (b) Describe how to do a chloride test. State the observation for the positive result. procedure for chloride test ........................................................................................................ ................................................................................................................................................... ................................................................................................................................................... observation ............................................................................................................................... [2] [Total: 4]

Mark scheme: 2(a) soak / dip (wooden) splint / (nichrome) wire in solution and put in(to) a blue / roaring (Bunsen) flame ; 2 yellow / orange ; 2(b) (dilute) nitric acid and (aqueous) silver nitrate ; 2 white ppt ;

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3 A student investigates how the length of a pendulum affects the time taken for it to oscillate. Fig. 3.1 shows the apparatus used. clamp l bob Fig. 3.1 (a) (i) Measure the pendulum length l on Fig. 3.1 in centimetres to the nearest 0.1 cm. l = .................................................... cm [1] (ii) The diagram in Fig. 3.1 is drawn to a scale of one‑fifth full size. Determine the actual length L of the pendulum used by the student. L = .................................................... cm [1] (iii) It is difficult to measure from the bottom of the clamp to the centre of the pendulum bob accurately. Describe how to make an accurate measurement. You may draw a diagram to help explain your answer. ........................................................................................................................................... ..................................................................................................................................... [1] (b) The student: • displaces the pendulum bob and releases it so that it swings • measures the time t taken for 10 complete oscillations. Explain why timing 10 oscillations gives a more accurate value for the period T than timing 1 oscillation. ................................................................................................................................................... ............................................................................................................................................. [1] (c) The procedure in 3(b) is repeated for two other pendulum lengths. The measurements are shown in Table 3.1. Table 3.1 L / cm t / s T / s T 2 / ................ 20.0 8.9 0.89 0.79 40.0 12.7 ................ ................ (i) Calculate the time period T for one complete oscillation for length L = 40.0 cm. Record this value in Table 3.1. [1] (ii) Complete the table heading with the unit for T 2. [1] (iii) Calculate the value of T 2 for length L = 40.0 cm. Record in Table 3.1 this value to two significant figures. [2] (iv) Use the information in Table 3.1 to estimate the time t for 10 oscillations for a pendulum of length L = 30.0 cm. time for 10 oscillations = ...................................................... s [1] (d) A student suggests that the value for T 2 will double when you double the length l of the pendulum. State if the data support this suggestion. Justify your answer by reference to the data in Table 3.1. ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ............................................................................................................................................. [2] (e) The student wants to plot a graph to investigate the relationship between the pendulum length l and T 2. (i) Suggest additional values of length l larger than 10.0 cm that the student uses. ........................................................................................................................................... ..................................................................................................................................... [1] (ii) Suggest why lengths smaller than 10.0 cm are not used. ........................................................................................................................................... ..................................................................................................................................... [1] [Total: 13]

Mark scheme: 3(a)(i) l = 10.0 (cm) ; 1 3(a)(ii) L = 50(.0) (cm) ; 1 3(a)(iii) any one from: 1 • average the lengths to the top and the bottom of the bob • measure the diameter of the bob using wooden blocks and add half to the length of the string 3(b) one oscillation is too quick (to time) ; 1 3(c)(i) 1.27 (s) ; 1 3(c)(ii) s2 ; 1 3(c)(iii) 1.6 ; 2 value recorded to 2 sig. fig. ; 3(c)(iv) within the range of 10.1 to 11.5 (s) ; 1 3(d) Expect clear implication of ‘yes’ ; 2 when T2 for L = 20 cm is doubled, the value is close to the value for L = 40 ; 3(e)(i) at least three additional values given > 10.0 cm ; 1 3(e)(ii) the oscillation would be too quick (to time) ; 1

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4 When an object falls through a liquid, the liquid causes a force resisting the motion of the object. This force affects the time taken for the object to fall through the liquid. Plan an experiment to investigate the relationship between the density of a liquid and the time taken for a plasticine ball to fall through the liquid. The following apparatus is available: • the apparatus shown in Fig. 4.1 • a selection of different liquids, each liquid labelled with its density value. measuring cylinder liquid plasticine ball Fig. 4.1 You may also use any apparatus commonly found in a school laboratory. Your plan should include: • a brief description of the method including any additional apparatus you will use • the variables you will control • the measurements you will make and how you will ensure they 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) • an explanation of how you will use your results to reach a conclusion. .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .................................................................................................................................................... [7]

Mark scheme: 4 procedure / additional apparatus 7 • drop a ball through different liquids (of different densities) • use of a stopwatch control variables • same volume / height of liquid • drop ball from same height each time • same mass / volume / shape of the ball • same temperature of liquid measurements & precautions • time how long it takes the ball to hit the bottom / fall a fixed distance • perpendicular viewing (to avoid parallax error) • repeat for each liquid and average table • columns to include density (of liquid) and time • with correct units processing • compare times (or speed) with different densities to see if / how the density affects the time • plot a graph of density against time • explanation of if / how the graph line shows density affects time

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