Cambridge IGCSE Physical Science 0652 — 2020 Oct/Nov Paper 5 · Variant 2

1 You are going to investigate the rate of reaction of magnesium with hydrochloric acid. You are going to use 2 different solutions of hydrochloric acid, H and J. (a) Procedure • Measure 50 cm3 hydrochloric acid H using a measuring cylinder and pour it into a conical flask. • Set up the apparatus shown in Fig. 1.1. delivery tube 100 cm3 measuring cylinder bung filled with water clamp conical large flask container stand hydrochloric acid water Fig. 1.1 • Remove the bung from the conical flask. • Add one 6.0 cm length of magnesium ribbon to the conical flask. • Replace the bung quickly. As soon as the bung is in place, start the stop-clock. • Measure the volume of gas produced every 30 seconds for 4 minutes or until the measuring cylinder is full. (i) Record in Table 1.1 on page 4 the volumes to the nearest 1 cm3. [2] (ii) • Rinse the conical flask. • Repeat the procedure in (a) using 50 cm3 hydrochloric acid J. Record in Table 1.1 the volumes to the nearest 1 cm3. [2] Table 1.1 hydrochloric acid H hydrochloric acid J time / s volume of gas / cm3 volume of gas / cm3 0 30 60 90 120 150 180 210 240 (b) You are going to plot a graph of both sets of results on the same grid. Consider both sets of data before you add the scales to the axes. On the grid provided on page 5, plot a graph of volume of gas produced (vertical axis) against time for hydrochloric acid H. Draw the line of best fit and label it H. On the same grid, plot a graph of volume of gas produced (vertical axis) against time for hydrochloric acid J. Draw the line of best fit and label it J. [5] (c) State which acid, H or J, is more concentrated. Explain your answer by referring to the graph. acid ........................................................................................................................................... explanation ............................................................................................................................... ............................................................................................................................................. [1] (d) A student repeats the experiment with acid H but first heats the acid to 50 °C. The same length of magnesium ribbon is used. The reaction happens more quickly. Draw a line on the grid to show the results expected. Label the line D. [2] (e) Suggest one change to the apparatus to improve the accuracy of the investigation. ................................................................................................................................................... ............................................................................................................................................. [1] [Total: 13]

Mark scheme: 1(a)(i) some volumes for H ; full set of volumes and increasing ; 2 1(a)(ii) full set of volumes for J ; smaller than (i) unless get to 100 cm3 ; 2 1(b) axes labelled with quantity and unit ; linear scale so points cover ⩾ half the grid ; points plotted correctly ; H best-fit and labelled ; J best-fit and labelled ; 5 1(c) H and steeper line / higher line ; 1 1(d) line above line H ; line stops at the same volume ; 2 1(e) pipette / burette / syringe AVP ; 1

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2 You are going to measure the spring constant k of a spring by two different methods. The spring constant k of a spring is a measure of the stiffness of the spring. (a) Method 1 Measure the unstretched length l0 of the spring in centimetres to the nearest millimetre. Do not include the loops at the end of the spring in your measurement. l0 = ................................................... cm [1] (b) • Attach the spring to the clamp as shown in Fig. 2.1. clamp spring (not to scale) mass Fig. 2.1 • Hang a 0.3 kg mass (300 g) on the spring. Measure the new length l1 of the spring. l1 = ......................................................... cm Leave the mass on the spring. Calculate the extension e of the spring produced by the mass. Use the equation: e = l1 – l0 e = ................................................... cm [1] (c) Calculate the spring constant k of the spring. Use the equation: W k = e where the weight W of the mass = 3 N. k = ............................................... N / cm [1] (d) Method 2 Pull the mass down approximately 2 cm and release it. The mass oscillates up and down. The period T of the oscillations is the time taken for one oscillation. One complete oscillation of the mass is shown in Fig. 2.2. highest position of mass one complete oscillation position of mass when at rest i.e. lowest highest lowest lowest position of mass start finish Fig. 2.2 (i) • Measure the time t for 20 oscillations. Record time t in Table 2.1. [1] Table 2.1 mass m / kg time t for period T / s T 2 / s2 20 oscillations / s 0.30 (ii) Use your answer from (i) to calculate the period T, the time for one oscillation of the mass. Record this value in Table 3.1. [1] (iii) Calculate the value of T 2. Record your answer in Table 2.1 to two significant figures. [1] (e) Calculate the spring constant k of the spring. Use the equation: 0.12 k = T 2 k = ............................................... N / cm [1] (f) Compare your values of k from (c) and (e). Explain whether they agree with each other within the limits of experimental error. ................................................................................................................................................... ............................................................................................................................................. [1] (g) In both methods, it is important to avoid line-of-sight (parallax) errors when measuring the length of the spring and when timing the oscillations. Describe how you avoided this error in each method. length of the spring method ...................................................................................................... ................................................................................................................................................... ................................................................................................................................................... timing the oscillations method .................................................................................................. ................................................................................................................................................... ................................................................................................................................................... [2] [Total: 10] Question 3 begins over the page

Mark scheme: 2(a) 2(b) l1 recorded and e correctly calculated ; 1 2(c) correct calculation of k ; 1 2(d)(i) t value present and in the range 12–14 s ; 1 2(d)(ii) T calculation correct ; 1 2(d)(iii) T2 to 2 significant figures ; 1 2(e) correct calculation of k ; 1 Question Answer Marks 2(f) expect YES and values are (very) close/not (too) far apart / close enough / <10% difference / equivalent ; 1 2(g) method 1: view perpendicularly to scale/at eye level / ruler close to spring ; 1 method 2: eye level with top / bottom / middle of oscillations ; 1

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3 You are going to investigate the effective resistance of two different combinations of lamps. The circuit shown in Fig. 3.1 has been set up for you. This is circuit 1. The voltmeter in the circuit is not shown in the circuit diagram. A circuit 1 P Q Fig. 3.1 (a) On Fig. 3.1, draw the symbol for the voltmeter connected to measure the potential difference (p.d.) between points P and Q. [1] (b) • Close the switch. • Measure and record in Table 3.1 the potential difference V between P and Q and the current I. • Open the switch. [2] Table 3.1 p.d. V / V current I/ A resistance R / ..... circuit 1 circuit 2 (c) Reconnect the lamps between P and Q as shown in Fig. 3.2. This is circuit 2. A circuit 2 P Q Fig. 3.2 Repeat the steps in (b). [2] (d) (i) Complete the column headings in Table 3.1 by giving the unit for resistance R. [1] (ii) Calculate and record in Table 3.1 the resistance R of circuits 1 and 2. Use the equation: V R = I [2] (e) A teacher makes the following statement. “If each lamp has the same resistance, resistance of circuit 2 = 2.25” resistance of circuit 1 State whether your results support the teacher’s suggestion. Justify your statement by using the values of R you have calculated in Table 3.1. ................................................................................................................................................... ................................................................................................................................................... ............................................................................................................................................. [1] (f) The resistance of a lamp is altered by a change in the temperature of its filament. During the experiment, a student observes that the lamps in the circuits have different brightnesses. Suggest how this might have affected the results of this experiment. ................................................................................................................................................... ............................................................................................................................................. [1] [Total: 10] 4 Aqueous sodium hydroxide is an alkali. When aqueous sodium hydroxide reacts with hydrochloric acid, a neutralisation reaction takes place and aqueous sodium chloride is made. The word equation for this reaction is shown. aqueous aqueous hydrochloric sodium + sodium + water acid hydroxide chloride To make pure aqueous sodium chloride, the amount of aqueous sodium hydroxide added needs to be the exact amount to just neutralise the hydrochloric acid. Plan an experiment to make a pure sample of sodium chloride solid. You may use any common laboratory apparatus, aqueous sodium hydroxide, hydrochloric acid and any named indicator. Your plan should include: • a brief description of the method including the apparatus you would use • safety precautions and explain why these are needed • how you make sure the sodium chloride is pure • the measurements you will make. A diagram is not required but you may draw one if it helps to explain your plan. You will not be doing this experiment.

Mark scheme: 3(a) correct parallel connection and correct symbol ; 1 3(b) V recorded and >0 but <3 V ; 1 I recorded and >0 but <1 A ; 1 3(c) V values to at least 1 decimal place and I values to at least 2 decimal places ; 1 I value < value in (b) ; 1 3(d)(i) Ω / ohms ; 1 3(d)(ii) R values correct ; 1 R value for circuit 2 > that for circuit 1 ; 1 3(e) Correct matching statement (YES / NO) given (expect NO) from a calculated ratio and suitable comment e.g. values are too different / not close enough, even allowing for experimental error ; 1 3(f) the lamps are at different temperatures / have different resistances (or currents) than expected ; 1

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4 Aqueous sodium hydroxide is an alkali. When aqueous sodium hydroxide reacts with hydrochloric acid, a neutralisation reaction takes place and aqueous sodium chloride is made. The word equation for this reaction is shown. aqueous aqueous hydrochloric sodium + sodium + water acid hydroxide chloride To make pure aqueous sodium chloride, the amount of aqueous sodium hydroxide added needs to be the exact amount to just neutralise the hydrochloric acid. Plan an experiment to make a pure sample of sodium chloride solid. You may use any common laboratory apparatus, aqueous sodium hydroxide, hydrochloric acid and any named indicator. Your plan should include: • a brief description of the method including the apparatus you would use • safety precautions and explain why these are needed • how you make sure the sodium chloride is pure • the measurements you will make. A diagram is not required but you may draw one if it helps to explain your plan. You will not be doing this experiment. .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... ..........................................................................................................................................................

Mark scheme: 4 At least one mark must be awarded from each section. The remaining three marks can be awarded from any section. apparatus acid in container (test-tube / beaker / conical flask / evaporating basin) (may have acid in burette and alkali in flask) AND use of burette / measuring cylinder / pipette ; Bunsen / evaporating basin ; method acid and add named indicator ; add NaOH (slowly) ; until indicator just changes colour ; repeat ; (repeat no indicator ;) heat to remove water goggles - acid corrosive / acid solution in eyes / solid spitting ; measurements measure volume acid and volume NaOH ; volume NaOH used = amount NaOH initially – amount NaOH left at end OR volume NaOH used = amount NaOH and HCl at end – amount of HCl ; purity repeat without indicator ;

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