February/March 2026 Paper 62

2026 · 3 questions · 16 parts · 40 marks

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1(a)(i)1(a)(ii)1(a)(iii)1(a)(iv)1(a)(v)1(a)(vi)1(b)1(c)(i)1(c)(ii)1(c)(iii)1(c)(iv)

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2(a)(i)2(a)(ii)2(b)(i)2(b)(ii)

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Context for question 1

Catalase is an enzyme that catalyses the breakdown of hydrogen peroxide to form water and oxygen. Catalase is found in potato tissue. The oxygen produced during the breakdown of hydrogen peroxide forms a foam. The height of the foam can be used as a measure of the activity of the catalase. A student investigated how the surface area of potato tissue affects the activity of catalase. The student was provided with three cubes of potato tissue. Each cube was 1 cm

\times

1 cm

\times

1 cm in size as shown in Figure 1.1. The total surface area of each cube of potato was 6 cm

^{2}

Figure 1.1, a cube of potato tissue with each side labelled 1 cm

The student used this method: step 1 Label three test‑tubes 1, 2 and 8. step 2 Put 10 cm

^{3}

of hydrogen peroxide solution into each of the test‑tubes. step 3 Put one of the cubes of potato into test‑tube 1. step 4 Put one of the remaining cubes of potato onto the white tile. Use the ruler and scalpel to measure and cut the cube of potato as shown in Figure 1.2. This will make two equal‑size pieces. The total surface area of the two pieces is 8 cm

^{2}

Figure 1.2, the potato cube with a dashed line labelled cut here down the middle, dividing it into two halves each 0.5 cm wide

step 5 Put both pieces of potato from step 4 into test‑tube 2. step 6 Put the remaining cube of potato onto the white tile. Use the ruler and scalpel to measure and cut the cube of potato as shown in Figure 1.3. This will make eight equal‑size cubes.

Figure 1.3, the potato cube with three dashed lines labelled cut here dividing it into eight small cubes, each side 0.5 cm

1(a)(i)Easy2 marks

Calculate the total surface area of the eight cubes of potato made in step 6.

Answer

Context for 1(a)

step 7 Put the eight cubes of potato into test‑tube 8. step 8 Start the stop‑clock and wait for five minutes. step 9 After five minutes, place the ruler against the outside of test‑tube 1. Measure the distance from the top of the liquid to the top of the foam. Record this measurement in your table in 1(a)(ii). step 10 Repeat step 9 using test‑tubes 2 and 8. Figure 1.4 shows the test‑tubes at the end of the investigation.

Figure 1.4, test-tubes 1, 2 and 8 at the end of the investigation, holding one cube, two pieces and eight small cubes of potato; the layer labelled foam is shortest in test-tube 1, taller in test-tube 2 and tallest in test-tube 8

1(a)(ii)Medium4 marks

Prepare a table and record the student’s results.

Draw with the mouse or a finger.

1(a)(iii)Easy1 mark

State a conclusion for these results.

1(a)(iv)Easy2 marks

State two variables that were kept constant in this investigation.

Two answers required.

1(a)(v)Easy1 mark

Identify one safety hazard in this investigation.

1(a)(vi)Hard4 marks

Identify two possible sources of error present in this investigation. Suggest an improvement for each of the errors that you have identified.

Your answer

1(b)Easy1 mark

Iodine solution can be used to show that potato tissue contains starch. State the result of a positive test with iodine solution.

Context for 1(c)

A student investigates the effect of copper sulfate concentration on the activity of catalase in potato tissue. When small discs of potato are dropped into hydrogen peroxide solution, they sink. The catalase in the potato breaks down the hydrogen peroxide solution producing bubbles of oxygen. The bubbles of oxygen cling to the discs of potato causing the discs of potato to rise back up to the surface of the hydrogen peroxide solution. The student:

places small discs of potato in different concentrations of copper sulfate solution and leaves them to soak for 10 minutes
drops the soaked discs of potato into the hydrogen peroxide solution
measures the time taken for the discs of potato to reach the surface of the hydrogen peroxide solution.

1(c)(i)Easy2 marks

State the dependent and independent variables in this investigation.

dependent variable

independent variable

1(c)(ii)Easy1 mark

Suggest a suitable control experiment for this investigation.

Your answer

1(c)(iii)Medium4 marks

Table 1.1 shows the results of the investigation.

Table 1.1

concentration of copper sulfate solution / mol per dm $^{3}$	time taken for disc of potato to rise / s
0.000	5
0.003	45
0.005	70
0.010	120
0.025	190

On the grid, use the data in Table 1.1 to plot a line graph to show the results of the investigation.

Draw with the mouse or a finger.

1(c)(iv)Medium2 marks

Use your graph to estimate the concentration of copper sulfate solution when a disc of potato took 80 s to rise. On the graph, show how you obtained your estimate.

Answer