2026 VJC H2 Biology Prelim P4 Ans

VICTORIA JUNIOR COLLEGE JC 2 TIME PRACTICE 2 2026 HIGHER 2 NAME : ………………………………………………….………………. CT CLASS : ………………..……… BIOLOGY 9477 Practical 07/07/2026 2 hour 30 minutes 1. Write your name, CT class shift number and laboratory in the spaces provided. 2. Answer all questions in the spaces provided on the Question Paper. The number of marks is given in brackets [ ] at the end of each question. 3. Write in dark blue or black pen. You may use an HB pencil for diagrams, tables and graphs. 4. This paper consists of 3 questions. Students with the microscope and slide must begin with question 3 . You may continue with the other questions after you have completed question 3. 5. 1 hr 15 min after the start of the exam, students with microscope and slide will need to pass the instrument to their bench partners. Shift For examiner’s use 1 / 23 Laboratory 2 / 12 3 / 15 Total / 50 This document consists of 17 printed pages

2 Answer all questions. 1 When potato cells are placed into different concentrations of sodium chloride solution, water moves between the sodium chloride solution and the potato cells. You will investigate the effect of different concentrations of sodium chloride solution on potato tissue. You will need to: • prepare different concentrations of sodium chloride solution, S • put potato tissue into the different concentrations of sodium chloride solution • record the distance the potato tissue bends • use your results to estimate the concentration of an unknown concentration of sodium chloride solution, U. You are provided with: • 6 pieces of potato tissue in a Petri dish • 10% sodium chloride solution in a container labelled S • unknown concentration of sodium chloride labelled U • distilled water labelled W. It is recommended that you wear suitable eye protection.

3 (a) You will need to prepare different concentrations of sodium chloride solution, using proportional dilution. You will need to prepare 50 cm3 of each concentration, using S and W. Table 1.1 shows how to make up two of the concentrations of sodium chloride solution you will use. Decide which other concentrations of sodium chloride solution you will use. (i) Complete Table 1.1 to show how you will prepare the concentrations of sodium chloride solutions you will use. [2] Table 1.1 percentage concentration of sodium chloride volume of S / cm3 volume of W / cm3 10.0 50.0 0.0 7.5 37.5 12.5 5.0 25.0 25.0 2.5 12.5 37.5 0.0 0.0 50.0 1. Three additional concentrations (between 10 and 0) at equal intervals ; 2. Correct volumes of S and W to make total volumes of 50.0 cm3 for each concentration + correct precision 1d.p. ; Proceed as follows. 1 Prepare the concentrations of sodium chloride solution as shown in Table 1. 1, in the containers provided. Mix well. 2 Label the Petri dishes with the concentrations of sodium chloride solution prepared in step 1. 3 Label another Petri dish U. 4 Put a piece of potato tissue into each of the Petri dishes you have labelled. You are to determine a suitable volume of the sodium chloride solution prepared in step 1 to add to each Petri dish containing a piece of potato tissue, as shown in Fig. 1.1.

4 (ii) On Fig. 1.1, draw a line to indicate the level of solution you would use. Fig. 1.1 State the volume of sodium chloride solution you will use. [1] 1. appropriate line + states a volume that is between 42.0 cm3 and 50.0 cm3 ; (iii) Explain why you chose this volume of sodium chloride solution. [2] 1. volume is sufficient to completely immerse / cover the potato tissue ; 2. ensures that all surfaces of the potato are exposed to the same sodium chloride concentration, allowing osmosis to occur uniformly and improving the reliability of the results. 5 Put the volume of each concentration of sodium chloride solution you have decided in (a)(ii) into the appropriately labelled Petri dish. 6 Repeat step 5 using U. 7 Leave the pieces of potato tissue in the sodium chloride solutions for 20 minutes. While you are waiting, use your time to continue with Question 1.

5 You will use graph paper to measure how far the pieces of potato tissue bend after being left for 20 minutes in the sodium chloride solutions. Fig. 1.2 shows how you will prepare the graph paper, as described in step 8 and step 9. Fig. 1.2 8 On the graph paper provided, draw two lines at right angles to each other, as shown in Fig. 1.2. Each line should be approximately 6 cm long. Draw a mark on the vertical line 3 cm below where the vertical line meets the horizontal line, as shown in Fig. 1.2. 9 On the same piece of graph paper repeat step 8 for each of the other concentrations of sodium chloride solution and for U. 10 After 20 minutes (step 7) remove the piece of potato tissue from the 10% sodium chloride solution and put it onto a paper towel to remove the excess liquid. 11 Put the piece of potato tissue on the vertical line of the graph paper, as shown in Fig. 1.3.

6 Fig. 1.3 12 Put your finger on the middle of the potato tissue at the 3 cm mark and press firmly, as shown in Fig. 1.4. Fig. 1.4 13 Hold the potato tissue firmly in this position. Move the top of the potato tissue, as shown in Fig. 1.5, until there is some resistance.

7 Fig. 1.5 14 Mark the position of the top of the potato tissue on the graph paper, as shown in Fig. 1.6. Fig. 1.6 15 Remove the potato tissue and put it in the container labelled For waste. 16 Measure the distance between the mark and the horizontal line on the graph paper, as shown in Fig. 1.6. 17 Record your result in (a)(iv). 18 Repeat step 10 to step 17 using the potato tissue from the other concentrations of sodium chloride solution. 19 Repeat step 10 to step 16 using the potato tissue from U. Record your result for U in (a)(v).

8 (iv) Record your results in an appropriate table. [3] percentage concentration of sodium chloride solution distance between the mark and the horizontal line / mm 0.0 0 2.5 2 5.0 4 7.5 6 10.0 16 1. Correct column headings + independent variable on left-most side ; 2. (Trend) distance increases when sodium chloride solution concentration increases ; 3. (Precision) whole numbers ; (v) Record the result for U. Use your results in (a)(iii) to estimate the concentration of sodium chloride in U. [1] 1. time for U is closest to the result for 5% sodium chloride ; (vi) Explain the trend shown by your results in terms of water potential. [3] 1. As the percentage concentration of sodium chloride increases, the water potential of the solution becomes more negative / lower ; 2. Water moves out of the plant tissue by osmosis from a region of higher water potential (inside the cells) to a region of lower water potential (the sodium chloride solution) ; 3. The cells lose water and become less turgid (or plasmolysed), causing greater shrinkage / bend more, so the distance between the mark and the horizontal line increases ; (vii) Suggest how you could make improvements to the procedure so that a more accurate estimate of the concentration of sodium chloride in U can be obtained. [2] 1. Test more sodium chloride concentrations, especially in smaller intervals around the estimated concentration of U ;

9 (viii) Identify one source of error in this investigation. Explain how this error could affect your results. [2] Source of error Explanation 1a Judging when there is "some resistance" when bending the potato strip 1b Different amounts of force may