2026 TJC JC2 Prelim H2 Biology P4 (QP)

1 [TURN OVER TEMASEK JUNIOR COLLEGE 2026 JC2 PRELIMINARY EXAMINATION Higher 2 CANDIDATE NAME CENTRE NUMBER S INDEX NUMBER BIOLOGY 9477/04 Paper 4 Practical 1 September 2026 2 hour 30 minutes Candidates answer on the Question Paper. Additional Materials: As listed in the Confidential Instructions. READ THESE INSTRUCTIONS FIRST Write your name, CG, Centre number, index number on all the work you hand in. Give details of the practical shift and laboratory, where appropriate, in the boxes provided. Write in dark blue or black pen. You may use an HB pencil for any diagrams or graphs. Do not use staples, paper clips, glue or correction fluid. This document consists of 19 printed pages and 1 blank page. Shift Laboratory For Examiner’s Use 1 /21 2 /14 3 /15 Total /50 Answer all questions in the spaces provided on the Question Paper. The use of an approved scientific calculator is expected, where appropriate. You may lose marks if you do not show your work or if you do no use appropriate units. At the end of the examination, fasten all your work securely together. The number of marks is given in brackets [ ] at the end of each question or part question.

2 Answer all questions. 1 Plant extracts contain molecules which have many uses in industry and as medicines. To find the best source of one of these molecules may require estimating the concentration of a useful molecule in plant extracts. You are required to estimate the concentration of molecule M in a sample of plant extract, U. Molecule M changes the colour of potassium manganate(VII) solution, K, from pink to colourless. The rate of the colour change depends on the concentration of molecule M in the sample. (a) Predict how increasing the concentration of molecule M will affect time taken for solution K to change from pink to colourless. ………………………………………………………………………………………………………………… ……………………………………………………………………………………………..……………… [1] You are required to: • prepare a simple dilution of a 10% solution of molecule M, labelled 10M • record the time taken for the pink colour of K to change to the end- point for each of the concentrations of molecule M. You are provided with: • 10% solution of molecule M, in a container labelled 10M • distilled water W, in a beaker labelled W • unknown concentration of molecule M in a plant extract, in a container labelled U • sulfuric acid A, in a container labelled A • potassium manganate (VII) solution K, in a container labelled K If A comes into contact with your skin, wash it off immediately under cold water. It is recommended that you wear suitable eye protection.

3 [TURN OVER (b) You are required to make proportional dilutions of the 10M solution which reduces the concentration between each successive dilution. You will need to prepare 20.0 cm3 of each concentration. (i) Decide which concentrations of molecule M to prepare using proportional dilutions of the 10M solution. Complete Table 1.1 to show how you will prepare the other concentrations. Table 1.1 concentration of molecule M / % volume of molecule M / cm3 volume of distilled water / cm3 [3] Proceed as follows: 1 Prepare the concentrations of molecule M as shown in Table 1.1. Before proceeding further, use the container labelled hot water to collect approximately 400 cm3 of hot water from where it is provided in the laboratory. You should also fill the container labelled tap water with water from a tap. 2 Using the hot water and tap water that you have collected, set up a water bath at 50 oC in the beaker labelled water-bath. You will need to maintain this temperature throughout the investigation. Place the beaker labelled water-bath on the white tile. 3 Put 1.0 cm3 of A into a test-tube. 4 Put 1.0 cm3 of K into the same test-tube and mix well. 5 Put 5.0 cm3 of 10M into the same test-tube and mix well. 6 Place the test-tube with the mixture of A, K and 10M into the water-bath prepared in step 2. Start timing immediately. Continue stirring the mixture from time to time. 7 Record the time taken to reach the end-point in (a)(ii).

4 If the end- point is not reached in 4 minutes record ‘more than 240 ’ and record the colour of the solution. 8 Repeat step 3 to step 7 one more time. 9 Repeat step 3 to step 8 for each of the concentrations of molecule M prepared in step 1. (ii) Prepare the space below and record your results for the known concentrations of molecule M. [4] You are now required to estimate the concentration of molecule M in a sample of plant extract, U. 10 Repeat step 3 to step 6 with U. Record the time taken to reach the end-point in (a)(iii). (iii) State the time taken to reach the end-point for sample U .................................................... [1] (iv) Use your results in (a)(ii) and (a)(iii) to estimate the concentration of molecule M in sample U. concentration = ................................................................ [1]

5 [TURN OVER (v) Describe how you could use this procedure to produce a more accurate estimate of the concentration of molecule M in the sample of plant extract U than the one given in (a)(iv). .................................................................................................................................................. .................................................................................................................................................. .................................................................................................................................................. .................................................................................................................................................. .................................................................................................................................................. .................................................................................................................................................. .............................................................................................................................................. [3]

6 (c) A student investigated the concentration of molecule M in extracts from different plants. The student prepared 5 Petri dishes containing agar (agar plates) which had each been inoculated with a pathogenic bacterium. A filter paper disc, soaked in plant extract containing chemical molecule M from each plant was put onto each agar plate. Chemical M diffused from the filter paper disc into the agar. The agar plates were incubated at 25 °C to allow the bacteria in the agar to reproduce. A clear zone, called a zone of inhibition (where the bacteria were not observed) is observed around the filter paper disc if the chemical is effective at preventing bacteria from reproducing, as shown in Fig. 1.1. Fig. 1.1 The student measured the diameter of the zone of inhibition produced in the agar for each of the plant extract. The results are shown in Table 1.2. Table 1.2 plant extract diameter of zone of inhibition / mm P 7.0 Q 24.0 R 18.0 S 15.5 T 19.0 filter paper disc soaked in plant extract

7 [TURN OVER (i) Use the grid to display the results shown in Table 1.2 in an appropriate form. Use a sharp pencil for your drawing. [4] (ii) A scientist studied the results in Table 1.2 and noticed that the pathogen bacterium was most affected by one plant extract. The scientist decided to carry out further experiments to learn more about the effects of chemical M from this plant extract. State which type of plant extrac