2021 CGSS Bio Prelim P3

CEDAR GIRLS’ SECONDARY SCHOOL End of Year Examination 2021 Year 4 CANDIDATE NAME CLASS 4 INDEX NUMBER BIOLOGY 6093/03 Paper 3 Practical Test 18 August 2021 1hour 50 minutes Additional Materials: As listed in the Confidential Instructions READ THESE INSTRUCTIONS FIRST Write your name and index number clearly in the spaces at the top of this page. Give details of the practical shift and laboratory where appropriate, in the boxes provided. Write in dark blue or black pen. You may use a 2B pencil for any diagrams or graphs. Do not use staples, paper clips, highlighters, glue or correction fluid. 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 working or if you do not use appropriate units. The number of marks is given in brackets [ ] at the end of each question or part question. For Examiner’s Use 1 2 Total Shift Laboratory This document consists of 12 printed pages. [Turn over

2 For Examiner's Use 1 You are advised to read the whole question before you start. Glucose formed from hydrolysis of carbohydrates is absorbed at certain parts of the alimentary canal. You will be investigating the movement of glucose solution. You are provided with:  20% glucose solution labelled G  distilled water  a 5cm3 syringe  four plastic droppers  a 50cm3 measuring cylinder  four boiling tubes  four test tubes  a rubber bung to fit a boiling tube  a 250 cm3 beaker labelled water bath  a stopwatch The apparatus that you will set up is shown in Fig. 1.1, using a boiling tube and a 5 cm3 syringe. Fig. 1.1 Step 1 Label the four boiling tubes as G4, G8, G12 and G16. Step 2 Put an empty 5 cm3 syringe into the boiling tube G4 as shown in Fig. 1.1. plunger of syringe barrel of syringe boiling tube mark nozzle of syringe

3 [Turn over For Examiner's Use Step 3 Using the marker provided, draw a mark on the boiling tube labelled G4, as shown in Fig. 1.1, so that the mark is level with the top of the nozzle of the syringe. (a) (i) Describe how you will use the apparatus provided to find the volume of distilled water needed to fill the boiling tube up to the mark. [2] (ii) Find the volume of distilled water needed to fill the boiling tube up to the mark, using the method you described in (a)(i). volume = cm3 [1] Step 4 Put the volume of distilled water stated in (a)(ii) into each of the four boiling tubes G4, G8, G12 and G16. Step 5 Fill a 5 cm3 syringe with slightly more than 5 cm3 of glucose solution, G. Push the plunger in until it reaches the 5 cm3 mark. This adjustment is done to ensure that there are no air bubbles in the nozzle. Step 6 Put the syringe into the first boiling tube, G4, as shown in Fig. 1.2. The nozzle of the syringe must be below the surface of the distilled water. Start the stopwatch. Fig. 1.2 5cm3 of 20% glucose solution, G boiling tube containing distilled water mark after 4 minutes, move syringe into G8 after another 4 minutes, move syringe into G12 after another 4 minutes, move syringe into G16 0 to 4 minutes boiling tube labelled G4 4 to 8 minutes boiling tube labelled G8 8 to 12 minutes boiling tube labelled G12 12 to 16 minutes boiling tube labelled G16

4 For Examiner's Use Step 7 Leave the syringe in the boiling tube G4 for 4 minutes, then remove the syringe and put it immediately into the next boiling tube, G8. The nozzle of the syringe must be below the surface of the distilled water. Leave for a further 4 minutes. Do not stop the stopwatch. Step 8 Repeat this process with each of the two remaining boiling tubes, G12 and G16, using the timings indicated in Fig. 1.2 . Remove the syringe from the last boiling tube, G16, at 16 minutes. Each time, the nozzle of the syringe must be below the surface of the distilled water. Refer to Fig. 1.2 for the overall setup for the experiment. Keep the setups G4 to G16 for the remaining part of the experiment. (b) Name the process for the movement of glucose solution from the syringe into the water in boiling tube G4. [1] (c) Name the part of the alimentary canal where the process identified in (b) is involved in the absorption of glucose. [1] To estimate the rate of movement of the glucose solution into distilled water, the solution collected in each boiling tube will be tested with Benedict’s test to measure the time taken for the first colour change to occur. This measurement allows Benedict’s test to be semi-quantitative. Step 9 Label four test tubes as T4, T8, T12 and T16. Step 10 Put a rubber bung into boiling tube G4 and shake the solution to mix well. Step 11 Remove the rubber bung from G4 and use a clean plastic dropper to transfer 2 cm3 of the solution in G4 into test tube T4. Step 12 Repeat step 10 to step 11 for each of the solutions in the remaining boiling tubes. 2 cm 3 of G8, G12 and G16 should be transferred to test tubes T8, T12 and T16 respectively.

5 [Turn over For Examiner's Use Step 13 Use the beaker labelled water bath to collect enough of the hot water supplied so that the water fills approximately half the height of the beaker. Use the Bunsen burner to boil the collected water. This water bath will be used for step 15. Step 14 Add 2 cm3 of Benedict’s solution to test tube T4. Shake to mix well. Step 15 Place test tube T4 into the boiling water bath and start timing using the stopwatch immediately. Step 16 Measure the time taken to the first appearance of a colour change in the test-tube. Step 17 Record in (d) the result from step 16. If there is no colour change after 180 seconds, stop timing and record the result in (d) as ‘more than 180’. Record all measurements to the nearest 0.01s. Step 18 Remove the test tube from the water bath and leave it to cool in the test tube rack. Step 19 Repeat step 14 to step 18 with T8, T12 and T16. (d) Record your results in an appropriate table. [3]

6 For Examiner's Use (e) How does the rate of movement of glucose solution from the syringe into the water in the boiling tube change with time? Explain your answer. [3] (f) State one variable that was kept the same in this investigation. Explain why it was important to keep this variable the same. variable explanation [2] (g) Explain the importance of ensuring that there are no air bubbles in the nozzle of the syringe. [2]

7 [Turn over For Examiner's Use (h) A student modified the procedure by:  using a 10% glucose solution in the syringe  collecting glucose solution from the syringe in two-minute periods over a total time of 10 minutes  collecting any precipitate (solid particles) formed during the Benedict’s test  drying and weighing the precipitate from each test to determine the mass of glucose that had been present. After carrying out the procedure, the student processed and analysed the results to calculate the rate of movement of the glucose solution at two- minute intervals, as shown in Table 1.1. Table 1.1 time/minutes rate of movement of glucose solution / arbitrary units (au) 2 0.18 4 0.09 6 0.04 8 0.02 10 0.01

8 For Examiner's Use