Dialysis tubing is a partially permeable membrane. Glucose molecules can diffuse through the dialysis tubing. You are required to investigate the diffusion of glucose across dialysis tubing. You are provided with the materials shown in Table 1.1. [Table 1.1] If any solution comes into contact with your skin, wash off immediately with cold water. It is recommended that you wear suitable eye protection. You will need to: • put glucose solution into dialysis tubing surrounded by water • take samples of the water surrounding the dialysis tubing • test for the presence of glucose in each sample of water. Carry out step 1 to step 11. step 1 Draw a mark 8 cm from the top of a large test-tube, as shown in Fig. 1.1. [Figure 1.1] step 2 Remove the dialysis tubing from beaker D. Tie a knot in the dialysis tubing as close as possible to one end, so that the end is sealed. step 3 The whole length of the dialysis tubing needs to be separated to allow the tubing to be filled with solution. To do this, rub the whole length gently between your finger and thumb. step 4 Put 10 cm³ of 20.0% glucose solution, G, into the open end of the dialysis tubing. step 5 Rinse the outside of the dialysis tubing by dipping it in the water in beaker D. step 6 Put the dialysis tubing containing G into the large test-tube and keep it in position using an elastic band as shown in Fig. 1.2. [Figure 1.2] step 7 Put distilled water into the large test-tube so that the top of the water is above the level of the glucose solution in the dialysis tubing. step 8 Start timing. You are required to take samples of the water surrounding the dialysis tubing every 5 minutes for 15 minutes. You will collect three samples. step 9 Label three test-tubes with the times the samples of water will be taken (5, 10 and 15). step 10 After 5 minutes (step 8), put a 1 cm³ syringe into the water surrounding the dialysis tubing so that the end of the syringe is level with the mark on the test-tube. Remove 1 cm³ from the water surrounding the dialysis tubing and put this into the test-tube labelled 5. Repeat this action to remove another 1 cm³ from the water surrounding the dialysis tubing and put this into the test-tube labelled 5. The test-tube labelled 5 will now contain a 2cm³ sample. Do not stop timing. step 11 Repeat step 10 at 10 minutes and at 15 minutes using the appropriately labelled test-tubes. You need to carry out a dilution of the 20.0% glucose solution, G, to make a 1.0% glucose solution. You will need 20cm³ of this 1.0% glucose solution.

1. (a)(i)Complete Table 1.2 to show the volume of distilled water, W, you will use to make 20 cm³ of a 1.0% glucose solution. [Table 1.2] 1[1]
2. (a)(ii)Complete Fig. 1.3 to show how you will prepare your serial dilution. Each beaker should have: • a labelled arrow to show the volume of glucose solution transferred • a labelled arrow to show the volume of distilled water, W, added. [Figure 1.3][2]
3. (a)(iii)You are required to carry out the Benedict's test on the glucose solutions that you have prepared in step 14. State the volume of Benedict's solution you will use for each reducing sugar test. Explain why you have selected this volume. volume of Benedict's solution ............................................... cm³ explanation ................................................................................................................................................................................................................................................................................................................................................................[1]
4. (a)(iv)Complete Table 1.3 to record your results. [Table 1.3][1]
5. (a)(v)Record your results in an appropriate table.[4]
6. (a)(vi)State one source of error when carrying out the Benedict's test.[1]
7. (a)(vii)Use your results in (a)(iv) and (a)(v) to estimate the percentage concentration of glucose in the samples taken at 5, 10 and 15 minutes. percentage concentration of glucose in sample 5 = ........................................................................ percentage concentration of glucose in sample 10 = ........................................................................ percentage concentration of glucose in sample 15 = ........................................................................[1]
8. (a)(viii)Suggest a reason for the percentage concentrations of glucose estimated in (a)(vii).[1]
9. (b)(i)Plot a line graph of the data in Table 1.4 on the grid in Fig. 1.5. Use a sharp pencil. [Figure 1.5][4]
10. (b)(ii)Calculate the percentage decrease in concentration of Q between 5 minutes and 20 minutes. Show your working and give your answer to two significant figures. ........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................... %[2]
11. (b)(iii)Suggest a reason for the rate of decrease in the concentration of Q from 0 to 10 minutes and from 10 to 20 minutes. 0 to 10 minutes .................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................... 10 to 20 minutes ....................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................[2]

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