Energy drinks contain a high concentration of carbohydrates, such as glucose, as a source of energy. Glucose is a monosaccharide which can be quickly metabolised by body cells, releasing energy during exercise. Glucose changes the colour of potassium manganate(VII) solution, P, from purple to colourless. The end-point is when P is completely colourless. You will need to: • prepare different concentrations of glucose solution • record the time taken to reach the end-point for the known glucose concentrations • use your results to estimate the concentration of glucose in an energy drink, U. You are provided with the materials shown in Table 1.1. Table 1.1 labelled | contents | risk | volume/cm³ G | 20% glucose solution | none | 50 W | distilled water | none | 20 A | dilute sulfuric acid | irritant | 20 P | potassium manganate(VII) solution | low risk irritant | 20 U | energy drink | none | 10 It is recommended that you wear suitable eye protection. If A or P come into contact with your skin, wash off immediately under cold water.

1. (a)(i)Complete Table 1.2 to show how you will prepare the concentrations of glucose you will use. Table 1.2 percentage concentration of glucose | volume of G/cm³ | volume of W/cm³ 20 | 10 | 0 12 | 6 | 4[2]
2. (a)(ii)Record your results in an appropriate table.[5]
3. (a)(iii)Record the time taken to reach the end-point for U. time for U = ................................................................ s[1]
4. (a)(iv)Estimate the percentage concentration of glucose in U. concentration in U = ................................................................ %[1]
5. (a)(v)Describe how you would modify this procedure to give a more accurate estimate of U.[3]
6. (a)(vi)State two significant sources of error when carrying out step 7.[2]
7. (a)(vii)Describe how you would modify this procedure to reduce one source of error as stated in (a)(vi).[1]
8. (b)An investigation was carried out into the effect of drinking an energy drink on blood glucose concentration over a period of 3 hours. The results are shown in Table 1.3. Table 1.3 time/hours | glucose concentration /mmol dm⁻³ 0.0 | 5.2 0.5 | 7.5 1.0 | 9.1 2.0 | 8.4 3.0 | 7.9 Plot a graph of the data in Table 1.3 on the grid in [Figure 1.1]. Use a sharp pencil for drawing graphs.[4]

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