Biology 0610/52 May/June 2024: question paper and mark scheme

Question

You are going to investigate the effect of acid concentration on the rate of diffusion. Bromothymol blue is an indicator that turns yellow in the presence of an acid. Read all the instructions but DO NOT DO THEM until you have drawn a table for your results in the space provided in 1(a)(iii). You should use the safety equipment provided while you are doing the practical work. Step 1 Label three beakers A1, A2 and A3. Step 2 Add 20 cm3 of 1 mol per dm3 hydrochloric acid solution to beaker A1. Step 3 Add 2 cm3 of 1 mol per dm3 hydrochloric acid solution to beaker A2. Step 4 Add 18 cm3 of distilled water to the hydrochloric acid solution in beaker A2 and mix well. Step 5 Use a clean syringe to transfer 2 cm3 of the solution from beaker A2 to beaker A3. Step 6 Add 18 cm3 of distilled water to beaker A3 and mix well. Table 1.1 shows the final concentrations of the hydrochloric acid solution in each beaker. Table 1.1 final concentration of the final volume of the beaker hydrochloric acid solution solution / cm3 / mol per dm3 A1 1.00 20 A2 0.10 A3 0.01 20 (a) (i) Complete Table 1.1 by calculating the final volume of the solution in beaker A2. Write your answer in Table 1.1. [1] You are provided with three test‑tubes containing bromothymol blue indicator in agar jelly. Step 7 Label the three test‑tubes A1, A2 and A3. Step 8 Use a clean syringe to transfer 5 cm3 of the hydrochloric acid solution from beaker A1 to test‑tube A1. Step 9 Use a clean syringe to transfer 5 cm3 of the hydrochloric acid solution from beaker A2 to test‑tube A2. Step 10 Use a clean syringe to transfer 5 cm3 of the hydrochloric acid solution from beaker A3 to test‑tube A3. Step 11 Raise your hand when you are ready for warm water to be poured into the beaker labelled water‑bath. Step 12 Place the three test‑tubes into the warm water‑bath and start the stop‑clock. Leave the test‑tubes in the water‑bath for 20 minutes. While you are waiting continue with the other questions. Step 13 After 20 minutes, remove the test‑tubes from the water‑bath and place them in the test‑tube rack. (ii) Record the temperature of the water in the water‑bath. temperature …… °C [1] Step 14 Remove the hydrochloric acid solution from each test‑tube by pouring the solution in each test‑tube into the beaker labelled waste. Step 15 For each test‑tube, measure the distance between the top of the agar and the point at which the blue agar has become yellow. Fig. 1.1 shows where to take the measurement. Record your measurements in your table in 1(a)(iii). top of the agar point at which the blue agar has distance to measure become yellow Fig. 1.1 (iii) Prepare a table and record your results in the space provided. Include the final concentration of hydrochloric acid in your table. [4] (iv) State a conclusion for your results. …… [1] (v) Suggest why the temperature of the water‑bath did not need to be maintained during the investigation. …… [1] (vi) Suggest why the hydrochloric acid was removed from the test‑tube in step 14 before measuring the distance of the yellow colour. …… [1] (vii) Identify the independent variable and the dependent variable in this investigation. independent variable …… dependent variable …… [2] (viii) Explain why suitable eye protection should be worn when doing this investigation. …… [1] (b) In an experiment, a student cut different‑sized cubes of agar containing bromothymol blue indicator. The student placed the cubes in hydrochloric acid and measured the time taken for each cube to become yellow. The results are shown in Table 1.2. Table 1.2 length of the volume of time taken for the cubes cube sides / mm the cube / mm3 to become yellow / s 2 8 35 4 60 6 216 170 8 512 275 10 1000 445 (i) Complete Table 1.2 by calculating the volume of the 4 mm cube. Write your answer in Table 1.2. [1] (ii) Plot a line graph on the grid of the length of the cube sides against the time taken for the cubes to become yellow. [4] (iii) Use your graph to estimate the time taken for a cube with a side length of 3 mm to become yellow. Show on your graph how you obtained your answer. …… s [2] (iv) State two variables that should have been kept constant in this investigation. 1 …… 2 …… [2] [Total: 21]

Question

(a) When a seed germinates it grows into a seedling. Fig. 2.1 is a photograph of a seedling. A B Fig. 2.1 (i) Make a large drawing of the seedling shown in Fig. 2.1. [4] (ii) Line AB represents the width of the seedling. Measure the length of line AB on Fig. 2.1. length of line AB …… mm The actual width of the seedling is 9 mm. Calculate the magnification of the seedling in Fig. 2.1 using the formula and your measurement. length of line AB in Fig. 2.1 magnification = actual width of the seedling Give your answer to two significant figures. Space for working. [3] (iii) Fig. 2.2 shows photographs of two different seedlings, P and Q. P Q Fig. 2.2 Describe one visible similarity and two visible differences between seedling P and seedling Q in Fig. 2.2. similarity 1 …… difference 1 …… difference 2 …… [3] (b) As seedlings grow, they change starch into reducing sugars. Describe the methods you would use to test a sample of seedlings for starch and reducing sugars. starch test …… reducing sugar test …… … [3] (c) When light shines from one side, seedlings grow towards the light. Fig. 2.3 shows a diagram of a seedling growing towards a light source. The angle of growth is shown on the diagram. light source Fig. 2.3 Plan an investigation to find out how light intensity affects the angle at which the seedling grows. …… [6] [Total: 19]