Biology 0610/62 May/June 2024: question paper and mark scheme

Question

A student investigated the effect of acid concentration on the rate of diffusion in agar jelly. The student was given three test‑tubes containing bromothymol blue indicator in agar jelly. Bromothymol blue is a blue indicator that turns yellow in the presence of an acid. The student used this method: Step 1 label three beakers A1, A2 and A3 Step 2 put 20 cm3 of 1 mol per dm3 hydrochloric acid solution into beaker A1 Step 3 put 2 cm3 of 1 mol per dm3 hydrochloric acid solution into beaker A2 Step 4 add 18 cm3 of distilled water to the hydrochloric acid solution in beaker A2 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 Table 1.1 shows the final concentrations of the hydrochloric acid solution in each beaker. Table 1.1 final concentration of final volume of the beaker the hydrochloric acid solution / cm3 solution / 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] Step 7 label the three test‑tubes that contain the bromothymol blue indicator in agar jelly A1, A2 and A3 Step 8 use a syringe to transfer 10 cm3 of the hydrochloric acid solution from beaker A1 to test‑tube A1 Step 9 use a syringe to transfer 10 cm3 of the hydrochloric acid solution from beaker A2 to test‑tube A2 Step 10 use a syringe to transfer 10 cm3 of the hydrochloric acid solution from beaker A3 to test‑tube A3 Step 11 place the three test‑tubes into a water‑bath at 35 °C Step 12 start a stop‑clock and leave the test‑tubes in the water‑bath for 20 minutes Step 13 after 20 minutes, remove the test‑tubes from the water‑bath Step 14 measure the temperature of the water in the water‑bath. Fig. 1.1 shows the three test‑tubes after they were removed from the water‑bath in step 13. A1 A2 A3 hydrochloric acid yellow agar jelly yellow agar jelly agar jelly containing bromothymol blue indicator blue agar jelly blue agar jelly Fig. 1.1 (ii) Measure the height of the yellow agar jelly in each test‑tube shown in Fig. 1.1. Prepare a table and record the results of the investigation. Include in your table: • your measurements from Fig. 1.1 • the final concentration of hydrochloric acid. [4] (iii) State a conclusion for the investigation. …… [1] (iv) Identify the independent variable and the dependent variable in this investigation. independent variable …… dependent variable …… [2] (v) Fig. 1.2 shows the reading on the thermometer in step 14. °C 30 20 10 Fig. 1.2 Record the temperature of the water in the water‑bath at the end of the investigation, shown in Fig. 1.2. temperature …… °C [1] (vi) The student stated that the change in the temperature of the water‑bath was not a significant source of error in the investigation. Explain why the student was correct to state this. …… [1] (vii) Suggest a control experiment for this investigation. …… [1] (viii) The student repeated the investigation but left the test‑tubes in the water‑bath for 30 minutes instead of 20 minutes. Suggest how the results for this second investigation would differ from the results for the first 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]