A student investigated how the size of a cube affects diffusion into it. She cut three cubes of different sizes from a block of agar jelly. The agar jelly contained an indicator that turns from pink to colourless when acid diffuses into it. She placed each cube into dilute acid and measured the time taken for the cube to turn completely colourless. The table shows her results.
Table: The surface area, the volume and the time taken to turn completely colourless for three cubes of agar jelly
| Side length in cm | Surface area in cm2 | Volume in cm3 | Time taken to turn colourless in seconds |
|---|---|---|---|
| 1 | 6 | 1 | 90 |
| 2 | 24 | 8 | 340 |
| 3 | 54 | 27 | 760 |
Calculate the surface area to volume ratio of the 3 cm cube.
Explain why the 3 cm cube took longer to turn completely colourless than the 1 cm cube.
Give one variable the student should have controlled in this investigation.
The student concluded that doubling the side length of a cube doubles the time taken for the cube to turn colourless. Use data from the table to evaluate this conclusion.
58 exam-style questions on AQA GCSE Biology 1.3 Transport in cells, covering 1.3.1 Diffusion, 1.3.2 Osmosis, and 1.3.3 Active transport. Each one has a worked solution and a mark scheme showing where the marks go.