Describe5 marksChallenge
A student investigates the effect of surface area to volume ratio on the rate of diffusion using agar cubes. Cubes of different sizes are cut from an agar gel containing a pH indicator that turns from blue to yellow in acidic conditions. Each cube is placed in a beaker of dilute hydrochloric acid and the time taken for the entire cube to turn yellow is recorded. The results are shown in the table below.
| Cube side length (mm) | Surface area (mm²) | Volume (mm³) | Surface area : volume ratio | Time to turn yellow (s) |
|---|---|---|---|---|
| 1 | 6 | 1 | 6:1 | 30 |
| 2 | 24 | 8 | 3:1 | 120 |
| 3 | 54 | 27 | 2:1 | 270 |
| 4 | 96 | 64 | 1.5:1 | 480 |
Describe the relationship between the surface area to volume ratio of the cubes and the time taken for the colour change to occur throughout the cube.