Describe5 marksChallenge
A student prepared agar cubes of three different sizes. Each cube contained a pH indicator that changes from purple to yellow in acidic conditions. The cubes were immersed in a beaker of dilute hydrochloric acid. The time taken for the entire cube to turn yellow was recorded.
| Cube side length (cm) | Surface area (cm²) | Volume (cm³) | Time to turn yellow (min) |
|---|---|---|---|
| 1 | 6 | 1 | 5 |
| 2 | 24 | 8 | 20 |
| 3 | 54 | 27 | 45 |
Describe the relationship between the size of the agar cube and the time taken for the acid to diffuse to the centre of the cube. Explain this relationship by referring to surface-area-to-volume ratio.