An experiment was conducted to investigate the effect of the surface-area-to-volume ratio of agar model cells on the rate of water uptake via osmosis. Three different-sized cubical blocks of agar gel were prepared with side lengths of 1.5 cm, 3.0 cm, and 4.5 cm. Their initial masses were recorded, they were immersed in a beaker of distilled water for 2 hours, and their final masses were determined.
The results of the experiment are shown in the table below:
| Agar cube size in cm | Original mass in g | Final mass in g | Percentage change in mass (%) |
|---|---|---|---|
| 1.5×1.5×1.51.5 \times 1.5 \times 1.51.5×1.5×1.5 | 3.50 | 4.12 | 17.71 |
| 3.0×3.0×3.03.0 \times 3.0 \times 3.03.0×3.0×3.0 | 28.10 | 30.45 | |
| 4.5×4.5×4.54.5 \times 4.5 \times 4.54.5×4.5×4.5 | 94.80 | 99.10 | 4.54 |
Calculate the percentage change in mass for the 3.0×3.0×3.0 cm3.0 \times 3.0 \times 3.0\text{ cm}3.0×3.0×3.0 cm agar cube. Show your working and give your answer to two decimal places.
Calculate the surface area (SA), volume (Vol), and SA:Vol ratio for the 4.5×4.5×4.5 cm4.5 \times 4.5 \times 4.5\text{ cm}4.5×4.5×4.5 cm agar cube using the following formulae:
SA=6×(side length in cm)2 \text{SA} = 6 \times (\text{side length in cm})^2 SA=6×(side length in cm)2 Vol=(side length in cm)3 \text{Vol} = (\text{side length in cm})^3 Vol=(side length in cm)323 exam-style questions on Edexcel IGCSE Biology Movement of substances into and out of cells. Each one has a worked solution and a mark scheme showing where the marks go.