A researcher compares two labelled gill exchange surfaces, P and Q, under the same experimental conditions. The measurements are shown in the table.
| Gill exchange surface | Surface area | Concentration difference | Membrane thickness |
|---|---|---|---|
| P | 10 cm2 | 4.0 mg dm−34.0\,\mathrm{mg\,dm^{-3}}4.0mgdm−3 | 0.020 mm |
| Q | 20 cm2 | 2.0 mg dm−32.0\,\mathrm{mg\,dm^{-3}}2.0mgdm−3 | 0.010 mm |
Using Fick's law, what is the ratio of the diffusion rate through surface Q to the diffusion rate through surface P?
Surface Q has a diffusion rate 2.02.02.0 times that of surface P
Surface Q has a diffusion rate 4.04.04.0 times that of surface P
Surface P has a diffusion rate 2.02.02.0 times that of surface Q
Surface P has a diffusion rate 4.04.04.0 times that of surface Q
102 exam-style questions on Edexcel GCSE Biology 8.1 Exchange surfaces and diffusion, covering 8.1.1 Introduction to exchange and transport, 8.1.2 Alveoli adapted for gas exchange, 8.1.3 Factors affecting rate of diffusion, and 8.1.4 Rate of diffusion using Fick's law. Each one has a worked solution and a mark scheme showing where the marks go.