A student wrote three statements about the rate of diffusion.
Statement 1: Diffusion is faster when the difference in concentration is smaller.
Statement 2: Diffusion is faster across a thick membrane than across a thin membrane.
Statement 3: Diffusion is faster across a large surface area than across a small surface area.
Explain why Statement 1 is incorrect.
Write a corrected version of Statement 2.
Use Statement 3 to explain why the lungs contain millions of alveoli.
Describe how a steep concentration gradient of oxygen is maintained between the air in the alveoli and the blood.
42 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.