B3.1 Diffusion

What is diffusion?

• Movement of particles from a high to a low concentration down a concentration gradient as a result of their random movement

• Occurs in gases, solids and liquids

Factors affecting the rate of diffusion

1. Diffusion distance: The smaller the diffusion distance, the faster the diffusion rate and vice versa

2. Concentration gradient: The steeper the concentration gradient, the faster the diffusion and vice versa

3. Surface area: The larger the surface area, the higher diffusion rate and vice versa

4. Temperature: The higher the temperature, the faster the diffusion rate because the molecules have more kinetic energy and vice versa

Examples of diffusion within the body

• Gas exchange in the lungs

• Oxygen delivery into the cells

• Nutrient absorption from intestines to blood

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