Diffusion

Molecules move from where there is high concentration to where there is a lower concentration. I.E They diffuse down a concentration gradient. This requires no energy and is a passive process.

Molecules move until they reach a state of equilibrium or DYNAMIC EQUILIBRIUM.

Factors which affect the rate of diffusion.

• Concentration gradient - the greater the difference in the difference in concentration of the molecules or ions on either side of the exchange surface, the faster the rate of diffusion.
• Area over which diffusion takes place - the larger the area of an exchange surface, the faster the rate of diffusion.
• Thickness of the exchange surface - the thinner the exchange surface, the faster the rate of reaction.