2. Diffusion in liquids and gases
The molecules that make up gases move more quickly than the molecules in liquids, and so the diffusion that takes place in liquids is slightly slower. But, the process is the same. Molecules randomly move from an area where they are most concentrated, to areas of lesser concentration.This is what is meant by the term concentration gradient - since molecules move from an area of high, to an area of low concentration, they are said to move down a concentration gradient.