What is diffusion?

Diffusion is the movement of particles of a substance in between the particles of another substance. Diffusion occurs slowest in solids, faster in liquids and the fastest in gases. This is due to the different arrangement of particles in solid, liquid and gas. The particles of a solid are packed closely together whereas the particles of a liquid are packed slightly loose. The particles of a gas are very far apart from each other and in a random arrangement.


The purple color of potassium manganite (VII), KMnO4 solution spreads slowly throughout the water. After a few hours, the water turns uniformly purple.