Short Notes:

Diffusion is the movement of molecules from a region of higher concentration to a region of lower concentration. Diffusion happens all the time in the air around us. For example, whenever we spray some perfume at one end of a room, another person at the other end of the room will eventually be able to sense it. This happens because the perfume molecules move from a region of higher concentration (point at which the perfume is sprayed) to a region of lower concentration.