Diffusion Diffusion is the movement of molecules from a high concentration to a low concentration.

Diffusion Diffusion results from the movement of particles in both liquids and gases.

Regardless of their type, particles in liquids and gases are in constant motion driven by energy which they absorb from the heat of their surroundings. This movement, called thermal motion, speeds up as the temperature of their surroundings warms up. Kinetic theory of matter

Consider the following example as a demonstration of dispersion and intermixing of molecules. A drop of perfume is placed on a desk top at the front of a classroom. Being volatile the perfume quickly begins to evaporate creating a high concentration of perfume molecules above the drop.

Since the perfume molecules are in constant random motion they bump into each other causing some molecules to be occasionally sent hurtling out of the mass. Gradually the molecules spread out from the drop on the front desk and are sensed by students in the front of the classroom.

Diffusion causes molecules to disperse from a centre of concentration

Further spreading of molecules carries the perfume molecules to the middle of the classroom and finally to the back of the room.

Eventually the perfume molecules are evenly intermixed with the nitrogen, oxygen and carbon dioxide molecules of the air such that one litre of air from the front of the room would contain the same number of perfume molecules as a litre of air from the back of the room.

DIFFUSION IS THE MOVEMENT OF MOLECULES FROM AN AREA OF HIGHER CONCENTRATION TO AN AREA OF LOWER CONCENTRATIONS.