Diffusion
Diffusion is the spread of particles through random motion from regions of higher concentration to regions of lower concentration.
It can apply to solids, liquids and gases. Below there are examples of diffusion in gases.
The animations below describe gases inside containers.
In a first moment, the gas atoms diffuse to occupy all the volume available to each of them (half of the total volume). Then, the blue gas diffuses into the red gas and vice versa.
1) Slow diffusion
2)Fast diffusion