Understand How High and Low Concentrations Relate to Diffusion

Diffusion is the movement of particles of a substance from an area of high concentration (where there are a lot of them) to an area of low concentration (where there are fewer of them). 

High concentration = A large number of particles of one substance in a specific volume of another substance.

Low concentration = A small number of particles of one substance in a specific volume of another substance.

As you can see in the picture below, there is an area where there is a high concentration (where the red particles are all grouped together). Diffusion is when a substance moves from an area where they are in high concentration to an area where there is a lower concentration of them - so in this case, to the right.

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