Substance consisting of particles that, although too tiny to be seen with the unaided eye (typically 1 nanometre to 10 micrometres), are substantially larger than atoms and ordinary molecules and that are dispersed in a continuous phase. Both the dispersed phase and the continuous phase may be solid, liquid, or gas; examples include suspensions, aerosols, smokes, emulsions, gels, sols, pastes, and foams. Colloids are often classified as reversible or irreversible, depending on whether their components can be separated. Dyes, detergents, polymers, proteins, and many other important substances exhibit colloidal behaviour.

This entry comes from Encyclopædia Britannica Concise.
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