Is Matter Around Us Pure - Suspensions and Colloids

A suspension is a heterogeneous mixture in which the solute particles do not dissolve but remain suspended throughout the bulk of the medium. The particles of a suspension are visible to the naked eye and have a diameter greater than $10^{-7} \text{ m}$ (or $100 \text{ nm}$).

Suspensions are unstable; if left undisturbed, the particles settle down. They can be separated from the mixture by the process of filtration. They scatter a beam of light passing through them (Tyndall Effect) until the particles settle down.

A colloid is a heterogeneous mixture where the particle size is intermediate between a true solution and a suspension, typically between $1 \text{ nm}$ and $100 \text{ nm}$ ($10^{-9} \text{ m}$ to $10^{-7} \text{ m}$).

Colloidal particles are too small to be seen individually by the naked eye but are big enough to scatter a beam of light. This scattering of light is known as the Tyndall Effect.

Colloids are quite stable; their particles do not settle down when left undisturbed. They cannot be separated by filtration but can be separated by a special technique known as centrifugation.

The components of a colloidal solution are the dispersed phase (the solute-like component) and the dispersion medium (the solvent-like medium).

Common examples of colloids include Aerosols (Fog, Clouds), Foam (Shaving cream), Emulsions (Milk, Face cream), and Sols (Milk of magnesia, Mud).