What is colloid?
 
A homogeneous non-crystalline substance consisting of large molecules or ultramicroscopic particles of one substance dispersed through a second substance. Colloids include gels, sols, and emulsions; the particles do not settle, and cannot be separated out by ordinary filtering or centrifuging like those in a suspension.

Properties of a colloid

• A colloid is a heterogeneous mixture.

• The size of particles of a colloid is too small to be individually seen by naked eyes.

• Colloids are big enough to scatter a beam of light passing through it and make its path visible.

• They do not settle down when left undisturbed, that is, a colloid is quite stable.

• They cannot be separated from the mixture by the process of filtration. But, a special technique of separation known as centrifugation can be used to separate the colloidal particles.

The components of a colloidal solution are the dispersed phase and the dispersion medium. The solute-like component or the dispersed particles in a colloid form the dispersed phase, and the component in which the dispersed phase is suspended is known as the dispersing medium. Colloids are classified according to the state (solid, liquid or gas) of the dispersing medium and the dispersed phase. A few common examples are given in Table. From this table you can see that they are very common everyday life.

What is colloid? Properties of Colloid | Common Examples of Colloids | Chemistry Lesson Plans

Common Examples of Colloids

Dispersing Phase

Dispersing Medium

Type

Example

Liquid

Gas

Aerosol

Fog, Clouds, Mist

Solid

Gas

Aerosol

Smoke, Automobile Exhaust

Gas

Liquid

Foam

Shaving Cream

Liquid

Liquid

Emulsion

Milk, Face Cream

Solid

Liquid

Sol

Milk of Magnesia, Mud

Gas

Solid

Foam

Foam, Rubber, Sponge, Pumice

Liquid

Solid

Gel

Jelly, Cheese, Butter

Solid

Solid

Solid sol

Coloured Gemstone, Milky Glass

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