Colloids

Last updated at April 16, 2024 by Teachoo

In a colloid, the size of particles is neither too small like in true solution and neither too large like in the suspension (1 - 100 nm).

Hence, there appear to be a homogeneous mixture but they are an actually heterogeneous mixture

Examples of Colloids

Soap Solutions, Milk, Ink, blood

Why is Milk a colloid?

If we examine a drop of milk under a microscope

We see small particles of fat floating in liquid which do not dissolve in liquid.

There are different types of Colloids depending on the Dispersed Phase (solute) and Dispersing Medium (solvent) , like

Sol - Tiny solid particles in liquid. Example - Blood, Mud
Solid Sol - Tiny solid particles in solid . Example - Coloured Gemstones (like Ruby), Milky Glass
Aerosols - A solid or a liquid in dispersed in gas. Example - Fog, Smoke
Emulsions - Minute droplets of one liquid in dispersed in another liquid (but is not miscible in it) . Example - Milk, Butter
Foam - Gas in dispersed in liquid. Example - Fire Extinguisher foam, Soap Bubbles, Beer Foam
Solid Foam - Gas in dispersed in Solid. Example - Sponge, Bread
Gel - Gel is a semi-solid, it is a continuous network of solid particles in a liquid m edium. The cross linked structure of the solid in the liquid makes it behave like a solid. Example - Fruit jelly, Hair Gel

Type	Dispersed Phase	Dispersing Medium	Example
Aerosol	Liquid	Gas	Fog, Clouds, mist
Aerosol	Solid	Gas	Smoke, automobile, exhaust
Sol	Solid	Liquid	Milk of magnesia, mud
Solid Sol	Solid	Solid	Coloured gemstone, milky glass
Foam	Gas	Liquid	Shaving Cream
Foam	Gas	Solid	Foam, rubber, sponge, Pumice
Emulsion	Liquid	Liquid	Milk, face Cream
Gel	Liquid	Solid	Jelly, cheese, butter

It is a heterogeneous mixture
Size of particles is neither too small nor too large (1 - 100nm) but are too small to be seen by the naked eye
However, particles are large enough to scatter a beam of light; Tyndall Effect
Particles are stable , they do not settle down when left undisturbed.