What are some examples of colloids and suspensions?

1 Answer
Aug 11, 2016

A colloid is a suspension, but it has mean particle size in the region 1 - 1000 nm. (#10^-9 - 10^-6# m).


Examples of colloids include:

Gas in liquid: Shaving cream.
Liquid in liquid (immiscible phases): Milk
Solid in liquid: Pigmented inks
Liquid in solid: Jelly

Aside from the dimensions of the dispersed phase, the other thing that is required to qualify a suspension as a coiloid is the stability of the system; it should not separate out into two phases on standing (or at least not for an extremely long time).

A suspension that would not be classified as a colloid would be something like soil in water (it separates into a soil layer and a water layer after a few hours, and some particulates will be well over 1000 nm diameter), or vinegar/oil salad dressing (a few minutes after being shaken it has separated into two immiscible layers again).