Colloids

Definition

Colloids are mixtures where one substance is dispersed evenly throughout another but does not dissolve. The dispersed particles are typically between 1 and 1000 nanometers in size.

5 Must Know Facts For Your Next Test

1. Colloids can be classified based on the phases of the dispersed and continuous mediums, such as aerosols, foams, emulsions, and sols.
2. The Tyndall effect is a phenomenon observed in colloids where light is scattered by the dispersed particles, making the path of light visible.
3. Stability of colloids can be influenced by factors like particle charge, presence of electrolytes, and pH levels.
4. Colloidal particles do not settle out upon standing due to Brownian motion, which keeps them suspended.
5. Common examples of colloids include milk (emulsion), fog (aerosol), and gelatin (gel).

Review Questions

• What is the size range of particles in a colloid?
• Explain how the Tyndall effect helps identify a colloid.
• Why don't colloidal particles settle out upon standing?

Related terms

Suspension:

A heterogeneous mixture where larger particles are dispersed in a liquid or gas but will eventually settle over time.

Solution:

A homogeneous mixture where one substance (solute) is completely dissolved in another substance (solvent).

Emulsion:

A type of colloid formed from two immiscible liquids where one liquid contains droplets of the other.