Colloid Examples in Chemistry

Colloids are uniform mixtures that don't separate or settle out. While colloidal mixtures are generally considered to be homogeneous mixtures, they often display heterogeneous quality when viewed on the microscopic scale. There are two parts to every colloid mixture: the particles and the dispersing medium. The colloid particles are solids or liquids that are suspended in the medium. These particles are larger than molecules, distinguishing a colloid from a solution. However, the particles in a colloid are smaller than those found in a suspension. In smoke, for examples, solid particles from combustion are suspended in a gas. Here are several other examples of colloids:

Aerosols

• fog
• insecticide spray
• clouds
• smoke
• dust

Foams

• whipped cream
• shaving cream

Solid Foams

• marshmallows
• Styrofoam

Emulsions

• milk
• mayonnaise
• lotion

Gels

• gelatin
• butter
• jelly

Sols

• ink
• rubber
• liquid detergent
• shampoo

Solid Sols

• pearl
• gemstones
• some colored glass
• some alloys

How to Tell a Colloid From a Solution or Suspension

At first glance, it may seem difficult to distinguish between a colloid, solution, and suspension, since you can't usually tell the size of the particles simply by looking at the mixture. However, there are two easy ways to identify a colloid:

1. Components of a suspension separate over time. Solutions and colloids don't separate.
2. If you shine a beam of light into a colloid, it displays the Tyndall effect, which makes the beam of light visible in the colloid because light is scattered by the particles. An example of the Tyndall effect is the visibility of light from car headlamps through fog.

How Colloids Are Formed

Colloids usually form one of two ways:

• Droplets of particles may be dispersed into another medium by spraying, milling, high-speed mixing, or shaking.
• Small dissolved particles may be condensed into colloidal particles by redox reactions, precipitation, or condensation.