Suspensions & Colloids

What is Suspension?

A suspension is defined as a homogenous mixture of particles with a diameter greater than 1000 nm such that the particles are visible to naked eyes. In this type of mixture, all the components are completely mixed and all the particles can be seen under a microscope.

Suspension & Precipitation

Suspension & Precipitation

If we take a glass full of water and mix mud in it, it will form a heterogeneous mixture. We can easily identify the components of these mixtures.  After some time we will observe that particles of mud settle down due to gravity. The particles in suspension are larger than the particles in a solution.

What is a Solution?

A solution is a homogeneous mixture of substances. For example, when salt dissolves in water, a homogeneous mixture, or solution, forms. The component of a mixture that is present in the greatest quantity or that determines the state of matter of the solution is called the solvent and the other component is called solute.

What is Colloid?

A Colloid is an intermediate between solution and suspension. It has particles with sizes between 2 to 1000 nanometers. A colloid is easily visible to the naked eye. Colloids can be distinguished from solutions using the Tyndall effect. Tyndall effect is defined as the scattering of light (light beam) through a colloidal solution. The particles are termed as colloidal particles and the mixture formed is known as colloidal dispersion. Liquid, solid and gases all mix together to form a colloidal dispersion.


Examples of Colloids

The different types of colloidal solution are:

  • Aerosols: Solid or liquid mixed with gas; Example: fog (liquid in gas)
  • Sols: Solid mixed with liquid; Example: Paint
  • Emulsion: Liquid with liquid; Example: oil and water
  • Gel: liquid in solid; Example: Fruit jelly

Difference between Colloid and Suspension

The difference between suspension and colloids are tabulated below.

                           Suspension                                   Colloid
It is a form of the homogeneous solution It is a form of heterogeneous solution
Particle size greater than 1000 nm Particle size range from 1-1000 nm
Particles settle down well Particles do not separate
Can be separated by filtration Cannot be separated by filtration
May scatter light Shows Tyndall effect (scatters light)
Opaque Translucent
Easily visible through the naked eye Not visible through the naked eye

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