Colloids

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.



Properties of Colloid

  • 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.

 

 

Difference between True solution, Suspension and Colloids

 

True Solution

Suspension

Colloid

It is a homogeneous mixture

It is a heterogeneous mixture

It is a heterogeneous mixture

Size of particles are very small (less than 1nm)

Size of particles are large (more than 100nm)

Size of particles is neither too small nor too large (1 - 100nm)

Individual Particles cannot be seen by the naked eyes

Particles of suspension can be seen by the naked eye

Particles of a colloid are too small to be seen by the naked eye

Particles are stable

they do not settle down when left undisturbed

Particles are not stable ,

 they settle down after some time

Particles are stable ,

 they do not settle down when left undisturbed

Particles of solution do not scatter light

Particles are large enough to scatter a beam of light

Particles are large enough to scatter a beam of light

Particles pass through filter paper, hence particles cannot be separated by filtration

Particles are large, they do no pass through filter paper, hence particles can be separated by filtration

Particles are small enough to pass through filter paper, hence particles cannot be separated by filtration

Examples

Examples

Examples

Solution of Salt and Water, Sugar and Water

Mixture of chalk and water, sand and water

Milk, blood

 

 

  1. Class 9
  2. Chapter 2 Class 9 - Is Matter Around Us Pure

About the Author

CA Maninder Singh's photo - Founder at Teachoo
CA Maninder Singh
CA Maninder Singh is a Chartered Accountant for the past 11 years and a teacher from the past 11 years. He teaches Science, Accounts and English at Teachoo