What are colloidal solutions? Give examples.

A colloidal solution is said to be intermediate state of the solution and the suspension. It is neither a true solution nor a suspension. In colloidal solution, the particle size is between 1 nm to 100 nm. For example, a solution of soap in water, milk, blood, writing inks are some of the colloidal solutions. Though these particles are 10 to 1000 times the size of a single small molecule, these are not visible to naked eyes. But these are large enough to scatter the light that passes through the dispersion medium. The medium of colloidal solution is known as dispersion phase (dispersion medium) and the particles dissolved are called dispersed phase. 

Properties of a colloid:

1) A colloid is a heterogeneous mixture. The size of particles of a colloid is too small to be individually seen by naked eyes.

2) Colloids are big enough to scatter a beam of light passing through it and make its path visible.

3) They do not settle down when left undisturbed, that is, a colloid is quite stable.

4)They cannot be separated from the mixture by the process of filtration. But, a special technique of separtion known as centrifuagtion can be used to separate the colloidal particels.