What are colloidal solutions ?

Explanation

A heterogeneous system in which one substance is dispei ed as large particles in another substance is called colloidal solution.
`to` In colloidal solution the particle size of the dispersed phase is of the order of `l mmu`- 1 `mu -1 mu` where as in true solution the particle size of the solute are the order of m`mu` or less.
`to `Colloidal solution is a heterogeneous binary system where as true solution is a homogeneous binary system.
On the basis of physica! states of dispersed phase and dispei sion medium colloidal solutions are classified into eight types.


On the basis of nature of difersion medium colloids are classified as follows.
`to` If the dispersion medium is 'air' , the sols are called aerosols. Eg: Smoke .
`to` If the dispersion medium is 'water' the sols are called hydrosol (or) aquasol .
Eg: Starch solution.
`to` If the disperison medium is 'alcohol ' then the sols are called alcosols.
The colloidal solution in which the dispersed phase has great affinity to the dispersion medium is called a Lyophillic colloid or Lyophilic solution. Ex: Starch solution.
The starch paste when dissolved in hot water, with stirring, the starch solution is formed. The starch particles (dispersed phase) has great affinity to water molecules (dispersion medium). So starch solution is a lyophilic solution or lyophilic colloid.
Lyophobic colloid : The colloidal solution in which there exists not much affinity between the dispersed phase and dispersion medium, it is called a Lyophobic colloid or Lyophobic solution. Ex : Gold solution.
Gold rods are placed in water containing alkali. Electric arc is applied between gold rods. the gold particles dissolves in water, to give gold solution.
Gold particles (dispersed phase) have not much affinity towards water (dispersion medium) . So this is a Lyophobic solution or Lyophobic colloid.