A heterogeneous mixture in which solute particles are larger than molecules or ions but cannot be seen by naked eye is called colloidal solution. A system which shows properties of colloidal solution is called colloidal system. Its example is clay in water or starch in water. The solvent is called the dispersion medium in a colloidal solution. The solid solute particles are called dispersed medium in colloidal solution. The dispersion medium may be a liquid, gas or solid.
- Smoke is composed of a solid dispersed in gas.
- Milk is a liquid dispersed in liquid
- Pumice stone is gas dispersed in s solids There are two forms of colloidal systems:
- 1. Sol: A system composed of non-viscous colloidal solution is called sol. For example milk.
2. Gel: A system composed of viscous colloidal solution is called gel. For example butter.
The colloidal systems can be classified into two general classes on the basis of their affinity for liquids: