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Colloids are classified in 2 different ways
Based on the physical state of the dispersed phase and dispersed medium:
| S.No | Dispersed Phase | Dispersed Medium | Name of Colloid | Examples |
| 1. | Solid | Solid | Solid sol | Gem stones |
| 2. | Solid | Liquid | Sol | Muddy water, Paint, cell fluids |
| 3. | Solid | Gas | Aerosol | Smoke,dust |
| 4. | Liquid | Solid | Gel | Cheese, butter, jelly |
| 5. | Liquid | Liquid | Emulsion | Milk, Hair cream |
| 6. | Liquid | Gas | Aerosol | Fog, mist, cloud |
| 7. | Gas | Solid | Solid Foam | Pumice Stone |
| 8. | Gas | Liquid | Foam | Froth, soap lather |
Based on nature of Interaction Between Dispersed Phase and Dispersed Medium
Lyophilic Colloids(liquid loving)-
- Some substances which can from colloids directly on mixing them with a suitable liquid(dispersion medium). These colloids are called lyophilic colloids. Examples of these substances are gum, geltine, starch, rubber.
- They are also called Reversible sols as in these sols(colloids) when the dispersion phase is separated from the dispersion medium (by say evaporation) , the sol can be formed again by just mixing the dispersion phase and medium again.
- They are also very stable and cannot be coagulated
Lyophobic colloids(liquid hating)
- Some substances cannot form colloid just by directly mixing them with a liquid. Their colloidal sols are prepared by special methods and are called lyophobic colloids. Examples of these substances are metals, metal sulphides.
- They are also called Irreversible colloids as on precipitation, they don’t give back the colloid on simply mixing the dispersed phase and the dispersed medium.
- They are unstable and coagulate easily by heating shaking or adding electrolytes. Stabilising agents are used to preserve them
Based on the Types of Particles of the Dispersed Phase-
- Multimolecular Colloids: Many particles(atoms or small molecules) of the dispersed phase aggregate together to form species having the size of a colloidal particle( 1-1000nm). These colloids are called multimolecular colloids. Example-gold sol, Sulphur sol
- Macromolecular colloids: Substances with large molecules (macromolecules) in suitable solvents form solutions but these macromolecules might be in the colloidal range. These solutions are called macromolecular colloids and resemble true solutions in many ways. Example- Starch, Cellulose, Proteins are natural macromolecules. Nylon, polythene, polystyrene are man-made macromolecules
- Associated Colloids: Some substances at high concentrations act as colloids due to the formation of aggregates. But at low concentrations they behave like normal strong electrolytes. These aggregates formed are called micelles. Such colloids are called associated colloids.
Kraft Temperature- The formation of micelles takes place only above a particular temperature called Kraft’s temperature
Critical Micelle Concentration(CMC) – The concentration above which micelle formation takes place
Example- Soaps, synthetic detergents
