Question

Justify the statement the cleansing action of soap is due to emulsification and micelle formation.

Answer 1

Soaps:

1. Soaps are sodium and potassium salts of $\mathrm{R}-\mathrm{COO}-{\mathrm{Na}}^{+}$ long-chain fatty acids. The end of the molecule to which the sodium is linked is polar, whereas the alkyl end is non-polar.
2. As a result, a soap molecule has both a hydrophilic (polar) and a hydrophobic (nonpolar) component.
3. When soap is dissolved in water, it separates into two parts: ${\mathrm{COO}}^{-}$ and ${\mathrm{Na}}^{+}$ ions, the hydrophilic part of the micelle being${\mathrm{COO}}^{-}$, which is present in the water, and the ${\mathrm{Na}}^{+}$ ions sticking to the oil molecules in the solution.
4. If in a container, we mix oil and water, and they are allowed to settle. Because oil is a less dense substance, it will float on water.
5. There will be a transient layer of emulsion if you shake them vigorously.
6. When we add soap or detergent as a surfactant, the emulsion of oil and water becomes more stable. Emulsification is the term for this procedure.
7. A surfactant, such as soap or detergent, is required. Water attracts the hydrophilic head of soap, while non-polar particles like dirt attract the hydrophobic end.
8. This results in the formation of a micelle.
9. When surfactants are above a threshold micelle concentration, micelles act as emulsifiers, making a molecule soluble in a solution that is normally insoluble.

Therefore, the cleansing action of soap is due to emulsification and micelle formation.