On which principle oleansing action of soap is based ?

Answer

### Step-by-Step Text Solution:

1. **Understanding the Composition of Soap**:
- Soap is primarily composed of sodium salts of fatty acids. A common example is sodium stearate, which has the chemical formula C17H35COONa.
- This molecule consists of two distinct parts: a long hydrophobic (water-repelling) hydrocarbon chain (C17H35) and a hydrophilic (water-attracting) carboxylate group (COO-).

2. **Hydrophobic and Hydrophilic Properties**:
- The long hydrocarbon chain (C17H35) is non-polar and does not interact favorably with water, making it hydrophobic.
- The carboxylate group (COO-) is polar and interacts well with water, making it hydrophilic.

3. **Micelle Formation**:
- When soap is added to water, the hydrophobic tails of the soap molecules tend to avoid water and aggregate together, while the hydrophilic heads remain in contact with the water.
- At a certain concentration known as the critical micelle concentration (CMC), the soap molecules form structures called micelles. In these micelles, the hydrophobic tails are shielded from water, while the hydrophilic heads face outward.

4. **Cleansing Action of Soap**:
- When soap is used for cleaning, the hydrophobic tails of the soap molecules attach to dirt and grease (which are also hydrophobic).
- The hydrophilic heads remain in contact with water. When rinsing with water, the micelles, which now encapsulate the dirt and grease, are washed away, effectively cleaning the surface.

5. **Conclusion**:
- The cleansing action of soap is based on the principle of micellar formation, which allows the soap to encapsulate dirt and grease, making it easier to wash them away with water.