What are micelles? How do they differ from a normal colloidal solution?

Answer

**Step-by-Step Solution:**

1. **Definition of Micelles:**
- Micelles are aggregates of surfactant molecules that form in a solution when the concentration of the surfactant exceeds a certain threshold known as the critical micelle concentration (CMC). At low concentrations, surfactants behave like normal solutes, but at concentrations above the CMC, they aggregate to form micelles.

2. **Structure of Micelles:**
- Micelles typically consist of a hydrophilic (water-attracting) head and hydrophobic (water-repelling) tails. For example, in soap, the sodium ion (Na⁺) is the hydrophilic part, while the fatty acid chain (represented by the -COO group) is the hydrophobic part.

3. **Behavior of Micelles:**
- At low concentrations, surfactants dissolve in water and do not form micelles. However, as the concentration increases and reaches the CMC, the surfactant molecules start to aggregate, forming micelles. This aggregation allows them to effectively trap and remove grease and dirt, which is why they are used in cleaning products.

4. **Difference from Normal Colloidal Solutions:**
- A normal colloidal solution consists of small particles that remain dispersed throughout the solvent without forming aggregates. In contrast, micelles are specifically formed by the aggregation of surfactant molecules at high concentrations.
- Additionally, micelles have lower colligative properties compared to regular colloidal solutions. This means that they exhibit different behaviors in terms of properties such as boiling point elevation, freezing point depression, and osmotic pressure.

5. **Summary of Differences:**
- Micelles are associated colloids formed at high concentrations of surfactants, while normal colloidal solutions consist of dispersed particles that do not aggregate. Micelles also show distinct colligative properties compared to typical colloidal solutions.

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