A substance which forms micelles in solutions contains 

Options

A. carboxylic group
B. alkyl group
C. water insoluble long hydrocarbon groups and water soluble polar groups
D. water soluble hydrocarbon group and water insoluble polar group

Answer

To solve the question regarding a substance that forms micelles in solution, we can break down the characteristics of such substances step by step.

### Step-by-Step Solution:

1. **Understanding Micelles**: Micelles are aggregates of surfactant molecules that form in a solution when the concentration of surfactants exceeds a certain threshold known as the critical micelle concentration (CMC).

2. **Components of Surfactants**: Surfactants, which form micelles, typically consist of two distinct parts:
- **Hydrophobic Part**: This is the long hydrocarbon chain that is water-insoluble. It repels water and is often referred to as the hydrophobic tail.
- **Hydrophilic Part**: This is the polar group that is water-soluble. It interacts favorably with water and is known as the hydrophilic head.

3. **Formation of Micelles**: In an aqueous solution, surfactant molecules arrange themselves such that the hydrophobic tails are shielded from water, while the hydrophilic heads remain in contact with the water. This arrangement leads to the formation of micelles, where the hydrophobic tails are oriented inward, away from the water, and the hydrophilic heads are oriented outward, in contact with the water.

4. **Conclusion**: Therefore, a substance that forms micelles in solution must contain:
- Water-insoluble long hydrocarbon groups (hydrophobic part)
- Water-soluble polar groups (hydrophilic part)

Thus, the correct answer is that a substance which forms micelles in solution contains water-insoluble long hydrocarbon groups and water-soluble polar groups.