There are certain substances which behave as normal, strong electrolyte at low concentration but at higher concentration they behave as colloidal solutions due to the formation of aggeregated particles. Such colloidals called associated colloids and the aggeregated particles are called micelles. The formation of micelles take place above certain concentration called critical micelization concentration called critical micellization concentration (CMC) and a characteristic temperature.
What type of molecules form micelles?

Options

A. Non-polar molecules
B. polar molecules
C. Surfactant molecules
D. Salt of weak acid and weak base

Answer

To answer the question regarding the type of molecules that form micelles, we can follow these steps:

### Step 1: Understand the Concept of Micelles
Micelles are formed when certain substances, known as surfactants, aggregate in solution above a specific concentration called the critical micelle concentration (CMC). At low concentrations, these substances behave as normal strong electrolytes, but at higher concentrations, they form colloidal solutions.

### Step 2: Identify the Characteristics of Surfactants
Surfactants are unique molecules that possess two distinct parts:
- **Hydrophobic (water-repelling) part**: This part of the molecule does not interact favorably with water and tends to avoid it.
- **Hydrophilic (water-loving) part**: This part of the molecule interacts favorably with water and is attracted to it.

### Step 3: Explain the Formation of Micelles
When surfactant molecules are added to water, the hydrophobic tails tend to aggregate away from the water, while the hydrophilic heads remain in contact with the water. This aggregation leads to the formation of micelles, where the hydrophobic tails are shielded from the water, and the hydrophilic heads are exposed to the aqueous environment.

### Step 4: Identify the Type of Molecules that Form Micelles
From the options provided (non-polar molecules, polar molecules, surfactant molecules, and salts of weak acids and weak bases), the only type that possesses both hydrophobic and hydrophilic parts is:
- **Surfactant molecules (Option C)**

### Conclusion
Therefore, the type of molecules that form micelles are surfactant molecules, as they have both hydrophobic and hydrophilic groups necessary for micelle formation.

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