At the critical micelle concentration, the surfactant molecules

Options

A. Decompose
B. Dissociate
C. Associate
D. Become completely soluble

Answer

To solve the question, "At the critical micelle concentration, the surfactant molecules," we need to understand the behavior of surfactants in solution, particularly at the critical micelle concentration (CMC). Here’s a step-by-step solution:

### Step 1: Understanding Surfactants
Surfactants are compounds that lower the surface tension between two substances, such as oil and water. They have a hydrophilic (water-attracting) head and a hydrophobic (water-repelling) tail.

**Hint:** Remember that surfactants have two distinct parts: a hydrophilic head and a hydrophobic tail.

### Step 2: Defining Critical Micelle Concentration (CMC)
The critical micelle concentration (CMC) is the concentration of surfactants in a bulk phase above which the surfactants start to form micelles. Below this concentration, surfactants exist as individual molecules in solution.

**Hint:** CMC is the threshold concentration where surfactants begin to aggregate into micelles.

### Step 3: Formation of Micelles
At concentrations above the CMC, surfactant molecules aggregate to form micelles. A micelle is a spherical structure where the hydrophobic tails are oriented inward, away from water, while the hydrophilic heads face outward, interacting with the aqueous environment.

**Hint:** Micelles form to minimize the energy associated with the presence of hydrophobic tails in water.

### Step 4: Conclusion
At the critical micelle concentration, surfactant molecules aggregate to form micelles. This aggregation is a key characteristic of surfactants and is crucial for their function in various applications, such as detergents and emulsifiers.

**Final Answer:** At the critical micelle concentration, the surfactant molecules aggregate to form micelles.