The critical micelle concentration CMC of a given surfactant is the concentration at which surfactant molecules in a solution start to aggregate and form micelles. Micelles are spherical structures formed by surfactant molecules, where the hydrophobic tails are directed towards the center, and the hydrophilic heads are on the surface, interacting with the surrounding solvent. The CMC is an important parameter in understanding the behavior of surfactants in various applications, such as detergents, emulsifiers, and drug delivery systems.The CMC affects the surface tension of a solution in the following way:1. Below the CMC: When the surfactant concentration is below the CMC, the surfactant molecules are primarily adsorbed at the air-water interface, reducing the surface tension of the solution. As the concentration of the surfactant increases, the surface tension continues to decrease.2. At the CMC: When the surfactant concentration reaches the CMC, the surface tension reaches a minimum value, and the surfactant molecules start to form micelles. At this point, the surface is saturated with surfactant molecules, and any additional surfactant added to the solution will primarily contribute to micelle formation rather than further reducing the surface tension.3. Above the CMC: When the surfactant concentration is above the CMC, the surface tension remains relatively constant, as the majority of the added surfactant molecules are forming micelles in the bulk solution rather than adsorbing at the air-water interface.In summary, the critical micelle concentration of a surfactant is the point at which micelle formation begins, and it affects the surface tension of a solution by causing a decrease in surface tension up to the CMC, after which the surface tension remains relatively constant.