The cohesive forces between the water molecules are very strong making the surface tension of water high. ... The intermolecular forces between surfactant and water molecule are much lower than between two water molecules and thus surface tension will decrease. When the surfactant concentration is high, they form micelles.

Which surfactant forms micelles?

Surfactants form aggregate molecules such as micelles. The hydrophobic end makes most of the micelles. The critical molar concentration is the concentration of surfactant molecules present in the bulk of the solution. The micelles start forming above this critical molar concentration.

Why do micelles form?

The number of individual molecules forming a micelle is called the aggregation number of the micelle. The formation of micelles is driven by the decrease of free energy in the system because of the removal of the hydrophobic segments from the aqueous environment and reestablishing of hydrogen bond network in water.