The surface tension of water at room temperature approximately 20-25C is around 72 millinewtons per meter mN/m .Surfactants, or surface-active agents, are compounds that lower the surface tension of a liquid. They do this by adsorbing at the liquid-air interface, reducing the cohesive forces between the liquid molecules. As a result, the liquid molecules at the surface are less attracted to each other, leading to a decrease in surface tension.When surfactants are added to water, they form a thin layer at the surface, disrupting the hydrogen bonding between water molecules. This reduces the energy required to create new surface area, thus lowering the surface tension. The extent to which the surface tension is reduced depends on the concentration and type of surfactant used. At a certain concentration, called the critical micelle concentration CMC , surfactants begin to form micelles, and the surface tension reaches its lowest value. Beyond the CMC, adding more surfactants will not significantly affect the surface tension.