What is surface tension

Surface tension is a property of the surface of a liquid that allows it to resist an external force. It is revealed, for example,

in floating of some objects on the surface of water, even though they are denser than water, and in the ability of some

insects (e. g. water striders) and even reptiles (basilisk) to run on the water surface. This property is caused by cohesion

of like molecules, and is responsible for many of the behaviors of liquids ...

The surface tension of water is 72 dynes/cm at 25°C. It would take a force of 72 dynes to break a surface film of water 1 cm long. The surface tension of water decreases significantly with temperature as shown in the graph. The surface tension arises from the polar nature of the water molecule. Hot water is a better cleaning agent because the lower surface tension makes it a better "wetting agent" to get into pores and fissures rather than bridging them with surface tension. Soaps and detergents further lower the surface tension.