The force existing in any boundary surface
of a liquid such that the surface tends to
assume a minimum possible area. It is defined as the force perpendicular
to a line of unit length drawn on the surface. Surface tension arises from
the cohesive forces between liquid molecules
and from the fact that a molecule in the interior of a liquid is pulled
equally from all sides by its neighbors, whereas a molecule at the surface
is only attracted by molecules below it in the liquid; it makes a liquid
surface behave as if it had an elastic membrane stretched over it.
|Surface tension effects allow adapted insects to
"skate" on the surface of a pond, or a needle to be "floated" in a
cup of water.
Surface tension is responsible for the formation of liquid drops and bubbles,
and governs the wetting properties of liquids, capillary
action, and the action of detergents.
Water has an extremely high surface tension.