London Forces - weak attractive forces between molecules resulting from small, instantaneous dipoles that occur because of the varying positions of the electrons during their motion about the nuclei. London Forces tend to increase with increasing molecular weight and with polarizability. Polarizability - ease of distortion of the electron cloud about the molecule or atom. The Liquid State - Physical properties can be explained on the basis of the intermolecular forces. Surface Tension - the energy required to increase the surface area of a liquid by a unit amount.
Surface area tends to be reduced as much as possible.
This is why drops of water are spherical. This is because molecules at the surface experience a net attraction by the molecules in the interior of the liquid. Capillary Rise - when a small diameter tube of glass is placed into water the water crawls up the sides of the glass tube due to the attractive force between the water molecules and the glass wall. As this occurs the surface area of the water increases, to decrease the surface area the water level rises. The level to which it rises it related to the attractive forces between the water molecules and the glass and the surface tension of water.