The formation of this film may be visualized on the basis of surface energy or work per unit area required to bring the molecules to the surface. The surface tension is then the stretching force required to from the film, obtained by dividing the surface-energy term by unit length of the film in equilibrium. the surface tension of water varies from about 0.074 N/m at 20 c to 0.059 N/mat 100 C. Surface tension, along with other properties, are given for a few common liquids in Table 1.2