
 Surface tension, or interfacial tension (, ) 
  The tension acting in the surface of tension is called the surface tension or interfacial tension and is expressed in terms of force per unit length. 
  In particular, surface tension is the intensive factor in the differential expression for the work required to increase the area of the surface of tension. 
  The surface tension may, therefore, also be expressed in terms of energy per unit area: it is not, however, in general equal either to the surface energy or to the surface Helmholtz energy per unit area (see §1.2.6). 
 www.iupac.org /reports/2001/colloid_2001/manual_of_s_and_t/node23.html (322 words) 
