ABSTRACT
This chapter discusses the concept of interfacial tension and calculates the free energy and composition profile as one goes from one phase, through the interface, to the other phase. The additional free energy per unit area to remove molecules from the bulk and create interface between two coexisting phases is known as the surface or interfacial tension which has the units of energy per unit area, or force per unit length. A rule of thumb in estimating interfacial tensions is that the interfacial tension is a characteristic energy divided by a characteristic area related to size of the interfacial region. To find the surface tension or interfacial tension, one inserts the solution back into the free energy per unit area and subtracts off the free energy per unit area of the bulk phases. Therefore the free energy cost of having a smooth interfacial profile for the composition is related to the surface tension.
