ABSTRACT
Interfacial energy is the excess energy due to the existence of an interface. This excess energy arises from unbalanced molecular interactions associated with interfacial molecular particles compared to the more symmetrical interactions with neighbouring particles that occur in bulk materials. This chapter explores surface behaviour with an energy model to compare the values of the various interfacial energies. It determines whether the new solid-liquid interfacial energy is less than the combined solid-air and liquid-air interfacial energies lost during the formation of the interface. Small variations in the adsorption energy from system to system make very considerable differences in the typical ‘adsorption time’ or residence time on the surface. More mundane but just as important are applications of aerogels in house insulation and solar energy collection. If some repulsive interaction is added to the model so that the collisions are less ‘sticky’, incoming particles are free to seek lower-energy sites with more near neighbours and a resulting increase in density.
