Surface energy quantifies the disruption of intermolecular bonds that occur when a surface is created. In the physics of solids, surfaces must be intrinsically less energetically favorable than the bulk of a material (the molecules on the surface have more energy compared with the molecules in the bulk of the material), otherwise there would be a driving force for surfaces to be created, removing the bulk of the material (see sublimation). The surface energy may therefore be defined as the excess energy at the surface of a material compared to the bulk.
For a liquid, the surface tension (force per unit length) and the surface energy density are identical. Water has a surface energy density of 0.072 J/m2 and a surface tension of 0.072 N/m.
Cutting a solid body into pieces disrupts its bonds, and therefore consumes energy. If the cutting is done reversibly (see reversible), then conservation of energy means that the energy consumed by the cutting process will be equal to the energy inherent in the two new surfaces created. The unit surface energy of a material would therefore be half of its energy of cohesion, all other things being equal; in practice, this is true only for a surface freshly prepared in vacuum. Surfaces often change their form away from the simple "cleaved bond" model just implied above. They are found to be highly dynamic regions, which readily rearrange or react, so that energy is often reduced by such processes as passivation or adsorption.
Read more about Surface Energy: Measuring The Surface Energy of A Liquid, Measuring The Surface Energy of A Solid, Calculating The Surface Energy of A Deformed Solid, Calculating The Surface Formation Energy of A Crystalline Solid
Famous quotes containing the words surface and/or energy:
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—Earl Felton, and Richard Fleischer. Captain Nemo (James Mason)
“Long before Einstein told us that matter is energy, Machiavelli and Hobbes and other modern political philosophers defined man as a lump of matter whose most politically relevant attribute is a form of energy called “self-interestedness.” This was not a portrait of man “warts and all.” It was all wart.”
—George F. Will (b. 1941)