Surface Tension Estimation of Binary System of Several Organic Liquids

摘要

One of the most striking demonstrations of the intermolecular forces is the tension at the surface of a liquid. Recently, a new expression for the surface tension prediction of a binary liquid system. Using the proposed equation, surface tensions are predicted within an overall 2.5 AAD%, which is better than the other available prediction methods. Surface tension is caused by the attraction between the molecules of the liquid by various intermolecular forces. In the bulk of the liquid each molecule is pulled equally in all directions by neighboring liquid molecules, resulting in a net force of zero. At the surface of the liquid, the molecules are pulled inwards by other molecules deeper inside the liquid but they are not attracted as intensely by the molecules in the neighboring medium (whether vacuum, air, or another liquid). Therefore, all of the molecules at the surface are subject to an inward force of molecular attraction that can be balanced only by the resistance of the liquid to compression. Thus, the liquid squeezes itself together until it has the locally lowest surface area possible. Another way to think about it is that a molecule in contact with a neighbor is in a lower state of energy than if it were not in contact with a neighbor. The interior molecules all have as many neighbors as they can possibly have, but the boundary molecules have fewer neighbors than interior molecules and are therefore in a higher state of energy. For the liquid to minimize its energy state, it must minimize its number of boundary molecules and therefore minimize its surface area (Adamson and Gast, 1997).