Instructor's Answer: Non-polar molecules usually associate with one another when added to water. These cohesive interactions minimize the surface areas of interaction between individual water-molecules and the non-polar molecules. Stable dispersion of non-polar molecules in water is accomplished when an amphipathic molecule, e.g., phosphatidyl choline, forms a bridge between individual water molecules and individual non-polar molecules.

Student A: The usual behavior of a nonpolar molecule can be described as hydrophobic or fear of water; due to the fact that a nonpolar molecule does not have a concentration of a charge whereas a polar molecule does. When a nonpolar molecule comes into contact with water, a polar molecule, the nonpolar molecule has a tendency to clump together or melt into each other, rather than react with the water. This phenomena, as seen in mixes of such substances as oil and water, occurs as a result of nonpolar attractions or Van Der Waals forces. The nonpolar molecules can be dispersed by an interceding molecule that has one hydrophobic end and one polar end. This type of molecule, usually a detergent, will intercede between the two molecules and disperse the nonpolar molecule throughout the water.

Student B: Nonpolar molecules, or more properly, van der Waals forces, are hydrophobic: meaning that they prefer to mix into each other instead of mixing into water. The nonpolar fat molecules will cling together and form globules which prevent any association with the polar water molecules. They will surround (the nonpolar molecules that is) and dissolve other nonpolar molecules such as grease. To disperse the nonpolar molecules there must be a special molecule with one end polar and the other hydrophobic. Soaps and detergents have this unique characteristic and they are able to disperse themselves in water using the nonpolar molecule and the polar molecule as a link.

Student C: An interesting phenomena is associated with nonpolar molecules and water. Nonpolar molecules usually behave in a slightly sticky manner when surrounded by water molecules. This behavior is caused by the van der Waal"s forces that effect nonpolar molecules. These forces tend to attract nonpolar molecules together into globules when suspended in water. Water is an excellent solvent for most molecules because it is polar, however, nonpolar molecules are unaffected by this polarity. It is possible though to disperse nonpolar molecules in water by adding another type of molecule to the solution of water and nonpolar molecules. The type of molecule that must be added is one that is polar on one end and nonpolar on the other. Soaps and laundry detergents are good examples of such molecules. These molecules serve as links between the water and nonpolar molecules. They attach to the water with their polar end (hydrogen bond) and the nonpolar molecules with the other, nonpolar, end (van der Waal's forces). This results in the dispersement of nonpolar molecules in water.

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