Nonpolar molecules have no attractions which can disturb the water lattice, and therefore cannot enter the lattice. When they are present in water, nonpolar molecules usually clump together which declines the surface area which is exposed to the water. This tendency for water to do that is referred to as a nonpolar association. The exemplary model of this is oil, which no matter how hard they are shaken, will not mixed with water. Polar substances are referred to as being hydrophilic, coming from the roots hydro, meaning water, and philic, meaning preferring.
Nonpolar substances are hydrophobic, coming from the root phobic, meaning avoiding.
Hydrogen Bonds Hydrogen bonds are set up between an atom of hydrogen and a negative charged atom, usually oxygen, sulfur, or nitrogen. These bonds are the strongest when the three atoms in the link are in a straight line. Although hydrogen bonds are weak, many links can form in molecules, and groups of hydrogen bonds are much stronger and tougher to break, providing stability to the complex three-dimensional molecules of proteins. Hydrogen bonds are also easily breakable at higher temperatures. They separate readily at temperatures above 50 degrees Celcius, and don't exist for the most part at 100 degrees Celcius.