Water, the common name applied to the liquid state of the hydrogen-oxygen compound H2O, is an odorless, tasteless liquid. It consists of millions of tiny particles called molecules. Each molecule consists of even smaller particles called atoms. Water molecules consist of atoms of hydrogen and oxygen. Hydrogen and oxygen by themselves are gases. However, when two atoms of hydrogen combine with one atom of oxygen, they form the chemical compound H2O, water. Under standard atmospheric pressure, 760 mm of mercury, the freezing point of water is 0° C (32° F) and its boiling point is 100° C (212° F).
             Depending on its temperature, water can occur in either three states of matter: solid, liquid, or gas. As a solid, or ice, it can be found as snow or hail. It occurs in the liquid state as rain; in addition, it covers three-quarters of the surface of the earth in different forms such as lakes, rivers, and oceans. It appears as fog and steam in the gaseous state (water vapor). The molecules that make up water are always moving, and the form water takes depends on how fast they move, which is controlled by the temperature. The molecules in solid water are far apart and almost motionless. The molecules in liquid water are compact and move about freely. The molecules in a gas move about very rapidly and bump into one another.
             In the liquid state, hydrogen bonds keep water molecules together. They prevent the molecules from separating and evaporating at a lower temperature; thus, allowing water to boil at such a high temperature. This type of chemical bond forms between molecules containing a hydrogen atom bonded to a strongly electronegative atom, an atom that attracts electrons. Because the electronegative atom pulls the electron from the hydrogen atom, the atoms form a polar molecule, meaning one end is negatively charged and the other end is positively charged. Hydrogen bonds form between these molecules because...