Scientists estimate that the hydrosphere contains about 1.36 billion cubic kilometers of this substance mostly in the form of a liquid that occupies topographic depressions on the Earth. Water is also essential for life. Water is the major constituent of almost all life forms. Without water life would have probably never have developed on our planet.
Water has a very simple atomic structure.
The nature of the atomic structure of water causes its molecules to have unique electrochemical properties. On the other side of the molecule a negative charge exists. The unique way in which the hydrogen atoms are attached to the oxygen atom causes one side of the molecule to have a negative charge and the area in the opposite direction to have a positive charge. The resulting polarity of charge causes molecules of water to be attracted to each other forming strong molecular bonds. The pattern taken by water when its is frozen, causes its volume to expand and its density to decrease.