Water
Water is one of the Earth's basic naturally occurring elements. It covers about 70% of the world's surface, and is one of the key parts to the survival of species. Up to 60% of the human body is water!
Scientific Makeup
Chemically, water(H2O) is two atoms of Hydrogen, and one atom of Oxygen. Water by definition is usually a liquid, although it can be converted to different states by the removal or addition of heat. Water heated to 100 degrees Celcius (the boiling point) begins to convert to steam, a gaseous state, and when cooled to 0 degrees Celcius (the freezing point) converts to ice, a solid state. Water is unique in that it is the only naturally occurring substance that is found in these three states.
Additionally, water is usually referred to as "the universal solvent" because of its ability to dissolve more substances than any other existing liquid. It has a neutral acidity, which on a pH scale has a measurement of 7.