Water

COMPOSITION of water

A.I. Lavoisier was the first scientist to experimentally show that water is a compound with hydrogen and oxygen as its constituents. It has been established that one molecule of water contains two atoms of hydrogen and one atom of oxygen.

OCCURRENCE of water

The distribution of water over the earth’s surface is not uniform throughout. Water is available in nature mostly in Free State and to a somewhat lesser extent in combined state.
Water exists in free in all the three physical states namely solid, liquid and gaseous states.

• Solid State: Certain regions on earths like high peaks of mountains, polar regions in Antarctica and the arctic circle contain water as snow or ice. In these places, water exists in solid state due to the very low temperatures prevailing in those regions.
• Liquid state: It is the most common state in which water exists. Most of the liquid water is found in oceans and seas. Apart from this, liquid water is also found in rivers, lakes, streams and other water bodies. Water available in the above sources is called surface water. Water present in oceans and seas contain appreciable proportions of dissolved salts, predominantly sodium chloride. The presence of these salts imparts salty taste to water and this water is hence called saline water.
• Gaseous State: In gaseous state, water exists as water vapour in the atmospheric air. Clouds, fog, mist etc., contain water vapour in condensed form.

Water exists in combined state in the form of body fluids in the body of living beings. Water is also present in combined state in hydrated crystals like CuCO₄.5H₂O, FeSO₄.7H₂O etc.