Water is essential for all living beings, humans, animals, plants. There can be no life without it. All living matter (unicellular or multi cellular), plant or animal contain 70% to 90% of water. This water is used by the organism to transport soluble food materials to the cells and for excretion of waste.
Water regulates our
body temperature. Water is essential for germination of seeds and growth of
plant. Water is used for drinking by human beings and animals.
It is used for cooking, washing, bathing, cleaning and a
number of other activities. Water is used for agriculture and power
generations.
Occurrence
Occurrence of water in Free State:
In Free State water occurs in solid, liquid and gaseous
state.
Solid state
In solid state, large amount of fresh water is found in the
form of snow or ice. Vast regions of Antarctica and Arctic circles have frozen
water. High peaks of mountains have seasonal/perpetual snow. Frost, hail, snow
are some other forms of solid state of water.
Liquid state
Most of the water is present in oceans though it is saline
and is not fit for drinking. On the surface of land, water is found in streams,
rivers, ponds, lakes etc. Water present under surface of earth is called ground
water. Well water is example of ground water.
Gaseous state
Water mostly occurs as water vapors present in air which on
condensation forms clouds. Mist and fog are other examples of water in gaseous
state.
Occurrence of water in
combined state
In plants and animals
Water occurs in combined state in tissues of plants and
animals. It has been estimated that 70% to 80% of body weight of plants and
animals is in the form of water in the combined state.
Water of
crystallization
Crystals of certain salts contain a fixed number of water
molecules. Such salts are called hydrated salts and the water molecules are
collectively called water of crystallization.
Hydrated copper sulphate: CuSO4. 5H2O
Hydrated ferrous sulphate: FeSO4. 7H2O
Hydrated sodium sulphate: Na2SO4.10H2O
Bauxite (ore): Al2O3.2H2O
Borax crystals: Na2B4O7.10H2O
Potash alum: K2SO4.Al2(SO4)3.24H2O
Read also: TheScientific History of Ships- The history of ships creations
