Water is essential for all living beings, humans, animals, and 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 the excretion of waste.
Water regulates our
body temperature. Water is essential for the germination of seeds and the growth of
plants. Water is used for drinking by human beings and animals.
It is used for cooking, washing, bathing, cleaning and several other activities. Water is used for agriculture and power
generation.
Occurrence
Occurrence of water in Free State:
In Free State, water occurs in solid, liquid and gaseous
states.
Solid state
In a solid state, a 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, and snow
are some other forms of solid states 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 the surface of the earth is called groundwater. Well, water is an example of groundwater.
Gaseous state
Water mostly occurs as water vapours present in the air which on
condensation form clouds. Mist and fog are other examples of water in a gaseous
state.
Occurrence of water in
combined state
In plants and animals
Water occurs in the combined state of tissues of plants and
animals. It has been estimated that 70% to 80% of the 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