Page 163 - Science Class 06

excre on of wastes from the body in v Big water bodies like rivers, lakes, seas
the form of urine and sweat. Water also
maintains our body temperature.
v Human beings need water for bathing,
cleaning, washing and cooking.
v Water is also essen al for the germi-
na on of seeds and growth of plants.
v Plants need water to carry out the
process of photosynthesis in which they
make their food and release oxygen.
Water is essen al for men, plants and animals.
v Water is used to irrigate fields.
v Water is used in number of industries
for producing goods.
v Water is used to generate electricity.
The electricity generated by the force of
moving water is called hydroelectricity.
In thermal power plants, water is used
to produce steam by hea ng. This
steam is, then, used to rotate the
blades of turbine.
Hydroelectric Plant
Science-6
and oceans are used for water transport.
v Many kinds of aqua c plants as well as
animals live in water. These water plants
and animals are useful for us in many
ways.
v Water bodies also help in maintaining
temperature on the earth. They make
the temperature of the earth liveable.
AVAILABILITY OF WATER FOR HUMAN
BEINGS
Water is a wonderful liquid as it is found in
the three physical states— solid (ice), liquid
(water) and gas (water vapour). But the
largest amount of water is present in liquid
form in seas, oceans, lakes, rivers, ponds,
etc. It is found in solid state trapped in ice
caps and glaciers. A nominal amount of
water is found in gaseous state as water
vapour. A small amount of water on the
earth is also present as ground water.
About 71% of the earth’s surface is covered
with water. Surface water, ground water and
ice caps including glaciers together cons tute
hydrosphere. About 97% of the hydrosphere
is contained in the world’s oceans. It is salty
and hence unfit for consump on and
agriculture. About 2.16% is available as
groundwater and only 0.03% of water is
available in rivers, lakes, ponds, etc. Only
0.01% of water is fit for consump on and
agricultural ac vi es.
SOURCES OF WATER
Water is available on the earth in two
natural sources.
v Underground water
v Surface water
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