Page 162 - Science Class 07

of in a hygienic way. fields.

v Animals should not be allowed to enter v Factory-wastes must be recycled or treated
water-bodies. They should be watered and duly.
washed with clean water. v Purifica on of water-bodies should be

v Biogas plants can help a lot in using the carried out off and on.
dung usefully. v Use of chemical fer lizer and pes cide
v Micro-organism (bacteria etc.) decompose should be minimzed.
excreta to produce biogas openly which is v Drip irriga on must be encouraged so as to
harmful. check percola on of harmful chemicals.

v Surroundings should be kept quite clean v Use of natural manure and natural
and dy. pes cides must be encouraged.

v Poodles of stagnant water must not be
allowed to develop.
v Defec on should never be done in open

Turbine : A huge fan like structure which is moved by running water or steam to
produce electricity
Evaporation : Process in which water turns into water vapour due to heat
Condensation : Process in which water vapour turns into water due to low temperature

Precipitation : Process in which condensed water comes to the earth’s surface in the form
of rain, snow, hail, etc.
Conservation
of water : Judiciously use of water

Potable water : Water which can be used for drinking
Water pollution : Mingling of harmful wastes with pure water

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i About 71% of the earth’s surface is covered with water.
i Water is made from two elements namely oxygen and hydrogen.
i About 65% of human body is constituted by water.
i Water also plays a vital role in economic development of a country.

i About 97.2% of the total available water is present in the seas and oceans which is salty.
i About 2.07% of the total water is locked in glacier and ice-caps.
i Less than one percent of water is potable.

i Circulation of water in the nature is called water cycle.

162 Science-7