2. Topics to be covered today are :-
1. What is water ?
2. Uses of Water
3. Why there is shortage of water ?
4. Importance of water in one’s lives
5. States of water
6. Sources of water
7. Water Cycle
3. Introduction
• About three fourth of the Earth’s surface is covered
with water.
• It is made up of tiny molecules of Hydrogen and
Oxygen. It is precisely made up of 2 Hydrogen atoms
(H2) and 1 Oxygen atom (O).
• Therefore, its chemical value is H2O.
• Pure drinking water has no smell, no taste and no
color.
6. Why there is shortage of Water ?
i. 97.4 of the available water is in seas and oceans
which cannot be directly used by us because of its
high salt content. A lot of freshwater is in form of
glaciers and in the polar ice caps. Thus, only 0.01% of
the water on the Earth is available to us for
consumption .
ii. There is also shortage of water because of increasing
population in country.
iii. This can also happen because of floods at some
places and droughts for years at some places.
7. Importance of Water
• Water is essential for life . A person can live without food for several weeks, but
without water, life cannot last for more than few days.
• Water makes it importance such as digestion of food, absorption of nutrients by
the body, distribution of nutrients to various parts of the body in humans and
animals takes place only in the presence of water.
• About 70% of human body consists of water.
• Plants use water, along with carbon-dioxide from the air, to make food in
presence of sunlight.
20. What are 4 stages of Water Cycle ?
• The four stages of Water Cycle are :-
• Evaporation
• Condensation
• Precipitation
• Collection
21. Evaporation
• Evaporation is when the sun heats up water in river or
lakes or the oceans and turns it into vapour or steam.
Water is the form of steam leaves the river, lake or ocean
and goes in the air.
22. Condensation
• Water vapour in air gets cold and changes back into
liquid, forming clouds. This is called Condensation.
23. Precipitation
• Precipitation occurs when so much water has condensed that the
air cannot hold it anymore. The clouds get heavy and water falls
back to the Earth in the form of rain, hail, sleet or snow.
24. Collection
• When water falls back to the Earth by precipitation, it may fall back in the
oceans, lakes or rivers or it may end up on land. When it end up on land it will
either soak in the Earth and become part in the “Groundwater” that plants and
animals used to drink or it may run over the soil and collect in the oceans, lakes
or rivers where the cycle starts.
