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What is water?
Water is the colorless and tasteless
liquid that covers about 71% of the earth. Ninety-seven percent of
the water on earth is salt water and the other 3% is freshwater.
Most of the freshwater is frozen at the North and South Poles. About
a third of the freshwater is in rivers, streams, aquifers, and springs
that are part of our drinking water.
Water is made up of hydrogen and oxygen.
The reason that we call it H2O is that there are two hydrogen atoms and
one oxygen atom in it.
What is the Water Cycle?
The water cycle is also known as the hydrologic
cycle. There is the same amount of water on the Earth now
as there was when the Earth began. The water cycle is how the
earth's water recycles itself.
The cycle includes precipitation,
evaporation, condensation,
and transpiration. Earth's water keeps
changing from liquid water to vapor and then back again. This cycle
happens because of the sun's heat and gravity.
How does the Water Cycle work?
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Water molecules
from lakes, rivers, streams, reservoirs, and the ocean get heated
by the sun and turn into vapor that rises into the air.
[evaporation] |
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Plants are heated by the
sun, too, and send water molecules into the air through their
leaves. [transpiration] |
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These water molecules
form into clouds. |
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When the air and the
water cool, they form drops of water that fall to the earth as
rain. If they are frozen, they become snow or sleet.
[condensation] The vapor has changed into a liquid. |
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Once the water reaches
the ground, it can flow across the land until it reaches rivers,
lakes, streams, or the ocean. This is surface water.
It can also sink into the ground and flow with gravity through
gaps in rock, gravel, and sand until it reaches these bodies of
water, too. This is groundwater. |
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The cycle begins again. |
Why is water important?
Many of us
think water will always be there for us when we want it.
Without water, living things would die. You will die if you go
without water for more than a week. Plants will die without water
and that would kill all of the animals that eat the plants.
When disasters happen, the first helpful thing
that we send is water. In the United States, we have become so used
to having water that we don't think about other countries that suffer
years and years of drought; where children
drink dirty water that makes them sick, and people walk miles just to get
that.
We learned from the water cycle that we are using and
re-using the same water that has been on earth since the beginning of
time. The scary part is that while the water is the same, the amount
of clean water has gone down. At some point, if we do not take care
of it, we will be left with only contaminated
water.
Go to Water Sources |
