Water Facts
- Water is a
common chemical substance that is essential to all known forms of life.
In typical usage, water refers only to its liquid form or state, but
the substance also has a solid state, ice, and a gaseous state, water
vapor.
- About 1,460
teratonnes (Tt) of water cover 71% of Earth's surface, mostly in oceans
and other large water bodies, with 1.6% of water below ground in
aquifers and 0.001% in the air as vapor, clouds (formed of solid and
liquid water particles suspended in air), and precipitation.
- Some of the
Earth's water is a part of man-made, and natural objects near the
earth's surface such as water towers, and animal and plant bodies,
manufactured products, and food stores.
- Saltwater
oceans hold 97.0% of surface water, glaciers and polar ice caps 2.4%,
and other land surface water such as riverslakes 0.6%. Water in these
forms moves perpetually through the water cycle of evaporation and
transpiration, precipitation, and runoff usually reaching the sea.
Winds carry water vapor over land at the same rate as runoff into the
sea, about 36 Tt per year.
- Over land,
evaporation and transpiration contribute another 71 Tt per year to the
precipitation of 107 Tt per year over land. Some water is trapped for
periods in ice caps, glaciers, aquifers, or in lakes, for varying
periods, sometimes providing fresh water for life on land. Clean, fresh
water is essential to human and other life. In many parts of the world,
it is in short supply.
- Many very
important chemical substances, such as salts, sugars, acids, alkalis,
some gasesoxygen), and many organic molecules dissolve in water.
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