Water is the most important
molecule on our planet. Viewed from space, one of the most striking features of
our planet is the water, in both liquid and frozen forms, that covers
approximately 75% of the Earth’s surface. It is the only known substance that
can naturally exist as a gas, a liquid, and solid within the relatively small
range of air temperatures and pressures found at the Earth’s surface.
In all, the Earth’s water content
is about 1.39 billion cubic kilometers , with the bulk of it, about 96.5%, being
in the global oceans. As for the rest, approximately 1.7% is stored in the polar
icecaps, glaciers, and permanent snow, and another 1.7% is stored in
groundwater, lakes, rivers, streams, and soil. Only a thousandth of 1% of the
water on Earth exists as water vapor in the atmosphere.
The volume of all water would be
about 332.5 million cubic miles (mi3), or 1,386 million cubic kilometers (km3).
A cubic mile of water equals more than 1.1 trillion gallons. A cubic kilometer
of water equals about 264 billion gallons.
• About 3,100 mi3 (12,900 km3)
of water, mostly in the form of water vapor, is in the atmosphere at any one
time. If it all fell as precipitation at once, the Earth would be covered with
only about 1 inch of water.
The 48 contiguous United States receives a total volume of about 4 mi3 (17.7
km3) of precipitation each day.
• Each day, 280 mi3 (1,170
km3)of water evaporate or transpire into the atmosphere.
• If all of the world's water
was poured on the United States, it would cover the land to a depth of 90
miles (145 kilometers).
• Of the freshwater on Earth,
much more is stored in the ground than is available in lakes and rivers. More
than 2,000,000 mi3 (8,400,000 km3)of freshwater is stored in the Earth, most
within one-half mile of the surface. But, if you really want to find
freshwater, the most is stored in the 7,000,000 mi3 (29,200,000 km3) of water
found in glaciers and icecaps, mainly in the polar regions and in Greenland.
And this is how much fresh water
there is, compared to Earth and the total amount of water:
Despite its small amount, this
water vapor has a huge influence on the planet. Water vapor is a powerful
greenhouse gas, and it is a major driver of the Earth’s weather and climate as
it travels around the globe, transporting latent heat
with it. Latent heat is heat obtained by water molecules as they transition from
liquid or solid to vapor; the heat is released when the molecules condense from
vapor back to liquid or solid form, creating cloud droplets and various forms of
South Bank University Graphic
Water's chemical description is
H2O, that is one atom of oxygen bound to two atoms of hydrogen. The hydrogen
atoms are "attached" to one side of the oxygen atom, resulting in a water
molecule having a positive charge on the side where the hydrogen atoms are and
a negative charge on the other side, where the oxygen atom is.
Since opposite electrical charges
attract, water molecules tend to attract each other, making water kind of
"sticky." The side with the hydrogen atoms (positive charge) attracts the
oxygen side (negative charge) of a different water molecule.
Water is unique in that it is
the only natural substance that is found in all three states -- liquid, solid
(ice), and gas (steam) -- at the temperatures normally found on Earth. Earth's
water is constantly interacting, changing, and in movement.
Water freezes at 32o
Fahrenheit (F) and boils at 212o F (at sea level, but 186.4°
at 14,000 feet). In fact, water's freezing and boiling points are the
baseline with which temperature is measured: 0o on the Celsius
scale is water's freezing point, and 100o is water's boiling point.
Water is unusual in that the solid form, ice, is less dense than the liquid
form, which is why ice floats. Water contracts until it reaches 4 C then it
expands until it is solid. Solid water is less dense that liquid water because
Water has a high specific heat
index. This means that water can absorb a lot of heat before it begins to get
hot. This is why water is valuable to industries and in your car's radiator as
a coolant. The high specific heat index of water also helps regulate the rate
at which air changes temperature, which is why the temperature change between
seasons is gradual rather than sudden, especially near the oceans.
Water has a very high surface
tension. In other words, water is sticky and elastic, and tends to clump
together in drops rather than spread out in a thin film. Surface tension is
responsible for capillary action, which allows water (and its dissolved
substances) to move through the roots of plants and through the tiny blood
vessels in our bodies.
Weight: 62.416 pounds per
cubic foot at 32°F
Weight: 61.998 pounds per
cubic foot at 100°F
pounds/gallon, 0.036 pounds/cubic inch
Density: 1 gram per cubic
centimeter (cc) at 39.2°F, 0.95865 gram per cc at 212°F
The States of Water
Water has three states. Below freezing water is a solid (ice or snowflakes),
between freezing and boiling water is a liquid, and above its boiling point
water is a gas.
Water changing from solid to liquid is said to be melting. When it changes from
liquid to gas it is evaporating. Water changing from gas to liquid is called
condensation . Frost formation is when water changes from gas directly to solid
form. When water changes directly from solid to gas the process is called
scales are in common use in science and industry
Two of those scales are SI
The degree Celsius (°C) scale was
devised by dividing the range of temperature between the freezing and boiling
temperatures of pure water at standard atmospheric conditions (sea level
pressure) into 100 equal parts. Temperatures on this scale were at one time
known as degrees centigrade, however it is no longer correct to use that
terminology. [In 1948 the official name was changed from "centigrade degree" to
"Celsius degree" by the 9th General Conference on Weights and Measures (CGPM).]
The kelvin (K) temperature scale is
an extension of the degree Celsius scale down to absolute zero, a
hypothetical temperature characterized by a complete absence of heat energy.
Temperatures on this scale are called kelvins, NOT degrees kelvin,
kelvin is not
capitalized, and the symbol (capital K) stands alone with no degree symbol. [In
1967 the new official name "kelvin" and symbol "K" were set by the 13th General
Conference on Weights and Measures (CGPM).]
The degree Fahrenheit (°F)
non-metric temperature scale was devised and evolved over time so that the
freezing and boiling temperatures of water are whole numbers, but not
round numbers as in the Celsius temperature scale.
Some baseline temperatures in
the three temperature scales:
boiling point of water
melting point of ice
Boiling Points Of Water
For human needs, the amount of freshwater on Earth—for drinking and
agriculture—is particularly important. Freshwater exists in lakes,
rivers, groundwater, and frozen as snow and ice. Estimates of
groundwater are particularly difficult to make, and they vary widely.
One estimate of global
Percent of Total Water
Percent of Fresh Water
Oceans, Seas, & Bays
Ice caps, Glaciers, & Permanent Snow
Ground Ice & Permafrost
The total water supply of the world is 326 million cubic miles. A
cubic mile of water equals more than one trillion gallons.
About 3,100 cubic miles of water, mostly in the form of water vapor,
is in the atmosphere at any one time. If it all fell as
precipitation at once, the Earth would be covered with only about 1
inch of water.
Each day, 280 cubic miles of water evaporate or transpire into the
Of the freshwater on Earth, much more is stored in the ground than
is available in lakes and rivers. More than 2,000,000 cubic miles of
fresh water is stored in the Earth, most within one-half mile of the
surface. Contrast that with the 60,000 cubic miles of water stored
as fresh water in lakes, inland seas, and rivers. The most is stored
in the 7,000,000 cubic miles of water found in glaciers and icecaps,
mainly in the polar regions and in Greenland.
Almost a billion people on the planet don’t have access to clean, safe
drinking water. 3.5 million people die each year from water-related
Unsafe water and lack of basic sanitation cause 80% of diseases and kill
more people every year than all forms of violence, including war.
Children are especially vulnerable, as their bodies aren't strong enough
to fight diarrhea, dysentery and other illnesses.
90% of the 42,000 deaths that occur every week from unsafe water and
unhygienic living conditions are to children under five years old. Many
of these diseases are preventable. The UN predicts that one tenth of the
global disease burden can be prevented simply by improving water supply
Data compiled from The
British Antarctic Study, NASA, Environment Canada, UNEP, EPA and
other sources as stated and credited Researched by Charles
Welch-Updated daily This Website is a project of the The Ozooe Hole