Before learning what the role of water, it is necessary to view
it at an atomic level so as to understand its composition. One molecule of water, or
dihydrogen oxide, contains two hydrogen atoms and an oxygen atom. It is formed through the
following chemical equation:
2H2 (g) + O2 (g) ¦ 2H2O
(l). Ironically, water has the same melting point and freezing point of 0° C and a
boiling point of 100° C. This life-giving liquid is clear, colorless, and odorless. In
addition, water is most dense at 4° C. It is also the only substance on earth that is
naturally present in three different forms. It can exist as a liquid, a solid (ice), and a
gas (water vapor). Now having gone through the molecular concept of water, let’s
learn about the mole.
The mole is a metric unit in chemistry that describes the number of particles and the
quantity of mass of some substance. One mole of any substance contains 6.023 x 1023
atoms. It is called Avogadro’s number in honor of the Italian physicist Amedeo
Avogadro. The weight in grams one mole of any substance is the same as the
substance’s formula mass. For example, water has two atoms of hydrogen that weigh 2
grams and one atom of oxygen that weighs 16 grams. Therefore, one mole of water roughly
equals 18. With these important facts out of the way, we can "jump into" the
world of water.
Without water, there can be no life. Every living thing - plants, animals, and people
-need water to live. In fact, every living thing consists mainly of water. The human body
is about two-thirds water. A chicken is about three-fourths water, and a pineapple is
about four-fifths water. From this information, scientists believe that life itself began
in the salty-water of oceans.
There are about 1.4 billion cubic kilometers of water on earth. Only about 3 per cent
of the earth’s water is fresh, and the rest being salt water. About three-fourths of
the fresh water is frozen in glaciers and icecaps. Glaciers and icecaps contain as much
water as flows in all the earth’s rivers.
On the average, a person takes in about 60,600 liters of water during his or her life.
Every glass of water a person drinks contains molecules of water that have been used
countless times before. However, the largest single use of water is by industry. It takes
about 568 liters of water to make the paper for one Sunday newspaper. Water is also used
for transportation by means of ships.
In nature, water circulates through a system called the water cycle or hydrologic
cycle. This cycle begins when heat from the sun causes ocean water to evaporate and become
water vapor. The atmosphere holds the water vapor while the vapor gradually cools and
forms clouds. The water eventually falls as rain or snow during the fall and winter. Most
of the falling water will return back into the ocean or go into the soil on land.
Water provides humans with many things. It can be used for recreational activities such
as swimming, boating, scuba diving, and other activities. It serves a greater purpose,
though. In oceans, it serves as a source of life and energy, and as a home to all marine
life. Above all else, the water in the sea helps keep the earth’s climate healthful
by regulating the air temperature and by supplying the moisture for rainfall. If there was
no water, life could not exist on this planet.
Water is the simplest chemical compound of importance to living things. It is the most
common found molecule in the human body. Most organisms consist of 50 to 95 per cent of
water. Many properties of water, described earlier, make it essential to life processes.
Its ability to dissolve a great variety of substances is vital because most chemical
reactions within organisms can occur only in a water solution. In addition, water itself
enters into many chemical reactions in living cells. Water also transports nutrients
within organisms.
Water is a very important tool in chemistry. Hydrolysis is a chemical reaction
involving water as one of the reacting substances. In industry, hydrolysis is important in
making soap, sugar, alcohols, hydroxides, and silicones. A hydrolysis reaction will
produce either two changes. The acidity of the reacting system will change, or the
molecules of the water and the other substance may split and recombine to form new
substances. One example of hydrolysis takes place in metabolism. The reaction takes place
in the mitochondrion of organisms and produces energy (ATP) that is necessary for life.
This concludes the chemically interesting world of water.
