Download Introduction Oxygen is a gaseous chemical element with atomic

Introduction
Oxygen is a gaseous chemical element with atomic number 8 and represented by the
symbol O.
It constitutes 21% (by volume) of air and more than 46% (by weight) of Earth’s
crust, where it is the most plentiful element.
It is a colourless, odourless and tasteless gas, occurring as the diatomic molecule O2
It is one of the life-sustaining elements on Earth
Oxygen is also used in many industrial, commercial, medical, and scientific applications.
It has valence 2 in compounds; the most important is water.
It forms oxides and is part of many other molecules and functional groups, including
nitrate, sulfate, phosphate, and carbonate; alcohols, aldehydes, carboxylic acids, and
ketones; and peroxides.
Function
Oxygen takes part in combustion and in corrosion but does not itself burn.
In respiration, it is taken up by animals and some bacteria (and by plants in the dark),
which give off carbon dioxide (CO2).
In photosynthesis, green plants assimilate carbon dioxide in the presence of sunlight and
give off oxygen. The small amount of oxygen that dissolves in water is essential for the
respiration of fish and other aquatic life.
Obtained for industrial use by distillation of liquefied air, oxygen is used in steelmaking
and other metallurgical processes and in the chemical industry.
Medical uses include respiratory therapy, incubators,
and inhaled anesthetics.
Oxygen is part of all gas mixtures for manned
spacecraft, scuba divers, workers in closed
environments, and hyperbaric chambers.
It is also used in rocket engines as an oxidizer (in
liquefied form) and in water and waste treatment
processes.
History of oxygen
Oxygen is one of the most abundant chemical elements on Earth. About one-half of the earth's
crust is made up of chemical compounds containing oxygen, and a fifth of our atmosphere is
oxygen gas. The human body is about two-thirds oxygen. Although oxygen has been present
since the beginning of scientific investigation, it wasn't discovered and recognized as a
separate element until 1774 when Joseph Priestley of England isolated it by heating mercuric
oxide in an inverted test tube with the focused rays of the sun. Priestley described his
discovery to the French scientist Antoine Lavoisier, who experimented further and determined
that it was one of the two main components of air. Lavoisier named the new gas oxygen using
the Greek words oxys, meaning sour or acid, and genes, meaning producing or forming,
because he believed it was an essential part of all acids.
In 1895, Karl Paul Gottfried von Linde of Germany and William Hampson of England
independently developed a process for lowering the temperature of air until it liquefied. By
carefully distillation of the liquid air, the various component gases could be boiled off one at a
time and captured. This process quickly became the principal source of high quality oxygen,
nitrogen, and argon.
In 1901, compressed oxygen gas was burned with acetylene gas in the first demonstration of
oxy-acetylene welding. This technique became a common industrial method of welding and
cutting metals.
The first use of liquid rocket propellants
came in 1923 when Robert Goddard of the
United States developed a rocket engine
using gasoline as the fuel and liquid oxygen
as the oxidizer. In 1926, he successfully
flew a small liquid-fueled rocket a distance
of 184 ft (56 m) at a speed of about 60 mph
(97 kph).
After World War II, new technologies
brought significant improvements to the air
separation process used to produce
oxygen. Production volumes and purity
levels increased while costs decreased. In
1991, over 470 billion cubic feet (13.4
billion cubic meters) of oxygen were
produced in the United States, making it the second-largest-volume industrial gas in use.
More about oxygen
Oxygen and acetylene are combusted together to provide the very high temperatures needed
for welding and metal cutting. When oxygen is cooled below -297° F (-183° C), it becomes a
pale blue liquid that is used as a rocket fuel.
Reference
http://www.answers.com/topic/oxygen
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