Composition  of Air.

By Julie-Ann Mc Clean (Y11 Ta 2002)

The air is a mixture of colourless gases, water vapour and dust particles, which together make up the Earth’s atmosphere. When water is removed from the air, it becomes known as dry air. Nitrogen is the most abundant gas in the atmosphere. Oxygen is also a very important gas. Almost 78% of air is made up of nitrogen,whilst 21% is made up of oxygen. People need oxygen to breath and to turn food into energy. Another gas in the atmosphere is carbon dioxide. Although it is present in very small amounts, it is vital to life on earth. Green plants use carbon dioxide in the process of making their food. Many other gases such as water vapour, sulphur dioxide and the noble gases such as helium and argon are present in small amounts and these to have important influences in the earth’s atmosphere.

Water vapour in the atmosphere is water in a gaseous form and is found in the lower part of the atmosphere. Water vapour is the source for all forms of precipitation and is an important absorber and emitter of infrared radiation.

The atmosphere of today is very different from that in the past. Today, our air is polluted in many ways due to chemicals released into the earth’s atmosphere through car exhausts and industry’s. Many people also receive more illnesses, many of which come from the chemicals in the air. Eg. Asthma.

The composition of clean, dry air in percentage by volume.

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