Air Around Us
Air is an invisible and colourless form of matter. It is a mixture of several gases—oxygen, nitrogen, carbon
dioxide, rare gases and water. Air occurs in the atmosphere above the Earth’s surface and in the water on
the Earth’s surface. No living thing can exist without air. Air is present everywhere around us.
What is atmosphere?
The earth’s surface is covered with a thick blanket of air called the atmosphere. It spreads above
500 km of the earth’s surface.
The following influence of the atmosphere on the earth are:
• It protects the earth’s surface from the UV rays of the sun.
• It maintains the water cycle process and the temperature of the earth.
• It contains required gases like oxygen and carbon dioxide that are responsible for the
breathing process of living things.
The amount of oxygen is less in the higher altitude regions. Therefore, we carry oxygen cylinders
with us to get the proper amount of oxygen to survive.
Properties of Air
Important Properties of Air:
• Air is a colourless, tasteless and odourless gaseoussubstance.
• It hasmass.
• It occupiesspace.
• It dissolves inwater.
• It can becompressed.
Constituents of Air
• Air and some other components form a very thin layer (when compared to the radius of the Earth)
over the Earth's surface. This layer is called theatmosphere.
• Gases such as hydrogen, oxygen, nitrogen, carbon dioxide and others along with dust particles
together form a mixture called air. In air, all the gases have their original properties and can be
recoveredseparately.
• The different gases present in the air have unique properties. Along with the composition of air,
they play a vital role in the creation and evolution oflife.
• Nitrogen makes up the major part of air (almost four-fifths). It is not required by us directly but
in the form of compounds. It is essential for plant and animal growth and has various otheruses.
• About one-fifth of the air is made of oxygen. It is required by all living things. Plants release
oxygen into the air through photosynthesis. Compressed oxygen in cylinders is used by
mountaineers and deep sea divers. Oxygen is essential forburning.
• The other important constituents of air are carbon dioxide, water vapour and inertgases.
• Carbon dioxide is required by plants to prepare their food duringphotosynthesis.
• Water vapour plays an important role in the water cycle. The amount of water vapour in the
air is a measure of the humidity of thatplace.
Uses of Air
Some of the important gases on earth are:
Nitrogen
• It occupies every four or fifth space filled by air.
• During the combustion of fuel, the burning is controlled by nitrogen.
• Plants absorb the molecules of nitrogen in the form of nitrates and nitrites.
These molecules are present in the soil that carried by the root along with the water.
• Animals get nitrogen through plants by eating them as food.
• For the production of drugs and dyes, the companies need nitrogen for producing many products.
• Nitrogen is also used for the preservation of foods.
Oxygen
• Every one-fifth presence of the air in space contains oxygen.
• All living organisms require oxygen to stay alive. It is released by the plants and taken by the animals.
• In aquatic regions, oxygen is dissolved in the water, which helps the aquatic animals and plants to breathe.
• The animals such as earthworms, snakes and rats get oxygen from the pores of the soil.
• Oxygen is also helpful in burning the combustion of fuel.
Carbon dioxide
• It is one of the essential gas that is required to perform many functions to maintain the balance of the survival.
• The amount of CO2 is very less. It aids in the process of photosynthesis in plants and respiration in animals.
• It is responsible for the greenhouse effect.
• It is used as a refrigerant and is also called dry ice because it can freeze at low temperatures and
converts into vapour without melting.
• It is used to manufacture soft drinks and urea.
• It is used to extinguish fire because it does not support combustion.
Water Vapour
• When water gets heated, it boils and starts forming vapours. This process is called evaporation.
These vapours are found in gaseous state move to the sky and the formation of clouds takes place.
The amount of water vapours present in the clouds is called humidity.
• The presence of water vapours is different in different regions and seasons. For example, coastal
areas like Chennai and Mumbai have higher concentration levels of water vapours than the other
areas like Rajasthan and Madhya Pradesh.
Dust and Smoke
• Air contains dust. For example, the corners of the room of the house and you may have observed
something that is uncleaned have dust on it. The construction sites have more dust as compared to
the well-furnished rooms.
• When we burn anything, the smokes come out and mix with the particles of air. The production of
products in the factories and burning woods in the house release smokes that goes out through the
chimneys(Figure 2).
Oxygen Cycle
• The maintenance of the amount of oxygen present in the atmosphere is done by plants by
the process of photosynthesis.
• The process of respiration in animals required oxygen all day and night. Most probably, photosynthesis
takes place in the daytime. During respiration in plants, the amount of oxygen released is sufficient to
maintain the level of oxygen in the atmosphere.
• The two main processes that maintain the amount of oxygen in the atmosphere are photosynthesis
and respiration.
• The consumption and releasing of the oxygen form a cycle called the oxygen cycle(Figure 3).
• The continuation of cutting trees and plants disturb the level of O2 present in the atmosphere.
Meanwhile, the level of CO2 is increasing rapidly.
• Due to the continuation of cutting trees and urbanization, global warming takes place.
Ozone Layer
The main work of the ozone layer is the absorption of UV rays by the sun. It absorbs 93-99% of
the UV rays. The ozone gas is present 10 to 50 kilometres high up in the earth’s atmosphere.
The UV rays can cause eye problems and skin cancer. The ozone layer is depleting due to the
use of chlorofluorocarbons.
Uses Of Air
• Air is one of the dispersal agents of pollen grains and seeds.
• Air is used to generating electricity by windmills and aerogenerators(Figure 4).
• Air is compressed to inflate tyres of vehicles.
• The important processes of living things such as respiration and photosynthesis required air.
• Flying objects like aeroplanes, helicopters and parachutes also required air to fly.
AIR POLLUTION
The involvement of harmful materials in the air molecules pollute the atmosphere. The substances
that pollute the air are called pollutants such as smokes come out from chimneys of the factories
The major causes of air pollution are:
(i) The emissions from factories.
(ii) Burning of coal and fuel.
(iii) Volcanic eruptions.
(iv) Forest fires.
(v) Decay processes of vegetation.
Air pollution causes several lungs disorders and eye problems.