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All about Air

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All about Air - Lesson Summary

Air is present everywhere on earth. Air is present as a thick blanket surrounding the surface of the earth.
  • The layer of gases around the earth is called as atmosphere.
  • The atmosphere is dense at the surface of the earth and becomes thinner as one moves up.
  • Air is essential for all living beings. It supports life on earth. 
  • Air is utilised by all the living organisms like plants, animals and microorganisms.
  • Air cannot be seen but is felt when it moves.
  • The movement of air is called breeze or wind depending on its velocity or speed.
  • Air fills in the empty space available every where.
  • We all breathe in air. Breathing is an essential part of respiration. We breathe in oxygen rich air and breathe out carbon dioxide rich air.

Components of air
Air contains mostly nitrogen and oxygen. Nitrogen occupies 78% of the air. Oxygen occupies 21% of the air. 1% of the air is made up of carbon dioxide, other gases, water vapour, dust particles etc.

Nitrogen: It is a lightest colourless, odourless gas. It generally occurs in its diatomic form N 2.
  • Nitrogen is used to control combustion.
  • Nitrogen is used by plants and animals to synthesise proteins in the body.
  • Nitrogen cannot be directly used by plants or animals. It has to be fixed into its nitrate or nitrite forms.
  • Nitrogen is used to manufacture fertilisers to increase soil fertility.
  • Nitrogen is used to manufacture ammonia used for in many industries.
  • Nitrogen oxidation of stored food in packets.

Oxygen: It is a chemical element in the form of gas. Mostly it is diatomic, made up of two atoms. O 2 is the molecular oxygen.
  • Oxygen is taken directly from the air by organisms living on land.
  • Oxygen helps in oxidising the food eaten by organisms to release energy.
  • Aquatic organisms take in oxygen dissolved in water.
  • Oxygen is required for combustion.
  • Oxygen in the form of ozone helps in protection of living organisms from dangerous UV rays coming out from the sun.
  • Oxygen is used as a fuel in rockets.
  • Oxygen stored in the cylinders is used to provide artificial respiration to patients in the hospital.

Carbon dioxide: It is the gas which is made up of one carbon atom combining with two atoms of oxygen.
  • CO2 is used by plants in synthesising their food by the process of photosynthesis.
  • CO2 is used in fire extinguishers.
  • CO2 is used in storing soft drinks.

Inert gases: These are also called as noble gases. They occupy a negligible percentage in air.
  • Argon is used to fill the bulbs to prevent their filament.
  • Helium is used in providing low temperatures.
  • Neon is used to fill special bulbs called as neon signs.
  • Radon is used in treating cancer patients.

Water vapour: It is a form of water present as gas in the air.
  • Amount of water vapour in the air varies with sun's heat.
  • Hot sun can evaporate more amount of water and convert it into water vapour.
  • It helps in the formation of clouds which later can come down as rain.

Dust and smoke: Air contains some amount of dust and smoke in it.
  • Dust and smoke are contributed by vehicles and industries releasing them.
  • These are harmful to human beings and can cause many respiratory diseases.

Oxygen-Carbon dioxide levels
Oxygen and carbon dioxide levels in the air are maintained by different processes like respiration and photosynthesis.
  • Respiration involves utilisation of oxygen from air by living organisms and releasing carbon dioxide into air. It occurs in all living organisms.
  • Photosynthesis involves utilisation of carbon dioxide from air and release of oxygen into the air.
  • Carbon dioxide is replenished by the process of respiration and oxygen is replenished by the process of photosynthesis.

Properties of air
Air is transparent. Air is a transparent medium which allows light to pass through it. The objects are seen clearly through air.
  • Air is colourless. It is not visible.
  • Air can be felt when it moves fast. Moving air is called as wind.
  • Air occupies space. Air is present everywhere. Air can be displaced by water.
  • Air exerts pressure.
  • Air can be compressed and filled into a container.

Other uses of air
Air is used to rotate wind mills, which can lift water.
  • Wind energy is a renewable form of energy.
  • Air is also used to rotate wind mills which can generate electrical energy by aerogenerators. 
  • Air is used in sail boats.


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