As you know there are nine planets in the solar system. Is there life on other planets?  NO?

Why is there life only on earth? Life on earth is possible because of the presence of air with an adequate number of components like oxygen, nitrogen, and carbon dioxide in right proportions which are crucial for existence.

Air covers the Earth in a layer over 400 miles high and maintains temperature on the earth surface.    

It is an essential supplier of energy and also supports water cycle. Air is a conducting medium for sound. Air helps in transport also.

It brings monsoon and also helps in pollination of crops

Moving air, called the wind, enables the movement of sailboats and gliders. It runs windmills, which are used to generate electricity. The Wind also helps in the dispersal of seeds.

Compressed air is used in a number of ways. Machines used in mining and digging and the drill used by dentists work on compressed air.

Apart from the above-mentioned uses, there are much more, which we will study in detail in this chapter.

Air is a mixture of gases. Air is an invisible form of matter which is free flowing and in a gaseous state.

The composition of air is:

  • Nitrogen: 78%
  • Oxygen: 21%
  • Carbon dioxide: 0.03-0.04%
  • Inert gases: 1%
  • Water vapour
  • Dust particles
  • The amount of water vapour and dust particle may vary from place to place but the percentage of other gases remains the same almost everywhere
  • Air is a mixture. The components do not react with each other and retain their individual properties.
  •  Air cannot be represented by a formula.

The importance of air:

1.The importance of Nitrogen in the air:

  • It is inert by nature and neither burns nor supports combustion. So it dilutes the effect of oxygen and controls the rate of combustion
  • It is an integral part of DNA, RNA, and proteins. Atmospheric nitrogen is converted by biological and non -biological fixation into nitrites and nitrates
  • It is used to manufacture nitric acid, ammonia, and nitrogenous fertilizers
  • It is used to package foodstuffs because it can provide an inert atmosphere and prevent oxidation of food.

2..Importance of oxygen in air

  • Oxygen is the breath of life
  • It sustains life on earth
  • It supports combustion and oxidation reactions
  • Acidic and basic oxides are used in various industries
  • Various fuels like CNG (Compressed Natural gas), LPG, wood, coal and petrol all burn only in the presence of oxygen

Fuel + Oxygenà Carbon dioxide + water + heat and light energy

3. Importance of carbon dioxide

  • Carbon dioxide is the raw material for photosynthesis
  • Carbon dioxide + water (in the presence of sunlight and chlorophyll)àglucose + oxygen.
  • It is a greenhouse gas and maintains temperature of the earth
  • Used in fire extinguishers

4. Water vapour

  • Presence of water vapour causes rain
  • Controls rate of evaporation from bodies of animals and plants
  • Essential for growth of plants and animals

5.Inert gases:

  • Helium is used in weather observation balloons
  • Neon is used in advertisement signs and tube lights
  • Argon is filled in electric bulbs to prevent oxidation of filaments
  • Radon is used in the treatment of cancer
  • Krypton and xenon are used in photography.

6. Dust particles:

  • The amount of dust particles varies from place to place. Water vapours condense around dust particles to form clouds
  • Dust particles trap heat and scatter light

Air pollution:

  • Air pollutants are gases and particles in the atmosphere that harm organisms and affect climate. Air pollution is the release of these particles and gases into the air.
  • Air pollution can cause asthma, bronchitis, allergies. Particulate pollutants can cause damage to soft organs and even paralysis
  • It can lower visibility and cause accidents due to the formation of smog

The  Balance of oxygen and carbon dioxide:

  • A balance of oxygen in the atmosphere is maintained by respiration and photosynthesis. This ensures oxygen is never depleted