Air: Composition And Its Properties

The matter is anything that occupies space. Air is a matter which is inevitable in our lives. The earth is covered with a blanket of air called the atmosphere. Among the few fundamental elements, it is the most important because no life can exist for a pulse of time without it. It is needed by every single organism for their survival.

In addition to breathing, it has an influential role in abiotic components of environment like wind, rain, climate, etc. Let us learn about its composition and properties in detail.


Chemical Composition of Air

Air is a mixture of gases which makes up the Earth’s atmosphere. These gases are colourless and odourless and hence, we can’t see them but only feel them. The atmosphere is an ocean of these gases. It consists of 78% nitrogen, 21% oxygen and 1 % other gases and water vapour. The moisture content varies from place to place. Arid regions have less moisture content as compared to wetlands.

  • The water vapour or moisture content of air varies. The maximum moisture carrying capacity of air depends primarily on temperature
  • The composition of air is unchanged until the elevation of approximately 10.000 m
  • The average air temperature diminishes at the rate of 0.6oC for each 100 m vertical height
  • “One Standard Atmosphere” is defined as the pressure which is equal to that exerted by a 760 mm column of mercury at C sea level and at standard gravity (32.174 ft/sec2)

Composition of Air

Composition of Air
Element Volume by % Weight by % PPM(Parts per Million) by Volume Symbol of the Element Molecular Weight of the element
Nitrogen 78.08 75.47 780790 N2 28.01
Oxygen 20.95 23.20 209445 O2 32.00
Argon 0.93 1.28 9339 Ar 39.95
Carbon Dioxide 0.040 0.062 404 CO2 44.01
Neon 0.0018 0.0012 18.21 Ne 20.18
Helium 0.0005 0.00007 5.24 He 4.00
Krypton 0.0001 0.0003 1.14 Kr 83.80
Hydrogen 0.00005 Negligible 0.50 H2 2.02
Xenon 8.7 x 10-6 0.00004 0.087 Xe 131.30

Other Components of Air

Some other components of air are mentioned below:

  • Sulfur dioxide(SO2) – 1.0 ppm
  • Methane(CH4 )2.0 ppm
  • Nitrous oxide(N2O) – 0.5 ppm
  • Ozone(O3) 0 to 0.07 ppm
  • Nitrogen dioxide(NO2) – 0.02 ppm
  • Iodine(I2) 0.01 ppm
  • Carbon monoxide(CO) – 0 to trace ppm
  • Ammonia(NH3) 0 to trace ppm

Properties of Air

As mentioned earlier, gases are matter. There are certain properties of gases like any other matter. Some common properties are as follows:

  • Colourless and odourless:

    Air generally has no colour or odour. It is an invisible matter that can only be felt. All living things breathe air for their survival. Moving air is called wind.

  • Occupy space:

    It is a mixture of different gases. Hence, like every other matter, they also occupy space. On blowing, a balloon expands because the air being blown into it fills up the empty space.

  • Air exerts pressure:

    It has weight, and the pressure exerted by the weight of air is known as air pressure. Due to gravity, this mixture of gases near the surface is denser than at high altitudes. This is why the gaseous atmosphere in the mountains is thinner than that at the surface.

  • Expansion:

    Another property is its expanding property. On heating, it expands and occupies more space. The more it expands, the thinner it becomes. Hence, the pressure of the warm wind is lower than that of cold wind.

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