Composition of Air

Air is defined as a mixture of gases whose constituent components can be easily separated and identified. We can study their properties. Air plays a vital role in our survival. In science, we mostly use the word atmosphere in place of air. It is a mixture of several gases and shows uniform physical properties. 

As we go through the lower layer of the atmosphere, the composition of air does not change; however, the number of molecules changes. As we travel higher through the atmosphere, the number of molecules decreases.

The composition of air varies from place to place. To be precise, air comprises 78.09% nitrogen, 20.95% oxygen, 0.93% argon, 0.04% carbon dioxide and some other gases. Air also contains water vapour and particles of dust in varying amounts.

Air and Its Composition

Air is a mixture of several gases and holds tiny particles called aerosols. 

Aerosols are picked up by wind naturally in dust and pollen. Air can also carry smoke, soot and other particles from power plants and other types of machinery. These are the significant contributors to air pollution.

Breathing is a major part of respiration, wherein all living things require oxygen from the air. This process gives energy and supports growth in every living thing

Some significant properties of air are:

• It takes space.

• It has mass.

• It exerts pressure.

• Its density is dependent on temperature.

Now let us move further and understand the components of air.

Components of air  are  divided into 3 categories :

 (i) Major components = N2, O2, water vapour. 

(ii) Minor components = Ar, CO2 

(iii) Negligible constituent = He, Ne, Kr, CH4, H2, CO, N2O, SO2, NO, NO2, HCHO, NH3, O3

Nitrogen

Nitrogen dilutes the effect of oxygen in the air, and controls rapid combustion and respiration. Nitrogen is the most abundant gas present in the air. As plants need protein; nitrogen is necessary to carry out the whole process. It is an essential constituent of protoplasm.

Oxygen

Oxygen is the most important gas present in the air. Most living beings such as humans, animals, and plants require oxygen for respiration. Green plants tend to produce oxygen during photosynthesis. It is also essential for the combustion of fuels, for example coal and petrol.

Carbon Dioxide

Carbon dioxide is an important gas present in the atmosphere as green plants require carbon dioxide to carry out photosynthesis.

Many living beings produce carbon dioxide during respiration. Carbon dioxide is also present in fire extinguishers.

Water Vapour

Vapour provides moisture for plant and animal growth. It prevents desiccation by controlling the rate of evaporation from plant and animal bodies. It also produces rain, mist, snow, etc. Hence it determines the climatic conditions.

Inert Gases

Air has a minute amount of inert gases. Helium is used in weather balloons. Neon and argon are used for electronic equipment and advertising signs.

Dust Particles

The air comprises some dust particles from the surroundings. Water vapour condenses on dust particles and hence causes rain.

Let us now discuss the atmosphere and its layers.

The Atmosphere and Its Structure

A thick layer of air that surrounds Earth is called the Atmosphere. It is the natural component of our environment on which living beings depend. Earth’s early atmosphere consisted of gases in the solar nebula, primarily hydrogen. The atmosphere changed over time as it was affected by numerous factors.

The atmosphere is made up of the troposphere, exosphere, mesosphere, thermosphere and stratosphere.

Troposphere

The air we breathe exists in the troposphere. 

It has following features:

• The average height of the troposphere is 13 km.

• Every weather phenomenon, including rainfall and hailstorm, occurs in this layer.

• Gases present in troposphere are N2, O2, CO2 and water vapour

• Temperature range  decrease from 15 to (– 56˚C)

Stratosphere

The layer above the troposphere is known as the stratosphere.

It has the following features:

• It extends to a height of 50 km

• It is completely free from clouds and weather conditions.

• Aeroplanes fly in this layer since it is free from weather conditions.

• Gases present in stratosphere are N2 , O2 , O3 , O- atom

• Temperature range increase from (– 56°C) to (– 2°C)

Mesosphere

This is the third layer of the atmosphere and falls above the stratosphere.

It has the following features:

• It extends up to 80 kms

• It protects the earth’s surface from the meteorites, which fall from space by burning them.

• Gases present in the mesosphere are N2 ,O2 ,NO+ and O2+

• Temperature range decrease from (–2°C) to (-92˚C)

Thermosphere

It is the fourth layer of the atmosphere, and lies above the mesosphere. The temperature in this layer increases rapidly with the increase in height. The ionosphere is a part of the thermosphere.

It has the following features:

• It extends from 80-400 km

• It helps in radio transmission as it reflects the radio waves from earth.

• Gases present in thermosphere are O2+  ,O+ ,NO + 

• Temperature range increase from (–92°C) to (1200˚C)

Exosphere

It is on the top of the atmosphere. It has a minimal amount of air in it. Gases like hydrogen-helium float to space from the exosphere.

Conclusion

We studied air and its components. We also studied the multiple layers of the atmosphere and its features. Air plays a vital role in our survival. Without air, life would not have been possible. It consists of some of the most important gases that are used by all living organisms for their sustainability.