Composition of Air

COMPOSITION OF AIR

Air is mainly a mixture of nitrogen and oxygen gases with small amounts of carbon dioxide gas, water vapour and other gases. Some dust particles may also be present in air.

Composition of Air

1. Nitrogen : 78 per cent
2. Oxygen : 21 per cent
3. Carbon dioxide, : 1 per cent

Water vapour,

Other gases, and

Dust particles

Components of air in detail.

NITROGEN

Nitrogen is a colourless, tasteless and odourless gas. Nitrogen gas is slightly soluble in water. Nitrogen gas in not essential for breathing (or respiration). Nitrogen gas neither burns itself nor supports the process of burning. That is nitrogen does not support combustion. Nitrogen is a very uncreative gas.

Nitrogen gas present in air is important for living things. All the living things need nitrogen compounds for their growth. The plants use nitrogen gas of the air to make proteins. These are used by the plants for their own growth as well as for the growth of human beings and other animals. Thus, nitrogen is needed by plants to make proteins.

Oxygen

Oxygen is a colourless, tasteless and odourless gas. Oxygen gas is slightly soluble in water. Oxygen gas is essential for breathing (or respiration). We can live for several days without food and water but we will die very quickly without oxygen. So, the oxygen present in air is important for the living things. All the living things need oxygen of air for breathing.

Oxygen gas does not burn itself but it allows other to burn in it. So, oxygen is supporter of burning (or supporter of combustion). Thus, oxygen (or air) is also necessary for the process of burning (or combustion) of fuels such as wood, coal, kerosene, petrol and LPG. Thus, oxygen supports life and combustion.

Oxygen is Necessary for Living Things

All the living things (animals and plants) use the oxygen of air for respiration. The animals and plants living on land take the oxygen required for breathing from the air around them. But the animals and plants living in water take the oxygen required for breathing from the air dissolved in water.

Under ordinary conditions, we use the air around us for breathing purposes. But under special situations oxygen gas cylinders are used for breathing purposes.

A patient undergoing a major surgical operation also has difficulty in breathing properly in the surrounding air. So, oxygen gas is given to patients in hospitals who have difficulty in breathing properly.

The air at high altitudes contains very little oxygen due to which it becomes difficult to breathe properly. The mountaineers use the oxygen gas contained in cylinders for breathing properly under conditions of high altitudes.

The little dissolved oxygen present in sea-water cannot be used for breathing by human beings such as a diver. It can be used only by animals like fish which live in water. That is why, When the divers go deep into sea-water, they carry oxygen gas cylinders with them.

Oxygen is Necessary for Burning (or Combustion)

The process of burning of a substance is called combustion. A substance cannot burn without air. Now, when a substance burns in air, it is actually the oxygen present in air which is used up in the process of burning. So, we can also say that oxygen is necessary for burning (or combustion)When we burn a candle, paper, kerosene, coal, wood or cooking gas (LPG), oxygen is needed. The oxygen need for the burning of the candle, paper, kerosene, coal, wood or cooking gas comes from the air around us. Thus, for burning a substance continuously so as to make fire, a continuous supply of fresh air is needed (to provide sufficient oxygen for the burning process).

If the burning coal is covered with a vessel, it stops burning after some time. This is because when we covered the burning coal with a vessel, then the supply of oxygen of fresh air to the burning coal cut off. And in the absence of oxygen of air, the coal stops burning.

If the clothes of a person catch fire (while working in the kitchen etc.) a woollen blanket is put around the burning clothes to extinguish the fire. Actually, when the burning clothes of a person are covered with a woollen blanket, then the supply of fresh air (or oxygen to the burning clothes is cut off and hence the clothes stop burning .

In all the above examples when the supply of air (or oxygen) to a burning substance is cut off then the process of burning (or combustion) also stops Thus, the presence of oxygen (of air) is necessary for combustion to take place.

CARBON DIOXIDE

Carbon dioxide is a colourless and odourless gas. It has a slightly sour taste. Carbon dioxide is moderately soluble in water. Carbon dioxide gas neither burns nor supports burning. Plants and animals consume oxygen from air for respiration and produce carbon dioxide. Plants and animals matter burns by consuming oxygen from air and produces mainly carbon dioxide and a few other gases.

Air contains only about 0.03 per cent of carbon dioxide gas. Green plants need carbon dioxide gas to make food. In sunlight, green plants use carbon dioxide from air and water from soil to make food by the process of photosynthesis. So, all the food which animals (including human beings) etc is made from carbon dioxide gas of the air.

Water Vapour

Air also contains water vapour. We cannot see ‘water vapour’ present in air because it is ‘water in the form of a gas’. The presence of water vapour in air is important for the working of water cycle in nature. This is because it is water vapour present in air which raises high in the sky along with hot air, gets cooled, condenses to from clouds and then brings rain on the earth.

Dust Particles

Dust particle are always present in air. The dust particles come into air from a number of sources such as blowing of wind, traffic on the roads, dusting at home, earth moving operations, construction activities and agricultural practices. The presence of dust particles in air varies from time to time and place to place. We normally breathe in air (inhale air) through our nose. This is because fine hair and mucus are present inside the nose to prevent dust particles from entering into our respiratory system.

Smoke

Smoke consists of fine carbon particles and some gases. Smoke is produced by the burning of fuels (such as wood, coal, kerosene, petrol, and diesel, etc.). Smoke is always harmful. Breathing in air containing smoke damages our health. We usually see tall chimneys in factories. The tall chimneys in factories are installed to take the smoke produced in the factory high up in the air so as to reduce its harmful effects on the ground.

How Does Oxygen Become Available to Animals and Plants Living in Soil

The animals which live in soil and the plant roots which grow in soil need oxygen to breathe (or respire). They get this oxygen from the air present in spaces between the soil particles. The earthworms normally live inside the soil. The earthworms come out of the soil only during heavy rains. During heavy rains, all the spaces in soil which contained air get filled by rainwater leaving no air in the soil for the earthworms to breathe in, Due to this, the earthworms have to come out of the soil to obtain air for breathing (or respiration).

How Does Oxygen Become Available to the Animals and Plants Living in Water?

The animals (like fish) which live in water are called aquatic animals. The plants which live in water are called aquatic plants. The aquatic animals and plants live in the water of ponds, lakes, rivers and sets (or oceans). The water of ponds, lakes, rivers and seas has some dissolved air in it. So, the animals and plants which live in water use the air dissolved in water for breathing (or respiration). Since air contains oxygen, therefore, we can also say that the animals and plants which live in water use the oxygen dissolved in water for breathing (or respiration).

How is Oxygen in Air (or Atmosphere) Replaced

The oxygen of air being consumed by animals (and plants) in respiration, and in the burning of fuels is constantly being replaced by plants through the process of photosynthesis. This happens as follows: In sunlight, plants use carbon dioxide and water to make food by the process of photosynthesis and produce oxygen gas. Plants also consume some of the oxygen for respiration but they produce much more oxygen than they consume. So, we say that plants produce oxygen gas.

The carbon dioxide of air being consumed by plants in photosynthesis is constantly being put back into air by the respiration of animals (and plants), as well as by the burning of fuels by human beings.

Uses of Air

Air is useful to human beings in many ways. Some of the important uses:

1. Air is used by human beings for breathing (or respiration).
2. Air is used for burning fuels (like wood, coal and kerosene, etc.) to make fire.
3. Compressed air is used to fill tyres of various kinds of vehicles such as bicycles, scooters, cars, buses, trucks and aeroplanes.
4. Air helps in the dispersal of seeds and pollen of flowers of several plants.
5. Blowing air (called wind) is used to turn the blades of wind-mills.
6. Air helps in the movement of yachts (sailing boats), parachutes, gliders and aeroplanes.
7. Air helps the birds, bats and insects in flying.
8. Air plays an important role in the water cycle in nature.