Air is one of the important resources which is necessary for survival. In this chapter, we shall discuss the presence of air, its uses, its composition, and the atmosphere.
You might have noticed that kite flies well when there is the movement of air. As the air moves, the movement of leaves, clothes, and your hair takes place. You can also make a firkin and rotate it in the presence of wind. Thus, the air in motion is called wind.
COMPONENTS OF AIR
Air is a mixture of different components.some of them are discussed below.
1. Air contains a large number of dust particles. These particles remain suspended in the air for a very long period of time. The number of dust particles will vary from one place to another.
The dust particles decrease visibility. Rainwater helps to settle down the dust particles after it has rained. Because of this reason, we are able to see clearly up to a long distance.
Similarly, if we do not wipe our glass mirror, it appears hazy due to the deposition of dust particles in the mirror. Whenever you wear spectacles, you clean the lens because dust particles settle on it.
Since air contains dust particles, it is advised to breathe through nostrils because our nose has fine hair and mucus which filters all the dust particles and it allows only pure air to reach our lungs.
2. Air also contains water vapor. When you take out a cold water bottle from the freezer, immediately you will see the formation of droplets on the water bottle made up of glass. This happens because water vapor present in the air condenses as soon as it comes in touch with cold surface A similar thing happens when water vapor comes in touch with the cold surface of a glass window. This results in the formation of frost on the glass window during winter.
3. Air is necessary for burning. Air contains oxygen that supports burning.
4. Air has various materials. Air has many materials in a fixed ratio. These substances increase or decrease due to various activities of nature and human beings such as volcanic eruptions, automobiles, industries, etc. It changes the composition and it is called air pollution.
The envelope of air around the earth’s crust is called the atmosphere. The layer of air is thick near the surface of oceans and becomes thin as we go higher and
higher and also becomes thin as we go deep inside the earth. It is because of this reason that divers and mountaineers carry oxygen cylinders with them.
All organisms require oxygen for survival. All types of organisms take oxygen from different sources. Terres trial organisms take oxygen from the air. Aerial animals like birds need oxygen which they take from the air as they fly in the sky
The aquatic animals like fish take oxygen which is dissolved in water Similarly, the dissolved oxygen of water is used by aquatic plants to prepare their food by the process of photosynthesis. Similarly, animals that live in burrows or in moist soil like squirrels and earthworms also take oxygen that is present in pore spaces of soil.
you have read that when it rains heavily, then all the soil organisms come out because water occupies the pore spaces in soil and replaces the oxygen. Thus, in the absence of oxygen, organisms come out to breathe.
Although oxygen is being continuously used by all living forms, its percentage is constant in the atmosphere. This is because plants take carbon dioxide produced by living organisms for photosynthesis and produce O, which returns to the atmosphere.
So, it is essential that the plant cover should be maintained as they supply oxygen which is required for survival. Oxygen is also produced in the upper atmosphere from nitrogen due to thunderstorm and lightning but the percentage of this oxygen is very less. Hence, plants are a major source of oxygen in the atmosphere.
This is another important component of air that is used by plants during the process of photosynthesis. But inhalation of carbon dioxide by living beings in large quantities may lead to suffocation and death.
Carbon dioxide is produced in the air by many industrial activities and the burning of fuels.
This carbon dioxide is used by plants and gets converted into food and oxygen is released finally. In this way, the balance of oxygen and carbon dioxide is maintained in nature.
USES OF AIR
Some uses of air are as follows:-
1. Windmills work with the energy of moving air,when the air is blown.As the blades of windmill rotate, the coil connected to it also moves which pumps water out of well.
2. Windmills also help in the grinding of wheat and more importantly in the generation of electricity. 3. Air helps in the movement of yachts, gliders, parachutes, kites and aircraft.
4. It is the medium which birds and insects fly.
5. Air acts as a medium for dispersal of seeds and it also helps in wind pollination.
6. Compressed air is filled in tyres of vehicles.
7. Nitrogen present in the air is used to prepare fertilisers.
8. It helps in the drying of clothes.
9. It helps in breathing, burning and respiration.
10. It also helps to extinguish the flame.
11. It helps in playing many musical instruments like flute, trumpet, tuba, saxophone, etc.
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