The invisible gaseous medium around us, mainly constituted by oxygen and nitrogen is known as air. It is through this air that we are able to carry out the process of respiration. Air is transparent and colourless. It occupies space and is present all around us.
Atmosphere: The thin blanket of air surrounding the surface of the Earth is called the atmosphere
The movement of air is called breeze or wind depending on its velocity or speed.
CONSTITUENTS OF AIR
Air is a mixture of a number of gases and some other particles such as:
1. Water Vapour: Air contains water vapour which helps maintain the water cycle. When air comes in contact with cold surfaces, it is these vapours that turn into or condense into droplets of water. The amount of water vapor in the air from place to place and time to time. At a normal 30°C for instance can contain say upto 4% of water vapour.
2. Oxygen: It is the oxygen in the air that helps humans and animals carry out the respiration process. Oxygen is also required for fire to keep burning. If we were to keep an inverted tumbler covering a burning candle, the candle will go off in a few seconds because of the lack of oxygen-containing air due to the tumbler. Dry air is said contain about 21% of oxygen.
3. Nitrogen: Dry air is said to contain about 78% of nitrogen. This component of air helps plants in their growth process.
4. Carbon dioxide: Carbon dioxide is a very small (only 0.04%) component of air and is a byproduct of respiration by humans and animals. Fire also uses up oxygen to burn and then produces carbon dioxide and a few other gases upon burning. This is why we feel suffocated if there is something burning inside a room. This happens due to an excess of carbon dioxide as the fire continues to burn in the room, choking out oxygen in the air.
5. Dust and Smoke: Smoke is another component given out when fire burns. It is very harmful and adds fine dust particles and a few other gases to the air. This is why industries use long chimneys in order to release this smoke in the air. But as we know this act is what contributes to air pollution in the environment.
Air also contains very fine dust particles which can be seen when a beam of light enters a dark room. The tiny particles flying around in the beam are actually these dust particles. It is hence advised by our elders to breathe only through our nose and not our mouths so that the fine hair and mucus in the nose is able to filter out these dust particles so that we don’t inhale them and harm ourselves.
Availability of Oxygen In water and Soil
It is often asked how animals under the soil and in water are able to breathe. The answer is that both soil and water have air dissolved in them.
Figure 3 Air bubbles can be seen when water is heated
Figure 4 Air particles present in soil
BALANCE OF OXYGEN IN THE ATMOSPHERE
It is common knowledge that humans and animals can’t survive without plants because they produce oxygen via photosynthesis. The balance of oxygen in the environment is thus maintained through the respiratory processes of plants and animals.
The importance of Air
Air has a number of uses:
Figure 5 A windmill in action
Figure 6 Air helps birds and insects fly