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Air, which is also generally known as the atmosphere, is a mixture of various gases. The first thought when one thinks of air is Oxygen, which is essential for life on Earth. The air is made up of more than just oxygen. Several other gases also contribute to life. Life on this planet depends entirely on the atmosphere. The air consists of three key components namely Nitrogen (78%), Oxygen (21%), Argon (1%), Carbon-dioxide (0.03%) and water vapour. The atmosphere also protects us from the harmful effects of the sun's rays through the ozone layer. In the absence of atmosphere, we would be burnt alive by the sun during the day and frozen during the night.
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Key Terms: Composition of Air, Oxygen, Nitrogen, Carbon Dioxide, Helium, Argon, Water Vapour, Ozone Layer, Dust Particles, Hydrogen, Respiration, Inhalation
Composition of Air
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Air is composed of various gases namely 78.09% nitrogen, 20.95% oxygen, 0.93% argon, 0.04% carbon dioxide, and other gases in small amounts. Water vapour is also an important constituent of air in varying amounts, along with dust particles. As we breathe, we inhale a mixture of gases. The two gases, Nitrogen and Oxygen make up most of the atmosphere. The masses of carbon dioxide, hydrogen, helium, ozone, and argon are smaller. The air also contains dust particles.
The most abundant gas is Nitrogen. When we breathe, we take some nitrogen into our lungs and exhale it. But plants need nitrogen for their survival. Directly absorbing nitrogen from the air is not possible. Plants can use nitrogen from the air because bacteria in the soil and roots of some plants change their form. Next to nitrogen is oxygen. While breathing, we take in oxygen from the air. Green plants are the ones that produce oxygen during photosynthesis. Carbon dioxide is another important gas. Green plants utilize carbon dioxide in order to make their food and release oxygen. Humans or animals release carbon dioxide.
Composition of Air
Read More: Role of Atmosphere in Climate Control
Main Components of Air
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The main components of air are elaborated in detail below:
Oxygen
The most important gas in the composition of air is oxygen. In addition to its importance for humans, oxygen is also vital for the atmosphere. It supports breathing for living beings, but, oxygen is a combustible gas, which means it can catch fire quickly. Thus, when we light a candle, it easily lights up because of the air. Try doing the same in a vacuum, and you cannot light it. This means air comprises combustible substances too. Therefore, the composition of oxygen in the air is just about 21%.
Oxygen Cycle
Read More: Aerobic Respiration
Nitrogen
To balance out oxygen, there is nitrogen. It is a non-combustible gas and involves the most noteworthy level of air. Therefore, when you blow on a candle, it is easily extinguished. This is done due to the presence of nitrogen. Nitrogen is likewise one of the most plentifully tracked down gases on the planet.
Carbon Dioxide
Carbon dioxide is infused into the air because of respiration. Living beings intake oxygen and exhale carbon dioxide. There are alternate ways by which carbon dioxide is mixed in the air, and its piece continues changing relying upon where you are. As a general rule, it ought to possess around 0.38% of the world's complete environment.
Argon
First detected by Henry Cavendish in 1785, Argon was confirmed by Lord Rayleigh and Sir William Ramsay in 1894. This gas occurs naturally in the environment and easily dissipates in a well-ventilated space. Argon is an asphyxiant and inhalation of it can prompt dizziness and sickness in an individual
Water Vapour
At the point when the water present in the water bodies evaporates because of hotness, it rises and blends into the environment. You can evaluate the presence of water vapour in the air by estimating the humidity level. You will see that as we draw nearer to the ocean, the degree of humidity rises. In coastal areas, the amount of water vapour is higher.
Read More: Factors Affecting Evaporation
Other Particles
Apart from the natural gases, the air also contains things like smoke and dust. The nearer you are to the city, the amount of these particles in the air increments. Fine strong particles are known as dust particles. Atmospheric dust is also known as Aeolian. These particles involve particles that begin from volcanic emissions, contamination of soil. These residue particles likewise contain dust, hair of people and creatures, ash particles in modest quantities.
The residue settled on the streets additionally became airborne because of the constant movement of vehicles. Coal dust is responsible for respiratory diseases. The residue particles likewise effectively affect certain individuals. If a large number of dust particles are available in the air, it can likewise decrease permeability and is a wellbeing risk.
Read More: Respiratory System Disorders
Things to Remember
- The atmosphere of the earth is composed of a mixture of gases.
- Components like nitrogen, oxygen, and argon remain constant over time and space, while trace components like CO2 and water vapour vary considerably over time.
- The atmosphere can be divided into various layers such as the thermosphere, mesosphere, stratosphere, and troposphere, and the boundaries between these layers are defined by changes in temperature gradients.
- The troposphere is the lowest layer of the Earth’s atmosphere with around three-fourths of the air. This layer of the atmosphere also contains water in all three phases (liquid, solid, and gas) as well as solid particles, called aerosols.
- The two major components of air are the two most abundant gases, i.e, nitrogen and oxygen.
- 78% of the air in the atmosphere is nitrogen. It is transported to plants, animals, and the environment through the means of the nitrogen cycle.
- CO2 is present in the air in a very small quantity, i.e. 0.03 – 0.04%. It is essential for the process of photosynthesis, the process by which CO2 and water are used up by green plants in the presence of sunlight to produce glucose and oxygen.
- Argon, an Inert gas, is the third most abundant gas that makes up about 1% of the atmosphere and comes mostly from the decay of potassium in the Earth’s crust.
Sample Questions
Ques. How can you explain that air is a necessity for burning? (3 Marks)
Ans. Take a candle and endeavour to light it in the air. Take a subsequent candle and attempt to light it while submerged in water. You'll see that the candle just consumes in the air and not in the water. This simple action shows that air is helpful for burning. This simple task might be done at home and is a tremendous method for finding out about the properties of the air that we breathe.
Ques. Explain if the water vapour content is low or high in desert regions? (3 Marks)
Ans. The water vapour content in desert areas is a lot lower than in normal spots. This is because of the way that deserts are for the most part hot areas because of an absence of water, and when water is absent, there is additionally a deficiency of water vapour in the air.
Ques. Name the components of air with their approximate percentage by volume in air. (3 Marks)
Ans. The composition of air is given as follows:
- Nitrogen – 78%
- Oxygen – 21%
- Carbon dioxide – 0.03%
- Inert gases – 0.9%
- Other components include dust, impurities and water vapour which depend on several factors like industrial activities, natural resources etc.
Ques. You are given a test tube with two outlets and a bottle of lime water. Using the same, how would you demonstrate experimentally the presence of carbon dioxide in the air? (3 Marks)
Ans. Here is how we will test the presence of carbon dioxide in the air:
- Procedure: Add lime water to a test tube with two outlets attached to it. Now, suck the air slowly from one outlet.
- Observation: You will observe that the lime water in the test tube turns milky.
- Conclusion: The air that has been sucked contains carbon dioxide which turns lime water milky.
Ques. Explain why water droplets appear on the outer surface of a tumbler containing ice. (3 Marks)
Ans. Ice is placed in a clean dry beaker and kept aside. After a few minutes, water droplets tend to appear on the outer surface of the beaker. Here, the water vapour starts to condense on the cooler surface of the beaker, which proves air contains water vapour.
Ques. Throw light on the importance of nitrogen in the air. (3 Marks)
Ans. Nitrogen is converted into soluble nitrogenous compounds in soil because of air and moisture. These compounds of nitrogen are absorbed by plants and used as proteins.
It is also present in living organisms in classes like nucleic acid, amino acids. Apart from that, artificially produced nitrogen is also a very important component in fertilizers. It also has applications in the field of medicine, the main usage being in various drugs and even in antibiotics.
Ques. Explain with a reason why nitrogen is filled in food packets and not oxygen. (3 Marks)
Ans. Nitrogen is an inert and unreactive gas that is filled in food packets to remove oxygen and moisture from them. Nitrogen thus helps to keep the food preserved and fresh by reducing the bacterial growth in the food packages.
Ques. State what would happen, if the air above the earth contained mainly oxygen and no nitrogen. (3 Marks)
Ans. Nitrogen is utilised by plants and is necessary for their growth and development. For this, it is first converted to soluble nitrogenous compounds in the soil in the presence of air and moisture. These compounds are then absorbed by plants and utilised as plant proteins. In the case of no nitrogen, plants will not be able to survive on earth.
Ques. Discuss the utilization of oxygen for respiration in (5 Marks)
(a) Living organisms
(b) Plants
Ans. (a) For Living Organisms
Respiration of living organisms involves inhaling oxygen to carbon & hydrogen present in food material which forms carbon dioxide, water vapour and energy in the form of heat.
Glucose + Oxygen → Carbon dioxide + water vapour + Energy
(b) Plant respiration is the process of plants using up the sugars made through photosynthesis and turning them into energy for growth, reproduction, and other life processes. The process of respiration of plants involves taking in oxygen and releasing it as carbon dioxide into the atmosphere (air).
In photosynthesis, with the help of solar energy, water and carbon dioxide are converted to glucose. Oxygen is released as a byproduct. In cellular respiration, oxygen is utilized in order to break down glucose, releasing chemical energy and heat in the process.
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