Air Composition Properties - Chemical Composition of Air, FAQs

Edited By Vishal kumar | Updated on Jul 02, 2025 05:01 PM IST

Air is the invisible gaseous substance that surrounds the earth, it is mainly a mixture of oxygen and nitrogen. In this article, we will discuss what is the composition of air, the properties of air/characteristics of air, the composition of gases in atmosphere, and gases in air or air content.

We know that matter occupies space. Air is also a matter and it is essential for our lives. Our planet Earth is covered by a blanket-like layer called the Atmosphere. Among all the other fundamental elements present in nature, it is vital because life cannot exist without air. So now let’s discuss the composition of air.

This Story also Contains

Introduction To Air Composition
What Is The Composition Of Air
Properties Of Air
Importance of Air Composition
Air Properties Table/Properties of Air Worksheet
Properties Of Air Experiments

Air Composition Properties - Chemical Composition of Air, FAQs

Introduction To Air Composition

Composition of air by mass: The atmospheric air composition of the earth consists of a mixture of gases called the air. The gases are usually odorless and colorless. As a result, we cannot touch or see the air. We can only feel the air. The earth’s atmosphere consists of 78% of Nitrogen, 21% of oxygen, 0.93% of Argon, 0.04% of Carbon dioxide, and traces of helium, methane, neon, krypton, and hydrogen, as well as water vapor.

The composition of air remains the same up to a height of approximately 10,000 m. The composition of air diagram is given below:

Composition of air by mass

Other minor components of air

Some other compositions of air percentage are as follows:-

Sulphur dioxide(1.0ppm), Methane(2.0ppm), Nitrous oxide(0.5ppm), Ozone(0 to 0.07ppm), Nitrogen dioxide(0.02ppm), Iodine(0.01ppm), Carbon monoxide(0 to trace ppm), and Ammonia(0 to trace ppm).

What Is The Composition Of Air

Let us describe the main components of air, one by one:

Here are the main gases in the air.

Nitrogen (N₂)

Nitrogen is the major component that is found in air. It is the most abundant gas present on the earth. It is required for the growth of plants and animals. Nitrogen in air has a composition of 78%.

Oxygen (O₂)

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The composition of Oxygen in air is 21% (approximately). Oxygen is required by all living organisms because they derive energy from food with the help of oxygen.

Carbon dioxide (CO₂)

Carbon dioxide occupies a small content of air around us. It is essential for plants and animals. Plants utilize carbon dioxide to make food during photosynthesis. The process of photosynthesis and respiration helps in maintaining the balance of oxygen and carbon dioxide in the atmosphere.

Minor components in air percentage:

Neon: 0.0018%
Helium: 0.0005%
Methane: 0.0002%
Krypton: 0.0001%
Hydrogen: 0.00001%
Nitrous Oxide: 0.00003%

Related Topics ,

Properties Of Air

(i) Physical Properties

Air occupies space.
Air has mass.
Heat affects the air.
Air exerts pressure.
Air is highly compressible.
Altitude affects air.
Air is colorless and odorless
Air has low viscosity
Air has several single boiling points
Air is a good insulator

(ii) Chemical Properties

Oxygen which is a main component of air is highly reactive.
At high temperatures, nitrogen forms reactive compounds.
Oxygen is a strong oxidizing agent
Air reacts with metals to form oxides.
Oxygen in air and moisture leads to corrosion of metals
Oxygen contributes to the combustion process.

Importance of Air Composition

Oxygen: It is vital for the respiration of living organisms. Oxygen aids to ozone layer formation.
Nitrogen: Helps in plant growth through nitrogen fixation. Nitrogen in air also helps in protein synthesis.
Carbon dioxide: It is an integral component of photosynthesis. It is also called a greenhouse gas for maintaining the earth's atmospheric temperature.
Argon: Used in welding and insulation

The composition of air is important for supporting life and the ecosystem on Earth. It also helps in maintaining Earth's climate and temperature.

Now, as we discuss further the properties of air, a question arises Air shows the properties of both oxygen and nitrogen. Why? The answer to this question is air shows the properties of both oxygen and nitrogen because air is a mixture of gases. That’s why it will show the properties of both oxygen and nitrogen present in it.

Q. Which is not a property of air among the following options? (a)Air has mass. (b) Air occupies space. (c) Air is compressible. (d) Air is a compound.

Ans. (d) Air is a compound.

Air Properties Table/Properties of Air Worksheet

Air Properties Table

Properties Of Air Experiments

Let’s take an empty glass bottle. Now, put the open mouth of the bottle into a container filled with water. It is observed that water does not enter the bottle when it is in an inverted position, as there is no space for air to escape. This shows that air occupies space.
Let’s hang two balloons at the end of a thin straw. If we one balloon is burst then the straw will move towards the balloon that is left. This shows that air has mass.

Also read -

Gases in Air

Composition of gases in air: Nitrogen (N2 ) is the most abundant occurring natural gas, and it makes up about 78% of air. The second most abundant gas is oxygen and it is about 21%. Argon (Ar), the inert gas is the third most abundant gas at 0.93%. Some other gases like carbon dioxide (CO2), nitrous oxide (NO), neon (Ne), krypton (Kr), helium (He), methane (CH4), hydrogen (H2), xenon (Xe), ozone (O3), iodine (I2), carbon monoxide (CO), and ammonia (NH3), etc. are also present in the atmosphere.

Does air occupy space?

How will you prove that air occupies space?

Let’s take an empty glass bottle. Now, put the open mouth of the bottle into a container filled with water. It is observed that water does not enter the bottle when it in an inverted position, as there is no space for air to escape. This shows that air occupies space.

Air occupies space examples

Let’s take a balloon and fill it up. The air from ours lungs enters the balloons and it expands because air inside it is taking up the space.

Air occupies space examples

Also read :

NCERT Solutions for Class 6 Science Chapter 15 - Air Around Us

Q. Why we can’t see air?

We can’t see air because it sends very little colour to our eyes. We see objects because they absorb some light wavelengths, and reflect others back to us. Objects appear to be the colour they reflect to our eyes.

We know that air is a mixture of gases and every gas has different wavelengths. When the light bump a molecule, it absorbs some colour and then reflect it back. The reflected light enters our eye and then we are able to see the object. But in case of air, wavelengths of light may pass by the molecules without hitting them.

When they do bump a molecule, it absorbs some colour and scatters some, spreading it out in all directions. Too little light reaches our eyes for us to notice. That’s why we can’t see air.

Physical Properties for Air

Physical Properties for Air Table

Frequently Asked Questions (FAQs)

1. Write any two properties of air/ State any two properties of air/ Write two properties of air.

(i) Air occupies space.

(ii)Air has mass.

2. Write the composition of air./What is the composition of air.

Definition of composition of air: Earth’s atmosphere consists of a mixture of gases called the air. The gases are usually odourless and colourless. As a result, we cannot touch or see the air. We can only feel the air. The earth’s atmosphere consists of 78% of Nitrogen, 21% of oxygen, 0.93% of Argon, 0.04% of Carbon dioxide, and traces of helium, methane, neon, krypton and hydrogen, as well as water vapour. This is also known as Air composition of Earth.

3. State the properties of air/Write the three properties of air or list the properties of air.

Air occupies space.

Air has mass.

Heat affect the air.

Air exerts pressure.

Air is compressible.

Altitude affects air.

4. Properties of atmosphere.

Troposphere
Water
Temperature
Pressure
Moisture
Wind

5. Does air have mass? Or Is air is a matter?

Yes, air is a matter. Hence it has mass.

6. Write the air content formula.

Air content (ac) = Va / Vv

Where, Va= volume of air present in the pores

Vv =total voids volume in the soil mass

7. What is the relationship between air density and temperature?

Air density and temperature have an inverse relationship: as temperature increases, air density decreases, and vice versa. This occurs because warmer air molecules have more kinetic energy and move faster, spreading out more and occupying a larger volume. This principle is fundamental to understanding many weather phenomena, such as the formation of warm and cold air masses and their movements.

8. What is the difference between absolute humidity and relative humidity?

Absolute humidity is the actual amount of water vapor present in a given volume of air, typically expressed in grams per cubic meter. Relative humidity, on the other hand, is the ratio of the current absolute humidity to the maximum possible humidity at the same temperature, expressed as a percentage. Relative humidity is more commonly used in weather reports as it gives a better sense of how the air feels to us. For instance, 100% relative humidity means the air is saturated and can't hold any more water vapor at that temperature.

9. How does air composition affect the color of the sky?

The color of the sky is primarily due to a phenomenon called Rayleigh scattering, which is influenced by air composition. The gases and particles in the air scatter sunlight, with shorter wavelengths (blue light) scattered more than longer wavelengths. This is why the sky appears blue during the day. Changes in air composition, such as increased pollution or water vapor, can alter this scattering, leading to different sky colors, especially during sunrise and sunset.

10. What role do aerosols play in the atmosphere?

Aerosols are tiny solid or liquid particles suspended in the air. They play various roles in the atmosphere:

11. How does air composition affect the formation of acid rain?

Acid rain forms when certain air pollutants, primarily sulfur dioxide and nitrogen oxides, react with water, oxygen, and other chemicals in the atmosphere. These pollutants, often emitted from industrial processes and vehicle exhaust, dissolve in water droplets in clouds. When it rains, these droplets fall as weak acids. The composition of air, particularly the concentration of these pollutants, directly affects the acidity of the rain. Clean air with low levels of these pollutants results in rain with a pH closer to neutral.

12. What role does carbon dioxide play in the atmosphere?

Carbon dioxide (CO2) plays a crucial role in the atmosphere as a greenhouse gas. It helps trap heat, maintaining Earth's temperature at livable levels. However, increasing CO2 levels due to human activities are contributing to global warming. CO2 is also essential for photosynthesis in plants.

13. What is the significance of the ozone layer in the atmosphere?

The ozone layer, located in the stratosphere, is crucial for life on Earth as it absorbs most of the Sun's harmful ultraviolet (UV) radiation. Without this protective layer, more UV radiation would reach the Earth's surface, potentially causing increased skin cancer rates, eye damage, and harm to plants and marine ecosystems.

14. How does air pollution affect the composition of the atmosphere?

Air pollution introduces additional substances into the atmosphere, such as particulate matter, sulfur dioxide, and nitrogen oxides. These pollutants can alter the chemical composition of air, leading to phenomena like acid rain, smog formation, and increased greenhouse effect. Some pollutants can also react with existing atmospheric components, further changing the air's composition.

15. Why is the percentage of oxygen in the atmosphere relatively constant?

The percentage of oxygen in the atmosphere remains relatively constant due to a balance between processes that produce and consume oxygen. Photosynthesis by plants and algae produces oxygen, while respiration by living organisms and various chemical reactions consume it. This natural cycle helps maintain a stable oxygen level in the atmosphere.

16. How do volcanic eruptions affect air composition?

Volcanic eruptions can significantly impact air composition by releasing large amounts of gases and particulate matter into the atmosphere. These emissions typically include water vapor, carbon dioxide, sulfur dioxide, and ash particles. In severe cases, volcanic activity can temporarily alter regional or even global air quality and climate patterns.

17. How does the presence of carbon dioxide in the atmosphere affect plant growth?

Carbon dioxide (CO2) is essential for plant growth as it's a key component in photosynthesis. Increased CO2 levels in the atmosphere can enhance plant growth to some extent, a phenomenon known as the "CO2 fertilization effect." However, this effect is complex and depends on other factors like water availability, temperature, and nutrient levels. While some plants may benefit from higher CO2 levels, it doesn't necessarily lead to overall ecosystem health, as it's associated with climate change that can negatively impact many plant species.

18. What is the role of methane in the atmosphere?

Methane (CH4) is a potent greenhouse gas in the atmosphere. Although present in much smaller quantities than CO2, it's about 25 times more effective at trapping heat over a 100-year period. Methane comes from both natural sources (e.g., wetlands, termites) and human activities (e.g., agriculture, landfills, natural gas production). In the atmosphere, methane reacts with hydroxyl radicals, eventually forming CO2 and water vapor. Its presence and increasing concentration contribute significantly to global warming and climate change.

19. What is the significance of the carbon cycle in maintaining atmospheric composition?

The carbon cycle is crucial for maintaining the Earth's atmospheric composition. It involves the movement of carbon between the atmosphere, biosphere, geosphere, and hydrosphere. This cycle regulates the amount of carbon dioxide in the atmosphere, which is essential for climate stability. Processes like photosynthesis remove CO2 from the air, while respiration and decomposition release it back. Human activities, such as burning fossil fuels, have disrupted this balance, leading to increased atmospheric CO2 levels and contributing to climate change.

20. How does air composition change during combustion processes?

During combustion, the composition of air changes significantly:

21. How does the presence of dust particles in the air affect cloud formation?

Dust particles play a crucial role in cloud formation as they act as cloud condensation nuclei (CCN). Water vapor in the air needs a surface to condense upon, and dust particles provide this surface. Without these particles, cloud formation would be much more difficult. The size and composition of dust particles can influence the type and characteristics of clouds formed. For instance, an abundance of small particles can lead to more but smaller cloud droplets, potentially affecting precipitation patterns. Additionally, certain types of dust, like those containing minerals, can influence cloud chemistry and the Earth's radiation balance.

22. What is the significance of the dew point in relation to air composition?

The dew point is the temperature at which water vapor in the air begins to condense into liquid water. It's directly related to the amount of water vapor in the air (humidity). When the air temperature drops to the dew point, the relative humidity reaches 100%, and condensation occurs. Understanding the dew point is crucial for predicting weather phenomena like fog, dew formation, and the likelihood of precipitation.

23. How does the composition of air affect sound transmission?

The composition of air affects sound transmission in several ways. The speed of sound in air depends on factors like temperature, humidity, and the mix of gases present. For instance, sound travels faster in warm, humid air compared to cold, dry air. Additionally, changes in air composition can affect how sound waves are absorbed or reflected, influencing how far and clearly sound can travel.

24. Why is carbon monoxide considered a dangerous air pollutant despite its low concentration in the atmosphere?

Carbon monoxide (CO) is dangerous even in low concentrations because it binds to hemoglobin in blood much more readily than oxygen does. This reduces the blood's capacity to carry oxygen to body tissues, potentially leading to asphyxiation. Unlike many other pollutants, CO is odorless and colorless, making it particularly hazardous as it can accumulate to dangerous levels without being detected by human senses.

25. How does the composition of air affect its specific heat capacity?

The specific heat capacity of air – the amount of heat required to raise the temperature of a unit mass of air by one degree – is influenced by its composition. Different gases have different specific heat capacities. For instance, water vapor has a higher specific heat capacity than dry air, so humid air can absorb more heat with less temperature change compared to dry air. This property affects how quickly air heats up or cools down, influencing weather patterns and climate.

26. How do trees and plants affect local air composition?

Trees and plants significantly influence local air composition through several processes. During photosynthesis, they absorb carbon dioxide and release oxygen, helping to purify the air. They also release water vapor through transpiration, affecting local humidity levels. Additionally, some plants emit volatile organic compounds (VOCs) that can react with other air components. Trees and plants also act as natural air filters, trapping particulate matter and other pollutants on their leaves and bark.

27. How does the presence of water vapor in air affect its density?

Water vapor in air actually makes the air less dense. This might seem counterintuitive, but water vapor (H2O) is lighter than the main components of dry air (nitrogen and oxygen). When water vapor replaces some of the dry air in a given volume, it decreases the overall density of that air. This property is crucial in understanding weather patterns, as less dense, moist air tends to rise, contributing to cloud formation and precipitation.

28. How does air pressure change with altitude and why?

Air pressure decreases with increasing altitude. This occurs because air pressure at any point is the result of the weight of all the air above that point. As you go higher, there's less air above you, resulting in lower pressure. This relationship is not linear; air pressure decreases more rapidly near the Earth's surface and more slowly at higher altitudes due to the compressibility of air and the effects of gravity.

29. How does the composition of air change with altitude?

The composition of air changes with altitude due to gravity and molecular weight differences. Heavier gases like carbon dioxide are more concentrated near the Earth's surface, while lighter gases like hydrogen and helium become more prevalent at higher altitudes. The overall percentage of nitrogen and oxygen remains relatively constant up to about 80 km.

30. How does water vapor in the atmosphere affect weather patterns?

Water vapor is a key component in atmospheric processes. It contributes to the formation of clouds and precipitation, plays a role in heat transfer through evaporation and condensation, and acts as a greenhouse gas. The amount of water vapor in the air affects humidity levels and influences weather patterns, including the formation of storms and the intensity of the water cycle.

31. Why doesn't the oxygen in the atmosphere combust spontaneously?

Oxygen doesn't combust spontaneously because it needs an ignition source and fuel to start a fire. Additionally, most of the oxygen in our atmosphere is in its diatomic form (O2), which is relatively stable. Combustion typically requires breaking these bonds and forming new ones with fuel molecules.

32. What is the main component of Earth's atmosphere?

The main component of Earth's atmosphere is nitrogen (N2), making up about 78% of the air we breathe. This is followed by oxygen (O2) at about 21%, with the remaining 1% consisting of various trace gases.

33. Why is argon more abundant in the atmosphere than carbon dioxide?

Argon is more abundant than carbon dioxide in the atmosphere because it's an inert gas that doesn't react with other elements or compounds. In contrast, carbon dioxide is constantly being removed from the atmosphere through processes like photosynthesis and dissolution in water, while also being added through respiration and human activities.

34. What is the difference between air and atmosphere?

While often used interchangeably, "air" and "atmosphere" have slightly different meanings. Air refers specifically to the mixture of gases we breathe, primarily nitrogen and oxygen. The atmosphere, on the other hand, is the entire gaseous layer surrounding the Earth, including all its layers from the troposphere to the exosphere, and encompasses not just air but also various phenomena like weather patterns and the ozone layer.

35. What is the role of trace gases in the atmosphere?

Trace gases, despite their small concentrations, play crucial roles in atmospheric processes. For example, carbon dioxide and methane act as greenhouse gases, trapping heat. Ozone in the stratosphere protects against UV radiation. Other trace gases like nitrogen oxides and sulfur dioxide can contribute to air pollution and acid rain. Some trace gases are also important for various chemical reactions in the atmosphere that affect air quality and climate.

36. What is the significance of the nitrogen cycle in maintaining atmospheric composition?

The nitrogen cycle is crucial for maintaining the atmosphere's composition. It involves the conversion of nitrogen gas (N2) from the air into forms that can be used by living organisms, and then back into atmospheric nitrogen. This cycle, involving processes like nitrogen fixation, nitrification, and denitrification, helps maintain the balance of nitrogen in the atmosphere, soil, and water. Without this cycle, the atmosphere's nitrogen content could be depleted or altered significantly.

37. How does the composition of air affect the spread of airborne diseases?

The composition of air can influence the spread of airborne diseases in several ways:

38. What is the relationship between air pressure and the boiling point of water?

Air pressure directly affects the boiling point of water. At standard atmospheric pressure (1 atm or 101.325 kPa), water boils at 100°C (212°F). As air pressure decreases, such as at higher altitudes, the boiling point of water also decreases. This is because lower air pressure exerts less force on the surface of the water, allowing water molecules to escape as vapor more easily. Conversely, in high-pressure environments, water requires more energy (higher temperature) to boil. This relationship is crucial in cooking, industrial processes, and understanding atmospheric phenomena.

39. What is the concept of "air quality index" and how is it related to air composition?

The Air Quality Index (AQI) is a standardized indicator of how clean or polluted the air is and what associated health effects might be a concern. It's directly related to air composition as it measures the levels of major air pollutants regulated by the Clean Air Act: ground-level ozone, particulate matter, carbon monoxide, sulfur dioxide, and nitrogen dioxide. The AQI typically ranges from 0 to 500, with higher values indicating worse air quality. It helps the public understand local air quality, its potential health impacts, and when to take precautionary measures.

40. How does the composition of air affect the formation of smog?

Smog formation is heavily influenced by air composition. It primarily occurs when sunlight reacts with nitrogen oxides and volatile organic compounds (VOCs) in the atmosphere. These pollutants, often from vehicle exhaust and industrial emissions, undergo photochemical reactions in the presence of sunlight to form ground-level ozone and other secondary pollutants. The presence of particulate matter further contributes to smog. Factors like temperature inversions can trap these pollutants near the ground, exacerbating smog conditions. The composition of air, particularly the levels of these precursor pollutants, directly affects the likelihood and severity of smog formation.

41. What is the role of noble gases in the Earth's atmosphere?

Noble gases (helium, neon, argon, krypton, xenon, and radon) play a unique role in the Earth's atmosphere:

42. How does the greenhouse effect relate to the composition of the atmosphere?

The greenhouse effect is directly related to the composition of the atmosphere, particularly the presence of greenhouse gases. These gases, primarily carbon dioxide, methane, and water