What Is Air?/ Chemical Composition of Air / Detailed Composition of Air

 

Understanding the Air Around Us: Composition, Properties & Importance 

Matter is anything that has mass and occupies space.

From the chair you’re sitting on to the air you’re breathing right now—everything is matter.

Air is one of the most essential types of matter because life cannot survive without it. Every breath we take, every fire that burns, every weather event that happens—all depend on air.

The Earth is surrounded by a blanket of air known as the atmosphere, and this invisible layer protects and supports life in powerful ways.

What Is Air?

Even though you cannot see air, it is everywhere around you. Air is a mixture of several gases, water vapour, dust particles, and other tiny substances.

From influencing weather and climate to supporting breathing, air is one of the most important components of our environment.

Apart from sustaining life, air drives:

• Wind

• Clouds

• Rain

• Storms

• Climate patterns

Everything you feel in the environment is shaped by the air that surrounds us.

Chemical Composition of Air

Air is not just one gas—it is a mixture of many gases that together form the Earth’s atmosphere. Most of these gases are colourless and odourless, which is why we cannot see them.

Here’s what air is made of:

Major Components of Air

Element	Volume %	Role
Nitrogen (78%)	Largest component	Helps plants grow, maintains balance in atmosphere
Oxygen (21%)	Essential for life	Needed for breathing and burning
Other gases (1%)	Includes CO₂, Argon, Neon, etc.	Small but important roles

Although only 1% of air consists of “other gases,” many of them are crucial for life and climate.

Important Notes:

• The composition of air remains the same up to nearly 10,000 meters above sea level.

• Only the number of air molecules decreases as you go higher (which is why breathing becomes harder at high altitudes).

• Air temperature reduces at an average of 0.6°C per 100 meters of height.

• One standard atmosphere (1 atm) is equal to the pressure exerted by a 760 mm column of mercury at sea level.

Detailed Composition of Air (Simplified Table)

Here is a more student-friendly version of the composition chart:

Gas	Volume %	Symbol	Why It’s Important
Nitrogen	78.08%	N₂	Makes up most of air; needed for plant growth
Oxygen	20.95%	O₂	Essential for breathing and burning
Argon	0.93%	Ar	An inert gas that does not react easily
Carbon Dioxide	0.04%	CO₂	Needed by plants; controls Earth’s temperature
Neon	0.0018%	Ne	Used in signboards
Helium	0.0005%	He	Light gas used in balloons
Krypton	0.0001%	Kr	Used in bulbs
Hydrogen	0.00005%	H₂	Lightest gas
Xenon	Trace	Xe	Used in special lamps

Even though these gases are present in very small amounts, they have major roles in climate, industry, and life processes.

Other Components of Air (Small But Significant)

Apart from the main gases, air contains traces of:

• Sulfur dioxide (SO₂) – causes acid rain

• Methane (CH₄) – greenhouse gas

• Nitrous oxide (N₂O) – also a greenhouse gas

• Ozone (O₃) – protects us from UV rays (in the upper atmosphere)

• Nitrogen dioxide (NO₂) – pollutant

• Carbon monoxide (CO) – harmful gas

• Ammonia (NH₃) – from decay and fertilizers

Though small, these gases can affect health, weather, and climate.

Properties of Air

Like all matter, air has certain physical properties. Understanding these helps explain weather, wind, and everyday observations.

1. Air Is Colourless and Odourless

You cannot see or smell air.
But you can feel it.

Example:
When the wind blows, you feel moving air on your skin.

2. Air Occupies Space

Air is matter, and all matter takes up space.

Example:
When you blow air into a balloon, it expands because air fills the empty space inside.

3. Air Has Weight and Exerts Pressure

Even though air is invisible, it still has weight.

• The weight of air pressing down on Earth is called air pressure.

• Air pressure is higher at sea level and lower at high altitudes.

• That is why people may feel breathless in mountains.

4. Air Expands When Heated

Warm air is lighter than cold air.

Examples:

• Hot air balloons rise because heated air expands.

• Warm air above the ground rises, creating wind patterns.

When air expands, it becomes thinner and exerts less pressure.

Frequently Asked Questions (FAQs)

Q1. Does air occupy space?

Yes. Since air has mass, it occupies space.

Q2. What are the main properties of air?

Air is:

• Colourless

• Odourless

• Occupies space

• Exerts pressure

• Expands when heated

Q3. What are the major components of air?

The main gases in air are:

1. Nitrogen

2. Oxygen

3. Argon

4. Carbon dioxide

5. Neon and other trace gases

Q4. What is meant by atmosphere?

The atmosphere is the layer of gases surrounding Earth. It protects life by:

• Blocking harmful UV rays

• Keeping temperatures stable

• Supporting breathing and weather

Q5. What are the layers of the Earth’s atmosphere?

From outermost to innermost:

1. Exosphere

2. Thermosphere

3. Mesosphere

4. Stratosphere

5. Troposphere

Each layer has different characteristics and functions.

Final Note from HN Series

Understanding the composition and properties of air is essential for studying:

• Weather

• Climate

• Respiration

• Environmental science

Air may be invisible, but its role in our lives is massive.

Stay connected with HN Series for more simple, engaging, and high-quality science explanations—designed to make learning enjoyable for every student.