Air

Air is the invisible mixture of gases that surrounds the Earth and is vital for all living organisms. It is primarily composed of nitrogen (78%), oxygen (21%), and small amounts of other gases such as argon, carbon dioxide, and water vapor.

Composition

The composition of air is relatively constant up to an altitude of about 10,000 meters. The primary components are:

• Nitrogen (N2) - 78.08%
• Oxygen (O2) - 20.95%
• Argon (Ar) - 0.93%
• Carbon dioxide (CO2) - 0.04%
• Trace amounts of other gases including neon, helium, methane, krypton, and hydrogen.

Properties

Air has several important properties:

• It is a fluid and can flow from one place to another.
• It has mass and weight.
• It exerts pressure, known as atmospheric pressure.
• It can be compressed and expanded.
• It is essential for combustion and respiration.

Atmospheric Layers

Air is divided into several layers based on temperature and composition:

• Troposphere: The lowest layer where weather occurs and where most of the air mass is found.
• Stratosphere: Contains the ozone layer which absorbs and scatters ultraviolet solar radiation.
• Mesosphere: The layer where most meteors burn up upon entering the Earth's atmosphere.
• Thermosphere: A layer with very thin air, where the auroras occur.
• Exosphere: The outermost layer, where air molecules are sparse and can escape into space.

Importance

Air is crucial for:

• Respiration: All aerobic organisms require oxygen to produce energy.
• Photosynthesis: Plants use carbon dioxide and release oxygen.
• Climate: Air circulation patterns influence weather and climate.
• Sound: Air is the medium through which sound waves travel.

Air Pollution

Air pollution is the presence of harmful substances in the air, which can have adverse effects on health and the environment. Common pollutants include:

• Particulate matter
• Nitrogen oxides
• Sulfur dioxide
• Carbon monoxide
• Volatile organic compounds

See Also

• Atmosphere of Earth
• Breathing
• Greenhouse gas
• Oxygen cycle
• Air quality index