7.1 Composition of Air

Air has mass and occupies space.
Clean air does not have colour or smell.

Composition of Air

Air contain nitrogen, oxygen, carbon dioxide, inert gases and other substances.
Nitrogen is 78% , oxygen is 21%, carbon dioxide is 0.03%, inert gases and other substances is 0.97%.
Inert gas: Helium, argon, neon, xenon and krypton.
Other substances are microorganisms, water vapour and dust.

The Importance of Gases

Nitrogen is an inactive gas which act as cooling agent.
Oxygen is needed for respiration, combustion and decomposition.
Carbon dioxide is needed for photosynthesis, fire extinguisher and carbon cycle.
Helium gas is filled into hot air balloons and meteorological balloons.
Argon gas is for lightbulb.
Neon gas is for advertisement billboard lamp.

Carbon Cycle and Oxygen Cycle

Carbon cycle is a cycle to maintains the content of carbon dioxide in the air.
Carbon cycle begins with green plants absorb carbon dioxide via photosynthesis.
Animals eat the plants.
When plants and animals die, they decompose.
Decomposition releases carbon dioxide.
Burning of fossil fuels releases carbon dioxide.
Respiration releases carbon dioxide.
These processes such as decomposition, combustion and respiration are balanced by photosynthesis.

Oxygen cycle is a continuos cycle that thakes oxygen from the air and returns it to the air.
Photosynthesis provides oxygen to respiration, rusting, combustion and decomposition.

Methods to Maintain the Oxygen and Carbon Cycles

Human activities such as logging and the uncontrolled usage of pesticides in agriculture will increase the amount of carbon dioxide.
This will affect the natural cycles include the oxygen and carbon cycles.
The methods to reduce the problem of interferences to the oxygen and carbon cycles are:

a. Prohibit illegal logging.

b. Avoid using excessive pesticides.

c. Reforestation.

d. Do not burn forests.

e. Prevent excessive release of smoke from vehicles.

f. Enforce the law.

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