• The air that surrounds us is a mixture of several gases.
Figure 2: Pie-chart of air composition
• Air is colourless and tasteless and is made up of about 78% nitrogen, 21% oxygen and 1% is composed of small quantities of other gases such as carbon dioxide, ozone, hydrogen, helium etc.
• It is the Earth’s gravity that holds the layer of air around our planet.
• Oxygen is a colourless, tasteless, gaseous element which forms 1/5 of the earth's atmosphere.
• One oxygen molecule is made up of two atoms of oxygen.
• Oxygen is the most common element found on or in the Earth.
• It is one of the main elements that make up air, and it is necessary for the survival of all plants and animals.
• The symbol for oxygen is O.
• Nitrogen is the most abundant element in our planet’s atmosphere.
• Approximately 78% of the atmosphere is comprised of nitrogen.
• Nitrogen is used by life forms to carry out many of the functions .
• This element is especially important to plant life. Yet nitrogen in its gaseous form is almost entirely unusable to life forms.
• Nitrogen gas is relatively inert, but bacteria present in the soil can 'fix' atmospheric nitrogen into a form that plants can use to make amino acids and proteins.
• Its presence in the air keeps the process of burning under control.
• Without nitrogen, even small fires would be uncontrollable.
• 1% of the atmosphere is comprised of other gases.
• Argon is a colourless and odourless gas.
• It is used in making light bulbs and fluorescent tubes.
• Water vapour, carbon dioxide, ozone, hydrogen, and helium are some other gases present in air.
• Carbon dioxide is used by green plants to make their food.
• Air forms a layer around the Earth. This layer is called the Earth's atmosphere.
• The first layer of the atmosphere is made up of the gases that we breathe. This layer is called troposphere.
• The troposphere is the layer that we live in.
• The next layer of our atmosphere is called the stratosphere. Above the stratosphere lies the mesosphere, followed by the thermosphere, and the exosphere.
Atmosphere helps us in many ways:
• Clean air is important because, it is what we need to survive.
• While ground level ozone is an air pollutant, the ozone layer in the Earth’s upper atmosphere provides protection from the UV rays.
• Meteoroids may cause harm if they hit the surface of the Earth. Most of these meteoroids burn in the atmosphere before they can reach the surface of the Earth.