- Air occupies space.
- It has no color.
- It is transparent.
- Our earth is surrounded by a thin layer of air. This layer extends up to many kilometers above the surface of the earth and is called atmosphere.
- Air is a mixture of many gases.
- Air contains water vapor. When air comes in contact with a cool surface, it condenses and drops of water appear on the cooled surfaces. The presence of water vapor in air is important for the water cycle in nature.
- Burning can occur only in the presence of oxygen.
- The major part of air (which does not support burning candle) is nitrogen. It takes up nearly four-fifth of the space that air fills.
- Carbon dioxide makes up a small component of the air around us. Plants and animals consume oxygen for respiration and produce carbon dioxide. Plant and animal matter on burning, also consumes oxygen and produces mainly carbon dioxide and a few other gases.
- The burning of fuel also produces smoke. Smoke contains a few gases and fine dust particles and is often harmful.
- We inhale air when we breathe through our nostrils. Fine hair and mucus are present inside the nose to prevent dust particles from getting into the respiratory system.
- Air contains some gases, water vapor and dust particles. The gases in air are mainly nitrogen, oxygen, small amount of carbon dioxide, and many other gases. However, there may be some variations in the composition of air from place to place.
- Nitrogen and oxygen together make up 99% of the air. The remaining 1% is constituted by carbon dioxide and a few other gases, water vapor and dust particles.
- The wind makes the windmill rotate. The windmill is used to draw water from tube wells and to run flour mills. Windmills are also used to generate electricity. Air helps in the movements of sailing yachts, gliders, parachutes and aero planes. Birds, bats and insects can fly due to the presence of air. Air also helps in the dispersal of seeds and pollen of flowers of several plants. Air plays an important role in water cycle.
- Atmosphere is essential for life on earth.
- Aquatic animals use dissolved air in water for respiration.
- Plants and animals depend on each other for exchange of oxygen and carbon dioxide from air.
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