Page 3 - COMPOSITION AND PROPERTIES OF AIR
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3. CARBON DIOXIDE:
Plants need carbon dioxide to prepare their own food by the process of
photosynthesis. All animals directly or indirectly depend on plants for
food.
Carbon dioxide is a very small (only 0.03% by volume) component of air
and is a by-product of respiration by humans and animals.
Fire also uses up oxygen to burn and then produces carbon dioxide and
a few other gases upon burning. This is why we feel suffocated if there
is something burning inside a room. This happens due to an excess of
carbon dioxide as the fire continues to burn in the room, choking out
oxygen in the air.
4. OTHER GASES:
Air also contains other gases such as argon, neon, hydrogen and helium.
Argon is used in making light bulbs and fluorescent tubes.
5. Water Vapour:
Air contains water vapour which helps maintain the water cycle. Water
vapour is formed due to the evaporation of water from different water
bodies such as rivers, lakes and seas. When air comes in contact with
cold surfaces, it is these vapours that turn into or condense into
droplets of water.
The amount of water vapours in the air from place to place and time
to time is known as humidity.
Places close to coastal areas have more humidity than places away from
the sea. Similarly, air has more humidity during the rainy season than
during the summer season.
6. DUST AND SMOKE:
Smoke is another component given out when fire burns. It is very
harmful and adds fine dust particles and a few other gases to the air.
This is why industries use long chimneys in order to release this smoke
in the air. But as we know this act is what contributes to air pollution in
the environment.
Air also contains very fine dust particles which can be seen when a
beam of light enters a dark room. The tiny particles flying around in the