Class 6 Notes Chapter 15-Air around us

1. VIDYA BHARTI EDUCATIONAL INSTITUTIONS
SCIENCE NOTES CLASS 6TH
AIR AROUND US
Air is present all around us. We cannot see the air around us but we can feel
its presence when the leaves rustle or branches away.
Importance of Air
We need air for breathing.
All living beings need air for breathing.
We need air to burn something.
Life is possible on earth because of air.
Composition of Air
Air is a mixture of gases, water vapour and dust particles. Some of the gases;
present in air; are discussed below.
Nitrogen: Nitrogen is the largest component of air. Nitrogen makes up 79% of
air around us. Nitrogen is used by plants to make protein. Plants cannot take
nitrogen directly from the air. Some nitrogen fixing bacteria live in soil. They
help in nitrogen fixation in soil. Thus, plants are able to take nitrogenous
compounds from the soil.
Oxygen: Oxygen is the second largest component of air. Oxygen makes up
21% of the air around us. Oxygen is used by living beings for respiration. After
respiration, the living beings produce carbon dioxide.
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2. VIDYA BHARTI EDUCATIONAL INSTITUTIONS
SCIENCE NOTES CLASS 6TH
AIR AROUND US
Carbon dioxide: The remaining 1% of air is composed of carbon dioxide, many
other gases, water vapour and dust particles. Carbon dioxide is also important
for living beings. Plant need carbon dioxide to make food during
photosynthesis. During photosynthesis, plants take in carbon dioxide and
release oxygen. Thus, green plants help in maintaining the balance of carbon
dioxide and oxygen in atmosphere.
Air in water: Air is also present in water. Aquatic animals breathe the air which
remains dissolved in water. When water is boiled, air bubbles can be seen
coming up from the bottom of the pan. This simple activity shows that air is
present in water.
Activity to show presence of oxygen, carbon dioxide and nitrogen in air:
For this, take a candle, a glass tumbler and a pan which is filled with some
water. Keep the candle upright in the pan and light the candle. Now cover the
candle with the glass tumbler. It is observed that the candle extinguishes after
some time.
This happens because oxygen in the air inside the glass tumbler is utilised in
burning the candle. All the oxygen gets converted into carbon dioxide. Carbon
dioxide does not support burning and hence candle stops burning.
Once the candle stops burning, some amount of water is sucked inside the
tumbler. This happens because the volume of cabron dioxide is less than the
volume of oxygen which was displaced.
It is also seen that a lot of air is still inside the tumbler. A major portion of this
air is nothing but nitrogen. Nitrogen too does not support burning.
CONTACT: 9654089891, 9811083910, 9953898004
HEAD OFFICE: 131/12 KRISHNA COLONY, STREET NO 4, NEAR SHIV MANDIR, GURGAON