Page 104 - ICSE Chemistry 6

Activity 5.3

Aim: To show that nitrogen does not support burning of candle
Materials required: Candle, container, water, jar

Procedure
• Place a candle in the middle of a container.

• Fill some water in the container.
• Mark the water level inside the jar.
• Light the candle and place an inverted glass jar over the candle.

Observa on: You will observe that the candle burns for some me and then gets ex nguished. Also, the
level of water rises up to 1/5th part of the
jar which previously contained air.
Conclusion: The part of the jar containing
ac ve air, i.e., oxygen supports burning of f
the candle. When oxygen is consumed, the
candle stops burning. However, the other
4/5th part of the jar contains inac ve air, i.e.,
nitrogen which does not support burning.

Carbon Dioxide

Atmosphere contains about 0.03 per cent of carbon dioxide. Carbon dioxide, though present in very small
amount as compared to nitrogen and oxygen, is crucial for sustaining life. The level of carbon dioxide in
the atmosphere also plays a role in determining the global temperature.

All food chains start with photosynthesis in which plants u lize carbon dioxide and water in the presence
of sunlight to make food (sugar). Human beings and animals release carbon dioxide during breathing.
In this way, plants and animals help each other through exchange of gases in the atmosphere.
Some other uses of carbon dioxide are men oned below.

• Carbon dioxide does not support combus on and hence is used in fi re ex nguishers.
• It maintains the temperature of the earth
by keeping it warm during night. Know Your Scientist
• Solid carbon dioxide is known as dry ice. It Joseph Black, a Sco sh chemist and physician, fi rst
is used as a refrigerant. iden fi ed carbon dioxide in 1750s. Black no ced
that upon hea ng, calcium carbonate produced a
• It is used to prepare fi zzy drinks such as
gas that was denser than air and could not sustain
soda water and so drinks.
fi re or life. He called this gas ‘fi xed air’.
• It is used in water treatment to neutralize
alkaline water.

Let’s perform Ac vity 5.4 to observe that human beings exhale (give out) carbon dioxide during breathing.

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