Page 203 - New Medley 5 Semester 2

Activity S E L Self-Management • Analysing

To show that air (oxygen) is necessary for burning
Take a lighted candle. Place a bell jar upside down over it and watch. Does
the candle keep on burning?
Repeat the activity with a bigger jar.
Does the candle in the bigger jar light for longer?

On inverting the bell jar, the ame of the candle gets smaller and weaker until
it nally goes out. e burning of the candle depends on the amount of oxygen

in the air of the jar. e smaller jar had less oxygen and hence, candle burnt
for a shorter period in it. e bigger jar had more oxygen and the candle burnt

for a longer period in it.

Nitrogen gas is very important to all living organisms. It is not used directly
from the air. Animals get it from plants. Plants get nitrogen from the soil.

e nitrogen from the air reaches the soil by the activity of soil bacteria. e

soil bacteria x the nitrogen with other elements like hydrogen and oxygen and
make them available to the plants.

e carbon dioxide gas present in the air is used by green plants to prepare
food by the process of photosynthesis. is process gives out oxygen.

In general, all organisms breathe in oxygen and give out carbon dioxide, while
green plants use carbon dioxide and give out oxygen. is keeps a balance in the

amount of oxygen and carbon dioxide in

the atmosphere. Water from waterbodies Knowledge Zone

evaporates to form water vapour. is Some plants like pea, gram, etc. have
is how air gets water vapour. e other bacteria in their roots. These root bacteria

gases present in the air do not have direct are capable of trapping the nitrogen of
the air and providing it to the plants.
importance for the living things.

PROPERTIES OF AIR

Air has Weight
• Analysing/Experiential Learning
Activity S E L Self-Management

Take two deflated footballs of the same size. Weigh them on a beam balance.

Inflate one of them. Weigh them again.
Which football is heavier?

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