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Principle: Carbon dioxide can be tested by
introducing potassium hydroxide into the test
tube, which will float up through the mercury and
on coming in contact with gas, will absorb the
carbon dioxide and level of mercury will again rise.
Materials required:
Mercury
Beakers
Test tubes
Pea seeds
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Inference: The seeds respire carbon dioxide gas.
Precaution:
The mercury should be handling carefully as it is
dangerous.
Experimental Setup for Anaerobic Respiration
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Procedure:
Take eight to ten soaked and peeled off peas.
Push them into the mouth of a test tube filled with mercury.
Invert the test tube filled with mercury in a beaker of
mercury.
As a control we will take the same experiment set up with
boiled seeds and sterilized with antiseptic.
Observation:
The seeds will float to the top and will be
completely surrounded by mercury.
After two days, the level of mercury in the test tube
will fall.
The liberated gas will be found to be carbon
dioxide.
In the control experiment, no gas will be liberated.
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Aim: An experiment to demonstrate transpiration
in green plants.
Principles:
There is no moisture in air.
Green plant s take transpiration
Material s required:
Bell jar
Potted plant
Seeds/wooden stick
Cobalt chloride paper
Procedures:
 Step A
 We took well watered potted plant with leaves.
 Enclosed the pot completely within a polythene
bag and tied the mouth of the bag firmly around
the base of the stem.
 It was done to prevent the escape of water vapor.
 Covered the entire plant under the bell jar.
 Step B
 Arranged another similar plant.
 Covered it with a bell jar exactly in the same as
the first one, except we had also kept a piece of
dry cobalt chloride paper by the side of the plant
inside the bell jar.
 The paper was pasted to a wooden stick.
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Experimental set up for transpiration in
green plants.
Step C
 We took third bell jar without plant but with
cobalt chloride paper.
 We kept all the bell jars together in the sun.
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Observation:
 After a day we observed:
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◦ The first bell jar (A) showed water droplets condensing
on its inner walls.
◦ The second bell jar (B) showed a similar condensation of
water droplets at the same time, the initially blue cobalt
chloride paper turned into pink.
◦ The blue colour of the cobalt paper in the third bell jar
(C) did not change and there was no water droplets
condensed on walls.
Inference
 The third bell jar (C) proves that there is no
moisture in the air.
 Condensation of water droplets and change of
colour in cobalt chloride paper form blue to
pink proves of transpiration in green plants.
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Precaution:
 All bell jars should be made air tight by
applying grease; otherwise air from out side
will get inside.
 All potted plants should be covered by
polythene bag and sure the water vapour from
pots does not escape.
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