Question

The figure given below represents an experimental set-up with a weighing machine to demonstrarte a particular process in plants. The experimental set-up was placed in bright sunlight. Study the diagram and answer the following questions: [5 MARKS]

(a) Name the process intended for study.
(b) Define the above-mentioned process.
(c) When the weight of the test tube (A and B) is taken before and after the experiment, what is observed? Give reasons to justify your observation in A and B.
(d) What is the purpose of keeping the test tube B in the experimental set-up?

Answer 1

a) 1 Mark
b) 1 Mark
c) 2 Marks
d) 1 Mark

(a) Transpiration
(b) It is the loss of water as water vapours from the aerial parts of the plant.
(c)

Test Tube	End of experiment(observation)	Reason
A	The test tube weighs less in comparison to the start of the experiment.	The plant leaves transpire resulting in loss of water and therefore the test tube weighs less at the end of the experiment.
B	The test tube weighs same before and after the experiment.	There is no plant so no water loss and the water surface in test tube is covered with a layer of oil which prevents evaporation of water.

(d) B serves as a control set-up.