Question

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


(a) Name the process intended for study.

(b) Define the above mentioned process.

(c) When the weight of the test tubes A and B is taken before and after the experiment, what change is observed? Justify.

(d) What is the purpose of keeping the test tube B in the experimental set up?

(e) What is the purpose of putting oil in the test tube?

Answer 1

(a) The process that intended for study by this experiment is transpiration.

(b) Transpiration is the process in which water is lost in the form of vapour from the aerial parts of the plant.

(d) After the experiment, we observe test tube A is raised up i.e., a loss of weight. In test tube B, the weight remains unchanged.

Reason : In test tube A, loses weight due to the plant transpires and loses water. In B there is no plant so there is no transpiration and the oil on the surface prevents direct evaporation and so weight remains unchanged.

(d) As a control experiment.

(e) Oil stops the evaporation of water from the surface.