Question

Rise in capillary tube _____________ with addition of detergent of pure water.
(A) Increases
(B) Decreases
(C) Remains same
(D) None of these

Answer 1

Hint:Detergents consist of surfactants or surface-active agents.Adding detergent into pure water changes the surface tension of the water.A change in surface tension leads to a change in the rise in the capillary tube.

Complete step by step answer:
From the given question, we know
We are adding detergent into pure water, which changes the surface tension of the water.
As a result, we observe a change in the rise in the capillary tube.So,the option number (C) and (D) are not valid in our case.Now, we have to check whether the rise in the capillary tube is increasing or decreasing.Adding the detergent into pure water leads to a decrease in the surface tension of the water molecules. The detergent holds surfactants or surface-active agents, which causes the same.Consequently, a decrease in surface tension causes a reduction in cohesive forces between the water molecules.Again, a decrease in surface tension also increases the adhesive force of water molecules towards the tube surface.
Hence, as a result, the rise in the capillary tube decreases.
So,the correct answer is (B) decreases.

Note:Adding detergent reduces the sticking ability of water molecules together.
It enhances the sticking ability of water to the other surfaces.The surfactants reside in detergent to help remove dirt from the clothes.