Question

Which of the following sentences is wrong?
A. Small drops of a liquid are spherical due surface tension
B. Oil rises through wick due to capillarity
C. In drinking cold drinks with straw, we use the phenomenon of capillarity
D. Gum is used to stick two surfaces. In this we use property of adhesion.

Answer 1

For solving his question we must go through surface tension, capillarity, and adhesion concept then relate these sentences with the phenomenon.

Complete step by step answer:
Droplets of liquid are spherical in shape because of cohesive forces of the surface layer of liquid, as cohesive force between liquid molecules causes surface tension and tries to shrink the droplet in spherical shape.
Oil rises through a wick due to capillarity as the thin pores of threads of wick acts like small capillaries, through these thin thread oil rises, as we know that due to capillarity liquid can rise or fall through small diameter tubes.
As we discussed above liquid can go up and fall through small diameter tubes, this phenomenon is known as capillarity. But in drinking cold drinks with straw we need to suction (low pressure) from mouth this will create a pressure difference and due to this pressure difference drinking cold drink with straw is possible.
Gum has the property of adhesion; it’s a property of material by virtue of which molecules of material can stick with the molecules of other material. That’s why gum is used to stick two surfaces.

So, the correct answer is “Option C”.

Note:
In straw the liquid rises upto a certain height, but it can’t reach at the end without any external force. So external force is required to pull liquid from straw. E.g. to pull water from the tube well, a pump is required.