Question

Which of the facts is not due to surface tension?
A) Dancing of a camphor piece over the surface
B) Small mercury drop itself becomes spherical
C) A liquid surface comes at rest after stopping
D) Mercury does not wet the glass vessel.

Answer 1

Just keep in mind that surface tension enables the material to get into the least surface area possible whereas viscosity restricts the motion of liquid particles by enabling force of friction between the particles.

Complete step by step solution:
Let us first define the surface tension.
The Surface tension is defined as the property of fluids to get into the minimum surface area possible. As we all know, liquid tends to acquire the least surface area possible. As we know, it depends upon the force of attraction between the liquids. Also, it depends on the force of attraction of solid, liquid, or gas.
Now, as we know, the surface tension of different particles will be different. Therefore, when camphor is placed in water, its impurities are dissolved in water. So, the surface tension of water decreases.

Therefore, this is the case of surface tension.
Now, you might have also observed that mercury drops become spherical itself, this is because of the surface tension. Also, the gravity of the drop is low. Therefore, the drop tries to get into the minimum surface area possible. So, this is also the case of surface tension.

Now, a liquid surface comes at rest after stopping due to viscosity. As viscosity is the measure of the resistance of the flow of fluid. Fluid with large viscosity resists the motion as the molecules enable the force of friction.

Therefore, option (C) is the correct option.

Additional Information:
The values of surface tension of various liquids are given below:

LIQUID	SURFACE TENSION ($N/m$)
Hydrogen	$2.4$
Helium	$0.16$
Water	$72.7$
Ethanol	$22.0$
Sodium chloride	$114$

Note: Surface tension and viscosity are dependent on molecular interactions. Surface tension is the difference of interactions between the molecules of the fluid with the molecules of the fluid material in contact whereas viscosity occurs due to the collaboration among molecules of the identical molecules located in the fluid.