Question

The wettability of a surface by a liquid depends primarily on:
(a)Viscosity
(b)Surface Tension
(c)Density
(d)Angle of contact between the surface and the liquid

Answer 1

Hint: Wettability is the ability or the preference of a liquid to be in contact with a solid substance. At the molecular level, this interaction defines whether a liquid will make good contact with the solid or poor contact with the solid surface, as we need both types of properties according to our need. This force of interaction at the molecular level is called Adhesion force.

Complete answer:
At the surface of contact of the liquid with the solid, the molecules of one type(liquid) interact with the molecules of another type(solid). This interaction between unlike molecules is called Adhesion and the force of interaction is called Adhesive force. It is the balance between these interactions that define the degree of wettability of a surface.
The measure of this interaction, that is, the measure of wettability can be done only by measuring the Angle of Contact between the surface and the liquid.

Hence, option (d) is the correct option.

Note:
Viscosity, surface tension and density are the properties of the liquid alone and do not affect the wettability of a surface by a liquid. They remain the same for different surfaces of solid in contact with the liquid. Also, a liquid making good contact with a solid, is generally used in coating the solid material like in electroplating, while a liquid not making a good contact with the solid surface, like Mercury is used in thermometers. The liquid inside a hydraulic press should also have low wettability in order to perform more efficiently.