Question

A liquid would wet the solid if adhesion forces as compared to cohesion forces are:
(a) less
(b) More
(c) Equal
(d) There is no such criterion

Answer 1

Hint: By comparing the two forces with the help of forces acting between any two particles of either same substances or different substances will result in better clarity. The fact that forces between molecules or particles of different substances should be more than the forces of the same but between two same particles.

Complete answer:
Cohesion: When a substance’s particles get attached with other particles of the same substance then, this comes under cohesion. The mixing of two molecules of water then we call that mixing together as cohesion. Under cohesion surface tension is created between the particles. When we say that two substances are experiencing cohesion then this means that they are being bonded by hydrogen bonding or Vander Waals forces are acting over them.
Adhesion: When a substance’s particles get attached with other particles of the different substance then, this comes under adhesion. If glass is filled with water then we say that these two are not mixing because of adhesion property. No surface tension is present here. If two substances are under adhesion then they are bonded by electrostatic forces or mechanical forces.
Therefore, a liquid will only wet the solid if the presence of adhesion forces is more as compared to cohesion forces.
Hence, the correct option is (b) more.

Note: When it acts as a property for substances then it generates a tension in the surface which lets the lighter objects move on the surface of the water. If there are water particles and they are forming themselves as droplets and not sipping from the surface then this means that there is a strong cohesive force working between two different particles of the same water. On the other hand if the water is present on the surface as spreading all over the surface according to its volume then this is due to the presence of adhesive forces that are acting between any two particles of different substances.