Question

The force of attraction between the same kind of molecules is called________and between different kinds of molecules is called
a) force of cohesion, force of adhesion
b) force of adhesion, force of cohesion
c) force of attraction, force of cohesion
d) force of cohesion, force of attraction

Answer 1

Force of attraction is basically the universal law of gravitation which is basically for any object or particle having mass. When we stick two different substances the agent which attaches them is called the adhesive. From this statement we can draw a conclusion which is the answer of the above question.

Complete step by step answer:
To begin with let us understand different forces that exist between any two particles having mass. Let us ignore the charge on the particle i.e. they are neutral in nature. Hence from universal law of gravitation if there are two bodies separated at a distance r and their respective mass is M and m, then force between them is given by,
$F=\dfrac{GMm}{{{r}^{2}}}N$ where G is the gravitational constant. Gravitational force is always attractive in nature and is a very weak force. It is independent of the type of molecules whether they are the same or different. In solids, the molecules of the same substance are held very close to each other. The force of attraction between the molecules of the same substance is called a cohesive force.
But if there is a force of attraction between the molecules of different substances then we call that force as adhesive force.

Hence the correct answer to the question is option a.

Note:
Pure form of mercury does not stick to the walls of any surface. This is because the cohesive force between the molecules of mercury are stronger than the adhesive force between mercury and the surface of the wall. While writing the ink sticks to the paper due to that adhesive forces being stronger than cohesive forces.