Define the terms –(a) Cohesive force(b) Range of molecular force(c) Sphere of influence

Answer:

(a) Cohesive force: The force of attraction between molecules of the same substance is called cohesive force (e.g. between water molecules).

(b) Range of molecular force: The maximum distance up to which the intermolecular force of attraction between two molecules is appreciable is called the range of molecular force. It is of the order of \(10^{-9}\) m (a few molecular diameters).

(c) Sphere of influence: An imaginary sphere drawn with a molecule at its centre and radius equal to the range of molecular force is called the sphere of influence of that molecule. The molecule attracts (and is attracted by) only those molecules that lie within this sphere.