Question

when common salt dissolve in liquid what will be change in volume and why

Answer 1

Umm this might be confusing but here If rock salt is added to a container of water, the volume would of course change to accomodate the displacement. If table salt is added to water and allowed to dissolve, the restructured water molecules will cause a slight loss of volume.

The interaction of the electrostatic field of an ion with water tends to align the dipolar water molecules in the direction of the field. In this way the field tends to disrupt hydrogen bonded structures in liquid water, and to compress the water molecules surrounding an ion. These electrostatic effect give rise to a shrinkage of the water.