Dipole - Dipole Forces:
The attractive forces present between the positive end of one molecule with the negative end of the other molecule are called dipole - dipole forces.
Polar molecules have charges at different parts of a molecule. These charges attract each other. Therefore, these forces are electrostatic attractions between permanent dipoles in a molecule.
Stronger the dipole - dipole forces, higher the value of thermodynamic properties like melting and boiling points, heat of vaporization, heat of sublimation etc.