Thus the p-dichlorobenzene boils easily and freezes easily. With p-dichlorobenzene the separation of one molecule from another within the lattice is taking place. There is no breaking apart of molecules. Van der Waals forces are being overcome. With KBr, ionic attractions must be overcome for melting to occur.
Intramolecular forces are greater in p-dichlorobenzene.
The intramolecular forces are covalent, and hold the carbon, hydrogen, and chlorine atoms together tightly in molecules of this substance.