p-Dichlorobenzene is more symmetrical than o-and m-isomers. For this reason, it fits more
closely than o-and m-isomers in the crystal lattice. Therefore, more energy is required to
break the crystal lattice of p dichlorobenzene. As a result, p-dichlorobenzene has a higher melting point and lower solubility than o-and m-isomers.