Question

Molecules that possess only London dispersion forces will have roughly the same melting points: True or False?

Answer 1

It is false.

Vanderwaal's forces of London forces depend on the effective surface area of the molecule.
Such situations are common in organic chemistry. Melting points of non polar molecules depends on factors like length of carbon chain , branching of molecules.

For example- Ethane has larger melting point than methane because of greater surface area of the molecule.