A series of compounds in which the same functional group substitutes in a carbon chain is called homologous series . For Example = CH₃OH , C₂H₅OH and C₃H₇OH.
The difference between successive members of a homologous series is equivalent to CH₂ or 14u in terms of molecular mass ( atomic mass of C is 12u and that of H is 1u).
Melting points and boiling points increase with increasing molecular mass in a homologous series .
Chemical properties which are determined by the functional group remain similar in a homologous series .