A homologous series is a series of chemical compounds having same functional group, general formula and chemical properties.

As there is a change in physical structures, we can say that there will be an increase in the size and mass of the molecules.

For example: Methane CH₄, Ethane CH₃CH₃, Propane CH₃CH₂CH₃ and Butane CH₃CH₂CH₂CH₃