Alkanes are compounds composed of carbon and hydrogen that contain only single carbon-carbon bonds. They follow the general formula CnH2n+2, where n is the number of carbons in the molecule.
Alkanes in which the carbons are continuously linked (without branching) are called linear chain alkanes.
The family of linear alkanes is an example of a homologous series. A homologous series of compounds is one in which successive members differ by a methylene group (CH2). The general formula for homologous alkanes is CH3(CH2)nCH3. Propane (CH3CH2CH3, with n=1) and butane (CH3CH2CH2CH3, with n=2) are homologous.
In a homologous series, the physical properties change continuously; both the melting and boiling points increase as the number of carbons in the molecule increases.
Alkanes with branching are called branched chain alkanes.