Homologous Series - GCSE Chemistry Definition

A homologous series is a group of organic compounds that have the same general formula and functional group. These compounds normally differ by a repeating unit, often a -CH₂ group. This means each compound in the series increases in size by one carbon and two hydrogen atoms. Members of a homologous series have similar chemical properties because they all have the same functional group, but their physical properties, like boiling and melting points, gradually change as you move along the series. The alkanes are an example of a homologous series, and they include compounds like methane, ethane, propane, and others.