Physical Properties of Alkenes

The first three members (ethene, propene, butene) are gases, the next fourteen are liquids, and the higher alkenes are waxy solids; all are colourless and odourless except ethene, which has a faint sweet smell. Melting and boiling points increase along the homologous series, and, as with alkanes, a straight-chain alkene has a higher boiling point than its branched isomers. Alkenes are onl …