The bonding within all hydrocarbon molecules is covalent bonding. The bonds between the non-polar molecules are weak intermolecular forces arising from transient dipoles. The single C-C in alkanes and the C-H bonds in alkanes and alkenes are all sigma bonds. The double bond in an alkene consists of a single sigma bond between two carbon atoms together with a pi bond. Risk assessment Before attempting any practical work based on the advice and suggestions on this website, you must do the following. Identify any hazards, assess the risks from these hazards, and then decide appropriate control measures to reduce the risks. You must have these approved by those in authority in your school or college laboratory. Do not rely on what is said on this website. For further guidance see our tutorial on Risk Assessment.