The alkenes – another family of hydrocarbons

Cracking Crude oil is mixture of molecules (hydrocarbons) called the alkanes.  Most of the alkanes are used as fuels (burning).  The larger alkane molecules are difficult to burn so are of little use. However, these larger alkanes can be turned into useful molecules if they are CRACKED (broken). Large alkaneSmall alkane + Alkene heat catalyst

Alkenes are unsaturated Alkenes are called unsaturated because they have one carbon=carbon double bond.

Cracking conditions

Cracking – An example C 10 H 22 C2H4C2H4 + C 8 H 18 Decane OctaneEthene PetrolMake plastics Not useful

AlkaneAlkene Testing for an alkane and an alkene 1. Add bromine water Both are colourless

AlkaneAlkene 2. Bromine water forms a layer below hydrocarbon Testing for an alkane and an alkene

AlkaneAlkene 3. Bromine water decolourises when shaken with alkene Testing for an alkane and an alkene