Products from oil

Cracking hydrocarbons

large hydrocarbons molecules can be broken down into smaller molecules by a process called cracking

cracking can be done in two ways:

• by heating a mixture hydrocarbon vapours and steam to a very high temperature
• by passing hydrocarbon vapours over a hot catalyst

during cracking thermal decomposition reactions produce a mixture of smaller molecules

some of the smaller molecules are alkanes, which are saturted hydrocarbons 

these alkanes with smaller molecules are more useful fuels

some of the other molecules formed are hydrocarbons, these are called alkenes

alkenes are unsaturated hydrocarbons because they contain fewer hydrogen atoms than alkanes with the same number of carbon atoms 

alkenes have a double bond between two carbon atoms and this makes them more reactive than alkanes 

alkenes react with bromine water turning it from orange to colourless

Making polymers from alkenes

plastics are made of very large molecules called polymers

polymers are made from many small molecules joined together

the small molecules used to make polymers are called monomers

the reaction…