After you have fractionally distilled crude oil, what are you left with?
Still both long and short hydrocarbons, but just not all mixed together
What does 'cracking' mean?
Splitting up long-chain hydrocarbons
Why do we crack long-chain hydrocarbons?
To produce shorter, more useful substances
Long-chain hydrocarbons form ____ ____ ____ like ____, which isn't very ____ at all.
Long-chain hydrocarbons form thick, gloopy liquids like tar, which isn't very useful at all.
Name 3 substances produced by cracking and their uses
1. Petrol - as fuel for cars
2. Paraffin - as fuel for jets
3. Ethene - for making plastics
How does cracking work?
By passing a vapourised long-chain hydrocarbon over a hot catalyst
What kind of a reaction if cracking?
Explain what is meant by the phrase 'Cracking is a thermal decomposition reaction'
It involves breaking down molecules by heating them
What are the 3 steps to cracking?
1. Heat the long-chain hydrocarbon to vapourise it
2. Pass the vapour over a powdered catalyst (aluminium oxide) at a temperature of about 400-700oC
3. The long-chain molecules split apart or 'crack' on the surface of the specks of catalyst
What are the 2 conditions needed for cracking?
1. Passed over a powdered catalyst of aluminium oxide
2. At 400oC - 700oC
What is an alternative way to crack long-chain hydrocarbons?
Mixing the vapour with steam at a very high temperature
What are the 2 main products of carcking?
Draw the craking of hexane (long-chain hydrocarbon) into butane (alkane) and ethene (alkene)
What is octane used for?