... by fractional distillation. This can be done because long chains have higher boiling points than short chains. Long chain molecules come off near the bottom of the column where it is hottest. Short chain molecules come out of the column near the top where it is coolest. Butane and light gases out Fractionating Column 400C Petrol out 1750C Kerosene out 2500C Diesel out Crude oil in 4000C Cracking Far more diesel is obtained than is needed. Its molecules are usually about 20 carbon atoms long. This excess diesel is turned into more useful short molecules by a process called catalytic cracking which breaks the long molecules up into short molecules containing double bonds. The conditions used for this cracking are high temperature (800oC) and in the presence of a catalyst (porous pot). Polymerisation The small molecules produced by cracking can be used to make polymers (plastics). For this to happen the little molecule(called a monomer) must have ...

See this essay or coursework document in full right now