First 105 words of the document:
Crude oil is formed from the remains of sea creatures which lived millions of years ago and were covered in layers of
sedimentary rock. Without oxygen the remains could not fully decompose. Millions of years of heat and pressure changed
the remains into natural gas and crude oil.
Crude oil is useless as it is a mixture of a very large number of different sized hydrocarbon molecules. Hydrocarbons
are compounds containing only hydrogen and carbon atoms. In order to make crude oil useful we must separate the
mixture into fractions of similar sizes using distillation.