How is oil changed in to petrol?

Answer 1

crude oil is a mixture of many different hydrocarbon molecules. Petrol, as we call it in the UK, is more acurately known as gasoline, and is one of these hydrocarbons. The different hydrocarbon molecules found in crude oil are all of different sizes, and hence have different temperatures at which they condense back to liquid form after being vapourized. It is this fact which is used in separating the different hydrocarbons found in oil - through the process of fractional distilation. In this process the oil is vaporized and allowed to rise up a column. further up the column the temperature gets cooler. At various levels within the column there are collection points where a hydrocarbon fraction can be collected when it condenses. Other fractions with higher temperatures of condensation will have been collected further down the column, whereas those with a lower condensation temperature will still be hot enough to be a gas and so will continue rising up the column until it is cool enough forr it to condense. more info and diagrams: http://en.wikipedia.org/wiki/Fractional_distillation