Fractional distillation

What is fractional distillation used for?

To separate a mixture of long-term chain hydrocarbons in crude oil into smaller, more useful fractions

What does each fraction contain?

Hydrocarbons of a similar chain length

What happens to the fractions due to different sizes of molecules?

They boil at different temperatures

Why are parts of crude oil called fractions?

Because they are a small part of the original crude oil

What column does crude oil enter when it is heated?

The fractionating column.

Where in the column is it hot?

At the bottom. Temperature decreases as it goes up

What happens as crude oil is heated?

It begins to evaporate and it's vapours rise up the column.

What happens to the vapours in the fractionating column?

They condense at different temperatures

Where are short chain hydrocarbons found in the column?

At the top

Why are shorter chain hydrocarbons at the top?

Because they are held together by weak intermolecular forces, meaning they have a low boiling point.

How do short chain hydrocarbons leave the fractionating column?

As a gas

Where are long chain hydrocarbons found in column?

At bottom of column

Why do long chain hydrocarbons have higher boiling points?

Held together by strong intermolecular forces

What hydrocarbon is directly at bottom of fractionating column?

Bitumen