Crude Oil & Fractional Distillation

Crude oil definition

Mixture of hydrocarbons

Hydrocarbon definition

Compound made of hydrogen and carbon only

Source of crude oil

Formed from dead marine organisms over millions of years

Type of mixture

Physical mixture, not chemically bonded

Separation method

Fractional distillation

Reason fractional distillation works

Different hydrocarbons have different boiling points

Fraction definition

Group of hydrocarbons with similar boiling points

Trend in boiling point

Longer chains = higher boiling point

Trend in viscosity

Longer chains = more viscous

Trend in flammability

Longer chains = less flammable

Trend in volatility

Longer chains = less volatile

Fractionating column

Tall tower with temperature gradient (hot bottom, cool top)

Process step 1

Crude oil heated and vaporised

Process step 2

Vapours rise up the column

Process step 3

Fractions condense at different heights depending on boiling point

Top of column

Cool, collects small molecules with low boiling points

Bottom of column

Hot, collects large molecules with high boiling points

Refinery gas use

Cooking and heating

Gasoline/petrol use

Fuel for cars

Naphtha use

Making chemicals and plastics

Kerosene use

Jet fuel

Diesel use

Fuel for lorries and buses

Fuel oil use

Ships and power stations

Bitumen use

Road surfacing and roofing

Key idea

Fractional distillation separates hydrocarbons by boiling point due to different chain lengths