Hydrocarbons & Alkanes & Crude Oil (+ Factional Distillation) & Fractions (+ uses)

What is crude oil?

Crude oil is a finite resource found in rocks. It is the remains of ancient biomass, mainly plankton, that was buried in mud.

Why is crude oil described as a finite resource?

It is being used faster than it is naturally formed, so supplies will eventually run out.

Is crude oil a pure substance?

No. Crude oil is a mixture of a very large number of compounds.

What type of compounds make up most of crude oil?

Hydrocarbons.

What is a hydrocarbon?

A compound containing hydrogen and carbon atoms only.

What type of hydrocarbons make up most of crude oil?

Alkanes.

What are alkanes?

A homologous series of saturated hydrocarbons.

What are the first four alkanes?

Methane — CH₄ -- Ethane — C₂H₆ -- Propane — C₃H₈ -- Butane — C₄H₁₀

What does saturated mean?

A saturated hydrocarbon contains only single carbon-carbon bonds.

Why is crude oil separated?

Crude oil contains many different hydrocarbons with different boiling points, allowing them to be separated into useful fractions.

What is a fraction?

A mixture containing hydrocarbons with a similar number of carbon atoms.

What process separates crude oil?

Fractional distillation.

Describe fractional distillation of crude oil.

Crude oil is heated so that most of it vaporises. -- The vapours enter a fractionating column. -- The column is hotter at the bottom and cooler at the top. -- Different hydrocarbons have different boiling points. -- As the vapours rise, they cool. -- Hydrocarbons condense when the temperature falls below their boiling point. -- Different fractions therefore condense at different levels of the column and can be collected.

What can fractions from crude oil be used for?

They can be processed to produce fuels and feedstock for the petrochemical industry.

Give examples of fuels obtained from crude oil.

Petrol, diesel oil, kerosene, heavy fuel oil and liquefied petroleum gases (LPG).

What is a feedstock?

A raw material used to produce other chemicals/materials.

Give useful materials made by the petrochemical industry.

Solvents, lubricants, polymers and detergents.