[ ] crude oil

[ BBC Bitesize 'Organic Chemistry ⇢ Crude oil, hydrocarbons and alkanes' 1-3 ]

Crude Oil

A mixture of hydrocarbons, mainly alkanes, formed from the remains of ancient biomass consisting mainly of plankton that was buried in the mud.

Hydrocarbons

Molecules that contain only hydrogen and carbon atoms.

Homologous Series

A family of hydrocarbons with similar chemical properties who share the same general formula.

Alkanes

Saturated hydrocarbons, they contain a carbon-carbon single bond only. General Formula = C_nH_2n+2

Examples of Alkanes:

• methane (CH₄)

• ethane (C₂H₆)

• propane (C₃H₈)

• butane (C₄H₁₀)

Uses of Crude Oil:

• fuel - can be burned to release energy

• chemical feedstock - components of crude oil can be used as building blocks to make more complex molecules

Examples of Fuels:

• petrol

• diesel

• kerosene

• heavy fuel oil

Examples of Chemical Feedstock:

• solvents

• lubricants

• polymer plastics

• detergents

Feedstock

A raw material used to provide reactants for an industrial reaction.

Hydrocarbons have many uses due to the…

…ability of the carbon atoms to form families of similar compounds.

Fractional Distillation

When a mixture of several substances, such as crude oil, is distilled and the evaporated components are collected as they condense at different temperatures.

Fractionating Column

Piece of apparatus in which mixtures separate during fractional distillation.

Fractions

Hydrocarbons that make up crude oil, with a similar number of carbon atoms and similar boiling points.

1st Stage in the Fractional Distillation of Crude Oil:

Crude oil enters the fractionating column, which has a temperature gradient, and is heated to about 350°C.

2nd Stage in the Fractional Distillation of Crude Oil:

Most of the hydrocarbons from the crude oil evaporate and form vapours which rise up the fractionating column.

3rd Stage in the Fractional Distillation of Crude Oil:

As the vapours rise, they cool. Long chain hydrocarbons will condense at the lower parts of the fractionating column, whereas shorter chain hydrocarbons will condense at the higher parts of the fractionating column.

4th Stage in the Fractional Distillation of Crude Oil:

Condensed fractions of crude oil will be separated from the rest of the vapours and flows out through a pipe to be collected.

5th Stage in the Fractional Distillation of Crude Oil:

Some of the hydrocarbons remain as liquid (eg. bitumen) and flows to the bottom of the fractionating column. Some of the hydrocarbons remain as vapours and rise out of the top of the fractionating column.

Crude Oil Fractions Acronym:

Lazy Penguins Never Keep Drinking Hot Beer

Crude Oil Fractions:

(top to bottom of fractionating column)

• Liquefied Petroleum Gases (LPGs) - fuel for domestic heating and cooking

• Petrol - fuel for cars

• Naph - used in chemical production

• Kerosene - fuel for aircrafts

• Diesel - fuel for some cars and trains

• Heavy Fuel Oil - fuel for ships and power stations

• Bitumen - used in roofs and roads

Long Chain Hydrocarbon Properties:

• high boiling points - stronger and more frequent intermolecular forces require more (heat) energy to break + more surface contact between molecules

• low volatility - volatility decreases with increase in chain length

• high viscosity - has more intermolecular forces than short chain hydrocarbons so the chains are stickier

• low flammability - less able to ignite and burn due to increased molecular size

Short Chain Hydrocarbon Properties:

• low boiling points - weaker and less frequent intermolecular forces require less (heat) energy to break + less surface contact between molecules

• high volatility - volatility increases with decrease in chain length

• low viscosity - has less intermolecular forces than long chain hydrocarbons so the chains are less stickier

• high flammability - more able to ignite and burn due to decreased molecular size

Complete Combustion

When a fuel is burned in an excess of oxygen. This produces a blue flame and more heat.

Complete Combustion Equation

fuel + oxygen → carbon dioxide + water

Incomplete Combustion

When a fuel is burned in a limited supply of oxygen. This produces a yellow/orange flame and soot.

Incomplete Combustion Equation

fuel + oxygen → carbon monoxide + water

Balance combustion equations in the order…

…carbon, hydrogen and oxygen