Hydrocarbons In Crude Oil (AQA GCSE Combined Science: Synergy: Physical Sciences): Revision Note

• Organic chemistry is the chemistry of carbon compounds

• Carbon forms a vast number of compounds because it can form strong covalent bonds with itself

• This enables it to form long chains and rings of carbon atoms

  • This is why an almost infinite variety of carbon compounds is known

Composition of crude oil

What is crude oil?

• Crude oil is a finite resource which we find in the Earth's crust

• Crude oil is a complex mixture of lots of different hydrocarbon compounds of different sizes

  • Crude oil is a main source of hydrocarbons and is used as a feedstock for the petrochemical industry

• Hydrocarbons are compounds that contain hydrogen and carbon atoms only

• It is a thick, sticky, black liquid that is found in porous rock (under the ground and under the sea)

• Crude oil formed over millions of years from the effects of high pressures and temperatures on the remains of biomass (plants and animals), mainly plankton that was buried in mud

• It is being used up much faster than it is being formed, which is why we say crude oil is a finite resource

Diagram to show the location of crude oil

Crude oil found under the sea

Alkanes

• Alkanes are a group of saturated hydrocarbons

• The term saturated means that they only have single carbon-carbon bonds, there are no double bonds

• The general formula for alkanes is C_nH_2n+2

• They are colourless compounds which have a gradual change in their physical properties as the number of carbon atoms in the chain increases

• Alkanes undergo combustion reactions and can be cracked into smaller, more useful molecules

• Methane is an alkane and is the major component of natural gas

Table of alkanes

Displayed formula	Name	Molecular formula
	methane	CH4
	ethane	C2H6
	propane	C3H8
	butane	C4H10

The first four members of the alkane homologous series