Crude oil contains a mixture of different compounds that have many uses. Mostly we separate these compounds to use as petrol or diesel.
Crude oil
A fossil fuel. It is a liquid that we find in porous rocks and it is a finite resource
Finite means that we are using it up faster than it can be made and one day we are going to run out!
Porous rock
A rock with many holes in it that allows air and water to travel through
How crude oil was formed
Crude oil is the remains of an ancient biomass consisting mainly of plankton that was buried in mud. Over millions of years, the remains were buried deeper and deeper. Heat and pressure turned it into oil and natural gas
Different compounds have different properties
We can separate the compounds based on their different properties
Fractional distillation
A process that separates crude oil into its different fractions based on their boiling points
Fractions of crude oil
Refinery gases
Gasoline
Naptha
Kerosene
Diesel fuels
Fuel oil
Bitumen
Crude oil consists of large molecules called hydrocarbons
Hydrocarbon
A molecule that contains only hydrogen and carbon atoms, joined together by covalent bonds
Most of the compounds in crude oil are hydrocarbons
Examples of hydrocarbons
Methane, CH4
Ethyne, C2H2
A hydrocarbon contains only hydrogen and carbon atoms, joined together by chemical bonds
Alkanes
As the number of carbons increases, the boiling point increases, the viscosity increases, and the flammability decreases
Intermolecular forces
The forces between hydrocarbon molecules that cause the trends in physical properties
Methane has a lower boiling point than hexane due to weaker intermolecular forces
Bitumen is more viscous than petrol due to its longer hydrocarbon chains
First 7 alkanes
Methane
Ethane
Propane
Butane
Pentane
Hexane
Heptane
Hydrocarbons are a type of molecule that contains only hydrogen and carbon atoms
Crude oil is a non-renewable energy source because it is being used up faster than it can be formed
Alkenes
Unsaturated hydrocarbons that contain at least one double covalent bond
Testing for alkenes vs alkanes
Alkenes decolourise bromine water, alkanes do not
Polymer
A very large molecule made when hundreds of monomers join together to form long chains
Plastics are synthetic polymers that can be shaped by heat or pressure
Addition polymerization
The process by which polymers like polyethene are made, where many monomers are added together
Polymers are made from alkenes, which contain at least one double covalent bond
Shorthand formula for polymers
Shows a repeating unit in brackets with 'n' to indicate a very large number of repeats
The monomer for polyvinylchloride (PVC) is a molecule with two carbon atoms joined by a double bond
Properties of plastics
They do not conduct electricity and are poor conductors of heat, they are unreactive - not affected by water, air or many chemicals
The unreactivity of plastics is both useful and problematic - it makes them durable but also means they persist in the environment for a long time
Methods of disposing of waste plastics
Landfill
Incineration (burning)
Recycling
Most plastics cannot be decomposed by micro-organisms and will remain in landfill sites for thousands of years without rotting
Plastic products carry a symbol that shows which type of polymer they are made from, to aid recycling
Usually, the only types of plastic to be recycled are PET, PVC and HDPE
If different polymers are mixed together during recycling, it can reduce the quality and value of the final recycled plastic
Landfill is a convenient method of waste disposal but it is only designed to bury rubbish, not to break it down
Most plastics are made up of tightly bonded molecules that cannot be decomposed by micro-organisms. These will remain buried at landfill sites for thousands of years without rotting
Plastic recycling symbol
Shows which type of polymer the plastic is made from
Many plastic items look and/or feel similar to each other but they are actually made from different materials, e.g. margarine tubs (polystyrene) and plant pots (polypropene)