Any molecule that is formed from carbon and hydrogen atoms only
Properties
Flammability
How easily it burns
As the size of the molecule increases the flammability decreases
Boiling point
How easily the gas condenses or liquid boiks
As the size of the molecule increases the boiling point increases
Viscosity
The lack of fluidity in a substance
As the size of the molecule increases the viscosity increases
Volatility
The tendency to turn into gas
As the sides of the molecule increases the volatility decreases
Alkanes
Alkanes are saturated hydrocarbons
General formula of alkanes
CnH2n+2
First four alkanes
Methane
CH4
Ethane
C2H6
Propane
C3H8
Butane
C4H10
Fossil fuels
Finite non renewable resources
Burned in power stations to generate electricity
Formation
The remains of microscopic animals and plants were buried in sediments
The sediments built up burying the remains deeper and deeper
Caused acts of heat and pressure to convert the material into coal and natural gas and oil
The sediments excluded the air
Kept oxygen away
Coal
Carboniferous rock that is mainly made up of carbon which often has sulphur dioxide impurities
Uses
Fuek
Generate elwrrifity
Formation
Formed by the act of heat and pressure on plants and trees
Oul
Uses
Cooking
Fuels
Generating electricity
Economy
Heating homes
Running cars
Formation
Formed by the act of heat and pressure on sea plants and animals
Natural gas
Mainly methane
Uses
Bunsen burners
Central heating
Burned in some power stations
Formatiob
Formed by the act of heat and pressure on sea animals and plants
Crude oil
Dark, thick, pungent liquid
Varies in colour from colourless to black
Mixture of many compounds which are mainly hydrocarbons, the majority of which are alkanes
They can be separated into the hydrocarbon compounds by fractional distillation
This works because there are a mixture of compounds which means a mixture of different sized hydrocarbon molecules with different boiling points and therefore they condense at different temperatures
Formation
The remains of microcosmic animals and plants fell to the bottom of the sea
They were then covered by layers of mud and as the layers of mud built up it pushed them deeper and deeper until the actions of heat and pressure changed them into rock
The decaying remains were then slowly converted into crude oil in the absence of oxygen causing the bacteria to respire anaerobically
As the oil is less dense than the water underneath it, it rose through the layers of porous rock
Earth movements cause the rock to be split and the crude oil to be trapped underneath layers of non porous rock
The oil became trapped underground with natural gas in pockets above or in it and when drilled it escapes to the surface
Fractional distillation of crude oil
Crude oil can be separated into the compounds it is made from by fractional distillation as it contains a mixture of compounds with different sized molecules and different boiling points
It can be done in a lab but the collection vessel must be changed to collect the fractions as the temperature rises
The hydrocarbons with the smallest molecules are collected nearer the top
Smaller molecules means smaller boiling point
Rise more before condensing
Condense at a lower temperature
The hydrocarbons with the largest molecules are collected nearer the bottom
Larger molecules means larger boiling point
Don’t have to ride as much before condensing
Process
Crude oil is heated until it boils in a furnace underneath the fractionating column
It is vaporised and enters the fractionating column as a gas
The fractionating column has trays in with holes in to allow the gases to rise to the section cooled to their boiling point
The fractionating column ha as temperature gradient meaning that the temperature decreases as the height increases
When the age reaches the level of their boiling point they are condensed into a liquid
The fractions can be collected and different fractions can be piped off at the levels at which they condense
They can be piped away into different storage containers