GCSE Chemistry C7 summarised revision

Hydrocarbons:

• A hydrocarbon is any compound that is formed from carbon and hydrogen atoms only
• Alkanes are the simplest of the hydrocarbons
• They have the general formula of CnH2+2
• The first four alkanes are Methane, Ethane, Propane and Butane
• Alkanes all have c-c single bonds

Hydrocarbon properties:

• The shorter the carbin chain, the more runny and less viscous it is
• Also the shorter it is the mmore flammable it is, short chains have lower boiling points as it is easier to break the chains using less energy

Combustion:

• Complete combustion occurs when there is enough oxygen
• Hydrocarbon + oxygen = carbon dioxide + water (+energy)
• During combustion both atoms in the hydrocarbon are oxidised

Fractional Distillation:

• Crude Oil is made over a long period of time, it is a fossil fuel
• Fractional distialltion is used to separate Hydrocarbons
• The oil is heated until most of it has been turned into gas, the gases enter a fractionating column, hot at the bottom and cooler as you go up, the hydrocarbons with the longest chains have the highest boiling points, as they cool they condense back into liquids
• You end up with the crude oil separated into different fractions that have a similar number of carbon…