Chemistry Paper 2 Topic 7 – Organic Chemistry
Hydrocarbons
A hydrocarbon is any compound that is formed from carbon and hydrogen atoms only.
So C10H22 (decane, an alkane) is a hydrocarbon, but CH3COOC3H7 (an ester) is not
because it contains oxygen.
Alkanes are the simplest type of hydrocarbon. They have the general formula CnH2n=2.
The alkanes are a homologous series – a group of organic compounds that react in a similar
way.
Alkanes are saturated compounds – each carbon atom forms four single covalent bonds.
The first four alkanes are methane, ethane, propane and butane.
, Chemistry Paper 2 Topic 7 – Organic Chemistry
As the length of the carbon chain changes, the properties of the hydrocarbon change.
The shorter the carbon chain, the more runny a hydrocarbon is – that is, the less
viscous (gloopy) it is.
Hydrocarbons with shorter carbon chains are also more volatile, i.e. they have lower
boiling points.
The shorter the carbon chain, the more flammable (easier to ignite) the hydrocarbon
is.
The properties of hydrocarbons affect how they are used for fuels.
E.g. short chain hydrocarbons with lower boiling points are used as
‘bottled gases’ – stored under pressure as liquids in bottles.
Complete Combustion:
The complete combustion of any hydrocarbon in oxygen releases lots of energy. The
only waste products are carbon dioxide and water vapour.
Hydrocarbons
A hydrocarbon is any compound that is formed from carbon and hydrogen atoms only.
So C10H22 (decane, an alkane) is a hydrocarbon, but CH3COOC3H7 (an ester) is not
because it contains oxygen.
Alkanes are the simplest type of hydrocarbon. They have the general formula CnH2n=2.
The alkanes are a homologous series – a group of organic compounds that react in a similar
way.
Alkanes are saturated compounds – each carbon atom forms four single covalent bonds.
The first four alkanes are methane, ethane, propane and butane.
, Chemistry Paper 2 Topic 7 – Organic Chemistry
As the length of the carbon chain changes, the properties of the hydrocarbon change.
The shorter the carbon chain, the more runny a hydrocarbon is – that is, the less
viscous (gloopy) it is.
Hydrocarbons with shorter carbon chains are also more volatile, i.e. they have lower
boiling points.
The shorter the carbon chain, the more flammable (easier to ignite) the hydrocarbon
is.
The properties of hydrocarbons affect how they are used for fuels.
E.g. short chain hydrocarbons with lower boiling points are used as
‘bottled gases’ – stored under pressure as liquids in bottles.
Complete Combustion:
The complete combustion of any hydrocarbon in oxygen releases lots of energy. The
only waste products are carbon dioxide and water vapour.
