Cracking means splitting
up long-chain
hydrocarbons by passing
vapour over a hot catalyst.
~Firstly you heat the
long-chain hydrocarbons to
vaporise it. ~Then the vapour is
passed over a powdered
catalyst at a temperature of
about 400-700 degrees
Celsius. ~Aluminium Oxide is
the catalyst used. ~ The
long-chain molecules split apart
on the surface of the specks of
catalyst.
Long-chain
hydrocarbons form
thick gloopy liquids
which aren't useful, so
a lot of the longer
molecules produced
from fractional
distillation are turned
into smaller ones by
the process of
cracking.
Some of the products of cracking
are useful as fuels: such as petrol
and paraffin. Cracking produces
substances like ethane too, which
are needed for making plastics.
Cracking is a thermal
decomposition reaction -
breaking down
molecules by heating
them.
Most of the products of cracking are
alkanes and unsaturated hydrocarbons
called alkenes.