in this video you will learn about the
process of cracking how it is carried
out and why it is done from our video
distillation you should know that crude
oil is a mixture of hydrocarbons with
different carbon chain lengths smaller
hydrocarbons have a lower boiling point
and a more volatile making them easy to
ignite and more useful as fuels larger
hydrocarbons have a higher boiling point
are harder to ignite therefore not as
useful as fuels we use a lot of fuels in
our day-to-day lives driving cars
aeroplanes lorries and even heating our
homes this means there is a very high
demand for small chain hydrocarbons
however after fractional distillation we
find that we have a large supply of
long-chain molecules the process of
cracking breaks down long-chain alkanes
into a smaller alkane an alkene molecule
this allows the supply of short chain
hydrocarbons to meet the demand for them
as the longer chain alkanes are broken
down into shorter alkanes and an alkene
the alkenes are also useful as these can
be used in the manufacture of plastics
here is an equation showing that c12 h22
into octane and beauty there isn't a set
way that these molecules are broken down
in fact c12 h22 also be broken down into
decade and effets or even Beauty pentane
and propane as these equations show the
large hydrocarbon is broken down in
quite a random way just note that in
each equation of course since we had 12
carbon atoms and 26 hydrogen's going
into the reaction the same must come out
the process of cracking is carried out
in one of two ways either by thermal
cracking using high temperature and
pressure or by catalytic cracking at low
temperatures and pressures but using a
catalyst in thermal cracking
the large hydrocarbons are heated to
temperatures up to 750 degrees C and a
high pressure of 70 atmospheres this
high temperature and pressure breaks the
bonds between carbon atoms to make
smaller molecules catalytic cracking is
the method used mostly in industry today
the large hydrocarbons are heated to
around 500 degrees C and a passed over a
zeolite catalyst the catalyst chosen
tend to break the bonds in the large
hydrocarbons and make molecules of
between 5 to 10 carbons in chain lengths
making them very useful in petrol now at
the end of this video tutorial you
should know that cracking is the process
in which large alkanes are turned into
smaller alkanes and an alkene molecule
and that there are two types of cracking
thermal cracking using high temperature
and pressure and catalytic cracking
which is the method preferred in
industry as it uses lower temperature
and pressure and produces more molecules
that are useful in petrol