cracking

Long chain hydrocarbons do not make good fuels as they are very flammable. So there is high demand for short chained hydrocarbons to be used. To solve that problem long chain hydrocarbons need to converted to short chained hydrocarbons.

To do that use a process called cracking

Cracking

a long chain alkane is broken down ( cracked) to produce smaller more useful molecules.

This makes a shorter chained alkane. Shorter chained alkanes are used for fuels.

In the reaction a different type of molecule is made which is a alkene.

Conditions for cracking

1) catalytic cracking—> High temperature and a catalyst to speed up the reaction.

2) steam cracking —→ high temperature and steam.

Alkenes and cracking equations

alkenes have a double covalent bond between two carbon atoms.

Alkenes are useful because they are used to make chemicals called polymers.

Alkenes are also used as a starting material for other useful chemicals.

Alkenes are more reactive than alkanes.

The test for alkenes—> using bromine water which is orange if we shake the alkene with bromine water then the bromine water turns colourless.

Balance the equation for cracking

C25H52 ——> C20H42 + C5H10

C40H82 —→ C33H68 + C7H14

Just work out the difference between the numbers.