Cracking and alkenes

What is cracking?

The thermal decomposition of longer alkanes into shorter alkanes and alkenes.

What is the process of catalytic cracking?

Heats the alkanes to vaporise them and then pass them over a hot catalyst.

What is the process of steam cracking?

Heat the alkanes to vaporise them, mix them with steam and then heat them to a very high temperature.

What type of reaction is cracking?

Thermal decomposition reaction.

What is the word equation for cracking?

Long chain alkane → shorter alkane + alkene

What is an alkene?

A homologous series of unsaturated hydrocarbons.

What is the general formula of alkenes?

Cn H2n

What is a functional group?

An atom or group of atoms responsible for most of the chemical reactions of a compound.

What is the functional group in alkenes?

C=C double bond

What is an addition reaction?

A reaction in which atoms bond to the atoms in a C=C double bond to form a saturated molecule.

Why are alkenes much more reactive than alkanes?

They contain a C=C double bond.

What is the test for alkenes?

Bromine water, It has an orange colour due to dissolved bromine molecules. When the bromine water reacts with the C=C double bond, the bromine molecules are used up and so the reaction mixture goes colourless.