Cracking involves breaking down long chain alkanes to shorter chain alkanes and alkenes. This reaction is important for obtaining many short chained unsaturated molecules.

Cracking is either done using a catalyst (zeolite) or steam, it can be done in a lab using the apparatus shown.

In a cracking equation the reactant will always be a long alkane and the products will be a shorter chain alkane and alkene. When writing equations remember there must be the same number of carbon and hydrogen atoms on both sides.

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C₁₅H₃₂ → C₁₂H₂₆ + C₃H₆

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It is done at a lower temperature, thus uses less energy and is therefore cheaper and more environmentally friendly.

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x = 20 and y = 5

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Steam method requires higher temperatures. The presence of a catalyst lowers the activation energy of the reaction and reduces the temperature needed.

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x = 12, y = 16