What happens to the molecules during hydrocarbon cracking?

1. Crude oil contains long, bulky alkanes that are of limited use as fuels. 2. Cracking breaks the carbon to carbon bonds in those long chains. 3. The products are shorter alkanes, which burn well, and unsaturated alkenes. 4. Thermal cracking uses high pressure and temperature with no catalyst, catalytic cracking uses milder conditions with a catalyst. 5. Joining short chains into longer ones is polymerisation, which is the opposite process. _Source: Siyavula Physical Sciences Grade 12 (Everything Science, CC BY 4.0), Chapter 4: Organic molecules_