Cracking is like chopping up long logs to make useful firewood. Crude oil gives you massive tree trunks (long alkanes like C₂₀H₄₂) that are hard to use. Cracking is your chemical axe that chops these into perfect-sized logs (petrol chains like C₈H₁₈) plus kindling (alkenes like C₂H₄) that's perfect for starting fires (making polymers).
Cracking solves the supply and demand mismatch in the oil industry. Natural crude oil contains too much of the heavy, long-chain hydrocarbons (like diesel and fuel oil) but not enough of the light, short-chain ones (like petrol and gas). Modern life demands more petrol for cars and ethene for plastic production than crude oil naturally provides.
The process breaks long alkanes into useful shorter ones. Cracking breaks C-C bonds in long hydrocarbon chains, producing a mixture of shorter alkanes and alkenes. The alkenes produced are incredibly valuable as the starting materials for making polymers.
This introduction covers The Oil Refinery Dilemma within Cracking (HT) for GCSE Chemistry. Revise Cracking (HT) in Organic Chemistry for GCSE Chemistry with 24 exam-style questions and 15 flashcards. This topic appears less often, but it can still be a useful differentiator on mixed-topic papers. It is section 1 of 14 in this topic. Use this introduction to connect the idea to the wider topic before moving on to questions and flashcards.
Practice questions for Cracking (HT)
What is cracking in chemistry?
Describe the conditions used in thermal cracking and state the types of product formed.