Cracking

Cracking definition

Breaking long‑chain hydrocarbons into shorter, more useful molecules

Reason cracking is needed

High demand for short chains like petrol; low demand for long chains

Products of cracking

Shorter alkanes + alkenes

Type of reaction

Thermal decomposition

Thermal cracking conditions

High temperature and high pressure

Catalytic cracking conditions

Zeolite catalyst, lower temperature, lower pressure

Catalytic cracking advantage

Cheaper and more efficient due to lower energy use

Alkene formation importance

Alkenes used to make polymers (plastics)

Example cracking reaction

Decane → octane + ethene

Test for alkenes

Bromine water decolourises

Why alkenes are useful

Feedstock for addition polymerisation

Why cracking is important

Matches supply of hydrocarbons to market demand

Type of bond broken

C–C bonds in long hydrocarbons

Key idea

Cracking converts large, low‑value hydrocarbons into smaller, high‑value fuels and alkenes