Cracking
Breaking large hydrocarbon molecules into smaller, more useful ones, using heat and a catalyst. It makes alkanes and alkenes.
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Analogy
Cracking is like snapping long spaghetti into short pieces so it fits the pot.
Example
C10H22 -> C8H18 + C2H4alkane -> shorter alkane + alkene
In practice
Refineries crack long, less useful fractions to make more petrol and ethene for plastics.
Practice
Flashcards
- What is cracking?Breaking long hydrocarbons into shorter, more useful ones.
Questions people ask
Why is cracking needed?
Crude oil gives more large molecules than are needed, while demand for small ones like petrol is high. Cracking converts surplus long chains into smaller molecules, balancing supply and demand. It also makes alkenes, which are raw materials for making plastics.
What conditions are used in cracking?
Long hydrocarbon vapours are heated to a high temperature, around 600 to 700 degrees Celsius, and passed over a hot catalyst such as aluminium oxide. Alternatively, steam is mixed with the vapour at a very high temperature. This is called thermal decomposition.