Catalysts — Chemistry, 11–13 years
How a substance can make a reaction faster without being used up. Chemistry, 11–13 years.
What a catalyst does
A catalyst gives reacting particles an easier route to follow, so a reaction can happen faster or at a lower temperature. It is still there afterwards, ready to help again; it is not one of the substances that gets used up.
Why catalysts are needed
Many useful reactions are too slow at ordinary temperatures, while heating them can waste fuel or damage materials. Catalysts solve this problem by lowering the energy barrier, so more particles can react successfully without supplying as much heat.
A yeast catalyst
Hydrogen peroxide slowly breaks down into water and oxygen. Add a little yeast: bubbles appear much faster because an enzyme in the yeast catalyses the change. The yeast is not the source of the bubbles and is still present afterwards, even though the peroxide is being used up.
The common mix-up
It is easy to think a catalyst is simply a fuel or an extra reactant, because the reaction becomes more energetic or produces bubbles after it is added. The key question is what remains afterwards: a catalyst helps the route, but it is not used up and does not become the main product.
Catalysts outside school
A car’s catalytic converter contains special materials that help change harmful exhaust gases into less harmful ones while the engine runs. Catalysts are also used to make medicines, fertilisers and many everyday chemicals more efficiently, with less heat and waste.
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