Helpers that speed up reactions — Chemistry, 7–10 years
Some substances make a chemical reaction faster without being used up themselves. Enzymes in living things are natural examples, and this idea helps explain digestion and some cleaning products.
A reaction helper
A catalyst is a substance that helps a chemical reaction happen faster, but it is still there afterwards. It gives the reacting particles an easier route to change. Only a small amount may be needed to help a much larger amount of material.
Why use a catalyst?
Some useful reactions would be too slow at ordinary temperatures. A catalyst lets them happen quickly without needing as much heat, which can save energy and reduce damage to other materials. Scientists look for safe catalysts when they want a process to be quicker.
An enzyme in digestion
Bread contains starch, a large substance that the body cannot use easily. In your mouth, an enzyme in saliva starts breaking some starch into smaller sugars. The enzyme is not the sugar and is not used up like food; it helps the change happen quickly at body temperature.
Not an ingredient
It is reasonable to think a substance must be used up if it helps make a new substance. A catalyst is different: it helps the reaction but is not one of the final products. A reaction can still need reactants; the catalyst only changes how easily they react.
In cars and living things
A car's catalytic converter contains special materials that help change some harmful gases in exhaust into less harmful gases. Your body uses enzymes as catalysts in digestion and many other reactions. In both cases, the helper makes a slow change practical without being the fuel or food itself.
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