1Speeding up a reaction
Hydrogen peroxide slowly breaks down into water and oxygen. Add a catalyst such as manganese dioxide and it fizzes quickly.
catalyst
Lesson 11.5 notes
Catalysts
Speeding up reactions without being used up: in the lab, in cars and in your body.
2Same amount, faster
More catalyst makes the gas come off faster, but the total volume at the end is the same.
rate of reaction
3Not used up
Filter out the catalyst, dry it and weigh it: its mass hasn't changed. It can be used again and again.
not used up
4Testing for oxygen
Oxygen relights a glowing splint. This shows that the gas from hydrogen peroxide is oxygen.
glowing splint
5An easier route
Particles need enough energy to react. A catalyst gives a route with a lower energy hill, so more particles react each second.
energy
6Catalytic converters
Platinum in a car's catalytic converter turns poisonous carbon monoxide and nitrogen oxides into carbon dioxide and nitrogen.
catalytic converter
7Enzymes
Enzymes are biological catalysts. Amylase in saliva speeds up breaking starch down into sugar.
enzyme
Explore: Catalyst race
Choose a catalyst, run the reaction and compare the lines on the graph.
Common mistake: A catalyst does not make more product
It makes the same amount of product, just faster. The final volume of gas is the same with more or less catalyst, and the catalyst is left unchanged at the end.
Remember
- A catalyst speeds up a reaction and is not used up. It doesn't change how much product is made.
- It gives the reaction an easier route that needs less energy.
- Examples: manganese dioxide, platinum in catalytic converters, and enzymes (biological catalysts).