What Makes a Reaction Speed Up?
- Chemistry
- Ages 8–11 · Grades 3–5
- Hands-on experiment
What you’ll find out
- Reactions happen at very different speeds.
- A catalyst makes a reaction go faster.
- A catalyst is not used up by the reaction.
No sign-up and no real names. In the lesson you check your understanding as you read, run the experiment yourself, and practise until it sticks.
Reactions go at different speeds
Not all reactions happen at the same speed. A reaction is when substances change into something new. A firework finishes in less than a second. The rust that forms on a bike chain takes months to appear. Both of these are real chemical reactions, but one is millions of times faster than the other. Working out why is a big part of chemistry.
A catalyst speeds things up
You can make a reaction go faster on purpose by adding a catalyst. Hydrogen peroxide is a clear liquid that slowly breaks down into water and oxygen gas. It happens so slowly that you cannot see anything change. If you add yeast, the same break-down happens in seconds and foam pours out of the flask. The yeast is the catalyst. It did not change what was made — only how fast it was made.
The catalyst is not used up
Here is the surprising part. A catalyst does not get used up. When the foam settles, the yeast is still sitting in the flask, unchanged. It helped the reaction happen and then it was ready to do it again. This is why a small amount of catalyst can keep working for a long time without being replaced.
Curriculum links: NGSS 5-PS1-4 · NGSS MS-PS1-2