Learn how to make dirty coins shine with this easy chemistry experiment for kids! Using vinegar and salt, discover the science of oxidation in just a few minutes.
Have you ever wondered why old coins lose their shine?
With just vinegar, salt and a few grubby coins, your child can become a mini chemist and discover the science behind oxidation in just a few minutes.
This quick experiment is perfect for curious children and uses everyday kitchen ingredients to reveal an amazing chemical reaction.
Watch the experiment
Watch our short video below to see the gleaming coins experiment in action.
You’ll need
- A glass jar
- 200ml white vinegar
- 1 teaspoon of salt
- Some grubby 1p or 2p coins
- Paper towels
- Running water
What happens?
When copper coins are exposed to air over time, they react with oxygen to form a dull layer called copper oxide.
Mixing vinegar (a weak acid) with salt creates a solution that dissolves this oxide layer, revealing the shiny copper underneath.
It’s a brilliant way to introduce children to the idea that chemistry is happening all around us—even on the loose change in your pocket!
The science behind it
Copper naturally reacts with oxygen in the air.
This reaction forms a coating called copper oxide, which makes the coin look brown and dull.
The acetic acid in vinegar helps loosen this layer, while the salt speeds up the reaction. Once the oxide has dissolved away, the shiny copper beneath is revealed.
Although it looks like magic, it’s actually chemistry!
Questions to ask your young scientist
Can you predict which coin will become the shiniest?
Why do you think older coins look dirtier than newer ones?
What happens if you leave the cleaned coin out in the air again?
Can you think of any other metal objects that change colour over time?
Safety
This experiment should be carried out with adult supervision.
Wash hands after handling coins and avoid drinking the vinegar solution.
Keep the science going!
If your child loved this experiment, they’ll love Whizz Pop Bang magazine.
Every month is packed with exciting experiments, fascinating facts, puzzles and hands-on STEM activities designed for children aged 6–12.