Background

Catalysts are substances that speed up chemical reactions. However, they do not directly take part in the reaction and are not used up themselves.

Cars contain catalysts in catalytic converters that split toxic substances released by the car’s engine into less harmful ones.

The gas bubbles inside coke are the result of a chemical reaction where carbonic acid decomposes to water and carbon dioxide gas. The bubbles you feel when drinking coke are carbon dioxide. The word equation for this reaction is:

Carbonic acid → Water + Carbon dioxide

Carbonic acid is the reactant. Water and carbon dioxide are the products.

Mentos can act as a catalyst and increase the speed of carbon dioxide production. This causes the foaming you can see when adding Mentos to coke. The scientific word for bubbles, fizzing or foaming is effervescence.

You will need:

• 1 bottle with coke or diet coke (Normal coke and diet coke both work, but diet coke is less sticky and easier to clean up afterwards.)
• 1 pack of Mentos

What to do:

1. Go outside to do this experiment.
2. Put the coke bottle on the floor and remove the lid.
3. Put about 5 pieces of Mentos inside at the same time.
4. Step back and watch.
5. You should see a lot of foaming due to the increased carbon dioxide production.

Questions

1. What is meant by a “catalyst”?
2. What is the catalyst in this reaction?
3. Is the Mentos used up in this reaction or not? Why?
4. What is meant by the “reactant” in a reaction? What is the reactant in this reaction?
5. What is meant by the “product” in a reaction? What are the products in this reaction?
6. Where are catalysts used in our everyday lives?
7. What is meant by “effervescence”?

You can watch this experiment on YouTube: