In this teacher demo, Mentos mints are used to unleash the dissolved carbon dioxide in a 2 L bottle of carbonated pop, producing a 2-3 m fountain.
Materials
- Plastic Apron
- Eye protection
- Package of Mentos mints
- 2 L bottle of diet carbonated pop
- Large test tube (the same diameter as the pop bottle)
- Business card
Procedure
Note: Do this activity outside on the lawn to avoid having to clean up the mess.
- Put on eye protection and a plastic apr
- Place the pop bottle on a flat stable surface like a pic- nic tabl
- Add the Mentos to the test tube so that the mints are stacked one on top of the other.
- Cover the test tube with car
- Open the
- Invert the test tube and card and place it on the mouth of the bottle so that the test tube and the mouth of the bottle are perfectly aligned. Hold the test tube securely in one hand.
- With your other hand, quickly remove the card and get out of the way as the Mentos fall into the bottle. Don’t drop the test tube!
What happens?
A 2-3 m fountain of pop is observed. Only about 10-20 % of the original volume of pop remains in the bottle at the end of the demonstration.
How does it work?
The gelatine and guar gum released as Mentos dissolve disrupt the surface tension of the water within the pop bottle. Further, the surface of each Mentos is covered with tiny pits. Each pit becomes a nucleation site for bubbles of carbon dioxide to form. A similar effect is sometimes observed when pasta is added to boiling water.
Presumably, materials released from the pasta disrupt the surface tension of the water enough to cause a rapid expulsion of dissolved gases, causing the pot to boil over.
Teaching Suggestions
This activity is useful when discussing surface tension or gas solubility in SCH3U or SCH4C. It could also be used as an example of a physical change in grades 8 and 9.
Diet pop is recommended because pop with sugar leaves a sticky residue which can be difficult to clean up.