Coke-Mentos + Balloon Experiment

A staple science experiment is the famous Diet Coke + Mentos reaction. Every child loves the impressive geyser created from combining these two ingredients. If you are not familiar with this classic, I highly recommend you try it out or at least watch this video: MythBusters

One problem with conducting this experiment in a classroom is the obvious messy factor. Another issue is having students actively participate instead of just watching an awesome explosion (still highly recommended). My twist on this experiment involves a smaller version of the reaction that is contained inside a balloon! Read on to learn more. 

Blow up a balloon using Diet Coke +  Mentos Reaction

Students will design their own experiment to determine the effect of one variable in blowing up the balloon. 

That's me demonstrating the Balloon + Coke+Mentos experiment!

Materials per team of 2 students

  • 2 0.5 Liter of Diet Coke
  • 3 Mentos
  • 2 Balloons 
  • Measuring cup (optional)
  • Paper towels
  • String
  • Ruler

Demonstrate procedure to the students: 

  1. Stretch out balloon. 
  2. Open up the Diet Coke and pour out half of the contents. 
  3. Place one Mentos inside the balloon. 
  4. Place balloon securely over the mouth of the bottle.  Very important! 
  5. Hold the balloon upright and force the Mentos down into the liquid. The reaction will start and the balloon will expand! 
  6. Keep the balloon upright. Shake it side to side so all the liquid falls back into the bottle. 
  7. Holding the neck of the balloon, pull it off from the bottle without releasing the gas. 
  8. Tie off the balloon. 

How does it work? 

The basic explanation is that the carbon dioxide gas inside the Diet Coke is being released. Initially water molecules are trapping the carbon dioxide. When the Mentos is dropped in and falls to the bottom it disrupts this water mesh. All the gas is released and literally pushes all the liquid up and out of the bottle. What remains in the balloon is release carbon dioxide gas. 

As a class, discuss what variables may effect the size of the balloon. The most influential include: number of Mentos released and amount of coke in the bottle. Now students can create an experiment to determine the effect of their variable. For example, how does the amount of Diet Coke change the balloon diameter? 

  1. Conduct the experiment with only 1/4 of the liquid in the bottle. Keep all other variables the same. Tie off the balloon.
  2. Repeat the experiment with 3/4 of the liquid. Tie off the balloon. 
  3. Which balloon is bigger? Use a piece of string to measure the diameter of each balloon to compare. 

Have fun!