Why do Mentos React with Soda?


It is well known that when a Mento is dropped into soda, something cool happens. But, what actually happens?

The dissolved CO2 in the soda is constantly looking for a place to accumulate and form a bubble. But, bubbles don’t form spontaneously because the water molecules keep the CO2 molecules trapped in its weak structure (connected by hydrogen bonds).

When a Mento is dropped into the soda, the CO2 molecules gather in small craters on the Mento, which can also be called nucleation sites. When enough CO2 molecules gather in a nucleation site, a bubble forms and is lifted up. Using the balloon, these bubbles can be captured, and the amount of CO2 can be measured.

The following experiment was created to show the effect of the amount of Mentos (hence, more surface area and nucleation sites) on the volume of CO2 released by the soda.

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Step 1: Defining the Problem for Investigation

Question: How does the number of Mentos affect the amount/rate of CO2 being released from soda?

The independent variable in this experiment is the number of Mentos put into a soda can.

The dependent variable is the amount of CO2 released from the soda and the rate at which it is released, as measured by the width of the balloon containing the CO2.

Hypothesis: If a certain amount of Mentos are dropped into a container of soda, then the container with the most Mentos dropped into it will produce the most CO2 at the fastest rate. This will happen because the dissolved CO2 will provide the most nucleation sites to come out of the solution.


  • Surrounding temperature
  • Type of soda used
  • Amount of soda used per trial
  • Type of Mento used

Step 2: Materials

This experiment should be conducted somewhere where the ground and wall coincide (this allows the metric tape measure to be taped to the wall), and where the temperature is fairly constant.

  • Safety glasses
  • 1 Beaker
  • 1 12-pack (cans) of soda
  • 2 Sticks of Mint Mentos (37.5 g/ 1.35 oz)
  • 3 Balloons
  • 6 Rubber bands
  • Metric tape measure
  • Duct tape
  • Scissors
  • Glass bottle or reusable plastic bottle with a small top
  • Permanent marker
  • Camera (optional)
sunshiine1 month ago

Nice instructable! Thanks so much for sharing your hard work! Have a super weekend!


astral_mage2 months ago

they alrdy proved in on myth busters on discovery channel......

JMRaphael2 months ago

Very nice experiment! From one scientist to another, a couple of useful notes: first, the precision that you get with your averages is based on the total number of significant figures (which you may or may not have experience with). A good explanation of sig. figs. can be found here: Second, balloons make for a tricky pressure/volume gauge. They're hard to inflate when they're small, but get easier as they get bigger (to a certain point). A more consistent way to measure might be some kind of piston mounted on top of the bottle. A piece of solid acrylic tube with a syringe plunger that is greased (to minimize friction while maintaining a seal) would be one possible example. All in all, very impressive! It's exciting to see someone taking an interest in scientific experimentation at an early age!

nodcah (author)  JMRaphael2 months ago

Thanks for the suggestion for the syringe on top of the bottle! I've definitely used one to measure volume before in school, but I didn't remember it for this experiment. Also, in regard to your second suggestion, should I add .0 to the end of numbers that only have 1 significant digit?

JMRaphael nodcah2 months ago

No problem! You should report all the numbers you accurately can, including zeroes to the right of the decimal. So, if you used a ruler with millimeter markings, you can report your measurements to the half millimeter. However, there's significant debate as to how much precision you can "eyeball." A lot of chemists recommend the 3-5-7 rule, where you would approximate between the smallest markings to either .3, .5, or .7 (or .00 if it's exactly on the mark). In short, you should be able to add a zero to the values you originally reported as a single digit. Have fun science-ing!

nodcah (author)  JMRaphael2 months ago

Thanks! I'll change what I can (w/the data I have now), and I will keep this in mind for future experiments!

bogie02212 months ago
Maybe I'll try it- not
nodcah (author)  bogie02212 months ago

I think the best way to respond to this comment is with a horrible pun. I really hope you didn't MENTO be mean, but some people might think you're SO DArn rude if you keep this up!

nqtronix nodcah2 months ago

Couldn't say it better (That pun actually made me laugh :D)

nqtronix2 months ago

Even though the title is a little misleading ("How does the amount of mentos affect the reaktion with coke?" or something like this would be better) I realy like what you did. You'd definitly get my vote if this becomes an entry to the contest. Right now there's no vote button, you know? ;)

nodcah (author)  nqtronix2 months ago

You should be able to vote now. I didn't want my title to be too long and I've changed it multiple times (as shown by the url). But thanks for the suggestion!


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