Animator Flash Point #7: Diet Coke and Mentos

October 25, 2017
Flash Points

Happy Chemistry Week! 

Today's Flash Point is on one of my favorite fun activities...the Diet Coke and Mentos Experiment!

 

I love this demonstration! We used it every year when my AP chemistry students taught 2nd graders in our annual Chemistry Day event. The high school students helped the youngsters understand mixtures and density. It was always one of the favorite activities for the students, both big and small.

The world’s Diet Coke and Mentos expert is without a doubt Tom Kuntzleman of Michigan. I read his post about his research with the demonstration on ChemEdX blog. He also published articles on the subject in the Journal of Chemical Education. Andy Brunning of Compound Interest designed a cool infographic on Tom’s work. Andy and I were both in the Tom’s workshop at ChemEd 2017 in South Dakota this summer.

I decided to use Animator to build an animation of Tom’s research. The video below is what I produced. (You can also access the Animator file by joining the group on our platform (group code: diet_coke_mentos)

 

I sent this video to Tom and Andy for review. Here is Tom’s reply:

“Wow, I just downloaded the Animator app and it’s a lot of fun! I used it to make my own animation of the process. I hate to be nitpicky on your animation, but I do have some suggestions, based on the way I envision the process. I’m not claiming what I propose below is 100% correct, but for now it’s the way I think about what’s going on:

  1. When dropped into water, the pits and pockets on Mentos candies (the nucleation sites) are not very wettable. Thus, when Mentos candies are dropped into a beverage, these sites essentially become tiny bubbles.
  2. These tiny bubbles – which are adhered to the Mentos candy – provide sites of air bubbles into which CO2 gas easily diffuses. Thus, these bubbles increase in size, which increases their buoyancy.
  3. At some point, the bubbles become buoyant enough to rise off the candy and through the liquid.

    Here is where things get different depending upon whether solutes are present or not.

  4. In the absence of solute, the rising bubbles coalesce into much larger bubbles. This resultant loss in surface area contact between bubbles and surrounding fluid slows further diffusion of dissolved CO2 into the rising bubbles.
  5.  In the presence of solute, the rising bubbles are inhibited from coalescence. Thus, the further diffusion of dissolved CO2 into the rising bubbles is not attenuated by loss in surface area contact.

I realize what I have described above may be too complicated to describe and/or animate. (I also realize that what I have written above may not be entirely clear!)

I’m happy to entertain any further comments or questions – or ideas on how to further probe my proposal above!! 

Thank you for considering all this and the interest in this experiment!”

 

I loved this!!  I had become the student, doing my best to understand the movement of chemicals that my instructor was trying to explain.  That is the whole goal of our product. It’s really a communication tool. Helping to transfer the moving models of chemistry from one person to another.

 

It would be great to see your vision of the Diet Coke and Mentos experiment in our Animator group! Feel free to add this or other favorite demonstrations to the group (group code: diet_coke_mentos).

 

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