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Try Science at Home
​Cool Chemistry

Mentos and Soda and Candy, Oh My!

6/1/2020

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We all know that Mentos and Diet Coke make a grand and glorious mess when they are mixed together.  But why stop there?  Do other candies make Diet Coke erupt too?  Do Mentos make other soda pop erupt as well?  Let’s find out!

Click and expand the tabs below to get started.
What YOu need
  • Mentos
  • Other small, hard or semi soft candies such as Tic Tacs, M&Ms, Altoids
  • Diet Coke (or the generic equivalent)
  • ​Other diet sodas (of course, you can use regular soda too, but diet sodas are less sticky)

​
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experimental procedure version 1

There are two versions of this experiment - Mentos and Diet Coke vs. Mentos and other diet sodas and Mentos and Diet Coke vs. other candies and Diet Coke.  The reason that there are two versions of this experiment is that scientists usually only change one thing (called a variable) at a time.  So, one version changes the soda that is used, and the other version changes the candy that is used.

Version 1 - Mentos and Diet Coke vs. Mentos and other diet sodas

  1. Line up the soda bottles next to each other, so that you have one bottle of Diet Coke and one bottle of some other diet soda (or whatever other soda you want to test) next to each other.  This way, you can see which one erupts higher.
  2. Drop in the same number of Mentos  (4 is a good amount for a two liter bottle) into the Diet Coke and the other bottle of soda at the same time.  Which one goes higher?
  3. Repeat with any other sodas that you want to test.  Be sure to have a bottle of Diet Coke to test with each other kind of soda, so that you have something to compare it to.  Scientists call this a control, because we know what will happen with the Diet Coke and Mentos, and we are comparing that to what will happen with other sodas.
​
experimental procedure version 2
  1. Line up the soda bottles next to each other, so that you have two bottles of Diet Coke side by side.  
  2. Have four Mentos, and about the same amount of whatever other candy you want to test ready to dump in the soda at the same time.
  3. Compare the height of the eruption produced with each candy.
  4. Repeat with all the types of candy that you want to test.
What's happening
It's all about the bubbles.  Have you ever been pranked by someone who secretly shook a can of soda pop before giving it to you to open?  Why does the can explode in a fountain of sticky foam?  The foam is the liquid from your drink plus lots of bubbles containing carbon dioxide gas added when the soda pop was made, and is what make carbonated drinks so fizzy.  This carbon dioxide gas actually dissolves into the liquid soda pop (just like when you stir sugar or salt into water), and manufacturers are able to dissolve much more carbon dioxide- making it even fizzier- by pushing gas into the can or bottle under very high pressure before sealing it.  This establishes an equilibrium, with the  ratio of the number of carbon dioxide gas molecules at the top of the can to the number of molecules dissolved into the flavored water below remaining constant.  When you open your drink, however (without shaking it first), the gas at the top quickly escapes (that's the "pssst" sound you hear) but this also disturbs the equilibrium.  This sudden drop in pressure forces a lot of the dissolved carbon dioxide to come out of solution and form gas bubbles in the liquid which quickly float to the surface, pushing some liquid with them and forming a layer of foam.  But it takes a lot of energy to initially create a gas bubble inside the liquid, as carbon dioxide molecules must push water molecules- which are strongly attracted to each other- out of the way, so most of the energy available is quickly used up.  This means that the bubbles remain fairly small, there isn't much foam, and you don't make a mess.  

You can't (usually) see what's happening inside a sealed aluminum can, but when you shake it the energy you add creates lots and lots of tiny bubbles (see the related activity below).  Now when you open the can the gas at the top quickly escapes, and just as before, much of the dissolved carbon dioxide comes out of solution as gas molecules.  But this time they don't need to waste their limited energy forming the bubbles, as your shaking has already created lots of tiny "starter" bubbles in the liquid, so all this extra carbon dioxide gas easily moves into these little bubbles, making them grow much bigger, much faster.  Bigger bubbles float to the surface faster, pushing a lot more liquid with them, and you get a foamy explosion!  BTW- if your can of soda is very warm you may not need to shake it to make a mess.  Can you guess why?

Shaking the can or bottle is one way to create a bubbly mess, but there are other ways, and some work MUCH better, as you saw in this experiment!  There are actually several different reactions happening at the same time to create bubbles when you mix Mentos with Diet Coke, and not all scientists agree about all of them, but here are the basic ideas.
  1. Nucleation sites - There are very tiny microscopic pits or dents in candy coating of the Mentos.  In our case the scientific word for such things is nucleation sites.  These are places where the chemicals in the soda can get together with the chemicals in the candy, and a reaction will occur to form a bubble.  The reaction that is occurring in this case is that carbon dioxide gas is being released from the soda very quickly, and so it comes bubbling out the top of the bottle.
  2. Carbon Dioxide gas - This gas is dissolved in soda, and it is what makes soda fizzy.  When the chemicals in the soda and the chemicals in the candy mix together at the nucleation sites, this gas comes out of solution to form bubbles in the soda really quickly, and causes the eruption that we all love to see.
  3. Aspartame - Aspartame is a chemical that tastes sweet, but doesn’t have calories, like sugar does.  It is a reactant in this reaction, which means it helps to make it happen.  If you don’t have aspartame in your soda, you may not have as much of an eruption.  This is another reason that diet soda might work better than regular soda, because regular soda does not usually have aspartame.
  4. Caffeine - Caffeine is a chemical in some soda that gives some people more energy.  It also makes these chemicals react better with each other.  So, if you use a soda that has no caffeine, you may not have as high of an eruption.  However, if you have a soda that has more caffeine, you might get a higher eruption!
  5. Potassium benzoate - This is a preservative, and is supposed to make the soda taste better for a longer period of time.  However, it also helps the chemicals react better with each other, and so sodas that do not have potassium benzoate might not react as well
  6. Gum arabic - Gum Arabic helps to make the Mentos chewy.  It also helps to make this reaction go faster.  You might want to look at the ingredients on other candies to see if you can find gum arabic on their ingredient list.
  7. Gelatin - Gelatin is also a reactant, and also in other candies besides just Mentos.  Check the label!

All of these things together combine to produce the reaction that we know and love when we put Mentos and Diet Coke together.  However, does that mean that the reaction between Mentos and Diet Coke is the best that it can possibly be?  Not necessarily!  What if you find a soda that has more of one of these reactants (like caffeine)?  Experiment with these variables, and see what you can find out!
variations and related activities
Rock salt (like you put on the sidewalk to melt ice) also reacts well with Diet Coke.  Try it.  You may also want to try granular salt (i.e. what's in your kitchen salt shaker).  Does it work as well (it's exactly the same chemically)?  Hint- think about the nucleation sites.

What if the hole that the carbon dioxide and soda came through was smaller?  What would happen to the height of the bubbles?  Remember, however, that pressure is building up in the bottle, and that it has to get out somewhere.

You can't see what happens inside an aluminum can of soda pop when shaken, but you can see through most plastic bottles.  Try shaking a bottle of clear soda pop (like 7-Up, Sprite or Ginger Ale) to see all the tiny bubbles created.  Unscrew the cap quickly and  you will get a foamy mess.  What happens if you wait until all of the bubbles float to the surface and pop before opening the bottle?


The wrinkles in raisins are also very good nucleation sites for carbon dioxide bubbles to form in soda pop.  Try adding 5 or 6 raisins (fresh ones work best) to a bottle or tall glass of a clear soda pop like 7-Up, Sprite or Ginger Ale.  You probably won't get an explosion, but there will be bubbles and you may be surprised what they do to the raisins!  Look for a new experiment page soon that will explain what's happening (or see the links below), but we think you can figure it out if you observe carefully.
​
References and links to more information
https://www.youtube.com/watch?v=zGMxEr2AxHM 
This is the Mythbusters episode that deconstructs what happens when you put Mentos in soda.  Parent note: There are a few shots of Kari Byron wearing a swimsuit that are a bit revealing, but other than that, the science explored here is well done and well tested.


https://www.youtube.com/watch?v=fBkbWKFv2pE
The original Eepybird video using Diet Coke and Mentos, which some people say started the craze.


https://www.eepybird.com/featured-video/coke-and-mentos-featured-video/science-of-coke-mentos 
More explanation from Eepybird.


https://www.acs.org/content/acs/en/education/whatischemistry/adventures-in-chemistry/experiments/mentos-diet-coke.html
Explanation from the American Chemical Society.


https://www.stevespanglerscience.com/lab/experiments/original-mentos-diet-coke-geyser/
Steve Spangler has some ideas about how to take this further, as well.

http://www.appstate.edu/~coffeyts/DietCokeandMentos.pdf
A bona fide scientific study of what is happening and why.

https://www.scientificamerican.com/article/why-does-a-shaken-soda-fi/
https://www.scienceabc.com/pure-sciences/why-a-soft-drink-bottle-fizzes-when-opened.html
https://chemistry.stackexchange.com/questions/40502/why-does-soda-pop-after-shaking
https://www.stevespanglerscience.com/lab/experiments/soda-can-shake-up-experiment/
https://www.livescience.com/34159-tap-soda-can-carbonation.html​
https://www.snopes.com/fact-check/on-tap/
More explanations of what happens when you shake a can of soda.  Some people think there is a trick to keep a shaken can from exploding, but others think it's a myth.  Maybe you should try to confirm or bust the myth!  Does this apply to plastic bottles too?

​https://funlearningforkids.com/dancing-raisins-science-experiment-kids/
https://www.thoughtco.com/the-dancing-raisin-science-experiment-2086765
https://www.stevespanglerscience.com/lab/experiments/dancing-raisins-the-bubble-lifter/​
Adding a few raisins to a glass of soda pop is a lot more fun than you may think!

Subject Tags
​
  • Food Chemistry
  • Kitchen Science​

All Chemistry Subject Tags

All
Acid/Base Chemistry
Bubbles
Crystals
Density
Food Chemistry
Heat/Cold
Kitchen Science
Milk Chemistry
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Polymers
Soap
Water

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