The Science of Diet Coke Mentos

Discussion in 'General Science & Technology' started by lixluke, Aug 25, 2006.

  1. lixluke Refined Reinvention Valued Senior Member

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    9,072
    Why is it that Diet Coke explodes when you put Mentos in it?
    What about Diet Pepsi or even regular Coke?
    Is it possible to blow up other soda's?
     
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  3. Fraggle Rocker Staff Member

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    24,690
    Here are two threads about that. Neither of them is well focused and they both allude to multiple possible causes for the same phenomenon. The basic principle is that carbonated water is simply carbon dioxide dissolved in water. Water is the universal solvent and dissolves any gas, including oxygen, which is why there is animal life in rivers and oceans, and carbon dioxide, which is why there is plant life in rivers and oceans. The H2O molecules combine with the CO2 molecules to form H2CO3, which is carbonic acid, a weak acid. The acid ionizes, leaving negatively charged hydrogen ions and positively charged carbonate ions floating around.

    The brewing process pumps a lot more CO2 into the liquid than it will normally hold at STP (standard temperature and pressure), which is why if you let it warm up and release the pressure by taking the cap off, it will soon go "flat," meaning that the CO2 evaporates back into the air.

    Certain materials simply catalyze (facilitate and accelerate) this natural process. There are various mechanisms for this. One is to change the pH (acidity) of the liquid. The new acid competes with the H2CO3, which then separates back into water and CO2, which is a much more volatile compound than H2CO3. Another is to change the surface tension of the liquid, creating a more permeable membrane that allows faster evaporation. If this happens quickly enough you'll get the same kind of "explosion" that you get by simply shaking a bottle of pop and uncapping it quickly.

    Other more complicated chemical reactions are suggested in these links and if you google it you'll probably find even more.

    As for the materials, it seems that the artificial sweetener itself is not germane to the process but the lack of sugar is since sugar changes the chemistry. One source says you should be able to use salt instead of Mentos. Another says that Australian Mentos don't work with Diet Coke.

    This is the sort of thing that doesn't get a lot of attention from the scientific community, so you'll have to be patient while popularizers like Mythbusters and perhaps Beakman work on it.

    http://www.stevespanglerscience.com/experiment/00000109

    http://digg.com/general_sciences/Mythbusters_explain_why_Diet_Coke_and_Mentos_explode
     
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  5. spidergoat pubic diorama Valued Senior Member

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    54,036
    Sugarless wintergreen lifesavers make sparks when you chew them.

    I went spelunking one time, and everyone did this in complete darkness, it lit up the whole chamber.
     
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  7. domesticated om Stickler for details Valued Senior Member

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    The mythbusters episode aired two or three weeks ago if I remember correctly.
     
  8. pasquala Living on a Prayer Registered Senior Member

    Messages:
    148
    I tried the wintergreen life savers thing one time and it worked
    Me and my kids got into a dark closet and started beating the life savers together and it really did spark. Only thing is that it was the tinyest little spark you ever did see. If you blinked, you missed it. Nevertheless, the kids had fun.
     
  9. HonorAndStrength I know nothing Registered Senior Member

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    155
    yeah
     
  10. Absane Rocket Surgeon Valued Senior Member

    Messages:
    8,989
    Grab a 20 oz. mountain dew bottle (I find these work better than others).

    Fill the bottom 1/4 with dry ice.

    Put enough water in the bottle to cover the 1/4 of dry ice.

    Put the cap back on

    Throw very quickly.

    Boom.
     

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