[edwinksl]

Try adding mentos to coke and see what happens!

Can anyone offer an explanation for what you see? I think it is a reaction between the carbonic acid in the coke and the carbonates in the mentos, resulting in the production of lots of CO2. 

[Kenichi]

It's a physical reaction. 

http://antoine.frostburg.edu/chem/senese/101/consumer/faq/mentos.shtml

[Kenichi]

http://www.chemicalforums.com/index.php?topic=6931.0

[Borek]

http://www.chemicalforums.com/index.php?topic=8401.0

[pantone159]

I just tried this, with two different trials.  I used one roll of Mentos per trial, which is about 15 mints or so (I forgot to count them), 37.5 g total.  A 25x150 mm test tube was the perfect size to hold them.  I held the test tube of mints upside down, with a plastic phone card held underneath to hold the mints in, and placed this over a 2 L bottle of soda.  Then I pulled the card away, and let the mints drop in.

Trial #1 - 'Mint' Mentos, and regular (sucrose) Sierra Mist.
Trial #2 - 'Mixed Fruit' Mentos, and Diet Coke.

Trial #1 was dissapointing.  The soda only sprayed up a meter or so, although over half of the bottle emptied.  The audience was underwhelmed.   
Trial #2 was much better, despite worse technique, as two of the mints missed the bottle.  This time the soda shot up approx 3-4 meters.  This time, everybody thought it was cool.   

The 'Mixed Fruit' mentos do list citric acid as an ingredient that the mint ones don't.

[Borek]

Trial #1 was dissapointing.  The soda only sprayed up a meter or so, although over half of the bottle emptied.  The audience was underwhelmed.   

Most likely soda has too high surface tension which makes bubbles too short living for good effects.

[constant thinker]

Last friday (June 16th), it was the last normal day of school before finals. During the second to last period lunch a kid took a 2 liter bottle of diet coke and put a bunch of Mentos in it. It shot up to the ceiling (like 8' give or take a foot). Then a huge food/water fight broke out and a vice principal walked in. Then I guess as she walked the bell rang and kids just took off running to get out of the cafeteria.

The kid did it with, I believe, 6 or 7 Mentos in a fresh 2 liter bottle of Diet Coke. Everyone in the lunch room at the time completely trashed it.

[hmx9123]

I was at an explosives conference this past week.  At it, all the scientsts gathered around with about 15 packs of mentos and 2L bottles of Diet Coke.  Of course, everyone wanted to experiment with things, but I heard from one of the guys there that it was speculated that in addition to the high surface area that the gum arabic in Mentos helped to evolve gasses.  I haven't checked the ingredient list or anything, so I don't know if there's any truth to that or not, but it sounded intriguing.  Of course, since it was a bunch of explosives people, they devised a way to close the cap on the 2L bottle before dumping the Mentos in, and, well, I'll leave the rest to your imagination.

[billnotgatez]

Surface tension change seems to be the accepted idea

http://www.museumofhoaxes.com/hoax/weblog/comments/3600/

[hmx9123]

Interesting.  I have a bunch of gum arabic at home; I'll have to bring some back here the next time I go home and try using it in the diet coke to see if it has the same effect.

[constant thinker]

I saw an episode of Mythbusters on the Discovery Channel, and the main myth was what causes the mentos + diet coke reaction.

They discovered that aspartame, sodium or calcium (I forget which one is in Diet Coke) benzoate, and caffeine enhance the bubbling. Also the rough surface of the mentos causes nucleation.

Sooo I just thought I'd post what I saw. They also blew up a bunch of other stuff.

They also hit over 34 feet with their spray.

[Dude]

How does the reaction of Mentos with beer compare to that of soda?

[Kenichi]

I can't imagine it would be as impressive as it is with soda.  Less carbonation, and I can't think of a beer container that would have a small opening like that of a soda bottle to shoot the foam.  Cans are too small to drop mentos into, and so are bottles I believe.  I don't believe I will try this, no reason to waste a good beer, making it flat and all.

[constant thinker]

They never tested beer mentos in beer on Mythbusters, but I have to agree with Kenichi.