Coke + Mentos=explosion : anyone tried it?

Question

i saw this on the Today show a few weeks ago and tried it but it didnt produce the geyser effect that it did on TV, the coke only poured out the top a little, how can i get it to work like on TV?

Answer 1

I think that it is related to nucleation rates. Carbon dioixde is dissolved in the coke at a high pressure and it wants to come out, but the rate that it escapes is kinetically controlled.

If you pour coke out into a smooth, transparent glass, you can see that a few bubbles form on the sides, grow, and fly up to the surface. The bubbles keep forming in the same spots, called nucleation sites. These nucleation sites are generally tiny imperfections that trap a small amount of gas, allowing for a more stable transtion from dissolved CO2 in liquid to CO2 gas.

If you pour coke out into a rough, transparent glass, you will see a lot more bubbles, because there are more nucleation sites.

If you pour coke in a glass and start adding granular sugar to it you may be suprised to see it froth up and spill all over the place. These grains of sugar bring entrain a small amount of air when they fall into the coke and have lots of surface area and roughness so the CO2 can enter the gas phase much more quickly. I imagine mentos work the same way (they have a rough surface and when you shove them in they entrain air the same way).

I think if you are having trouble with mentos, granular sugar might work better. It has a lot more surface area. A long time ago, my parents bought some flavored carbonated water that I thought tasted terrible, so I added some sugar to it to improve drinkability. It sprayed all over the place and made a mess. (I think it was like a bubbling geyser about 3" high from the can/glass. And now that I completed my undergraduate education in chemical engineering...I know why :)

Good luck and have fun!

Answer 2

I did it at work and have a video on cd. Yes it's very explosive if you get the mentos all in at once. I have some ideas on how to make it better. If you drill a small hole in the cap and thread 4 mentos onto the string, you can replace the cap and tie a knot so that they can all be released at once. Otherwise you need to release them from a rolled up piece of paper with a card under it.

Answer 3

you dont. now stop trying. if you really want "explosion", try throw some K or even Rb into H20. be wary. really! or mixing S, P, and someother junks. i think it is the precursor to a bomb, 3000 years ago.

Answer 4

just do it like they did it. use a bottle and drop in granular sugar or hard candy like mentos and it'll work.