I miss MB already: I've got a chemistry question!

[roisin]

Diet coke and mentoes - what is the chemistry? What is going on?

ahh you put the mentoes into the coke bottle and it reacts and the coke shoots about 15 foot in the air, covering everything in coke - great science type thing - god knows how it works though!

let me google!

same with wimpy milkshake
as we found out accidentally as kids

straw out of coke into milkshake
back into coke
massive explotion
allll over table

not happy parents I can tell you

here you go , cool eh?

this is a good example

But what is the CHEMISTRY?!

PHOSPHORIC Acid in coke reacting with Sodium Bicarbiate to produce carbon dioxide

If you have a liquid that is supersaturated with gas (like coke), bubbles can form on scratches on a surface or specks of dust ? anywhere that you have a high surface area in a very small volume. These are called nucleation sites.

Mentos seem to be loaded with nucleation sites -- i.e. there are so many microscopic nooks and crannies on the surface of a Mento that an incredible number of bubbles will form when you drop it into coke. Since the Mentos are also heavy enough to sink, they react with the coke the way to the bottom and the pressure builds dramatically.

I've just found an explanation here

Which - rather annoyingly - was dh's hypothesis, based on something Stephen Fry said on QI about Champagne.

Actually, I was slightly wrong there -- it's the tiny bubbles of air trapped in the roughness on the outside of a Mento that act as nucleation sites, not the roughness itself.

See here for possibly more discussion on the issue than you could ever wish to read...

lemonaid I did read your post honest but by the time it got to my brain all I heard was blahblahblahblah.

You are CLEVER! me I can just find cool things on google

Fab link LucyCat - amazing!