Question: i was just wondering rich (by the way im voting for you) when i get a glass of coke and put an ice cube in carefully it fizz around the ice cube ....... Weird why does it do this many thanks tom

Richard Badge answered on 12 Jun 2011:

Hi Tom,

Thanks for the vote of confidence!

As for the coke question… the gas in coke is carbon dioxide (as I am sure you know!) that is added to the drink under pressure during manufacturing. As a result your coke is really a staturated solution of carbon dioxide diluted in water (and some flavouring).

As soon as you open the can / bottle the pressure is relieved and the carbon dioxide comes out of solution and becomes a gas again, forming bubbles that rise to the top.

I think that the increased bubbling around the ice cube probably involves two processes- firstly the coke in contact with the ice cube cools and as a result cannot hold as much dissolved carbon dioxide as the warmer coke not in contact with the ice cube.

The other process is nucleation – the formation of bubbles works better around a surface or point (you get more bubbles forming on the walls of the glass than in the centre). The ice cube surface is not completely smooth and also can contain dust particles that help the nucleation of carbon dioxide bubbles…

I have read that if you make ice with very pure water, or wash the ice in pure water first this makes fewer bubbles. That sounds like an experiment I could do, so my science sense is tingling now… why don’t you have a go too and we could compare results?

Richard