|MadSci Network: Chemistry|
What a great experiment, Marcus! The wintergreen mint is causing the carbon dioxide bubbles to form faster in the bottle than they would normally and escape from the beverage more quickly, which is how the geiser happens. The term "nucleation" refers to the formation of (in this case) bubbles on a surface, where the mint is the 'site' and the nucleation is done by the CO2. The same term can be used when you are describing crystal growth - you can add nucleation sites (non-reactive surfaces) to a super-saturated solution and trigger a physical change. It sounds like the article didn't explain very well - it is really the mint that acts as a nucleation site for the carbon dioxide. The soda does not 'activate the mint's nucleated sites'. Almost anything you put into the soda will help the gas bubbles to escape faster because it gives the carbon dioxide bubbles more surface area on which to form, so the beverage will fizz more. The rougher the surface (the more surface area) of the object you put in the soda, the faster the bubbles will form and the bigger your geiser. The real question now is: which soda will make the better geiser - a cold one or a warm one? There are some clues in our Mad Science archives about CO2 solubility varying with temperature that might help you guess the answer. ;) Thanks so much for your question and for giving me a great experiment idea! Kieran
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