It is well known that when a Mento is dropped into soda, something cool happens. But, what actually happens?
The dissolved CO2 in the soda is constantly looking for a place to accumulate and form a bubble. But, bubbles don’t form spontaneously because the water molecules keep the CO2 molecules trapped in its weak structure (connected by hydrogen bonds).
When a Mento is dropped into the soda, the CO2 molecules gather in small craters on the Mento, which can also be called nucleation sites. When enough CO2 molecules gather in a nucleation site, a bubble forms and is lifted up. Using the balloon, these bubbles can be captured, and the amount of CO2 can be measured.
The following experiment was created to show the effect of the amount of Mentos (hence, more surface area and nucleation sites) on the volume of CO2 released by the soda.