The science experiments my children talk about for months afterwards are generally the messy ones, like our splatter patterns, glow in the dark oobleck, baking soda experiments and the well known coca cola and mento trick.
If you try this I’d definitely do it outside, it’s VERY messy and sticky.
We dropped two Mentos into a bottle of normal Cola and Diet Cola. I used the cheapest brands available in our local supermarket.
Once you drop the Mentos in, stand back, it’s VERY explosive.
Why does this happen?
There are several theories, but it’s thought that the many small pores on the candy’s surface speed up the release of carbon dioxide (CO2) gas from the soda as they give a larger surface area for the reaction to occur over, causing foam to erupt at a super fast rate.
Any fizzy drink beverage will produce a similar effect, but diet drinks seem to work best, as we found in our investigation. This is most likely due to the particular chemicals in diet drinks.
See Steve Spangler for a much more thorough explanation of the Coke and Mento Eruption.
Could you test fruit flavoured Mentos instead of mint flavoured?
What would happen if you left the top off the Cola for a few minutes before adding the Mento?
Does any flavoured fizzy drink work?
Could you use the reaction to power something? Maybe a LEGO car?