Question: why is it that when mentos go into cola it makes an explosion/??

Senga Robertson answered on 13 Nov 2017:

Hi Ellzy

I love this question, especially because scientists have actually argued a little bit about how it works. Some used to think it was a chemical reaction but now most agree it’s because of something called nucleation. Cola (especially diet cola) has a lot of carbon dioxide squeezed in to it to make it fizzy, this carbon dioxide is always looking for a way out of the liquid so it’s drawn to tiny bumps in the bottle that it can grab on to, these are called nucleation sites. (You’ll see when you pour cola into a glass if there are little scratches on the inside of the glass that bubbles will cling to them). Now, the surface of mentos is sprayed with lots and lots of layers of liquid sugar, not only does this make mentos tasty it also means it is covered in lots and lots of nucleation sites. So it’s covered in microscopic nooks and crannies…when you drop it into the cola bottle the carbon dioxide bubbles rush towards these nooks and crannies on the surface of the mentos, since the mentos are heavy enough to sink to the bottom of the cola bottle it means the sweet is in contact with loads of carbon dioxide bubbles very quickly…the escaping bubbles build pressure really fast and create a big bubbly foam that has to escape……..and we all know how it escapes!

Have you ever tried this experiment? I did once but added 3 mentos at once! I’m glad I did it outside!

Senga 🙂