Great question Bronagh,
It actually only works with certain sweets. The classic experiment is with Mentos mints and cocacola though, as its very colourful and powerful!
But any fizzy drink will work really. Basically, the rough surface of the sweets act as a “catalyst” to help release the CO2 gas from the drink rapidly. It doesn’t really get consumed by the reaction, but it helps it along very quickly! Then, the combination of the sugar and the gum in some sweets makes the foam we see piling out of the bottle!
It’s all the very small holes on the surface of the mint with all its tiny holes (creating what are called “nucleation sites” for gas bubbles to form). Just like the way bubbles form and stick to a straw in a fizzy drink. It won’t work with really smooth sweets at all! Try it with Skittles or Smarties!
Hahaha I take it you mean the classic Mentos and Coke explosion!
Well there are a few theories but its likely due to a reaction involving the carbon dioxide in fizzy drinks (what makes them fizzy) and the sugar or other chemicals in sweets. The reason Mentos seem to work so well is because of the little dimples on the surface of them – they increase the surface area allowing more bubble to form, causing a big explosion!
Interesting question Bronagh! Well, we know that fizzy drinks are basically sugar, flavoring, water, preservatives and most importantly, invisible carbon dioxide gas (the thing that makes soda bubbly). This gas is pumped into bottles at the bottling factory using tons of pressure. When you drop sweets in your drink, the dissolving candy breaks the surface tension… this disrupts the water mesh, so that it takes less work to expand and form new bubbles. Each sweet has thousands of tiny pits all over the surface. These tiny pits are called nucleation sites and are perfect places for carbon dioxide bubbles to form. As soon as the sweets hit the soda, bubbles form all over the surface of the candy causing a little explosion. Imagine adding loads of sweets all at once! you could create your own little volcanic eruption 😉 Hope that helps!