Make a Coca-cola geyser
A classic Science project that will entertain and educate kids of all ages - dropping mentos in to a soda bottle to create a powerful eruption several feet high. It's messy, so you will want to do this outdoors or in a bathroom.
What You Need
- Roll of Mentos (any flavour!)
-2-litre bottle of diet Coke or Pepsi (TIP: it will work with regular Coca-cola or Pepsi but the diet variety makes it less sticky to clean up!)
-Index card
-Test tube or sheet of paper
Instructions
First, stack the Mentos. The easiest way is to do this in a test tube (if you have one handy). Or roll a sheet of paper into a tube just wide enough to hold a stack of Mentos.
Hold an index card over the opening of the test tube or end of the paper tube to hold the sweets in place.
Open your bottle of Coke. Be warned that the eruption happens very quickly so set things up first. You want the open bottle-index card-roll of Mentos lined up so that as soon as you remove the index card, the Mentos will drop smoothly into the bottle.
When you're ready, drop in the sweets and watch the soda jet stream!
The Coke and Mentos geyser is the result of a physical process rather than a chemical reaction. Because there’s carbon dioxide in the soda giving it its fizz, when you drop Mentos in, tiny bumps on the sweets’ surface give the carbon dioxide molecules a nucleation site or place to stick. As more and more carbon dioxide molecules accumulate, bubbles form. Because Mentos sink, they interact with the carbon dioxide all the way to the bottom of the container creating millions of bubbles. Because there’s no where else for these bubbles to go, the pressure builds up and erupts through the top of the bottle. Don’t tell us we didn’t warn you, it all happens VERY quickly so step back!