Elephant toothpaste. The name is sure to spark your little one’s curiosity. This is a fun, messy experiment that can be done in just a few minutes, and since most of the mess is soap foam, clean-up is easy and safe for your child to help.

Here’s what you need: 1 teaspoon yeast, and two tablespoons warm water. Swish these together in a cup, and set them aside for a minute. Then, set a soda bottle in the middle of a cookie sheet on your table or counter. In your soda bottle, mix ½ cup of 6% or greater hydrogen peroxide (you can get this on Amazon or at a beauty store. The 3% stuff from the grocery store will not work very well), a few drops of food coloring, and a teaspoon of dish soap.

Ready for the good part?

Pour the yeast/water mix into your soda bottle. Whoosh!

If your little scientist is old enough for the chemistry side of things, here’s the science. Hydrogen Peroxide is H2O2, which naturally breaks down into water and oxygen when exposed to light (which is why it’s always sold in opaque bottles). Catalase, an enzyme in yeast, speeds this up (a lot!), and the dish soap catches the released oxygen and makes foam very fast. And because the whole process releases the energy that used to hold the oxygen and water together as heat, the foam and bottle will both feel warm. This means the reaction is exothermic.

Do yourself a favor and get a big bottle of the hydrogen peroxide – this is one your kids will want to do again.