Elephant Toothpaste

Elephant toothpaste erupts a foam that children can create in this experiment that resembles toothpaste being squeezed from a tube.

Materials Required

Take 1 teaspoon of yeast and dissolve it in 2 teaspoons of very warm water. You need to mix them well so that there are no yeast lumps in the mixture.
Now place the bottle on the work table. Add ½ cup of hydrogen peroxide to the bottle.
You could also add the liquid watercolour now.
Now place the funnel into the bottle and add the yeast mixture into the bottle through it.
Quickly remove the funnel and see your elephant toothpaste erupting.

6% hydrogen peroxide will work best for this experiment. Lesser than this would not give the desired result. Of course, you can try more than 6%. But be prepared for the tremendous eruption.
While using the dish soap, make sure they are not antibacterial ones as they are not apt for this activity.
Make sure you place the bottle in a large tray or container to collect all the foam.
As soon as you start adding yeast, the reaction starts in the bottle with bubbles starting to come up. So, you need to be very quick while doing this step.
Keep the kids at a distance while you do this experiment.
You can even make the kids wear safety goggles if they involve themselves in adding of the ingredients. But still, they need to be under your constant supervision and stay a few feet away.
Kids could help you out by dissolving the yeast in water. This is a nice fine motor activity for tiny hands.
The foam which comes out is a perfect sensory play for the kids. They are absolutely safe to touch. They are soft and fluffy too. Let your kids enjoy themselves and have a fun time.

Reference
Funathomewithkids.com