I’ve seen this on other homeschooling blogs and on the Steve Spangler website. It’s a fun experiment called, Elephant Toothpaste.
Your child will need:
20-volume hydrogen peroxide, which you can buy from a beauty supply store.
Liquid Dawn dish soap
A dry yeast packet (Mix one-third to half of the contents with warm water in a separate small dish.)
An empty, clean soda bottle, with the label removed.
A disposable tray to contain the mess.
Marcus explains the steps pretty well in this video so I’ll let him take it from here.