This is a fun experiment that the kids can easily replicate at home. You can also call it a magic trick if you like. It is very simple, but a necessary lesson to move onto other experiments that include water.
Fill up the bowl with water.
Stuff the paper towel into the top of the cup and get ready to dunk it in the bowl.
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Dunk the cup straight down into the bowl so that it is completely submerged. Tell the kids to look at the paper towel and see if it looks wet.
Take the cup out of the water and remove the towel and have the kids check to see if it's wet or not.
Explain to the kids that the water does not enter the cup because the air in the cup had nowhere to go. If the air cannot leave the cup through bubbles out of the bottom or a hole in the top, then the air must stay in the cup.