Warning: please do not attempt this experiment without adult supervision. With proper supervision it is safe, but if you don't feel comfortable with it, try another experiment!
What is Needed
* One aluminum can
* One oven mitt or other hand protection
* Some tap water
* A stovetop burner (electric or gas is OK)
* One bowl of cold water. The bowl must be able to hold at least 20 ounces of water. Try using a sauce pan that holds a few quarts of water.
What to Do
First of all, do this experiment with adult supervision. If you are not careful with this experiment, you can burn yourself or someone else. This experiment can be done in a safe manner if some common sense is used.
Take the empty aluminum can and put about two tablespoons of water in it. Then set the can on a burner on the stove. Turn the burner on. Leave the burner on until the water in the pop can boils. When you start to see steam come out of the can opening turn off the burner. When the burner is off, pick up the can with the hand that has the oven mitt on it. Immediately take the can and turn it over into the bowl of cold water. You will hear an immediate pop, as the can implodes.
What is Happening?
What you are doing is turning the water in the can into steam. This steam fills the can and replaces almost all of the air inside the can. When you invert the can into a bowl of cold water, the steam condenses into water very quickly. The can is then left with very low pressure inside of it and...(more later)
Other Things to Try
Check out the Balloon in a Bottle experiment for more fun with steam.