At-home STEM Activities: Collapsing Can
Last week, Faithe posted a series of videos about atmospheric pressure. This activity is related to those videos, so before trying this, we suggest watching those videos!
There are plenty of ways to crush a can using your own strength, but you can give your muscles a break and let physics do the work for you.
Let’s collapse a can using only water, heat, and a physical phenomenon!
Materials:
Empty soda can
Tongs
Water
Sauce pan or bowl filled with cold water
Stove
**Since we’re using a stove for this activity, adult supervision is needed!**
Instructions:
1. Pour a small amount of water into the can, enough to fill the can about a half inch.
2. If you have an electric stove, place the can on one of the elements and turn on to medium heat. If you have a gas stove, carefully hold the can with tongs over one burner set at a medium flame. Let the water in the can come to a boil. You’ll know it’s boiling when you hear the bubbles and see steam coming out the top. Allow to boil for about 30 seconds.
3. Turn off the burner. Quickly and carefully, flip the can over into the pan of water, so that the opening in the top of the can is submerged, and watch the can implode!
So why does the can implode?
When we begin our experiment, there is water and air inside the can. As we boil the water in the can, the water turns to steam and pushes the air out of the can. When we flip the can over into the cold water, the water momentarily seals off the can, so now the steam is trapped in the can. Since the water and air on the outside of the can is cooler than the steam inside, the steam condenses into a few drops of water. The drops of water on the inside of the can can’t exert the same amount of pressure as the water and air outside that can, so it collapses.
You may have also noticed that the can was full of water after it was crushed. This was due to unequal pressure on the inside and outside of the can, as well. Since pressure inside the can was less than the water pushing into it, the water ended up pushing itself into the can.
This experiment can be conducted on a much larger scale—check out this video where the same technique is used to crush a 55-gallon steel drum!
