HAMILTON, Mich. — Bentheim Elementary students are learning all about changing atmospheric pressure within and around an object by crushing a can. All you need for this experiment is adult supervision, an empty soda can, a saucepan, the stovetop, kitchen tongs, ice-cold water and safety glasses.
First, you will fill the soda can with a small amount of water just enough to cover the bottom of the can. Next place the can upright in a saucepan on the stove top. Heat up the can until the water inside starts to boil and let the water boil for about 30 seconds. Grab the can with kitchen tongs and quickly flip the can and dunk it into the bowl of cold ice water. Finally, watch the can collapse and get crushed by atmospheric pressure!
When we heated the can we caused the water to boil and create the water vapor. That vapor pushed air out of the can escaping out of the top. We dunked the can in the cold ice water suddenly cooling the can caused the water vapor to condense and create a partial vacuum making extremely low pressure inside the can. This makes it possible for the pressure of the air outside of the can to crush it. A can is crushed when the pressure outside is greater than the pressure inside and that pressure difference is greater than the can is able to withstand.
Usually, the air pressure inside an open can is the same as the pressure outside. However, for this experiment, the air was driven out of the can and replaced by the water vapor. That water vapor takes up more space than air molecules so the pressure inside the can became greater but when the water vapor condensed once we dunked it in the ice-cold water the pressure inside the can became much less than the air pressure outside so it crushed the can.