An average can of soda at room temperature measures 55 psi before you ever crack it open. (In comparison, most car tires run on 35 psi, so that gives you an idea how much pressure there is inside the can!)
If you heat a can of soda, you’ll run the pressure over 80 psi before the can ruptures, soaking the interior of your house with its sugary contents. Still, you will have learned something worthwhile: adding energy (heat) to a system (can of soda) causes a pressure increase. It also causes a volume increase (kaboom!).
How about trying a safer variation of this experiment using water, an open can, and implosion instead of explosion?
Materials – An empty soda can, water, a pan, a bowl, tongs, and a grown-up assistant.
NOTE: If you can get a hold of one, use a beer can – they tend to work better for this experiment. But you can also do this with a regular old soda can. And no, I am not suggesting that kids should be drinking alcohol! Go ask a parent to find you one – and check the recycling bin.
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Prepare an ice bath by putting about ½” of ice water in a shallow dish. With an adult, place a few tablespoons of water in an empty soda or beer can and place the can upright in a skillet on the stove. When the can emits a think trickle of steam, grab the can with tongs and quickly invert it into the ice dish. CRACK!
Troubleshooting: The trick to making this work is that the can needs to be full of hot steam, which is why you only want to use a tablespoon or two of water in the bottom of the can. It’s alright if a bit of water is still at the bottom of the can when you flip it into the ice bath. In fact, there should be some water remaining or you’ll superheat the steam and eventually melt the can. You want enough water in the ice bath to completely submerge the top of the can.
Always use tongs when handling the heated can and make sure you completely submerge the top of the can in the icy water. The water needs to seal the hole in the top of the can so the steam doesn’t escape. Be prepared for a good, loud CRACK! when you get it right.
Why does this work? By heating up the water in the can, you’re changing the state of water from a liquid to a has (called water vapor), which drives out the air, leaving the steam inside. When inverted and cooled, the steam condenses to a small volume of liquid water (much smaller than if it was just hot air). The molecules in water vapor are a lot further apart than when they are in a liquid state. Since the air inside the can has been replaced by the steam, when it cools quickly, it creates a lower air pressure region in the can, so the air pressure surrounding the outside of the can rapidly crushes the can.
If you look really carefully as it condenses, you’ll see cold water from the bowl zoom into the can, just like when you suck water through a straw. The vacuum created int he can by the condensing steam creates a lower pressure, which pushes water into the can itself. When you suck from a straw, you’re creating a lower air pressure region in your mouth so that the surrounding air pressure pushes liquid up the straw to equalize the pressure.
Remember, high pressure always pushes!
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