I'm trying to figure out why a can of pop collapses when it is filled with warm water and then placed in water

Question

The can is placed into a shallow pan of water after it has warm water put into it. Then the can collapses, why?

Answer 1

This is one of my favorite demonstrations! You take an otherwise empty soda can, put in a little water (a few tablespoons), and heat it up to boiling. Then, carefully and quickly, remove the can from the heat (with tongs!) and place it upside-down in a bowl of room-temperature (or cooler) water - it only needs to be only 1 inch deep or so. And the can is crushed! So much fun!

Here's why it happens: When you were heating the can, not only was the air inside it heating up and therefore expanding, it was also filling with hot water vapor. When you put the can in the bowl of water, you provided a cool(er) surface for the water vapor to condense on. Take the water vapor (a gas) out of the can, now there's a lot less air (a gas) in the can, so the air pressure inside the can is very low, so the outside air pressure crushed the can. You'll also notice that the can "sucked" up water into itself - actually the outside air pressure pushed water inside it.

Another demo that's a little less exciting, but still neat, is to take a large can like an oil can, heat it up (again with a little water inside), put an air-tight cap on, and wait. While it cools, the air pressure inside gets lower due to the loss of heat and some of the water vapor condensing. Slowly, the can is crushed from the outside air pressure.

Answer 2

Does this really happen?

I imagine that it's because the density of the warm water inside the can is different from the water in the pan, and the pressure makes it collapse....

I'll try this one out myself.

Answer 3

Whenever matter is heated, it expands. Conversely, when it cools it contracts. The warm water that you put into the can expanded as it was heated and will contract as it is cooled by the cooler water into which you place the pop can. As it cools and contracts it causes the pressure in the sealed can to become less than that on the outside of the can. Therefore, the outside pressure crushes the pop can as the water inside cools and contracts.

Answer 4

difference in pressure.