Yesterday, I made an experiment. I filled an empty (but contains air) soda can with a little bit of water. Then I turn on fire at the sides of the soda can so that the water starts boiling. Next, I prepare bucket filled with normal temperature water. And when the water inside the soda can starts evaporating, I quickly turn the SC upside down inside the bucket and then, CRANK! The air pressure made it's effect on the soda can.

However, I don't know why.

I explained it by saying: "The water vapour eliminates the air in the soda can, when we reverse it into the bucket, the water vapour quickly becomes liquid and we have a vacuum now in the soda so the effect of air pressure will be important."

But is it true?

  • $\begingroup$ I don't think anything "eliminates" the air. It probably cools it down and causes the water vapor in the air from boiling to condensate. This in turn causes a decrease in density and pressure that results in the can collapsing, which apparently happens faster than the rate at which water flows in from the opening below. $\endgroup$ – SimpleLikeAnEgg Nov 1 '13 at 23:41
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    $\begingroup$ No, the air is actually being forced out. See SnoringFrog. $\endgroup$ – DumpsterDoofus Nov 2 '13 at 2:32

Boiling water in the can produces steam which forces the air out of the can. Placing the can into the much cooler (compared to the boiling water) water causes the steam to condense back into liquid form. Flipping the can upside down prevents any air from rushing into the can. This results in the pressure inside the can (which is empty except for the liquid water) being much less than the air outside, crushing the can.

Sources: http://uw.physics.wisc.edu/~wonders/CollapseCan.html http://scienceline.ucsb.edu/getkey.php?key=1447


The fact that the soda can (from the heating) is hot will also have made it easier for the water in the bucket to crush the can.

By the way what did you use to move the can?

If its possible, try placing a balloon within the can, inflate it using a bicycle tyre pump or similar and then invert into the bucket again and see if the crush pattern is similar. If there is a clear difference then heating the soda can did help weaken its structure. Else not.

  • $\begingroup$ PS: The water is responsible for crushing only if the can is fully immersed. Else it'd be air. Also including a balloon is not the right way to confirm if heating the can assisted in any way. you'd simply have to let the can cool (but retain the steam) and retry the same expirement. I was wrong to suggest including a balloon. $\endgroup$ – Ravindra HV Jul 20 '14 at 7:17

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