A small amount of water (a few millilitres) of water is heated in a 12-ounce soda can (photograph at left below) until the water boils, producing steam as evidenced by the condensation coming out of the can (photograph at the center below). The steam-filled can is then grabbed by a pair of tongs and quickly placed upside down on a dish of room-temperature water, as seen in the photograph at the right below, taken just before the top of the can reaches the water. You can see how the demonstration is set up in an mpeg video by clicking your mouse on the photographs, or on this link.

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The question this week involves exactly what happens after the can hits the water.

When the can reaches the surface of the water:

  • (a) The can will RAPIDLY implode.
  • (b) The can will SLOWLY implode.
  • (c) Water will be pulled up into the can, filling the can with water.
  • (d) Nothing will happen.

On or after 3/27, click Read More for the answer.


The answer is (a) The can will RAPIDLY implode, as seen in a video by clicking your mouse on the photograph of the imploded can below.

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When the can is removed from the hot plate and rapidly cooled by the water, the steam in the can immediately condenses, creating a partial vacuum in the can, thus causing it to collapse. This process occurs much too rapidly for water to be drawn up into the can by the low pressure relative to the outside atmosphere. The only way for the pressure in the can to be equalized so rapidly is for the can to collapse.

After the can rapidly collapses with a loud "thunk," the remaining volume of the collapsed can does in fact fill with water, due to the reduced pressure in the can.