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Imploding can
Science at Home


      Aluminum can.
      Lamp of alcohol.
      Tripod and metal net.
      Soup plate.
      Two forks.

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     1. Pour some water to the can, filling about 1/8 of the total volume.

     2. Fill a soup plate with water.

     3. Heat the can, until the water begins ebullition. Let the water boiling during five minutes. (The water should boil more time because that fact turns the effect more evident. Be careful because you are working with boiling water (100 ºC), what can implicate severe burns to you. The metal of the aluminum can seems cold, but it isn't)

     4. With caution remove the can of the heating with two forks. Give a turn of 180 degrees to the can, that is, place the opening down and, at the same time, dive it immediately in the plate cold water. (as instruments to turn the can I used two forks because they are perfect for this application)

     5. In the same moment that you dive the can in the cold water, it is instantly compressed, in other words, it implodes.

During the heating of the water inside the can, the water temperature arises to 100 ºC (ebullition), being approximately its pressure equal to the atmospheric. When it is in ebullition it passes from liquid to gaseous state, being the volume of the can completely filled by water in liquid state in equilibrium with its vapour.

When the can is turned 180°, the water vapour is kept inside it and the liquid passes to the hole.

When diving the inverted can in the plate water, that is at a smaller temperature (20 ºC), it will cause an abrupt change in the temperature. The vapour inside the can will be suddenly cooled and condenses immediately.

It is known that a certain number of molecules, in the gaseous state, occupy higher volume than the same number of molecules in the liquid state. That is explained by the fact that the space between molecules is larger when it is in the gas state. The most part of the can internal volume was filled by water vapour and, therefore, the condensation of it will imply an abrupt decrease of pressure.

The can will shrink until a new equilibrium state is reached. It means, when the vapour condenses, the can will have a certain free space that has to be filled out. As the can doesn't offer great mechanical resistance, it implodes until compensating the abrupt decrease of pressure. The can doesn't implodes more because the cold water also enters inside through the hole.

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