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Edited by Joel Palmer, Josh W., Ben Rubenstein, Paintsaint and 37 others

This article provides suggestions for an experiment that uses air pressure to crush a soft drink can. This can be a great visual demonstration of some simple scientific principles, and with supervision, can be performed by students.

Edit Steps

  1. 1
    Rinse a soda can with water, and leave a small amount (approximately 2 tbsp.) of water in the bottom of the can.

  2. 2
    Prepare a bowl of ice water.

  3. 3
    Place the can upright on a stove and heat until the water is boiling inside the can.

  4. 4
    Using tongs held with your palm facing upward, pick up the hot can, quickly turn it over and plunge the top of the can into the bowl of water.
  5. 5
    In a fraction of a second the can will be crushed with a very loud noise!


In a Classroom Setting

  1. 1
    Ask the students: "What caused the can to be crushed?"

  2. 2
    Listen to the students' responses. This will help you find out what they already know. Do not affirm or deny any of the answers. Just acknowledge and accept them, and ask the students to explain their thinking.
  3. 3
    Based on their answers, you may need to explain what happened, or if they offer a good explanation, go on to the next step. (See explanations in the "Tips" section)
  4. 4
    Ask the students to suggest things to change in the experiment to test the explanation.

  5. 5
    The students should repeat the activity and vary the conditions. They should record their results and draw conclusions. Have them share their findings with one another to see if they agree.

Edit Video

Edit Tips

  • Possible variables to change:
    • Amount of water in the can
    • Temperature of water in the bowl
  • Explanation:
    • When the can is heated, it becomes filled with water vapor. This vapor occupies approximately 1000 times more space than it did as a liquid. When you turn the can over into the cool water, the water vapor turns back to liquid water very quickly, creating a partial vacuum in the can.
  • Increasing the time between removing the can from the heat and placing it in the water.
  • Why doesn't the water in the bowl just get pushed up into the can rather than the can being crushed? Water has mass, which means it also has inertia. Inertia can be thought of as a resistance to change in motion. (That is not technically correct, but will suffice for the purposes of illustration.) The water must be pulled up, and it must go from a state of little or no motion and start moving upward. This requires more force than the sides of the can will be able to withstand, so the can is crushed by air pressure before the water can move in. Some water will move into the can and will be seen draining out when you lift the can out of the water.
  • The average coke can has about 49 square inches of surface area. The can would therefore experience a total crushing force of 441 lbs. If a total vacuum were formed, the crushing force would be about 686 lbs.
  • Do not flip and let go. Flip the can and put (do not drop) it in the water.
  • Let's assume that the can only acquires a 2/3 vacuum. (This could be a much lower pressure.) Atmospheric pressure is 14 lbs/square inch. A 2/3 vacuum would produce an inside pressure of approximately 5 lbs/square inch. This is a differential of 9 lbs/square inch. That means each square inch of the can is subjected to an inward force of 11 lbs.
  • (Numbers are rounded for simplicity; the English system is used to make the forces a little more understandable for the layperson)
  • Holding the tongs palm up makes it much easier to flip the can into the water.
  • Practice before doing this in front of the students.

Edit Warnings

  • Older children (ages 10+) may be able to do the activity themselves with adult supervision but you, as the adult, must watch carefully. You are responsible for safety! Never allow more than one person to do the demonstration at a time!
  • The can and the water inside will be hot. Make sure that as the can is flipped into the water, no one is standing in a position where they might be injured by the water flying out of the can.
  • Splash-proof goggles are necessary for all participants. (Can be purchased at most hardware and home centers. Be careful to make sure they are splash-proof.)

Edit Things You'll Need

  • Empty aluminum soda cans
  • Tongs large enough to comfortably handle the hot cans
  • Stove or hot plate
  • Shallow, clear, bowl of cool water
  • Bunsen burner may be used as heat source

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