Physics & Physical Science Demos, Labs, & Projects for High School Teachers

Crushing a Can and Floating Layers

Posted on: October 23, 2008

Today my Physical Science classes did two short labs in one period.  Both of these mini-labs came from the book “Super Science with Simple Stuff!” by Susan Popelka.  The book is geared towards middle school, but that never bothers me.

The first was using air pressure to crush a soda can.  I was going to do this as a demonstration, but when I tried it this morning, the impact of the event was so powerful, I decided to have the kids do it themselves.

What you do is take a soda can and put about 1/4″ of water in it.  Heat the can over a bunsen burner until the water is boiling.  If you have a triangle support on a ring stand, it takes about one minute.  If you have an asbestos wire mesh, it takes a couple more minutes.  When the water in the can is boiling, use tongs and invert the can into a bowl of water.  The can implodes instantly and dramatically.  I’m a jaded science geek and it impressed me.  The kids absolutely loved it.  I had extra  cans so they could do it again, they used up all my cans in both my classes.

The second lab uses Corn Syrup, Water, Vegetable Oil, and Rubbing Alcohol.  I used a 250ml beaker and had them put 50ml of each liquid.  First the corn syrup, then the water.  Before adding the water, they added a drop of blue food coloring.  Next they added the oil, but poured it over the back of a spoon so it would cause the layers to mix.  Last the alcohol with a drop of red food coloring, again poured in over the back of a spoon.  You get four very distinct layers.  Then use random items to see if they float in between the layers.  I used wooden toothpicks, bits of a plastic spoon, beans, and bits of Styrofoam from a cup.

The kids all commented how cool the lab was today.  They enjoyed it and were really excited.


4 Responses to "Crushing a Can and Floating Layers"

Hey-what a thrill to hear about how you are using the activties in my book and how much the kids love them. I love that pop can demo! Thanks for sharing! I teach precalculus now at the high school level and use science activities as often as I can.

Sue Popelka

this expirement is cool!!!

Do you cover the opening to the pop can. I tried it once without sealing the opening and it did not work. Tried it again with duct tape over the opening and it worked.

Hi Bonnie,
No, the trick is first, to have only about 1/4″ of water boiling hard in the can, and second, to quickly invert the mouth of the can into a pan of cool water. If the can hits the water with any other part of the can before the opening does, it will condense enough of the steam to ruin the demo.

Get a pile of cans and try it, you will quickly get the hang of it.

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