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Submarines, Secrets, and Spies
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Ideas from Teachers
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(Gr. 9-12)
Students often do not understand the idea of pressure, particularly the pressure that air exerts (14 pounds per square inch) or that water exerts. These concepts fit nicely into a unit on physical properties, gases, molecular spacing, or phases of matter. We do the following activity: Students bring a small amount of water (1/3 cup or less) to boiling in a pop can and then, once the molecules of water are moving quickly and lots of steam is forming, quickly invert the can (open top down) into a dishpan of water. (Students use tongs to handle the hot can.) The pressure of the air exceeds the pressure provided by the vapor molecules inside the can and the can crushes instantly. A student thens places the can on the floor (open tab facing up) and stands on the can to increase the pressure while another student taps the can sharply with a meter stick. Again, the increased pressure of the student's weight causes the can's rigidity to fail. The class watches NOVA's "Submarines, Secrets, and Spies" program and discusses the enormous pressures acting on the submarines. This is a great opportunity to do some math to find out just how much pressure there is at different depths. Students also calculate how much pressure caused the can to fail in the air and with their weight. The students get an idea of how difficult building a submarine is from an engineering standpoint and how much science theory figures into the design. Lastly we have a World War II submarine veteran come in an talk about sub duty. He describes the sounds and the "sweating" of the metal, as well as the close quarters and what it's like during silent running. There are lots of local veterans who do a fantastic job of tying this program back to real life. Sent in by
Shannon C'de Baca
Thomas Jefferson High
Council Bluffs, IA 
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