In the Classroom Tested Demonstrations
A More Dramatic Container to Crush by Atmospheric Pressure submitted by:
Robert D. Meyers and Gordon T. Yee* Department of Chemistry and Biochemistry, University of Colorado, Boulder, CO 80309-0215; *
[email protected] checked by:
Tom Hanninen Department of Chemistry, Kutztown University, Kutztown, PA 19530
The well-known demonstration of crushing an aluminum beverage can by heating a small amount of water to boiling in it and quickly inverting the can into ice water (1) is lacking in one respect: a student using her foot can effect a similar change. In addressing this shortcoming, we have found that an empty 20-liter steel solvent drum1 may also be used in this demonstration, with a second identical drum offered to the class as a “control”. The control drum may be somewhat dented by a strong and determined student, but this pales by comparison to what can be achieved by the pressure of the atmosphere.2 To prepare the drum for this demonstration, the plastic spout must be carefully removed using a razor blade or utility knife. Two hundred milliliters (200 mL) of water is poured into the empty, clean drum1 and the drum placed on a large hot-plate.3 With the hot-plate set on high, it typically takes about 15 minutes to boil the water and get the drum warm.4 Once the water is boiling, a #111/2 black rubber stopper5 is set loosely into the opening at the top of the drum to act as a pressure relief and anti-back-flow device as the air inside of the drum is displaced by water vapor. When the drum is full of water vapor and steam is being vented fairly regularly, one simply presses the stopper in tight and removes the drum from the hot-plate. A slight deflection of the sides of the drum will be evident almost immediately, but after about five minutes, the drum will dramatically collapse almost completely. W ARNING: The drum will also likely tip over at the time it collapses, so proper precautions should be taken. When the
drum is cool, the stopper may be removed and the concomitant hissing sound will convince students that a vacuum was indeed created within the drum. Notes 1. These drums are commonly used to contain organic solvents (e.g., acetone) available from Fisher Scientific, 7811 Forbes Ave., Pittsburgh, PA 15219-4785. At the University of Colorado, we dispose of these regularly. WARNING: empty solvent drums can contain explosive vapors or dangerous residues and should be rinsed with water before being used for this demonstration. 2. The reviewer points out that Bill Nye, the Science Guy, has performed this demonstration on television with a 55-gallon drum. 3. We used a Corning PC-600 hot-plate, 10" × 10", 1043 W. 4. Alternatively, three ring stands may be arranged in a triangle to support the drum over a Meker-type burner or two. This has the advantage of heating the water more quickly but requires a natural gas supply. We thank the reviewer for this suggestion. 5. Solid rubber stoppers are available from Fisher Scientific, 7811 Forbes Ave., Pittsburgh, PA 15219-4785. A #11 stopper will also work, although it may be somewhat more difficult to remove at the end of the demonstration.
Literature Cited 1. Shakhashiri, B. Z. Chemical Demonstrations: A Handbook for Teachers of Chemistry, Vol. 2; University of Wisconsin Press: Madison, 1985; p 6. A related demonstration is performed with a duplicating fluid can, which is also easy to crush.
JChemEd.chem.wisc.edu • Vol. 76 No. 7 July 1999 • Journal of Chemical Education
933
