Boyle's Law and the Monster Marshmallow When teaching Boyle's law to general chemistry students, a visual demonstration of the inverse proportionality of gas pressure and volume is most helpful to assist the student's intuitive understanding of this principle. One commonly employed demonstration involves the use of a vacuum pump and a balloon. This demonstration illustrates the principle quite well, but I have found that student interest is sparked by a modification of this demonstration: I simply substitute several marshmallows for the balloon. Marshmallows are made primarily of sugar, gelatin, and artificial colors and flavors. The mixture is whipped before the marshmallows "set up." This introduces air huhhles into the marshmallow. Beeause the gelatin body of the marshmallows is somewhat elastic, a reduction in pressure outside the marshmallow will cause the air bubbles to expand. The marshmallow "grows" in vacuum to several times its normal size! (Note: Using marshmallows that are fresh and moist will give the best results.) 'The gelatin is not too elnntir so leaving the vacuum pump i m too long will cause the tiny bubbles in the marshmallows to burst.Then when the pressure is returned t
