The Case of the Missing Coffee Cup (opens in new tab)

This article was first published in The Montreal Gazette. Where did the coffee cup go? It is a demonstration that never fails to draw oohs and ahhs from students. Pour a small amount of acetone into the bottom of a beaker and drop in a foamed plastic coffee cup. It instantly seems to melt into the liquid and within seconds just vanishes. Of course, matter cannot just vanish, but it can change from one form into another. Like sugar dissolving in water, the plastic dissolves in the acetone. How...