An Unexpected Variable

Sometimes science experiments don't go the way you expect them to. 

To illustrate the principle of heat conduction today, Joy put butter on a plastic spoon, a metal spoon, and a wooden craft stick.  She then stuck a Cheerio on each glob of butter, placed the spoons and craft stick in a mug of very hot water, and asked which Cheerio's butter glob would melt first, allowing it to drop into the water.

Her attentive students remembered that she said metal was an excellent heat conductor, so we guessed the Cheerio on the metal spoon would drop first.  We all failed to realize that . . .

. . . the metal spoon was much longer than the other two items, so it stuck out over the table, protecting its butter glob from the steam rising above the hot water.  The plastic spoon's butter got hit with a lot more steam, so it melted long before the metal spoon's butter.  The conduction demo was a bust, but I guess we all learned something about the power of steam (and the importance of testing demos before class).