When copper faces off with aluminum

My students have been doing some experiments with copper sulfate. The waste from these experiments was sitting on a bench in my lab and I wanted to evaporate it so I could reclaim the copper sulfate. Well, late Wednesday night (and I mean late...it was after parent teacher conferences) I decided to pour the copper sulfate solution into some shallow aluminum pie pans to help it evaporate faster. On Thursday morning, I walked into my classroom and looked across the room at the pans. They were empty. Weird thought I. Then I noticed a huge puddle about 3 feet away from the pans. Double weird. Well, I walked over to inspect the mess and this is what happened (I think). The copper sulfate reacted with the aluminum in the pie plate (yes, Miss Carr forgot to consider the activity series of metals) and the copper was reduced and the aluminum was oxidized. Translation: The copper sulfate ate away holes in the pie plate and copper metal was formed under the pie tin. The holes resulted in a leak of the copper sulfate solution and apparently the bench has a slight slope so the puddle ended up a ways down stream. Copper sulfate is blue and forms blue crystals when it evaporates so eventually the puddle turned into a large bed of fine blue crystals. So, now you all know that when copper and aluminum go to war, copper wins!