This chemical reaction is very interesting. If one dissolves copper sulfate in water and places a bare iron nail in that, the iron replaces the copper in the sulfate salt and makes very fascinating hairy growths on the nail. I did this reaction with some of my copper sulfate, commonly available as root killer for sewers, and it turned out quite well. I like how the solution turns a greenish color and the nail becomes a furry, coppery tree trunk. Check out my YouTube time lapse I made of the reaction!