The mass of an iron plate dipped into a solution of copper sulfate increases. Explain the observed phenomenon.

First, due to the fact that iron (Fe) in the electrochemical series of metal voltages is to the left of copper (Cu), that is, it is a more active metal and thereby displaces copper from its salt, forming its own salt. A redox reaction occurs, in which pure copper is deposited on the plate. Since the atomic mass of copper is greater than that of iron, then, accordingly, the plate becomes heavier.