This is written as a static display, but can easily become a hands-on experiment for learners. One stoppered flask contains a piece of metal copper, the other contains a blue solution and a piece of copper covered with silver crystals. The crystals form when copper metal (Cu) is added to a solution of silver nitrate (AgNO3). The copper replaces the silver in the solution forming blue copper nitrate (CuNO3), and solid silver crystals (Ag) form on the surface of the copper. The exchange reaction is quick, learners can actually see the crystals grow. For safety reasons, this activity should be conducted as a demonstration for younger audiences.