Looking for an easy, hands-on experiment to use in your classroom at the beginning of the school year? In the June, 2013 issue of the Journal of Chemical Education, Isao Ikemoto and Kouichi Saitou describe a simple experiment to demonstrate the electrolytic dissolution of copper ions from a copper electrode. This experiment can be conducted using only items that are easily obtained around the home or in grocery stores.
In short, copper wires are attached to the opposite terminals of a 9V battery. The copper wires are submerged in gel comprised of sodium polyacrylate collected from disposable diapers. Electrons are removed from the copper wire attached to the positive terminal of the battery, forming copper ion:
If ammonia is added to this copper wire, the copper ion produced forms a deep blue copper-ammonia complex:
The electrons removed from the copper wire on the positive terminal travel through the battery to the copper wire attached to the negative battery terminal. The electrons on this second copper wire contact water in the gel solution, reducing the water to hydroxide ion and hydrogen gas:
Ikemoto and Saitou report that, given sufficient time, the copper-ammonia complex produced at the wire attached to the positive battery terminal will migrate to the wire attached to the negative battery terminal. When this occurs, the copper ion is reduced back to copper metal:
In the video below, you can view how to carry out this experiment. When I conducted the experiment, I didn’t wait for the copper complex to migrate to the wire at the negative battery terminal to be reduced. Rather, I decided to test the identity of the gas produced at the negative battery terminal.
Ikemoto and Saitou describe how to carry out this experiment as a classroom demonstration. However, this process is so easy to carry out it makes me wonder if students could conduct this experiment on their own as a hands-on lesson. I’d like to hear from any of you if you present this lesson in your classroom – either as a demonstration or a hands-on experiment.