Important note: I used a Potato Clock kit from Green Science for this lesson. However, you can assemble these materials without a kit as well.
- 2 potatoes
- 1 low-voltage LED/LCD clock (if it doesn’t have wires coming out, you need 2 alligator clips)
- Connecting wire (or 1 alligator clip)
- Copper and zinc strips (or copper wire and galvanized nails)
Note: the alligator clips should be connected by wire
If your LED/LCD clock still has a battery in it, remove it before the experiment. In each potato, insert one copper strip (or a piece of copper wire) and one zinc strip (or galvanized nail. In the video, the clock I used already had 2 wires coming out of it- a red wire (positive) and a black wire (negative). However, if your clock does not have these wires, use alligator clips to connect the potatoes to the clock. In order to do this, note that within the clock’s battery compartment there should be a positive terminal and a negative terminal which would align with the battery when you would insert it into the clock. Connect the positive terminal to the copper strip/piece of wire in one potato and connect the negative terminal to the zinc strip/galvanized nail in the other potato. Then, use the connecting wire (or third alligator clip) to connect the remaining copper and zinc in the two potatoes. The clock should turn on!
When you insert the zinc (the negative electrode) into the potato, the zinc starts to dissolve because potatoes have phosphoric acid. When this happens, the zinc atoms lose electrons, creating zinc atoms with a positive charge and electrons, which have a negative charge.
The electrons are now attracted to the positive hydrogen ions where the copper (the positive electrode) was inserted into the potato. However, the electrons can’t travel through the potato itself. Instead, they have to travel through the wire that connects the zinc and copper together. Once the electrons combine with the hydrogen ions where the copper was inserted, hydrogen gas is produced. This movement of electrons is called an electrical current, and is what powers the clock!