Difficulty: Moderately Easy
When I first saw the 'potato clock,' I was actually looking for a way to show third through fifth graders how humans absorb energy from food; vegetables and fruits/plants. The clock illustrates quite nicely how chemical energy stored in the potato transfers to electrochemical energy strong enough to run the clock. Much in the same way we take in chemical energy stored in the plant, but convert it into chemical energy for our bodies, to run.
For all, there is a chemical reaction within the potato battery that causes the electrons to move. The electromotive force within each potato is the ability it carries to move electric current. In the electrochemical cell, such as the potato battery, the copper wire makes the electrons move in the potato, causing energy to move into the clock. More, the copper and the zinc (found in the galvanized nails) are called electrodes, and the potato is called an electrolyte. Fruit and other vegetables work well too. They contain plenty of particles that allow current to flow between the metal stips.
The first battery was made by Italian scientist Alessandro Volta (1745-1827). He built a pile of metal discs with card soaked in salty water between them. It produced a small electric current. This battery is known as a Voltaic pile. Copper is a great conductor of electricity. It is used to make wires and cables. Zinc is important because it used to galvanize steel objects such as garden tools and screws. The objects are coated with zinc, which protects the steel from rusting.
Before attempting this lesson, teachers should think about ways to incorporate the following topics:
- The Digestive System: For elementary students, I use an internal organ vest showing the digestive and respiratory systems.
- An overview of Lipid Function: I incorporate an interactive link to: http://www.wiley.com/legacy/college/boyer/04.
- Terms such as nutrition, absorption, storage efficiency, metabolic changes and the caloric content of food should be defined and included in the conversation.