Galvanic Reaction

Background:

The first battery was made in 1800 by an Italian scientist, Alessandro Volta. Volta discovered that some metals and a liquid could work together to produce electricity.

Volta made a "sandwich" of paper soaked in salt water between a piece of silver and a piece of zinc. When he joined the two metals with a wire, he found that a current flowed through the wire. Because the current was very weak, he made a "pile" of his "sandwiches" and when he touched a wire from the top of the pile to a wire from the bottom, he got sparks of electricity.

A unit of electricity, the volt, was named after Alessandro Volta.

Problem: Can a battery be made of pennies?

Hypothesis:

Materials:

4 pennies salt water 4 washers tape paper towel 2 wires

Procedure:

1. Soak 4 small squares (2cm x 2cm) of paper towel in the salt water.

2. Sandwich a piece of the salty paper towel between a penny and a washer.

3. Make three more "sandwiches" and pile them up. See Figure 1.

4. Tape the bare end of one wire to the top penny.

5. Tape the bare end of the other wire to the bottom washer.

6. Take the free end of each wire and touch both ends lightly to your tongue. Note your observations.

7. Connect the free ends of your battery to the voltmeter. Record the voltage on the board.

Observations:

1. With the wires touching your tongue, you should feel a light tingle of electricity. In your battery, chemical reactions cause a tiny electric current. The current flows from one wire through your tongue and into the other wire. You will feel a tiny tingle but will not be harmed.

2. Compare the voltage of your battery to those of the other students.

Summary:

1. What is the average voltage of the batteries made by your class?

Teacher Notes (Remove this section before giving to students.)

1. Subject and category: Resources - Laboratory Activity

2. I use pieces of felt in place of the paper towel.

3. If I left something out, you can e-mail me at teacher@aloha.net. Bob Brennan, Castle High School, Kaneohe, Hawaii.