Salt Water Energy

Research Question:

• How can you make electricity from simple objects around the house?
• How does the amount of salt in a solution affect the solution’s ability to conduct energy?

We use batteries in everything – from IPods to cars. But how does a battery work? In this science project, you will build a battery and see how one of its components contributes to its ability to generate electricity.

Materials:

• 水
• Small glass jar
• Salt
• Measuring spoons
• Zinc-coated nail
• Tape
• Copper-coated wire
• 2 insulated wires with alligator clips on both ends.
• Voltmeter (borrowed)
• Graph paper, optional


Experimental Procedure:

1. Make a saltwater solution by mixing a small jar of water with a teaspoon of salt.
2. Place a zinc-coated nail into the solution, and tape it to one side of the cup securely. This will be the negative electrode.
3. Place a copper-coated wire into the solution, and tape it to the other side of the cup securely. This will be the positive electrode.
4. Open the alligator clip on one wire by squeezing it, and attach it to the end of the zinc-coated wire sticking out of the solution.
5. Open the alligator clip on the other end of the wire, and attach it to the negative pole of the voltmeter.
6. Repeat Steps 4 and 5 to connect the copper-coated nail to the positive pole of the voltmeter.
7. Look at the dial on the voltmeter. How much current does it show flowing between the two electrodes?
8. Add another teaspoon of salt to the water. How much current does the voltmeter show now? Continue adding teaspoons of salt and recording the reading on the voltmeter in a chart, such as the one below.

If you’d like, you can make a line graph showing the relationship between the amount of salt in the water and the current that flows between the two electrodes. Is there a point at which the current stops increasing?

Terms/Concepts:Voltage; How does a voltmeter work?; What are the parts of a battery (e.g., electrodes)?

References:

• Easy Genius Science Projects with Chemistry, by Robert Gardener. Pp 55-57.