Charge from Change: Make a Coin Battery
Have you ever wondered why your phone, computer, or a flashlight works without being plugged into a power outlet? Where does the electrical energy come from that makes all these portable devices function? You probably know the answer: they use batteries! But do you know how these batteries work? Batteries store electrical energy in the form of chemical energy, which means that electrochemical reactions inside the batteries create electricity. It may sound complicated, but it is simpler than you think! In this activity, you will create a basic homemade battery with just construction paper, vinegar, salt and a handful of pennies and washers, and prove that it works by lighting an LED!
This activity is not appropriate for use as a science fair project. Good science fair projects have a stronger focus on controlling variables, taking accurate measurements, and analyzing data. To find a science fair project that is just right for you, browse our library of over 1,200 Science Fair Project Ideas or use the Topic Selection Wizard to get a personalized project recommendation.
Electricity is the presence of an electric charge, which can be either positive or negative. An electric current is generated by moving charges, usually in the form of electrons or ions. In batteries, these moving charges are created from chemical reactions, meaning that electrical energy is derived from chemical energy. The main components of a battery are two electrodes, typically made from carbon or two different metals, and the electrolyte, which is a liquid or paste that is in contact with both electrodes. The electrodes and electrolyte need to be electrically conductive to allow electrons and ions to flow from one electrode to the other. The question now is where do the electrons come from? Here is where chemistry comes into play.
Electrons are generated through electrochemical reactions, called redox (reduction-oxidation) reactions, where negative charges (in the form of electrons) are transferred from one chemical (or metal) to another. The electrons and ions that are released during these reactions travel through the electrolyte from one electrode to the other. During that process, one electrode releases electrons while the other accepts electrons to complete the electric circuit. There are many different battery types that use different chemical reactions to generate electrons; two common examples are the lithium ion battery and the nickel cadmium battery. In this activity, you will make a copper zinc battery using a vinegar/salt solution as the electrolyte. Do you think your battery will generate enough electricity to power an LED?
Note: In this activity, you will make a very low-voltage battery. The amount of electricity generated by this homemade battery is safe; higher voltages of electricity, however, can be very dangerous and even deadly, and you should never experiment with commercial batteries or wall outlets!
Extra: How many coins and washers do you need to light up the LED? Does the amount matter at all? Try lowering the number of coins and washers that you stack. What is the minimum number of coins and washers that you need to light up the LED?
Extra: Could you power other devices with your self-made coin battery? Test this by connecting other devices, such as a calculator or a little clock, to your battery! (You might need the help of an adult to figure out which wires inside the device you have to connect to the battery.)
Extra: What would happen if you exchanged the washers with another type of material, like aluminum foil? Would you still get a functional battery? Cut coin-sized pieces of aluminum foil and create a stack of coins and aluminum foil to find out!
Extra: If you have a multimeter at home, you can measure the voltage of your battery and how much current it produces. How does the voltage and current change as you add more coins to your battery?
Observations and Results
Did you manage to get the LED to light up? Probably not with the first two stacks, which consisted of only coins or washers. Pennies are coated with copper, which turns your penny into a copper electrode for this experiment. The galvanized washers, on the other hand, are made of zinc on the outside, which is a different metal and functions as a zinc electrode in your battery. The key to a functional battery is that an electrochemical reaction has to occur between the two electrodes. If both electrodes are made of the same material, no reaction will take place and no electricity will be generated.
However, when you alternate the pennies with the washers, you create a battery with two different electrodes: a zinc and a copper electrode. Now an electrochemical reaction can happen between the zinc and copper that releases electrons to travel through the electrolyte (vinegar/salt-soaked construction paper) to generate an electric current. This is why the LED should have lit up in the third stack that you created by alternating coins and washers. When you removed the electrolyte and used dry paper pieces instead, the electrons were no longer able to move from one electrode to the other, so no electric current was produced, and the LED did not light up!
Rinse the coins and washers with tap water and dry them off. You can reuse them afterwards. Discard the soaked construction paper and wipe down your work area.
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Svenja Lohner, PhD, Science Buddies
Science Buddies |
Electricity, battery, electrochemistry, chemical reaction
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