• Babies
• Building a Family
• Children
• General Parenting
• Newborns
• Teenagers
• Toddlers
• Pregnancy

Science Experiments for Kids: Make a Lemon Clock

Learning About Electricity

Science Experiments for Kids: Make a Lemon Clock

As part of a generation of children growing up in an increasingly green and eco-conscious world, things like low-energy light bulbs and hybrid cars are the norm for your child. Making a clock that runs on citrus power is not only a powerful way to reinforce the idea that there are alternative energy sources to be found everywhere, but it's also a great way for her to learn more about electricity and conductive materials. Note that though using alligator clips is ideal for this experiment, you can only use them if the terminals in the battery compartment of the clock are large enough to clip onto. If they are not, you will need to use electrical tape to secure the ends of the wire to the terminals.

Skills Being Practiced

• Scientific method
• Basic understanding of how electricity works
• Exploration of conductive materials

What You Need

• 2 large lemons or other citrus fruits
• 3 copper wires, approximately 1' long each
• 2 copper pennies or copper nails
• 2 large galvanized zinc nails (at least 2" long)
• Battery-powered clock (one that uses a single battery, and does not also have an outlet cord)
• 2 alligator (electrical) clips or electrical tape
• AA battery
• Paper and pencil
• Permanent marker

Learn about Electricity, Electrons, and Batteries

• You and your child can look at the AA battery together to note that one end has a "+" sign on it, and the other end has a "-" sign on it. These are known as positive and negative terminals. For further exploration, open up the clock's battery compartment and note that it, too, has positive and negative terminals.
• Tiny particles of electricity known as electrons can travel between a negative and positive terminal, if there is something connecting them that allows those electrons to flow between them. That connection is known as a conductor, and some materials, including zinc and copper, are much better conductors than other materials. When two different metals are used as terminals, the electrons push harder in one direction than the other, creating a current.
• In battery-powered devices, the battery itself makes electrons through a chemical reaction that occurs when a conductive circuit is created by putting the battery in between the positive and negative terminals in a battery compartment. The chemical reaction only takes place when the battery is in place.
• When conductive materials are placed in acidic solutions and juices (like those found in citrus fruits), it also creates a chemical reaction. That reaction breaks down the structure of the metal, releasing electrons into the solution.

Conduct Your Experiment

Create a Hypothesis

1. Go over the background information about electricity and batteries here with your child to make sure she has a basic understanding of how batteries and conduction work. Show your child the materials you have, and tell her that you are going use them to make the clock work without a battery.
2. Identify each of the materials by name and composition (i.e., a copper nail, a zinc nail), and ask her to predict what will happen if you connect all these materials together.
3. Have her make a basic diagram of what she thinks you need to do and what will happen. This will serve as her plan and hypothesis.

How to Play

1. Securely attach one end of a piece of copper wire just below the head of one of the zinc nails by wrapping it around the nail. Attach a small alligator clip to the other end of the wire. If you do not have alligator clips, leave the end of the wire as it is.
2. Attach the end of a second piece of copper wire to a copper nail by twisting it around the nail (or, if you are using a penny, attach it with electrical tape). Attach the other alligator clip to the other end of this wire. Again, if you do not have alligator clips, leave the end of this wire as it is.
3. Secure a zinc nail to one end of the third piece of wire and a copper nail (or penny) to the other end of it.
4. Set aside the wiring for a moment, and prepare the lemons. Use a permanent marker to label one lemon as Lemon 1 and the other as Lemon 2. Next you need to loosen the pulp inside and release some of the juice into the lemons without breaking the peels by squeezing the lemons gently, and/or rolling them on a table while applying gentle pressure.
5. Place Lemon 1 and Lemon 2 next to each other on a table. Locate the wire attached to the first zinc nail, and poke the nail into Lemon 1, making sure the nail pierces the peel and is embedded in the pulpy portion of the lemon but does not come out the other side of the lemon.
6. Locate the wire attached to the copper nail or penny. Drive that nail into Lemon 2 (or cut a deep slit in the lemon, and place the penny in the slit).
7. Next, take the wire with a copper nail on one end and the zinc nail on the other end. Drive the zinc nail into Lemon 2, approximately an inch away from the copper nail or penny already embedded in the lemon.
8. Insert the copper nail/penny end of the same wire into Lemon 1, about an inch away from the already embedded zinc nail. 9. Connect the free end of the wire in Lemon 1 to the clock by clipping the alligator clip onto one of the battery terminals in the clock. If you do not have alligator clips, attach the end of the wire to the terminal with electrical tape. Complete the circuit by attaching the free end of the wire in Lemon 2 to the other battery terminal in the same way. Completing the circuit should power the clock. If the clock isn't running, it may be that the connections are loose, the ends of the wires connected to the clock are attached to the same metals, or that the current from the lemon is just too weak. If all the connections are right, try substituting potatoes for lemons.

Observations

Ask Yourself:

• Why do you think we needed to use zinc and copper nails?
• Why is the clock lighting up?
• Why do we need to connect Lemon 1 and Lemon 2 to each other?
• How are the lemons like a battery when they are attached?
• What is it about the lemon that allows it to conduct electricity?
• What other foods do you think would conduct electricity?

What's Going On

When you put the zinc and copper in the lemon juice, it creates a chemical reaction that changes chemical energy into electrical energy. This change of energy is a voltaic reaction, which turns the lemons into a voltaic battery. The chemical reactions push the electrons that are being released from each metal through the copper wire and, because the metals are different, the electrons push harder in one direction. They move in a circular direction, going through the wires to the clock terminals and back to the lemon, making an electric current that may be powerful enough to power the clock. Once the lemon juice starts to dry up, the reaction will lessen, and you will need to change the "battery."

Extend the Learning

Try using different citrus fruits, orange juice, or soda to see how they work as voltaic batteries.