All you need in order to see electrolysis in action is a battery and a couple pencils! (Adult supervision required.)
What You Need:
What You Do:
- Fill the beaker or glass with warm water.
- Carefully remove the erasers and metal sleeves so you can sharpen both ends of each pencil. These pencils are your electrodes. The graphite in them will conduct electricity, but won't dissolve into the water.
- Cut a piece of the cardboard to fit over the beaker, then punch two holes in the center of the cardboard about an inch apart. Push the pencils through the holes and set them in the glass. They should extend into the water, but not touch the bottom of the glass. The cardboard will hold them in place.
- Connect each pencil to the battery with an alligator clip lead attached to the exposed graphite (pencil lead). If you don't have alligator clip leads, use two lengths of wire and strip an inch of insulation off each end. Wrap the wire around the graphite of each pencil and connect the wires to the battery. You may need to use tape to hold the wires in place.
As soon as you connect the wires to the battery, you will see bubbles appearing around each of the pencil tips in the water and floating upward. Those bubbles are the components of water—hydrogen and oxygen gas—that have been split apart by the electricity as it travels through the water from one pencil to the other. The pencil attached to the negative terminal of the battery collects hydrogen gas while the one connected to the positive terminal collects oxygen. Does one pencil collect more bubbles than the other? Which one? Why do you think this is? (Hint: Water's chemical name is H2O because it has two hydrogen atoms to every one oxygen atom.)
- Try adding an electrolyte to the water in the beaker. Water doesn't conduct electricity that well by itself, but you can speed up the process by adding some table salt to the water. Do the bubbles form more rapidly when you do this? (Safety Note: using salt may produce small amounts of chlorine gas, similar to the amount present when using bleach.)
- Try different types of batteries. Can you make electrolysis happen with a 1.5-volt battery? What about if you add an electrolyte?
- With some real electrolysis equipment you can collect the two gases in test tubes to measure the different amounts produced and test their different reactions to a flame.
- For electrolysis to work as true renewable energy, you need to use a clean energy source to run the reaction. Do this project again using solar cells instead of a battery.