How to Do Electrolysis of Water

Electrolysis is a big word that simply means using electricity to split molecules. Water is made of H2O: two hydrogen atoms attached to one oxygen atom. You can use a safe source of electricity (a 9-volt battery) to pull the atoms apart, making pure hydrogen gas and pure oxygen gas.

Difficulty: Easy

Instructions

Things You'll Need:

• New pencil
• Saw (or bread knife)
• Pencil sharpener
• Two 8-inch pieces of insulated wire
• Wire stripper (or sharp scissors)
• 9-volt battery
• Tape
• Index card
• Small glass jar
• Tap water

1. Saw or cut the metal end off the pencil, then saw or cut the pencil in half.

2. 

   Sharpen both pencils halves at both ends.

3. Strip an inch of insulation off each end of both insulted wires.

4. Attach one end of each wire to one of the terminals on the battery. You may need to use some tape to secure the wires so they do not slip off the terminals.

5. Attach the other end of each wire to the tip of a pencil. This may be a little tricky, and you will probably need some tape to help them stay in place. The electricity will travel through the graphite in the pencil.

6. 

   Push the free ends of the pencil stubs through the index card, about an inch apart.

7. Pour water into the glass jar so that it is about three-quarters full.

8. 

   Set the card with the pencils in it on top of the glass jar so that the free ends of the pencils are submerged in the water.

9. Make sure all your wire connections are still good and have not slipped off.

10. Observe tiny bubbles forming on the ends of the pencils. The bubbles on the pencil that is connected to the positive terminal are oxygen. The bubbles on the pencil that is connected to the negative terminal are hydrogen. Notice that there are more bubbles of hydrogen than oxygen. This is because in a water molecule there are two hydrogens for every oxygen.

Tips & Warnings

• If you do not see bubbles forming, add a few grains of salt to improve the conductivity of the water.
• Perform this experiment again, but use distilled water instead of tap water. You will not see any bubbles at all because distilled water does not conduct electricity.
• Never use electricity from a wall outlet to do this experiment!