Sharpen three to four round pencils, making sure that each has an even, sharp point. Fill a resealable plastic bag half way with water. Carefully push each pencil into the water area of the plastic bag. This demonstrates that the water does not leak around the pencils. After the demonstration, hold the bag over a sink or container to remove the pencils.
Add interest and drama to the experiment by holding the plastic bag over a student's head as the bag is being pierced. After the demonstration, explain to the students that the plastic bag is composed of long chains of polymers that actually slip aside as the plastic is pierced and then seal around the pencils, thereby preventing leakage.
Pour 12 ounces of water into a glass pint jar. Add and dissolve a teaspoon of salt in the water. Sharpen both ends of two pencils. Punch two holes into a thin four-inch square piece of cardboard and insert the pencils three-fourths of the way through the holes. Set the long end of the pencils in the glass. Use two foot-long pieces of electrical wire to connect the graphite (lead) ends of each pencil to a nine-vault battery with one wire connected to the positive side of the battery and one to the negative side.
Before conducting the pencil and battery hydro electrolysis demonstration, solicit and record predictions about the possible results of using pencils and water to conduct electricity. Observe that gas bubbles collect around the pencil points in the water during the demonstration. Note that the gas bubbles result when the hydrogen atoms from the water collect around one pencil point and chlorine atoms from the salt collect around the other pencil point.