Water Breakdown

You may know that water is also known as H₂O, with two hydrogen and one oxygen atoms. We think of water as being very stable, and not very likely to break down into hydrogen and oxygen. But with a little help from a battery, you can do just that!

What you'll need:
Small glass or clear plastic cup
Water
9-volt battery
2 pencil leads (actually a form of carbon called graphite)
2 short pieces of wire with the insulation stripped off the ends

4 alligator clips

Attach the clips to each end of a wire piece. Fill the glass with water and put the pencil lead electrodes in the water so that they do not touch each other. Clip one wire onto one electrode, and the other clip to the second lead. Attached the free ends to the terminals on top of the 9-volt battery. This gets a current flowing through the water. Watch carefully - what do you see happening?

After a minute or so, you will notice some bubbles of gas forming around each electrode. One of the electrodes will be generating about twice as much gas as the other. This is the electrode creating hydrogen; the other gas is oxygen!

This is an example of a process called electrolysis. As you know, water doesn't just break down like this normally. You have to put energy into the system, and in this case, the flowing electrons from the battery provide that energy. So electrons aren't just useful for powering your toys and other electronic gadgets - they can rip molecules apart, too!