Last month was Science Fair month and I helped Zoe show the electrolysis of water. For those of that never studied, electrolysis is the use of electricity to break down molecules in liquid form into their component atoms. In this case, we are breaking done water into the component elements of oxygen and hydrogen.

The circuit is fairly simple to build.

I used two 9 volt batteries in series to create an 18V drop. I bought a few 9V battery clips and soldered them to hookup wire. I then carefully wrapped the wire around one of sharpened pencils. The graphite in a pencil makes an excellent electrode.

The solder won't really attach to the graphite well, so the wire needs to wrap around a bit and the solder acts as a cap. The electrical tape provides tension, keeping the connection.

The other end of pencil should be sharpened to expose as much graphite as possible.

When you have a tall glass of water ready, attached the battiers.

You'll see the bubbles start to form immediately. The side with more bubbles is the hydrogen side. Remember that there are two hydrogen atoms for each atom of oxygen in water.

Seeing the gas appear out of water is impressive to people.

Water itself is a poor conductor of electricity. We added a bit of salt into the water. Salt water is a much better conductor of water, so the reaction is much more prominent.

Remember that salt is sodium chloride, chorilde being chorline. When the electrolysis occurs in salt water, the salt molecules are also split, freeing up the chorline atoms to make, you guessed it, chorline gas.

So when you smell salt water during electrolysis, it smells exactly like swimming pool water.

Here's a short video to show exactly how much gas is produced from my setup:

Posted by michael at February 03, 2007 05:06 PM