The Electrolysis of Water is another term for the action of the decomposition of water using an electrical current -- it is not a method of aquatic hair removal.
By passing a small amount of electrical current through a quantity of water what has been slightly doped with a conductor (usually salt or food colouring), an electron flow is formed between the anode and cathode -- and the resulting reaction liberates the individual atoms from the H2O molecule.
Want to try this at home?
Of course you do.
I had a science itch last night, so I'll share my prodecure with you all. Sure, it's a bit adolescent, but it makes bubbles! Everyone can appreciate bubbles!
The first thing you'll need is a quantitiy of water; I prefer a wide-mouth mason jar, but I'm sure most anything non-metal would work. Fill it with water and add a small amount of salt, in the ratio of a few parts per thousand (hereafter 'a pinch'). Next you'll need the controller from the electric train set your uncle Herb gave you when you were 7 years old. Any DC source should work, but I prefer train transformers because their voltage is variable. Two lengths of copper wire and two test-tubes should complete our kit.
Here's where it gets tricky -- you need to put the test tubes upside-down in the water, while they are filled with water, so there is no air in them, and then you need to find a way to continue holding the that way. Then take your anode and cathode (your two pieces of copper wire, genius) and make some 90-degree (or so) crooks in them so the bared ends (you bared the ends, right?) are poking up into the mouths of the water-filled upside-down test tubes; but not to far, because we still need an easy path for electron flow between them. Then connect the other ends of you wire to the positive (+) and negative (-) terminals of your power source.
Now the fun begins. Turn on your Power source, and watch as little bubbles form on your electrodes and slowly bubble up into your test tubes. Obviouly, since the forumla for water is "H2O", the electrode with most bubbles is where the hydrogen is being collected. The ratio will be "stoichiometric", meaning it will be the same ratio as occured in the molecule.
You can't really do to much with this, because the amount of the gasses you're collecting is very minute -- you might be able to make a small fireball out of your hydrogen, or get a quick high from the oxygen; but don't count on it. You could use a larger power supply, but I wouldn't recommend it unless you're a chemistry major or an EE.
One more thing -- because this is the same process they use for purifying Copper, your Cathode will slowly disolve as it's Copper molecules move from it to the Anode.
Alex.Tan: I am not a chemist. All I know it that one of the electrode *does* disolve, whilst the other rapidly oxides. If someone can explain why this happens in in real terms, that would be great. I was hunting over the net all day trying to figure it out with no avail. Anyway, bubbles are fun :)