Simple Electrolysis

Water is made of oxygen atoms and hydrogen atoms combined.  They are chemically bonded together.  But you can break water molecules apart into oxygen atoms and hydrogen atoms with this simple electrolysis experiment.waterYou need:

  • a small glass or jar
  • a 9 volt battery
  • copper wire
  • 4 alligator clips
  • 2 pieces of mechanical pencil lead
  • scotch tape
  • water
  1. Fill your glass with about 2 inches of water.
  2. Tape the 2 pieces of pencil lead to the inside of the glass.  Make sure the bottoms are touching the water and the tops are above the glass rim.
  3. Now attach the copper wire (with ends exposed) to the lead with the alligator clips, and also to each side of a 9 volt battery with alligator clips like this:


If you look really closely at the ends of the pencil lead that are in the water, you will see tiny bubbles form all along it.  The lead, actually made of carbon, is acting like an electrode.  Carbon and water both conduct electricity, so this is actually making a complete electrical circuit.  In the process, the hydrogen and oxygen molecules from the water are separated.  Look closely at the ends of the pencil lead in the water:

See the bubbles?  One of those electrodes (our pencil lead) has hydrogen bubbles and the other electrode has oxygen bubbles forming on it.  The water molecules are quietly being broken apart.  That’s called electrolysis.

Additional Layers

  • Hydrogen and oxygen aren’t so quiet when they come TOGETHER instead of break APART.  Find out what happens when they combine. (Note: this can’t happen at room temperature.  The reaction takes more energy than that)
  • Scientists use hydrogen to fuel rockets; they’d like to be able to make a hydrogen fuel for a car engine that is inexpensive and light enough for us to use in cars.  It would be clean fuel, but it’s way too expensive to be a feasible solution right now.
  • Hydrogen is the most plentiful element in the universe.  Make a list of other things that include hydrogen besides water.
  • Stars are made of hydrogen.  Go observe and map the night sky tonight.
  • Hydrogen gas by itself is very explosive.  It’s what was inside of the Hindenburg blimp that caught on fire and crashed in New Jersey.  Do you think they still use hydrogen inside of blimps?
Image courtesy of Nationaal Archief @ Flickr Commons, public domain.

Leave a Reply

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.