Supported by:
Pencil Electrolysis
Example Indiana Science Indicators Addressed:
1.1.1 Observe, describe, draw and sort objects carefully to learn about them.
1.1.2 Investigate and make observations to seek answers to questions about the world.
3.1.4 Discuss the results of investigations and consider the explanations of others.
4.2.3 Make simple and safe electrical connections with various sockets, plugs and
terminals.
6.3.19 Investigate that materials may be composed of parts that are too small to be seen
without magnification.
Materials:
Two regular number 2 pencils Apparatus:
(remove eraser and metal part on
the ends)
2 transparent plastic cups per
group
water
table salt (NaCl)
spoon (for mixing)
1 9V battery/group
2 pieces of cardboard (enough to
cover the opening)
2 connecting wires (optional)
tape (optional)
Caution: Use only 9V batteries (direct http://www.energyquest.ca.gov/
current) for this experiment. projects/split_h2o.html
Procedure:
Sharpen each pencil at both ends.
Cut the cardboard to fit over glass.
Push the two pencils into the cardboard, about 1.5 centimeters apart.
Dissolve about a teaspoon of salt into the warm water and let sit for a while. The
salt helps conduct the electricity better in the water.
(Option 1) Using one piece of the electrical wire, connect one end on the positive
side of the battery and the other to the black graphite (the "lead" of the pencil) at
the top of the sharpened pencil. Do the same for the negative side connecting it to
the second pencil top.
(Option 2) Connect the battery to the pencil tips directly. They can be secured by
using tape or simply hold them in place.
Place the other two ends of the pencil into the salted water.
Bubble should appear
Extension:
Repeat above procedures, this time without adding salt to the water. Observe the rate of
bubble production in each cup. The increase in bubble production for the salt-water
solution supports the idea that the salt helps increase the water’s conductivity.
Background:
Water is a simple chemical made from two gases -- hydrogen and oxygen. Every
molecule of water has two atoms of hydrogen for every atom of oxygen. H2O is the
chemical formula for a molecule of water.
If an electrical current is passed through water between electrodes (the positive and
minus poles of a battery), the water is split into its two parts: oxygen and hydrogen. This
process is called electrolysis and is used in industry in many ways, such as making metals
like aluminum.
You can use electricity to split hydrogen gas out of the water similar to the process called
electrolysis.
The chemical reaction is below:
H2O(liquid) 2 parts H2(gas) + 1 part O2(gas)
The electrode where more bubbles are forming is where the hydrogen gas forms.
Sources:
California Energy Commission “H2O Analysis: Splitting Water”
http://www.energyquest.ca.gov/projects/split_h2o.html (Last accessed October 27, 2004)
Additional resources available at:
Experiments from Everyday Life, “Pencil Electrolysis”
http://www.americanchemistry.com/chemmag.nsf/WebMagazineArticle?
ReadForm&mfpk-524ny9
New Mexico Solar Energy Association, “Electrolysis: Obtaining hydrogen from water:
The Basis for a Solar-Hydrogen Economy”
http://www.nmsea.org/Curriculum/7_12/electrolysis/electrolysis.htm
