activity page will offer:
introduction to the use of hydrogen as an automobile power source
hands-on activity in generating hydrogen
opportunity to bleach food coloring
Whether it is to be used as a clean-burning fuel or as a reactant
in fuel cells, sources of hydrogen must be identified. The good
news is that hydrogen is all around, especially in water. Every
molecule of water contains two atoms of hydrogen. Freed from the
water molecule, hydrogen atoms can combine together to form hydrogen
gas. In this activity, you'll generate hydrogen gas by splitting
water in a process called electrolysis.
Connecting wires with alligator clips at both ends
beaker (or large jar)
#2 graphite pencils (With graphite exposed at both ends)*
CAUTION: If students extend the activity to include steps 7-10,
remind them of the dangers of inhaling chlorine gas. These steps
should only be performed in a fumehood.
*Teacher note: Prior to the activity, obtain a set of #2 pencils
with eraser ends that have been removed. Use a pencil sharpener
to expose graphite at both ends of the pencil. Then, dull the
pencil points prior to distributing them to students.
Work in teams of two. Cut out a section of cardboard that is larger
than the mouth of the 400-mL beaker.
insert two prepared pencils into side-by-side slots punched into
the cardboard. Make sure the holes are small enough to hold the
pencils tightly in place.
Fill the beaker halfway with tap water.
the cardboard on top of the beaker. Adjust the heights of the
pencils so that the exposed graphite is near the bottom of the
connecting wires to attach the top of each pencil to one of the
Over time, you'll observe gas bubbles collecting on both of the
exposed graphite shafts of the immersed pencils.
a small beaker halfway with water and add about 1/2 teaspoon of
Add a drop of blue food coloring and mix up the solution.
Use a dropper to transfer about one mL to this dyed saline solution
to the surface of a sheet of wax paper. Place this sheet of paper
in a fumehood.
Within the fumehood, position the exposed pencil tips so they
extend into the liquid. Wait a few moments and you will observe
both the appearance of bubbles and a change in the dye's intensity.
This change in color is caused by the bleaching effect of generated
CAUTION: Do not inhale the generated gas. Chlorine is an irritant.
Consider the polarity of the ions released when the water decomposed.
Which gas collected at the cathode? Why?
were there more hydrogen bubbles than oxygen bubbles?
did the chlorine gas generated in step 10 come from?
In addition to generating free chlorine gas, how
might adding a "pinch" of salt affect the decomposition of water?
the process by which water is decomposed into hydrogen and oxygen
gas. Then, compare and contrast it with the fuel cell process in
which these same gases are combined to produce water. Using toothpicks
and gumdrops, construct a representation of this reversible reaction.
People often connect hydrogen gas with the Hindenburg disaster.
The Hindenburg was a German airship that was filled with hydrogen
gas. It exploded at its mooring post in Lake Hurst, New Jersey on
May 6, 1937. See a Quicktime video and learn
more about this disaster at http://www.vidicom-tv.com/tohiburg.htm.
the Lead Out
Although the inner part of a pencil is commonly called "lead," it's
not. It's a carbon compound called graphite. Graphite is a soft
carbon material that easily breaks apart in molecular sheets. Use
Internet and print resources to find out why a pencil's graphite
is mistaken for lead. You
can learn more about the history of pencils and their components
at the URL: http://www.museums.org.za/sang/exhib/tri_arch/pencil.htm
Fuel Cells Work
A great and easy-to-follow introduction to the science of fuel cells.
of Water and Fuel Cell Operation
The chemistry and thermodynamics of electrolysis of water and fuel
Fuel Cells & Infrastructure Technologies Program
Department of Energy site that includes information about hydrogen
and fuel cells.
Advisors for this Guide:
Suzanne Panico, Science Teacher Mentor, Cambridge Public Schools,
Anne E. Jones, Science Department, Wayland Middle School, Wayland,
Gary Pinkall, Middle School Science Teacher, Great Bend Public Schools,
Great Bend, KS
Cam Bennet Physics/Math Instructor Dauphin Regional Comprehensive
Secondary School Dauphin, MB Canada