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This
activity page will offer:
- An
introduction to the use of hydrogen as an automobile power source
- A
hands-on activity in generating hydrogen through electrolysis
Getting
Hydrogen
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.
Materials
-
Connecting wires with alligator clips at both ends
- 400
mL beaker (or large jar)
- Scrap
cardboard
- Two
#2 graphite pencils (With graphite exposed at both ends)*
- One
9-volt battery
*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.
Procedure
Basic
Prototype
-
Work in teams of two. Cut out a section of cardboard that is larger
than the mouth of the 400-mL beaker.
-
Carefully punch two side-by-side holes in the center of the cardboard.
Make sure the holes are small enough to hold the pencils tightly
in place.
-
Insert two prepared pencils (graphite exposed on either end) into
the slots.
- Fill
the beaker halfway with tap water.
-
Position the cardboard on top of the beaker. Adjust the heights
of the pencils so that the exposed graphite is near the bottom
of the beaker.
-
Use connecting wires to attach the top of each pencil to one of
the 9-volt terminals.
- Over
time, you'll observe the generation of gas bubbles collecting
on both of the graphite shafts of the immersed pencils.
Questions
-
What device supplied the energy needed to split the water molecule
into its component atoms?
-
What are the components of water that are released during its
decomposition?
- Why
did you need to expose graphite on both ends of each pencil?
Inferring
Why didn't gas bubbles collect along the wooden
shaft of the pencil?
Make
a Model
Consider
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.
Hindenberg
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.
Getting
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
Web
Connection
How
Fuel Cells Work
http://auto.howstuffworks.com/fuel-cell.htm
A great and easy-to-follow introduction to the science of fuel cells.
Fuel
Cell Bus Programs Worldwide
http://www.cleanairnet.org/infopool/1411/propertyvalue-19516.html
A site on the global profile and use of fuel cell buses.
Hydrogen,
Fuel Cells & Infrastructure Technologies Program
http://www.eere.energy.gov/hydrogenandfuelcells/
Department of Energy site that includes information about hydrogen
and fuel cells.
Academic
Advisors for this Guide:
Suzanne Panico, Science Teacher Mentor, Cambridge Public Schools,
Cambridge, MA
Anne E. Jones, Science Department, Wayland Middle School, Wayland,
MA
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
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