NOVA scienceNOW: Fuel Cells
Write the definition of energy on the board. (Energy is the capacity to
do work.) Make a two-column chart on the board similar to the one below and
have students brainstorm examples for each form of energy.
Form of Energy
being metabolized or fuel being burned
from light bulb
A fuel cell is a type of battery and has the same parts as a household battery.
From the Web or in a textbook, find a diagram of a battery for students to look
at. Ask students how they think a battery generates electricity. Discuss the
A battery converts chemical energy into electrical energy.
Batteries have two electrodes—an electron donor and an electron
acceptor. The anode (the electron donor) is made of a material
that gives up electrons easily, and the cathode (the electron
acceptor) is made of a material that accepts electrons easily.
The anode and cathode are surrounded by a mix of chemicals
(called electrolytes) that help produce an electric charge.
Different kinds of batteries use different electrolytes.
Ask students to describe characteristics important for batteries (e.g.,
long-lasting, inexpensive, light in weight, safe, easy to use, and
Similar to household batteries, fuel cells power electrical circuits. Remind
students that electricity is the flow of electrons and that a
circuit provides a path for electrons to flow from the anode to
the cathode. On the board, draw a simple circuit that includes a
battery, bulb, and wires. (Alternatively, find a circuit diagram on the Web or
in a textbook.) Trace how electrons flow through the circuit. (Electrons
leave the battery's negative, electron-donating terminal [anode], travel
through the wires toward the positive, electron-accepting terminal
[cathode]. Along the way, they pass through the filament in the
bulb.) Have students annotate the diagram to show where energy is being
converted from one form to another.
of the Circuit
Conversion Taking Place
Chemical to electrical
as a waste product
to light and heat
Fuel cells use hydrogen and oxygen to generate electricity. Ask, "What is
the most common substance that contains hydrogen and oxygen?" (Water)
Ask students to name some gases that are presently used as a fuel source
(e.g., propane, natural gas) and the precautions that must be taken when
using them as a fuel. (They require proper handling and storage to prevent
As an extension for students studying chemistry, have them locate hydrogen and
oxygen on the periodic table and state their atomic mass and number. Draw
students' attention to the number of electrons in the outer shell of both
elements and discuss how these electrons influence their reactivity. (Both
gases are highly reactive. To achieve a more stable atomic state, hydrogen
readily donates its electron and oxygen readily accepts two electrons.)
Discuss how hydrogen and oxygen bond covalently to produce water.
Have students list ways a fuel cell and household battery are alike and
different. (Batteries and fuel cells both have anodes and cathodes and
produce electricity. However, their chemicals differ.) Print the NOVA
scienceNOW fuel cell diagram
(pbs.org/wgbh/nova/sciencenow/3210/01-fcw.html) and discuss with
students how it works. Divide the class into teams and ask them to construct
model fuel cells that include an anode, cathode,
proton-exchange membrane (conducts positively charged ions and blocks
electrons), and catalyst (material that facilitates the reaction between
oxygen and hydrogen). Supply teams with common materials to make their models
(e.g., foam sheets, cardboard, plastic wrap, foil, pipe cleaners, and
string). Have teams display their models and explain how their fuel cells
Have students visit the clickable fuel-cell car on the NOVA scienceNOW
Web site (pbs.org/wgbh/nova/sciencenow/3210/01.html), or download the
printable version of the car. Ask student pairs to identify the energy
conversions that occur in a fuel-cell car and share their list of conversions.
Draw a two-column chart on the board and have students brainstorm the
pros and cons of hydrogen fuel cells, including where they would be most and
least viable. (Providing a reliable supply of hydrogen and oxygen for
small-scale or mobile uses, such as cars, necessitates solving a host of
storage and distribution issues related to these reactive gases. These include
developing a system of high-pressure tanks and pipelines, finding convenient
ways to fill a fuel cell's gas tanks, and minimizing the risk of burns and
explosions. Producing hydrogen and oxygen on-site avoids many of the
challenges associated with transporting and storing these gases.) Assign
students a place where fuel cells could be used: a car, train, home, apartment
complex, or factory. Ask them to create an advertising poster that promotes the
use of fuel cells as an energy source for their assigned location.
4. Robert Krulwich made the statement that there is plenty of hydrogen on
Earth, but that it is always stuck to other stuff (i.e., other atoms). "It's in
the foods we eat, the fuels we burn, the beverages we drink, and the plastics
and plant materials we use to construct our world. In fact, hydrogen is so
chemically reactive that it does not naturally occur as a pure element on
Earth." To give students a sense of how challenging it is to produce hydrogen
and oxygen by splitting water, have them do one of the electrolysis
activities suggested in the Links and Books section. These include:
Collect oxygen and hydrogen using a battery or DC power supply to provide
Collect oxygen and hydrogen using a hand-crank generator to provide the
energy. Students will experience—and likely be surprised by—just
how much energy is required to produce a small amount of gas.
the History of Fuel Cells
Explains how different fuel cells work and offers historical information about
each type, including proton-exchange membranes.
Fuel Cells 2000
Offers information on fuel-cell basics and includes a section on hydrogen fuel
Scientific American Frontiers—Electrolysis activity
Presents an electrolysis activity recommended for grades 9-12.
Energy by Marek Walisiewicz. Dorling Kindersley, 2002.
Focuses on the future of energy technology, including hydrogen fuel cells.
Jack Challoner. Dorling Kindersley, 1998.
Provides an overview of energy and how it is used.