Name:_________________
Period:________________
Fuel Cell Car Lab: Qualitative Gas Analysis
Objectives:
1. Students will assemble the fuel cell car kit according to instructions and produce gases in test tubes.
2. Students will test these gases with the “pop test” and the “glow test” to determine the nature of the gas.
Background:
The most common way to obtain electricity from a combustible fuel is to burn the fuel and use the heat
produced to boil water. The steam is used to turn a turbine (sort of like a windmill). This turbine turns a
generator which generates electricity. This is how coal burning power plants work and that is where the US
gets about 55% of its electricity from. The problem with burning fuels to generate electricity is that it is not
very efficient, and it often produces large amounts of pollution and green-house gases that contribute to global
warming.
electrons pass through
motor which does work
(like spins a wheel).
A fuel cell is a device that
Figure 1:
can use a constant supply
Fuel Cell
of fuel and convert it directly
to electricity without the
need for combustion. We will
be using a special type of fuel
O2 gas enters
fuel cell here
cell today called a Proton
+
H
Exchange Membrane
+
+
O
O
H
H
H H
O
O
+
(PEM) fuel cell.
H H
H
H H
This type of fuel cell
H H
O
O
+
H H
H
H H
O
O
uses hydrogen gas as
+
H
+
+
H2 gas enters
the fuel, and it works to
H
H
H
H
+
H
fuel cell here
+
separate the electrons
H
H H
+
H
from the protons. The
H
O
H
H
+
electrons travel one way
H
H
H H
O
O
+
+
through a circuit and
H
H
H H
H
H H
O
power an electric motor.
Proton permeable
H
H2O leaves
+
The protons (H+) travel a
H
H H
membrane
fuel cell here
different path -- through the
ANODE
CATHODE
proton exchange membrane -and rejoin the electrons
Solar panel converts light energy
on the other side of the
Figure 2:
into an electric current, pumping
fuel cell where they react
Reverse
electrons backwards through the
with oxygen gas to form
fuel cell
Fuel
Cell
water as shown in Figure 1
above.
In this exercise, we will
use the fuel cell in reverse
to split water into hydrogen
gas and oxygen gas
H H
(See Figure 2 at right.)
H
This requires a power
source such as a solar
H2 gas leaves
panel or a battery.
fuel cell here
In a later experiment we
will use the fuel cell in
its more commonly used
manner to use hydrogen
gas as a fuel to power the
electric motor on the car.
H
H
H
+
H
H
H
+
H
H
H
H
H
H
H
+
H
+
H
H
H
H
H
H
H
+
+
+
O
O
O
O
O
O
+
H
O
O
+
H
+
H
H
+
O
H
O
H
+
Proton permeable
membrane
CATHODE
+
+
+
H
H
+
H
H
+
H
H
H
O2 gas leaves
fuel cell here
+
H
H
O
H
+
H
ANODE
H
O
H
H2O enters fuel
cell here
You will need the following materials:
 Safety glasses
 Solar panel
 Electric Light (60-100 watt bulb)
 Car body with fuel cell
 Syringe with tubing nozzle
1. Distilled water (Use only distilled water for experiments with the fuel cell. The water
must be free of all ions and salts or it can destroy the fuel cell. NEVER USE WATER
FROM THE TAP OR BOTTLED DRINKING WATER.)
2. Small plastic basin
3. Bunsen burner and starter
4. Wooden splints
5. Test tube
Setting up:
1. Fill the plastic basin about 2/3 full with distilled water.
2. Look at the fuel cell. Notice how one side is slightly red in color and one side is slightly
blue. It should have four tubes sticking out of it: Two short tubes with red stoppers, one
on each side at the top, and two long tubes with clear plastic nozzles, one on each
side at the bottom.
a. [The long tubes should not be attached to the hydrogen and oxygen tanks.
but if they are, gently remove one end of the tube from the fuel cell and
push the whole piece of tubing down through the tank -- it may be
stuck tight, press gently down where the tubing meets the tank. This
will free the tube from the tank. Reattach the end of the tubing
without the clear nozzle to the fuel cell.]
3. Place the ends of the long tubing in the basin of distilled water.
4. Prepare the fuel cell as follows:
a. Remove the red stopper from the short tubing on one side of the
cell.
b. Fill the syringe half-full with distilled water.
c. Insert the syringe nozzle into the short tubing as shown at right.
d. Gently push on the end of the syringe to push water through the fuel
cell.
e. When no more bubbles are seen exiting the fuel cell, remove the
syringe and recap the short tubing on the fuel cell with the red
stopper.
f. Discard the distilled water from the syringe back into the basin
g. Repeat this procedure for the other side of the fuel cell.
5. Connect the solar panel wires to the fuel cell as indicated in the figure below.
Make sure to connect the red wire to the red side of the cell and the black wire to
the blue side.
syringe with
distilled
water
red stoppers
fuel
cell
Figure 3:
preparing the
fuel cell
Figure 4: Setting up
the light
red wire
long tubes
extending
into tub of
distilled
water
Figure 5: Connecting
the solar panel to the
fuel cell
solar panel
black wire
6. Set up the light on a ring stand as shown in figure 4. Turn on the light and position it about 10 cm from the solar panel
so that the light is shining directly onto it. If the light is closer than 10 cm the heat from the bulb can damage the solar
cell.
7. After a few seconds, you should start to see gas bubbles coming from the ends of the long tubes that are under the
water in the basin
Collecting Gases and Performing the “Pop test” and the “Glow test”
1. First, just look at the bubbling rate of the gases coming out the red
side tubing compared to the blue-side tubing. Is one of them faster
than the other? Make note of this in the Data Table below.
2. Now start with the tubing coming out of the blue-colored side of the fuel
cell. (Take the other long tubing out of the water for the time being.)
3. Submerge the test tube in the basin to completely fill it with distilled
water. Then turn it upside-down (so the open end is pointing downward
as shown at right) and position the tubing so that bubbles flow into the
water-filled test tube. The test tube should be held with the opening
pointing down so that the gas will rise to the top and be collected. What
do you notice about the water level of the test tube?
4. Once the test tube is 1/3 filled with gas, lift it straight up to let the rest of
the water drain out into the basin (you may need to shake the test tube
slightly to get all the water out. Put your finger over one end and turn it
upside down and then back again to help mix the gas with the air inside.
Hold the test tube mouth downward over a flame. Do you hear a “pop”?
Record your observations in the data table below.
5. Refill the test tube with the gas from the blue side again just as you did
above. Then remove it the exact same way but this time carefully insert
a glowing wood splint (see below). What do you notice? Record your
result in the data table.
a. How to prepare a glowing wood splint: Light the end of a wood
splint with a flame. Quickly blow out the flame so that only a glowing
ember remains. If you do not see a red glowing ember, relight the tip
of the splint and blow it out again. Be very careful with the glowing
wood splint as it may flame up at any moment.
6. When you have finished both the “pop test” and the “glow test” with the
gas from the blue side, take the tubing from the blue side out of the
water and put the tubing from the red side of the fuel cell into the water.
Fill the test tube with gas from the red side just as you did above and
repeat the two tests. Record your data in the data table.
upsidedown test
tube filled
with water
blue-side red-side
tubing
tubing
Figure 6: Collecting the gases
Data analysis:
Now that we know the results of the “pop test” and the “glow test”, we can try to figure out which gas (hydrogen or oxygen)
is coming from which side. Hydrogen is a highly reactive and explosive gas. It is likely to result in a “pop” when in contact
with a flame. Oxygen is necessary for combustion and if more oxygen is present, a fire will glow more brightly. Based on
this information, write which gas you think is coming from each side of the fuel cell.
Data Table:
Gas from:
Bubbling rate
(fast/slow)
Blue side
Red side
Pop test result
Glow test result
Name of gas
Questions:
1. Write a balanced chemical reaction for the decomposition of water: ______________________________________
2. Is this reaction endothermic or exothermic? _____________
Why do you think this? ___________________________________________________________________________
3. Fill in the following blanks with E for electrical energy, C for chemical energy, L for light energy, M for mechanical
energy, S for sound energy, and H for heat energy.
It all begins with the light source which converts ___ into ___. This shines upon the solar panel which converts the
___ back into ___. Then, in the fuel cell, this ___ is converted into ___ (in the form of hydrogen and oxygen gas).
During the Pop test, this ___ is converted into ___ and ___ and ___.
4. Look back at the two diagrams on page 1. Which of these Figures (1 or 2) describes how we used the fuel cell in this
activity? _____ How can you tell? _____________________________________
5 Using that diagram, copy down the reaction happening at the cathode:
6. According to this reaction, which gas is being produced at the cathode (H2 or O2)? _______
7. Using the same diagram, copy down the reaction happening at the anode:
8. According to this reaction, which gas is being produced at the anode (H2 or O2)? _______
9. So when the fuel cell is being used like this, is the red side of the cell the anode or the cathode? ____________ How
can you tell? ____________________________________ What is the blue side? ______________________________
10. A reaction that takes in electrons (has e- on the reactant side of the equation) is known as a “reduction” reaction. A
reaction that gives off electrons (has e- on the product side) is known as an “oxidation” reaction. What kind of reaction is
happening at the cathode? _______________ and at the anode? _____________
11. Label the two reactions you wrote above in #5 and #7: “oxidation” and “reduction”.
12. Notice how the reduction reaction takes in 2 e-, but the oxidation reaction gives off 4 e-. To balance this out, multiply
the entire reduction reaction above by 2 and rewrite it here:
13. Just to have it nearby, rewrite the oxid. reaction above just as it is:________________________
14. Now add these two equations together, writing all the reactants on the left and all the products on the right. (This is
known as a redox equation: red + ox = redox).
15. Anything that occurs on both sides of the equation above should be canceled out. Draw a line through those things,
and rewrite what is left:
16. How does you answer for #15 compare with your answer for #1? _______________________________
17. In the “pop test”, oxygen from the air combines with hydrogen and the energy released causes a “pop”. Write a
balanced chemical reaction for this process. ________________________________________________
18. How does you answer for #17 compare with your answer for #15? _______________________________