The Fuel of the Future – On Earth and Beyond
Hydrogen as an energy source
Hydrogen, the lightest element, may someday replace heavier compounds as a source of energy for
transportation and many other applications. Although low-cost technology to allow this odorless, colorless gas
to be collected and used may be decades away, hydrogen’s potential to be a clean energy source has some
people hopeful about a future “hydrogen economy” that would not rely on fossil fuels. Finding sources of
hydrogen fuel is harder than you might think. Although hydrogen is the most abundant material in the universe,
very little of it exists in free form in our atmosphere. It must be extracted from other compounds. Natural gas
and methanol provide much of the raw material for hydrogen today. Another source is water (H2O). The
hydrogen and oxygen in water can be dissociated with an electric current in a process called electrolysis.
Making’ Hydrogen
Electrolysis uses electrical energy to separate the hydrogen and oxygen atoms in water molecules. The electrical
energy can come from any electricity source, including solar energy. Some scientists envision a future in which
large arrays of solar panels will provide this electric current.
Fuel cells
Another mechanism for producing energy using hydrogen gas is the fuel cell. A fuel cell uses hydrogen to
produce an electric current. A fuel cell is like a battery—it has electrodes, electrolyte, and positive and negative
terminals. But it produces electric current continuously rather than recharging and storing chemical energy. Fuel
cells require no recharging. As long as fuel and air are supplied, they can continue to produce energy
indefinitely. The chemical process can be more efficient than combustion because it does not waste as much
energy in creating heat. A fuel cell can be about twice as efficient as a gasoline-fueled internal combustion
engine, and its primary by-product is water.
Fuel cells are routinely used in space flight, and today space shuttles use fuel cells to power such things as
computers, life-support systems, and lighting. In addition, the cells do double duty, synthesizing pure water for
the astronauts to drink and use.
When fueled with hydrogen and air (or oxygen) the cells provide power without chemical emissions. However,
they tend to be heavy, and extracting and storing hydrogen as a fuel is still expensive. So, fuel cells are
primarily used where their characteristics are more important than their price tag—as in the self-sufficient,
enclosed world inside a shuttlecraft or space station.
Fuel cells can be used wherever electricity is needed and can be used to power mobile phones, cars, houses, or
laptops. Miniature fuel cells are being designed for use in small portable devices like an iPod. Efficiency,
cleanliness, quiet operation, and abundant renewable fuel supply may promote widespread fuel cell use in the
future, including as a power source for personal transportation. However, the research needed to make this
practical to general society is still in development.
Check out http://www.lanl.gov/mst/mst11/animation.htm to examine the structure and basic function of fuel
cells.
The Fuel of the Future – On Earth and Beyond
Electrolysis – Background
An electrode is a conductor in a circuit that carries electrons to or from a substance. The negative electrode, at
which electrons are produced, is called the anode. The electrode at which electrons are consumed is the
cathode and is labeled as the positive electrode.
Electrolysis can be used to demonstrate the opposite process to that occurring in a battery: how electrical energy
can be converted to chemical energy. Electrolysis means passing an electric current through a solution to cause
chemical decomposition. The container in which electrolysis is carried out is called an electrolytic cell. An
electric current passing through an electrolytic cell can trigger chemical reactions that heat alone cannot initiate.
Electrolysis only occurs when enough electrically charged ions are present in an electrolyte to carry an electric
current. Distilled water does not conduct electric current, because distilled water contains no ions of dissolved
salts or minerals. However, the presence of a small amount of an electrolyte, such as sodium chloride, allows
water to conduct electricity. Under these conditions, water (H2O) can be separated into hydrogen and oxygen.
Electrons flow from the anode to the cathode. When a current is passed through a salt-water electrolyte,
positively charged hydrogen ions (H+) are drawn to the anode. At the anode they gain an electron and become
hydrogen atoms (H). Pairs of hydrogen atoms then combine to form molecules of hydrogen gas (H2), which
bubbles up from the anode. Similarly, oxygen gas (O2) is produced at the cathode side of the electrolytic cell by
a process involving the loss of electrons.
Part A: Initial Investigation
Introduction: This activity is designed for you to investigate a method to produce oxygen and hydrogen from
water. The insight gained from this investigation should help you address some of the challenges you might face
when planning your space mission. In particular, the generation of oxygen for human respiration and hydrogen
as a potential fuel source in fuel cells.
Problem: Does the electrolysis of water produce greater quantities of oxygen or of hydrogen?
Hypothesis: Write a statement that answers the problem.
Materials
goggles or eye protection
DC power source
two electrical wires
two test tubes
water
250 ml beaker
150 ml distilled water
5 grams of sodium sulphate
wooden splints
stopwatch
Procedure
1.
2.
3.
4.
Put on your eye protection.
Fill a 250 ml beaker with distilled water to within 3 cm from the top.
Add 5 g of sodium sulphate to the beaker and set aside the remaining 10 grams.
Assemble the electrolytic cell as demonstrated by your teacher. It should resemble the apparatus shown
in Figure 2 on page 52 of your textbook. Be sure that the switch of the power source is in the off
position. Set the voltage dial to the maximum.
5. Have your teacher check your assembly before proceeding.
6. Turn on the switch and record your qualitative observations. Turn off the switch after 10 minutes have
elapsed.
7. Compare the quantities of gases produced in each cylinder
Analysis
1. What is the identity of the gases in each test tube? Explain.
2. Can you think of a possible explanation for the differences in the volumes produced?
Conclusion: Write a concluding statement for this investigation. Be sure to address the problem and your
hypothesis.
Part B: Exploring Electrolysis – Design your own investigations
Based on your initial investigation and using the Scientific Inquiry (pgs. 526-527) section of the Skills
Handbook design an experiment to test ONE of the following questions:
Problem 2: What effect does increasing the circuit voltage have on the rate of gas production?
Problem 3: What effect does increasing the concentration of the electrolyte have on the rate of gas production?
Problem 4: Which electrolyte, potassium iodide or sodium sulfate, is most suitable for the production of oxygen
and hydrogen gas?
You must write a hypothesis, a step by step procedure and create data tables for recording your observations
before conducting the investigation.
Communicating your results
Using the Communicating (pgs. 564-565) section of your textbook as a guide write a formal, typewritten report
which includes the following sections:
a.
b.
c.
d.
e.
f.
g.
h.
i.
j.
Cover page
Title
Introduction
Problems you investigated
Hypothesis
Materials
Diagram of the apparatus
Numbered procedure
Qualitative Observations – Data tables
Conclusion
You should write one lab report that presents the findings of all the questions that you investigated. Check the
rubric for specific expectations for each section of the report.