Standard Statements

3.1.10a - Discriminate among the concepts of systems, subsystems, feedback and control in solving technological problems.
3.1.10d - Apply scale as a way of relating concepts and ideas to one another by some measure.
3.1.12e - Evaluate change in nature, physical systems, and man-made systems.
3.2.10b - Apply process knowledge and organize scientific and technological phenomena in varied ways.
3.2.12c - Apply the elements of scientific inquiry to solve multi-step problems.
3.2.12d - Analyze and use the technological design process to solve problems.
3.4.12a - Apply concepts about the structure and properties of matter.
3.4.12b - Apply and analyze energy sources and conversions and their relationship to heat and temperature.
3.8.12a - Synthesize and evaluate the interactions and constraints of science and technology on society.
3.8.10c - Evaluate the possibilities, consequences, and impacts of scientific and technological solutions.

Content Objectives

1. A fuel cell uses hydrogen and oxygen to produce an electrical current.
2. Hydrolysis is the process whereby which water molecules are split into hydrogen and oxygen in a two to one stoichiometric ratio.
3. Reverse hydrolysis is the fuel cell reaction and is the process whereby which hydrogen molecules and oxygen molecules combine to give water and energy.
4. Hydrolysis requires an energy input to drive it forward, whereas reverse hydrolysis proceeds on its own accord and yields an energy output.
5. There are qualitative tests that can be performed to demonstrate the presence of hydrogen and oxygen gas.
6. A reversible fuel cell performs both hydrolysis and reverse hydrolysis, but not all fuel cells are reversible
7. Platinum is the catalyst used in fuel cells.
8. Despite their modern, high-tech appeal, the idea of a fuel cell has been around for over 150 years.
9. Fuel cells first had the name of “gas batteries.”
10. Scientific research on fuel cells has been heavily influenced over the years by societal and economic factors.
11. Scientific research is not always a means to cut-and-dry conclusions on which all scientists agree.
12. There is an imperfect and human side to science that is inevitable.
13. Fuel cell technologies only eliminate dilemmas with fossil fuels when the hydrogen production does not involve using fossil fuels.

Process Objectives

1. Generate questions about a technological device they see in action.
2. Construct explanations from observations made about a reversible fuel cell as it operates.
3. Brainstorm about what is needed to answer questions about a reversible fuel cell.
4. Write balanced reactions for hydrolysis and reverse hydrolysis while keeping track of molecules that exist as diatomic entities.
5. Deduce a stoichiometric ratio from a balanced chemical reaction.
6. Propose and carry out a procedure to provide evidence that the reversible fuel cell produces hydrogen and oxygen gas in a 2:1 ratio while in electrolyzer mode.
7. Synthesize pieces of evidence into a cohesive argument.
8. Provide reasoning behind why the reversible fuel cell is considered to be “reversible.”
9. Explain how the law of conservation of mass is obeyed with the reversible fuel cell, even though it appears that none of the water initially placed in the fuel cell “gets used up.”
10. Construct a diagram of a fuel cell and describe how it works after viewing online animated tutorials.

Assessment Strategies

1. Completion of Part 1 as a pre-assessment, and then completion of Part 8 as a post-assessment.
2. Completion of essay at the end of Part 2 where students synthesize evidence and make a case for hydrolysis.
3. Class discussions held at the specified points of the activity.
4. Completion of the entire student handout, over several days of instruction.

Suggested Level

Grades 9-12

Standard Category

3.1 - Unifying Themes

3.2 - Inquiry and Design

3.4 - Physical Science

3.8 - Science, Technology and Human Endeavors

Materials

• Heliocentris hydro-Genius TM reversible hydrogen fuel cell
• Heliocentris “HYCO” Model Car chassis
• Distilled water (approx.100 mL)
• Solar panel OR 2V rechargeable battery, OR two 1.5V AA batteries
• Clean beakers (presence of any contaminants will harm the fuel cell during transfer of water from beaker to fuel cell)
• Stopwatch
• Sunlight, halogen lamp, or filament lamp (only if using the solar panel)
• Patch Cords / Cables (one red, one black)

• Overhead projector and screen
• 2 small test tubes
• Matches (or any device that will light a wooden splint)
• Wooden splint
• Overhead transparencies provided in the Teacher Notes copied onto transparency film

Instructional Strategies

Procedures

Part 1 (2, 45-min class periods)

1. Have the students read the overview provided at the beginning of their student handout.
2. Ask the students to spend a few minutes thinking about what a fuel cell is and what it does, and have them record what they think in the box provided in their student handout.
3. Invite students to share what they think in a class discussion. You may want to record student responses on the board, or assign a student to this task.
4. Tell the students that now you will be providing them with a special kind of fuel cell for this activity so that they will be able to learn what a fuel cell is, what it does, and how it works. Have an example of a reversible fuel cell to show the students as you are talking. Explain to the students that these fuel cells must be handled carefully, as they are expensive.
5. Warn the students that only distilled water should be used in these fuel cells. Tap water or any other substance will destroy the fuel cells and their use is strictly prohibited.
6. Project the overhead of the diagram of the basic parts of the fuel cell onto a projector screen. Point out where the tip-jacks, overflow compartments, and storage chambers are on the reversible fuel cell. Tell the students that the directions in Part 1 also generically refer to the storage and overflow compartments as “upper and lower compartments,” which distinction should be obvious.
7. Go over the directions provided in their handout for filling the fuel cell with distilled water. A short demonstration on how to do this may be appropriate here. Make sure you have the distilled water stations clearly marked.
8. Decide how you want the students to supply power to the fuel cell (using a solar panel, a 2V rechargeable battery, or two 1.5V batteries in series), and instruct them to circle the appropriate set of directions in their handout.
9. Divide the class up into groups of three, four, or five. Have all students wash their hands with warm, soapy water and dry completely. Once they have made sure that their working surface / space is also clean and free from all other chemicals or debris, distribute a Heliocentris hydro-Genius TM reversible fuel cell to each group, and instruct them to follow the directions in their student handout for the remainder of Part 1. Instruct the students to stop when the handout tells them to participate in a class discussion (item #9).
10. At the appropriate place in Part 1 (see student handout), conduct a class discussion where students share the questions they are generating about their reversible fuel cell. Again, you may want to write these on the board.
11. Assign the completion of item #10 for homework.

Part 2 (2, 45-min class periods)

1. Recap what the students did in Part 1. Have the students share some of the observations they made in Part 1 during a brief class discussion. (Refer to the student handout for observations they were asked to record and ideas about what you could ask.)
2. Tell the students that now they will conduct some investigations that are intended to help them learn a little bit more about what is going on with their reversible fuel cells.
3. Instruct the students to read about hydrolysis and reverse hydrolysis in the Additional Resources section of their handout, and then have them follow the directions for item #12 individually.
4. Monitor student progress on this task (writing balanced chemical equations for hydrolysis and reverse hydrolysis), and then tailor a brief lecture on the correct balanced reactions accordingly. (You may need to tell / remind students of diatomic molecules, how to balance equations, etc.)
5. Have the students work in groups to devise and carry out a procedure to gain evidence that hydrogen and oxygen are being produced in a 2:1 ratio while the fuel cell is in hydrolysis mode (receiving power from an external energy source). Check each group’s proposed procedure before they carry it out.
6. Allow the students to share their procedures and the data they collected in a class discussion. Have the students answer the questions in their handout about this discussion.
7. Have the students read about the qualitative gas tests for hydrogen and oxygen in the Additional Resources section of their handout. Perform these tests as a demonstration using the directions provided in the teacher notes.
8. Assign the remainder of Part 2 as a homework (or in-class) assignment. If desired, collect the essays that students are asked to construct at the end of Part 2.

Part 3 (30-min)

1. Explain that in Part 2 the students obtained evidence that hydrogen and oxygen gases are indeed being produced by the fuel cell with it is supplied with power. Tell them that in Part 3, they will try to make more sense of some of the things they saw in Part 1.
2. Have the students work in groups to complete the questions in Part 3.
3. After the students have tried to make sense of it on their own, discuss why the fuel cell is considered “reversible” (item #22). Be sure the students understand that not all fuel cells are reversible. The questions asking them about why the water gets displaced into the upper compartments (#23) and why it ends up back in the lower compartments (#24) are preparing the students to discuss these phenomena as a class in Part 4.

Part 4 (1, 45-min class period)

1. Have a class discussion about why the water ends up where it does when the fuel cell is connected to a power source and when it powers the car. (Items #25 and #26). Tell the students to draw on what their responses in Part 3.
2. Make sure the students understand the last item (#32) in Part 4 regarding the law of conservation of mass. Although it appears that the same amount of water you filled the reversible fuel cell with ends up in the upper compartments and then back in the lower compartments, there is indeed a difference, albeit very small.
3. Remind the students that equal quantities of gases and liquids occupy vastly different volumes. Gases occupy much larger volumes. Splitting less than a droplet size amount of water generates the amount of hydrogen and oxygen gas that the students see being generated (about 15 mL).

Part 5 (1, 45-min class period)

1. Assign the tasks in Part 5 either as a homework or an in-class assignment. If completed in class, the students will need access to computers with the internet.
2. Use the overheads provided in the teacher notes that depict hydrolysis and reverse hydrolysis in the reversible fuel cell to review what the students learned on the internet about how fuel cells work. Vary the depth of chemistry coverage according to the abilities of your class.

Part 6 (20-min)

1. Assign the reading tasks in Part 6 either as a homework or an in-class assignment. Review the questions as a class, placing particular emphasis on the questions dealing with the nature of science.

Part 7 (1, 45-min class period)

1. Project the overhead provided in the teacher notes of the diagram showing how hydrogen can be clean, sustainable, and renewable if fossil fuels are not used.
2. As a class discuss the following the meaning of the following quote (students have it printed in their handout):
   Some futurists envision an electrolysis box in every garage, producing hydrogen from tap water. The catch is that electrolysis requires electricity. Lots of it. And if that electricity is being produced in the conventional fashion—from fossil fuels—then again we're just running in place in terms of producing clean energy.
3. Help the students to understand that using fuel cells does not guarantee a clean, sustainable future. An electrolyzer powered by the sun, wind, or water power can produce hydrogen from water without using fossil fuels. This hydrogen can be used in a fuel cell, where it recombines with oxygen to produce water once again. This creates a closed system. Hydrogen produced and used in this fashion is clean, sustainable, and renewable.
4. Have the students summarize the class discussion in the appropriate area of their handout.
5. Assign the remainder of Part 7 either as homework or as an in-class assignment.

Part 8 (Variable)

1. Have the students complete Part 8 as a post-assessment activity.

Hydrogen: Future Fuel? On the Road to a Hydrogen Economy,” ResearchPennState. http://www.rps.psu.edu/hydrogen/unbound.html