Metals and Hydrogen Cars (High School Chemistry)

Lesson Summary

This is an approximately week long lesson aimed at high school chemistry.  The chemistry content that is used concerns heats of reaction, activation energy diagrams, and Gibbs Free Energy.  The students will use and study these concepts in the context of the use of hydrogen in vehicles.

The progress of the lesson is from a brief introduction to hydrogen technology, then into looking at a couple of endothermic or exothermic reactions. Following that, the students are introduced via a lecture to activation and Gibbs Free Energy.  Using that knowledge, they are then asked to generalize their knowledge to the area of hydrogen cars and possible metals that could be used.  Groups construct a ranking for various metals and finally the class decides which metal would be the most likely candidate for future research. 

Teacher notes:
I felt overall that this lesson worked, but there were some things that should be changed.  First, I think the students need to be given a goal at the beginning to have something to focus their attentions.  I did not do that, and throughout the lesson I think students had trouble connecting the various pieces of knowledge because they hadn't been trying to think about them in terms of a hydrogen car as they learned it.

Second, in the third and fourth parts of the lesson, students need to be monitored very closely to make sure they are understanding.  If not, then class discussions would be a good way to make sure everyone is able to see what they need to do.

Also, I feel that this lesson is a bit advanced for a regular chem course.  Our honors would do it as a regular lesson, but in regular chemistry, this is an extension beyond where we normally go.  It can fit into the students' learning, but it needs to be carefully done so that they don't get overwhelmed.

5 E's Lesson Plan
Description of each section of the 5E model
Teacher Lessons
State Standard Indicators for each activity
I Engagement:
This activity captures the students' attention, stimulates their thinking, and helps them to access prior knowledge

Why investigate Metal Hydrides?

In order to grab the students' interest, they will watch a video about hydrogen fuels and where hydrogen comes from.  The video was made by PBS and Scientific American and is a little under 30 min in length.  After the video, the students can discuss in small groups their reaction to the video and what difficulties they see for use of hydrogen in the near future.  If there is time, there is also a second short video made by Nova that can be useful.
Chemical Thermodynamics 7bInvestigation&Experimentation-Grades 9 to 12- 1lInvestigation&Experimentation-Grades 9 to 12- 1m
II Exploration:
In this section students are given time to think, plan, investigate, collect and organize information.

Experiment!

Here, students will perform 1-2 experiments (depending on time) exploring exothermic and endothermic reactions.  From their investigations, they will calculate the heats of the reactions.  Either both reactions can be done by a group of 4, or students can be split up and share their results at the end.

When acetic acid reacts with sodium carbonate, an endothermic reaction happens.  And when Copper sulfate reacts with zinc metal, an exothermic reaction happens.  By submerging a test tube of the reaction in a styrofoam cup of water, students can measure the heat of the reaction.
Chemical Thermodynamics 7bChemical Thermodynamics 7dConservation of Matter and Stoichiometry 3a
III: Explanation:
Students are now involved in an analysis of their own explorations. Their understanding is clarified and modified because of the reflective nature of the activities.

Analysis/Lecture Time!

Students are introduced to the activation energy curve and the effect of a catalyst on it for both exo and endothermic reactions.  After being shown how the heat of the reaction is displayed on the graph, students make their own graphs based on their experiments.  They then compare their graphs with each other to see what they calculated as the heat of the reactions.

After the comparison, introduce Gibbs Free Energy to the students.  Describe the terms entropy and enthalpy, and what makes a reaction spontaneous.


 Chemical Thermodynamics 7bChemical Thermodynamics 7fReaction Rates 8cReaction Rates 8d
IV Extension:
This section gives students an opportunity to expand and solidify their understanding of the concepts and to apply them in a real-world context.

Hydrogen Cars!

Students are given data for 9 metals that fits the equation for Gibbs free energy, however pieces are missing from the data.  Students can then use their knowledge to fill out the missing information and share their answers.  Once it is filled in, students are given more data on the metals (such as weights/densities, reaction with air and water, stability).  Using the information from the sheet and the other data, students come up with evaluation criteria for the metals and decide in groups which metals they think would be the best to use as a storage material in a hydrogen car.  They form a ranking of the 9 metals for their group.  


Chemical Thermodynamics 7bChemical Thermodynamics 7fInvestigation&Experimentation-Grades 9 to 12- 1dInvestigation&Experimentation-Grades 9 to 12- 1kInvestigation&Experimentation-Grades 9 to 12- 1lInvestigation&Experimentation-Grades 9 to 12- 1m
V Evaluation:
This performance-based activity helps students to connect all of the pieces of information involved in these lessons. .

Wrap Up

Groups will share their rankings from the previous activity and present the reasons that they have chosen to rank them that way.  Then, through a class discussion, a more finalized list will be developed.  Finally, students will write up a reflection paragraph of the ideas and concepts that they learned and explored in the lab/activity.
Investigation&Experimentation-Grades 9 to 12- 1dInvestigation&Experimentation-Grades 9 to 12- 1l

Why investigate Metal Hydrides?

In order to grab the students' interest, they will watch a video about hydrogen fuels and where hydrogen comes from.  The video was made by PBS and Scientific American and is a little under 30 min in length.  After the video, the students can discuss in small groups their reaction to the video and what difficulties they see for use of hydrogen in the near future.  If there is time, there is also a second short video made by Nova that can be useful.

Objectives
  • To introduce students to the concept of hydrogen as a fuel and its use in cars with metal hydrides.
  • To show students some of the ways that hydrogen is produced and some of the difficulties in it.
  • To have students come up in their own groups with some ideas of problems that might be found in the future use of hydrogen in the world.
Materials
Projector and Internet access
OR
Video that discusses hydrogen fuels and cars
Procedure
1. Students watch the video(s)
2. Students brainstorm and discuss energy and the current problems the world is facing and will face in the future and the feasibility of using hydrogen as a way to help the problems.
3. Students share out some of what they came up with in a brief class discussion section.


(If there is additional time, the 2nd video by Nova can be added to the Scientific American one.  It focuses more on how the hydrogen is used in the car and not on metal hydrides, but is an interesting show that includes the CarTalk guys.  )

Teacher Notes:
I had the students do a reading log (viewing log) of the videos.  One column was I saw (from the video), and one was their thoughts once they finished the video.  That helped them to go back and remember what they saw and write down their reactions to the ideas presented.  The discussion in their groups mainly focused around understanding the concepts and the implications to the US.

I had the students watch all the videos, mainly so they had a wider view on the use of hydrogen and production.  The Nova video plus the first part of the Scientific American video are probably the most useful from a purely hydrogen car perspective.  On a technical note, if your school internet is not the best, it would be a good idea to try to find the videos on DVD. 
References

State Standards
Chemical Thermodynamics 7b-
7. Energy is exchanged or transformed in all chemical reactions and physical changes of matter. As a basis for understanding this concept:
    b. Students know chemical processes can either release (exothermic) or absorb (endothermic) thermal energy.
 

Investigation&Experimentation-Grades 9 to 12- 1l-
1. Scientific progress is made by asking meaningful questions and conducting careful investigations. As a basis for understanding this concept and addressing the content in the other four strands, students should develop their own questions and perform investigations. Students will:
    l. Analyze situations and solve problems that require combining and applying concepts from more than one area of science.
   

Investigation&Experimentation-Grades 9 to 12- 1m-
1. Scientific progress is made by asking meaningful questions and conducting careful investigations. As a basis for understanding this concept and addressing the content in the other four strands, students should develop their own questions and perform investigations. Students will:
    m. Investigate a science-based societal issue by researching the literature, analyzing data, and communicating the findings. Examples of issues include irradiation of food, cloning of animals by somatic cell nuclear transfer, choice of energy sources, and land and water use decisions in California.

Lesson Resources
Why investigate Metal Hydrides?: Nova

http://iisme.5ecommunity.org
Why investigate Metal Hydrides?: Scientific American

http://iisme.5ecommunity.org

Experiment!

Here, students will perform 1-2 experiments (depending on time) exploring exothermic and endothermic reactions.  From their investigations, they will calculate the heats of the reactions.  Either both reactions can be done by a group of 4, or students can be split up and share their results at the end.

When acetic acid reacts with sodium carbonate, an endothermic reaction happens.  And when Copper sulfate reacts with zinc metal, an exothermic reaction happens.  By submerging a test tube of the reaction in a styrofoam cup of water, students can measure the heat of the reaction.

Objectives
  • Students will experience 2 reactions, one endothermic and one exothermic
  • Students will measure the temperature change caused by the reaction and calculate heats of reaction
  • Students will use the terminology of system and surroundings to discuss their findings.
Materials
Chemicals:
  • Acetic Acid
  • Sodium Carbonate
  • Zinc metal pieces
  • Copper sulfate solution
Lab Supplies (per group):
  • Styrofoam Cups (2-3)
  • Test tubes (medium size) (2-3)
  • stoppers for test tubes (with pass through holes) (2-3)
  • thermometers (2-3)
  • water
  • balances (1, can be shared between groups)
  • graduated cylinders (100mL and 10mL)
  • glass stir rods (2-3)
Procedure
Teacher Prep:
Distribute lab supplies to each lab station for groups. 
Make up a copper sulfate and acetic acid solution in advance to be dispensed. 
Put out the sodium carbonate and zinc next to the balances so students can weigh them out.

This section is open to you (the teacher) as to how experimental you let your students be.  If you feel comfortable letting them take the supplies to figure out how to measure the heat of a reaction and what chemicals to mix together in what quantities, then let them at it.  Depending on their level of experience in the lab, students may be able to design their own procedures, although it is unlikely they will determine amounts on their own, so suggesting mL and grams would be a good idea to avoid overly wasting the chemical supplies.  Some suggestions to give the students about how to set up their procedure if you leave it open would be:
  • Make sure you minimize the amount of heat "lost" that you can't measure.  Which of the materials will help minimize heat loss?
  • Make sure you make all the measurements you need to in order to calculate your heat (have them figure out the equations in advance)
  • Refer them to a picture of a calorimeter (either in their book or in a drawing).  That can give them a good idea of what their setup should be similar to.

If you want to give more guidance, you could provide an example (such as measuring the heat of ice melting) previous to this explore section.  Or you may specify how much and which  of the chemicals to be combined by the students to ensure they obtain measurable temperature changes. A suggested student procedure is given below, it will help the students obtain reasonably accurate results.

Student Experiment:
  1. Fill the cups with 100-150 mL of water (measured exactly)
  2. Measure the temperature of the water before the reaction
  3. Weigh out a given amount of either the sodium carbonate or zinc
  4. Measure out the volume of acetic acid or copper sulfate.
  5. Insert the test tube into the water with the bottom below the water line.
  6. Put in the solid, then dump in the liquid and cap off the test tube.  Shake/swirl lightly to ensure reaction.
  7. Measure the temperature of the water every 10 seconds. 
  8. Make sure to record the highest temperature attained.
After Experiment:
Students can calculate the heat of the reaction by first calculating the heat change in the water (surroundings) and then figuring out the reaction (system) change.  They will need to use q=mc(deltaT) for the water, then realize the heat of the reaction is the negative of that.

Teacher Notes:
This part of the lesson went quite well on its own, but I didn't necessarily feel like the students were able to connect it to the idea of heat in a different setting like the hydrogen car.  It definitely helped them understand heat and how to calculate heats of reactions, but connecting that to hydrogen gas reacting with the solid metal in a car was difficult for most.  It provides them with necessarily knowledge to work with, but the connections between heat of reaction here and in the car engine need to be made very explicit.
References
Endothermic reaction: http://chemistry.about.com/od/lecturenotesl3/a/endorxns.htm
Exothermic Reaction: NSTA 2006 CD
 
State Standards
Chemical Thermodynamics 7b-
7. Energy is exchanged or transformed in all chemical reactions and physical changes of matter. As a basis for understanding this concept:
    b. Students know chemical processes can either release (exothermic) or absorb (endothermic) thermal energy.
 

Chemical Thermodynamics 7d-
7. Energy is exchanged or transformed in all chemical reactions and physical changes of matter. As a basis for understanding this concept:
    d. Students know how to solve problems involving heat flow and temperature changes, using known values of specific heat and latent heat of phase change.

Conservation of Matter and Stoichiometry 3a-
3. The conservation of atoms in chemical reactions leads to the principle of conservation of matter and the ability to calculate the mass of products and reactants. As a basis for understanding this concept:
  1. Students know how to describe chemical reactions by writing balanced equations
Lesson Resources
Experiment!: Calorimeter Drawing

http://iisme.5ecommunity.org

Analysis/Lecture Time!

Students are introduced to the activation energy curve and the effect of a catalyst on it for both exo and endothermic reactions.  After being shown how the heat of the reaction is displayed on the graph, students make their own graphs based on their experiments.  They then compare their graphs with each other to see what they calculated as the heat of the reactions.

After the comparison, introduce Gibbs Free Energy to the students.  Describe the terms entropy and enthalpy, and what makes a reaction spontaneous.

Objectives
  • Students will learn about activation energy curves and catalysts
  • Students will connect their experimental findings to energy diagrams
  • Students will learn about gibbs free energy, entropy, and enthalpy
Materials
Lecture materials (whiteboard/chalkboard/Powerpoint)
Students results from lab experiment calculating heat of reaction
Procedure
Make sure students have calculated their heats of reaction from the previous day's experiment. 
Introduce students to the concept of activation energy and the diagrams for exothermic and endothermic reactions.  Also, discuss the role of a catalyst and how it affect the energy diagram.

Once students have taken notes on activation energy, have them draw out diagrams for the two reactions they did in lab and label the sections of the graph.  Have students within groups and then between groups compare their graphs to see any differences in how they are drawn and different numbers obtained.

When students have finished comparing their data from lab, introduce them to the concept of Gibbs free energy, enthalpy, and entropy.  Also include that reactions are spontaneous when deltaG is negative.  DG = DH - TDS

Teacher Notes:
The students grasped the idea of activation energy and drawing their energy diagrams fairly quickly, but Gibbs free energy, enthalpy and entropy left them extremely confused.  Part of this was because our book (which they'd read prior to this) does not discuss entropy, enthalpy and free energy in any detail.  They understood the equation and how to use it by plugging in numbers, but I think their actual grasp of what each quantity means is still lacking.  I don't necessarily feel they came out knowing less than they should in the context of the class, as those are advanced concepts, but it meant I had to explain carefully in the next section as they didn't instinctively know what different numbers meant for a reaction.
References
Energy Diagram References:
http://www.sparknotes.com/testprep/books/sat2/chemistry/chapter8section1.rhtml
http://www.gcsescience.com/rc23.htm

Gibbs Free Energy References:
http://wine1.sb.fsu.edu/chm1046/notes/Thermody/Gibbs/Gibbs.htm
http://xenon.che.ilstu.edu/genchemhelphomepage/topicreview/bp/ch21/gibbs.html
http://mc2.cchem.berkeley.edu/Java/Gibbs/Gibbs.html

 
State Standards
Chemical Thermodynamics 7b-
7. Energy is exchanged or transformed in all chemical reactions and physical changes of matter. As a basis for understanding this concept:
    b. Students know chemical processes can either release (exothermic) or absorb (endothermic) thermal energy.
 

Chemical Thermodynamics 7f-
7. Energy is exchanged or transformed in all chemical reactions and physical changes of matter. As a basis for understanding this concept:
    f. * Students know how to use the Gibbs free energy equation to determine whether a reaction would be spontaneous.

Reaction Rates 8c-
8. Chemical reaction rates depend on factors that influence the frequency of collision of reactant molecules. As a basis for understanding this concept:
    c. Students know the role a catalyst plays in increasing the reaction rate.

Reaction Rates 8d-
8. Chemical reaction rates depend on factors that influence the frequency of collision of reactant molecules. As a basis for understanding this concept:
    d. * Students know the definition and role of activation energy in a chemical reaction.

Lesson Resources

Hydrogen Cars!

Students are given data for 9 metals that fits the equation for Gibbs free energy, however pieces are missing from the data.  Students can then use their knowledge to fill out the missing information and share their answers.  Once it is filled in, students are given more data on the metals (such as weights/densities, reaction with air and water, stability).  Using the information from the sheet and the other data, students come up with evaluation criteria for the metals and decide in groups which metals they think would be the best to use as a storage material in a hydrogen car.  They form a ranking of the 9 metals for their group.  



Objectives
  1. To have students analyze various data sets and learn information on different metals
  2. To have students come up with various criteria that they will evaluate the metals on for their use in hydrogen cars
  3. To have students rank the metals in terms of which they think would be the most viable for use in a hydrogen car.

Materials
Data on various types of metals
- Heats of reactions (enthalpy, entropy, gibbs free energy and temperature)
- Weights/Densities
- Other information (reaction with air and water, stability)
Procedure
  1. Give students data sheets on various metals.  Assign one-two metals per group and have them quickly fill in the missing information, then share out the data to the rest of the class so others can fill in their sheets
  2. Give students additional information sheets with properties of metals
  3. Ask students to evaluate the different metals in relation to the possibility of using them as a storage material. 
  4. Suggest they pick good, bad and okay metals first, then rank within those categories.  That will help them break it up into smaller chunks.

For teacher:
For the students to use the thermodynamic data and evaluate it for which metal would work the best, they're going to need to go back to the activation energy diagram.  First, the hydride should be at a lower energy then the metal and hydrogen gas, so that in a car at rest the hydrogen would remain bound up.  Therefore, the metals with a negative delta G will work the best.  Second, neither the products or the reactants should be *too* stable relative to the other, or the reaction will never reverse.  So the closer the reactants and the products are, the easier it will be to go backwards and forwards.

You may want to tell that information to your students, hint at it, or let them try to come up with it themselves.  Depends on your assessment of your class.

Teacher Notes:
I had to do a lot more scaffolding to help the students understand the various properties than I had expected.  Very few groups were able to evaluate the properties and determine on their own what "bad' and "good" looked like.  Once I realized this, I led a fairly quick class discussion of each of the properties, and had students think about whether a high melting temp or low would be good or whether they want it to react with water or not.  That helped them grasp the idea and move on to evaluating the metals as a group.  The data that was hardest for them to grasp was the thermodynamic data.  They struggled to figure out if they wanted positive or negative numbers, large or small numbers, and which quantities (entropy, enthalpy, free energy, temperature) were most important to look at. 

I had to guide them to realizing they wanted a medium sized free energy so that their reaction could go both forwards and backwards.  And that they wanted it to be negative so that it wouldn't spontaneously release the hydrogen, but would release with the application of a little energy.  With that, they settled into ranking the metals with the thermo data and incorporating the other properties to get their final rankings.

Once the students got going, they argued amongst each other and hashed out rankings fairly quickly. 


References
Heats of Reaction Data:
Chemical Reaction and Equilibrium Software HSC Chemistry 5.11

Properties Data:
http://www.webelements.com
 
State Standards
Chemical Thermodynamics 7b-
7. Energy is exchanged or transformed in all chemical reactions and physical changes of matter. As a basis for understanding this concept:
    b. Students know chemical processes can either release (exothermic) or absorb (endothermic) thermal energy.
 

Chemical Thermodynamics 7f-
7. Energy is exchanged or transformed in all chemical reactions and physical changes of matter. As a basis for understanding this concept:
    f. * Students know how to use the Gibbs free energy equation to determine whether a reaction would be spontaneous.

Investigation&Experimentation-Grades 9 to 12- 1d-
1. Scientific progress is made by asking meaningful questions and conducting careful investigations. As a basis for understanding this concept and addressing the content in the other four strands, students should develop their own questions and perform investigations. Students will:
    d. Formulate explanations by using logic and evidence.

Investigation&Experimentation-Grades 9 to 12- 1k-
1. Scientific progress is made by asking meaningful questions and conducting careful investigations. As a basis for understanding this concept and addressing the content in the other four strands, students should develop their own questions and perform investigations. Students will:
    k. Recognize the cumulative nature of scientific evidence.

Investigation&Experimentation-Grades 9 to 12- 1l-
1. Scientific progress is made by asking meaningful questions and conducting careful investigations. As a basis for understanding this concept and addressing the content in the other four strands, students should develop their own questions and perform investigations. Students will:
    l. Analyze situations and solve problems that require combining and applying concepts from more than one area of science.
   

Investigation&Experimentation-Grades 9 to 12- 1m-
1. Scientific progress is made by asking meaningful questions and conducting careful investigations. As a basis for understanding this concept and addressing the content in the other four strands, students should develop their own questions and perform investigations. Students will:
    m. Investigate a science-based societal issue by researching the literature, analyzing data, and communicating the findings. Examples of issues include irradiation of food, cloning of animals by somatic cell nuclear transfer, choice of energy sources, and land and water use decisions in California.

Lesson Resources
Hydrogen Cars!: Heats of Reaction Data

http://iisme.5ecommunity.org/members/krotter/images/1154460ion.xls
Hydrogen Cars!: Properties of Metals

http://iisme.5ecommunity.org/members/krotter/images/1154465als.doc

Wrap Up

Groups will share their rankings from the previous activity and present the reasons that they have chosen to rank them that way.  Then, through a class discussion, a more finalized list will be developed.  Finally, students will write up a reflection paragraph of the ideas and concepts that they learned and explored in the lab/activity.

Objectives
1. Have students/groups as a class share their rankings for the metals
2. Come to a class decision on the best metal(s) for hydrogen car research
3. Have students evaluate their learning in the activity and a wrapup
Materials
1. Previous work on rankings
2. Lab results from lab
Procedure
1. Have groups prepare a brief (minute or two) presentation on why they ranked the metals in their order.  Which pieces of information did they find most helpful to look at?
2. Write the rankings on the front board for each group. 
3. Have a teacher led discussion of the criteria students' used and what differences in the rankings mean.
4. Have students individually evaluate their learning.
  1. What were some of the tradeoffs you had to make when your group settled on the best metal for hydrogen cars?  How did you decide what was most important?
  2. During this lab, what new knowledge or understanding have you gained concerning hydrogen cars, heats of reactions, and/or the Gibbs free energy equation?
  3. Aside from hydrogen fuel/vehicles, where else in the world could you use the knowledge you have gained in this lab?
Teacher Notes:
Groups definitely had different rankings when they did their comparison, but the differences tended to be small, placing one in 2 vs 3.  They had them grouped into good, bad, and okay consistently across the class.  There was some debate over which criteria mattered the most, but some metals were ranked low because of high free energy, a low melting point, or being very reactive with air/water.  Some groups chose to change their rankings and some elected to stick with them, which was fine.

In their evaluations, most students felt they learned a lot about energies of reaction and how a hydrogen car operates.  Their discussion of the tradeoffs, for the most part, indicated they felt confident in the end of evaluating the different metals.
References
 
State Standards
Investigation&Experimentation-Grades 9 to 12- 1d-
1. Scientific progress is made by asking meaningful questions and conducting careful investigations. As a basis for understanding this concept and addressing the content in the other four strands, students should develop their own questions and perform investigations. Students will:
    d. Formulate explanations by using logic and evidence.

Investigation&Experimentation-Grades 9 to 12- 1l-
1. Scientific progress is made by asking meaningful questions and conducting careful investigations. As a basis for understanding this concept and addressing the content in the other four strands, students should develop their own questions and perform investigations. Students will:
    l. Analyze situations and solve problems that require combining and applying concepts from more than one area of science.
   

Lesson Resources