Lesson 2 of 6
Objective: Students will be able to describe the difference between a primary and secondary energy resource, between renewable and nonrenewable energy resources, and be able to describe the sources, uses, and effects of different energy resources.
This lesson covers the different energy resources that societies use to meet their energy needs. Unlike many of my "direct instruction" lessons throughout my curriculum, this lesson is not attached to any particular textbook reading or homework assignment. The reasons for this are practical,
- the textbook my class uses presents this information in too many disparate chapters
- I presented this lesson at the end of the school year when time was at a premium and students were engaged in their final project during their out of class time.
The lesson essentially consists of two parts:
1. An in class presentation.
2. An critical thinking activity to be completed in small groups.
3. A short class discussion to review the concepts presented in this and the preceding lesson.
If you do prefer to precede this lesson with a reading, the concepts covered in this presentation that I would look for in a different text are...
- Primary vs. secondary energy resources
- Renewable vs. nonrenewable energy resources
- Practical examples of the 1st and 2nd Laws of Thermodynamics
- How electricity is generated
- The basic chemistry of a combustion reaction
- Greenhouse gases, the greenhouse effect, and global warming
- Energy efficiency
- Specific information on the following energy resources:
- natural gas
- nuclear power
- wind power
- hydroelectric power
- solar power
- geothermal power
Alternately, the powerpoint attached to the Direct Instruction section could stand on its own without a text as I have used it here.
Although this lesson presents new material, it essentially builds on the concepts from the previous lesson, so the presentation itself affords opportunities for students to ask questions and clarify their understanding of the concepts of energy use and the laws of thermodynamics.
Connection to Standards:
In this lesson, students will establish familiarity with relevant scientific vocabulary and then draw evidence from the text to support arguments and opinions presented as part of their participation in a group discussion.
The warm up for this lesson is pretty quick. I just want students to remember what we had discussed in the previous lesson and review the concept of the 1st and 2nd law of thermodynamics.
I present the students with a scenario:
"A shopper drives their car a few miles to a store and when they park and get out of the car, they notice that the hood above the engine is warm. When they return to their car after shopping, the hood is no longer warm."
I then ask the question, "How does this situation relate to the 1st and 2nd Law of Thermodynamics?".
This is very similar to a question on the homework assignment for the previous lesson, so hopefully students can answer that:
- The 1st law is represented by the fact that chemical energy (in the gasoline) has been converted to mechanical energy (of the moving car) and thermal energy (the heat coming from the engine). Nothing was created or destroyed, just converted.
- The 2nd law is represented by the fact that the engine got warm because some of the chemical energy was wasted in the conversion from chemical to mechanical. The engine getting warm was a result of waste heat. Also, the engine cooling down represents the 2nd law because the concentrated (useful) energy dissipated as entropy increased.
Once students have shared their responses and we have covered the points above, I let students know that we will be discussing the implication of these laws and the ways we obtain and use the energy our societies need to function. We then begin the presentation described in the next section.
Following the quick warm up, I begin the powerpoint presentation for this lesson.
As I've mentioned in previous lessons, offering students a note sheet provides a readymade study guide for later and allows students to focus on their thoughts and the concepts being discussed as opposed to focusing all of their attention on copying down copies amounts of notes.
Wondering WHY I use lectures as a pedagogical strategy? Watch this video.
Wondering HOW I use the Powerpoint to differentiate instruction? Watch this video.
Wondering why I choose to have a reading assignment AND a lecture on the same content? Read this rationale.
Wondering how you might use this lesson's resources if you don't plan on presenting a lecture? Read this reflection.
During the presentation, I make sure to continually solicit student involvement by asking for them to provide personal experiences that might relate to the content and encouraging them to ask questions when they arise.
The content of this presentation discusses energy resources in the context of the laws of thermodynamics introduced in the previous lesson and then offers a short introduction of different energy resources (e.g., coal, natural gas, solar, etc.) without going into too much detail about their relative merits. Students will have an opportunity to do their own investigations of the advantages and disadvantages of different energy resources in the next lesson.
As I mentioned in the previous lesson, my approach to these direct instruction lessons has evolved throughout the year. In this final unit I try to include some short group activity for the students to get involved in so they can more meaningfully integrate the new content into their existing knowledge.
In this particular lesson, the final section of the presentation deals with energy efficiency. This is both a connection to the 2nd Law of Thermodynamics that was discussed in the previous lesson and a segue into discussing the hard choices societies must make in establishing energy security and environmental stability in the future, which ties into the next lesson on the pros and cons of the various energy resources presented in this lesson.
When I show them the slide showing the breakdown of how electricity is generated in the U.S., I ask them to do some quick calculations with their group:
- What percent of our electricity is generated by renewable energy resources? (~13%)
- What percent of our electricity is generated by nonrenewable energy resources? (~86%)
- What percent of our electricity is generated by fossil fuels? (~67% [nonrenewable - nuclear])
After the groups have had a few minutes to make the calculations (I'm talking 3 minutes, tops), I have the class share out the totals. I then ask for their impressions, and what trends they notice. Hopefully they come up with the obvious:
- The grand majority of our electricity comes from nonrenewable resources.
- Two-thirds of our electricity is generated by fossil fuels, which in addition to being nonrenewable resources, they also contribute to global warming.
After these basic facts about electricity generation have been established, I present the final slide of the presentation, which asks, "Is electricity a "green" energy resource? Why or why not?" This question is intended to get students really discussing and contemplating the realities of our energy needs and the ultimate environmental costs of fulfilling them.
I allow groups about five minutes to discuss the question and then let them know that I expect each group to share their answer, with supporting reasons. Once about 2-3 more minutes have passed, I ask for groups to volunteer their answers. There are many ways to answer this question, but I hope the following points are brought up in the discussion:
- You can't simply call electricity "green" or "not green" on its own because it's a secondary energy resource, meaning another energy resource must be used to produce it. The answer to this question really depends on the primary energy resource being used.
- Some energy resources used to generate electricity are inherently more threatening to the environment than others (e.g., the threat of radioactive wastes that persist for hundreds of millenia make nuclear power a dicey prospect, and fossil fuels contribute to global warming and have global effects on ecosystems)
- Even the "better" resources such as solar, wind, and water have some environmental costs. (e.g., the materials to produce photovoltaic cells in solar panels must be mined and the production of the panels requires energy that is usually provided by fossil fuels.)
- This all amounts to tie back to the previous lesson and the 1st and 2nd Law of Thermodynamics: energy has to come from somewhere and conversions from one form to another always waste some energy.
This discussion then, in the end, isn't meant to answer the question definitively... its intent is to point to the fact that our energy needs put us in a precarious place when we're trying to balance them with a desire to preserve the environment. That said, I hope students also understand that we can (and must) do a better job of managing the resources we use to supply our power.
I end the lesson by letting the students know that in the next lesson, we will discuss the pros and cons of the various energy resources and chart a course for meeting our energy needs in the future.