Taking a Stand on Nuclear Power?

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Objective

SWBAT compare and contrast nuclear processes (fission, fusion and radioactive decay) in terms of changes in numbers of subatomic particle and characteristics of emitted energy.

Big Idea

A formal explanation of fission and fusion is provided to accompany the exploration of fission from the previous lesson. Students begin to formulate an opinion of nuclear power

Introduction

In this lesson students continue to explore the NGSS Performance Expectation HS-PS1-8:  Develop models to illustrate the changes in the composition of the nucleus of the atom and the energy released during the processes of fission, fusion and radioactive decay. This lesson builds on the previous lesson by providing them with an explanation about what was explored during the PhET fission simulation.  The lesson begins with notes on fission and fusion that describe the energy output of each and the mechanics of each process.  The lesson is concluded with Eyes of Nye: Nuclear Energy, a video which talks about the pros and cons of nuclear power as a clean source of energy.   

This lesson focuses on the explain sequence of the 5E model.  The 5E model of inquiry use a series of stages:  Engage, Explore, Explain, Elaborate and Evaluate, to provide students with information about a concept or topic.  The 5 stages can all be done in one lesson, or spread out over a series of lessons as I have done in this unit.  In this lesson the Explain portion of the 5E model gives students a formal explanation of a concept they might have prior knowledge on.  

This lesson does not incorporate any of the NGSS Science and Engineering practices, however, it does continue to explore the Crosscutting Concept, Energy and Matter.  This lesson enables students to scaffold what they explored about fission and fusion to a formal explanation of the energy capabilities of each process.

Warm-up

5 minutes

This lesson begins with students performing a think-pair-share about what they concluded from the previous day’s lesson.  I instruct the class to take out their journals and discuss with their lab partner what they learned from the previous day’s investigation on fission and chain reactions.  The previous lesson was concluded with students writing in their journals three things they learned, two things they are not sure about and one thing they will try to understand for the next day (homework); these journal entries are the basis for the think-pair-share. 

Most times after a 3-2-1 activity, I like to follow up the next day with students revisiting their thoughts because it helps intiate though about what was learned the previous day and aids in scaffolding the previous days information with what will be learned during the days lesson.  Combining a 3-2-1 with a T-P-S is an excellent way to get students to engage in science discourse and think about what others got out of a lesson.

After a couple minutes of pairing up and discussing, I take volunteers to discuss what they learned from the previous day’s lesson.  Typical responses are:

  • A neutron is used to split U-235
  • A neutron that is fired at U-238 will not cause it to become unstable and split.
  • A chain reaction is caused when U-235 releases 3 neutrons which can hit other U-235 isotopes

I then take a couple volunteers to share what they are still uncertain about fission.  Typical responses are:

  • What are control rods?
  • How much uranium is need to heat power a chain reaction?
  • How much energy is released from U-235?

I typically don’t spend too much time discussing their questions, just enough time to explain that many of their questions will be answered during notes and the video. 

Explain (notes)

15 minutes

These note only take about 15 minutes to deliver.  Sometimes I provide students with note sheets, but for this set of notes I don't becuase it is short and I want to give students practice of writing their own notes.  So as I’m setting up the Powerpoint I have students take out their notebooks.

Slide 1:  Is a description of fission that explains that a larger isotope is split into two smaller element.  I show them a picture of U-235 being bombarded with a neutron being split into two smaller elements and three neutron being released.

I explain that some of the neutrons will hit other U-235 causing to the process to continue (a chain reaction).  I also make a connection to the NGSS crosscutting concept that energy is released in the process, and that the energy can be harnessed to create power.  I conclude this slide by say that the number of protons and neutrons are conserved in the process; however, in the process a small amount of mass is converted into a tremendous amount of energy in the process.  This can be explained by E=MC2 which will not be discussed during this unit.   

Slide 2:  Is a description of fusion that explains that a larger amount of energy is released when smaller elements, such as deuterium and tritium, join together to form a larger element.

While showing the slide I explain that a tremendous amount of energy is released during fusion and provide the example of the sun.  I then ask if the sun produces a lot of energy.  It’s a silly question, but leads to the conversation that fusion is very hard to control, unlike fission.

Slide 3:  Is a comparison of fission, fusion and chemical reactions in terms energy output, example of each, fuel sources and size of starting and finishing elements.

When showing this slide I focus on the energy released because many of the students have not learned what a chemical reaction is, or how energy is used to produce power.  I thinks it's important to show concentrate that different reactions produce different amounts of energy.  The next slide shows how a power plant works and reference the source of energy and their output, to explain how power is generated in the next slide.

Slide 4:  Is a picture of a nuclear reactor.  This demonstrates practical application for fission.

During this slide I describe the process of how a nuclear reactor is used to generate electricity.  I explain that that U-235 is fissioned and in the process the energy is used to create steam.  The stream is then harnessed to turn a turbine that is connected to a generator which produces electricity.  I conclude by explaining that regardless of the energy source, coal or U-235, electricity is essential produced the same way and the energy source just used to create steam.  The main difference between coal and U-235 is that coal produces greenhouse gases and nuclear energy does not.

I don’t want students to think that there are no draw backs to nuclear power, so after this slide I show them Eyes of Nye:  Nuclear Power.

Elaborate

30 minutes

As students were completing the notes I handout the Fusion-Fission & Eyes of Nye video worksheet.  Before showing the movie, I have students read the short introduction at the beginning worksheet and answer the first 9 questions (Fission-Fusion student work) sumarizing fission and fusion.  Each of the questions can be answered with either fission or fusion.  I let them work with a partner and should only take 5 minutes to complete.  If it takes longer they can complete it for homework.  The questions act as a good summary of fission and fusion and act as a good introduction to the video.

After 5 minutes I start the Eyes of Nye Nuclear Energy video.  This video is about 25 minutes and can be streamed online.  In the video Bill Nye talks about the pros and cons of nuclear power and coal, but primarily focuses on nuclear power. 

Some of the issues that are discussed are availability of U-235, power plant construction, pollution, cost benefits and disposal.  Overall the video is very informative and provides an summary of the arguments for and against nuclear power.  However, towards the end of the video there is a slight bias against nuclear power, so I briefly stop the video and I let the students know that they should make their own decision based on the facts.  Even though the video does have a slight bias, I still believe that it is worth showing because it does a thorough job on discussing all aspects of nuclear power.

I let my class know that at the 4:00 minute mark I will stop the video and have them answer the first question.  This helps provide a reference point for when they need to write things down and they can more easily focus their attention on content of  the video.

The video will take the remainder of the period which leaves no time for a discussion, so the next class period will begin with a brief debate over pros and cons of nuclear power.  The video sheet is fairly straight forward, so students have no questions and are able to answer all the questions without a problem.

Homework

2 minutes

Two minute before the video ends, I stop the video and let them know that the worksheet will be due tomorrow and they will be responsible for taking a stand on nuclear energy.  I encourage them to do a little research on the pros and cons of nuclear power beyond what they have seen in the video.  They should take some notes because we will have a discussion/mini debate about the pros and cons of nuclear power. 

As a suggestion I suggest they watch the Ted TV, Debate:  Does the World Need Nuclear Energy Debate?  This is not a formal homework assignment, due to the fact that not all kids have readily available internet access.  I would typically show it in class, but due to the end of the semester approaching I chose to show the Bill Nye video instead.  The hope is that enough students will watch it, so that a factual debate can occur during the next class period.

Both videos are worth showing, but due to the end of semester time constraint not enough time is available to show both in class.  However, I do find it important that students watch both and begin to formulate an opinion so that they can be exposed to argumentation through evidence.