teaching energy

Reviews, ideas, or complete lesson plans. Please include the subject and perhaps the appropriate grade level in your subject line.
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Greg Schubert
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Joined: Tue Aug 07, 2007 8:33 am

defining energy

Post by Greg Schubert »

Hi Energy Teachers,

I was just at a week long workshop for K-12 teachers in PA on environment and ecology. I asked the question of how to teach students what energy is to my ninth grade Biology students and did not got an adequate answer.

"The ability to do work" definition leads conceptually to defining work, force, acceleration, velocity and displacement which is better approached in the reverse order in a physics class.

The reason that I believe that they have no understanding of what energy is comes from an activity I do to introduce a topic. I provide the students a diagram of five types of energy represented by symbols. The sun represents light, a bubbling flask represents chemical, some gears represent mechanical, flames represent heat and something else for electrical. When asked to provide examples of devices which convert energy from one form to another, most of my honors students from an affluent suburban school district, can think of very little.

If I provide an example, it prompts a few more ideas, but consistently it seems that my students have never thought in these terms before. Unless I address this, the First Law of thermodynamics and an understanding of the need to conserve natural resources, are doomed.

Similarly, it is very difficult for my students to understand why or even that only 10% of the energy gets from one trophic level to the next. Any help explaining this concept would also be greatly appreciated.



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re: defining energy

Post by shawn »

Greg, I think you make some good points about how shallowly many try to teach energy.
There are several approaches to take to refine the concept of energy with your students.
First, you should measure what they think energy is.
You could (and probably already do) discuss food calories. How could all of the energy consumed by one being be available to the being that ate that one? What would be left for the first to use to pass the time? Instead of telling the students about the trophic pyramid, students should induce it or deduce it from observing or considering the evidence that beings don't exist merely to be consumed by another, but to live their own lives and carry out other activities which require energy, such as procreation, consuming, metabolizing, migrating, etc.
What I do is have students consider how many joules they eat then see how much time on a bicycle generator it would take to remove those joules from their body via the pedals. Just a bottle of soda could generate 50W for hours. So, where does the energy go? It must radiate out the skin, be stored, exhaled, or wasted. The students get my implicit message that all the energy they consume is converted, through "chemical" means, to all the energy they expend or store.
Then there are analogies. Just as you add energy the system of a ball and a planet, which is evident when you then drop the ball, plants add energy to an almond/atmosphere system by separating carbon and oxygen, placing carbon in the almond and oxygen in the air, which you later combine in your body to retrieve that energy.

Now about defining energy, I am thinking of this: Energy is required to change the state of something (lift a mass, change a molecule, change velocity...). I disagree with the implication in the previous post that "work" must be taught from first principles of kinematics and dynamics. I think that argument is based on tradition, not educational research.
The way we physics folks treat energy with such facility is not that we followed a careful, prescribed path to understanding it, but that we worked with it from so many different angles. Thus, I prescribe patience.
I think those symbols, gears, flames, flasks, etc. only confuse students by throwing a symbology divorced from real experience and expecting them to change quickly their conceptual models they've built over 10 years.

I think it's our job as teachers/mentors/coaches to come up with creative ways for students to discover what energy is and isn't.

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Re: teaching energy

Post by amweinbl »

I teach 7th grade science, and I'm currently trying to plan a mini unit that will introduce students to the big idea that energy is always the ability to make things change their motion, that it can be converted from one seemingly different from to another, and that it can be stored and released. My goal is to intro these ideas during the first few weeks of school and then draw on them over the course of the year so we can "follow the energy" when we study bio, physics, and earth history.
Shawn, I like your definition of energy as the ability to change the state of something, and I'm planning on using it. Now I'm in the market for activities that students can do with manipulatives that can help them develop a more intuitive sense of energy and energy transfer. I'm also looking for existing curricula or lessons on the nature of energy directed towards middle schoolers, rather than high schoolers.

Has anyone out there got some ideas?


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Re: teaching energy

Post by shawn »

I took a workshop at the American Association of Physics Teachers conference last month, and we explored an activity where groups of four students kept tabs on energy at the surface, lower atmosphere, and higher atmosphere, as the emissivity in far IR of the lower and upper atmospheres increased due to extra CO2, all the while experiencing day-night cycles. One student acted as outer space, including the sun, so giving energy to the surface and taking it from the upper atmosphere. The other three students acted as each of the earth-atmosphere components mentioned.
The complete teacher's guide is online at the Little Shop of Physics:
http://www.lsop.colostate.edu/wp-conten ... AModel.pdf
To understand how energy comes to us from the sun mostly as visible and infrared light, but leaves mostly as infrared light, I like to work with regular and infrared cameras, a lamp or sunlight, and glass. You can shine a green laser, absolutely no infrared, on a piece of black paper to warm it, and see the resulting surplus of emission of IR with an infrared camera.
Good students should question the workings of the IR camera or thermometer, and for that they need to look at very cold things and ask how the cold thing cools the sensor in the camera/thermometer. Ask me if you need any equipment.

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