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Larry's Letters

Larry Malone, Co-Director of FOSS, Lawrence Hall of Science
September 06, 2006 | Observations by Larry

From: Kathy Weber
Date: May 31, 2006 6:56:12 AM PDT
Subject: a question about an experiment

To Whom It May Concern:
I am writing this email to you because I had something happen to me with this module that never happened before. I am using the Magnetism and Electricity Module right now (third grade). One of the activities we were to do involved creating a circuit with a switch. The students are supposed to open the switch and see if they can use the test items to complete the circuit, therefore learning that things made of metal are conductors and will complete the circuit. The magnetite is one of the items in the test bag. It is not supposed to conduct electricity, but I had a student who did use it to complete the circuit. My question is, "What do I tell the students?" I suppose it has to do with the amount of metal in the magnetite, but I am not sure. Can you clear this up for me? Also for the assessment, one of the questions asks the students to list an item in the test bag that sticks to a magnet but does not conduct electricity. The students were confused because from what we found there wasn"t anything. Is this correct? I hope you can help me with this.
Mrs. Kathy Weber
Seville Elementary
3rd Grade

Hi, Kathy,

Great discovery! And what a surprise for you! Magnetite is an ironrich mineral, and, as you and your students discovered, on occasion the concentration of iron will create a conductive pathway. Your assessment of the situation was exactly right. What I would tell the students is something like, "I"m surprised that the black rock (magnetite) conducts electricity. I"m wondering if all the black rocks conduct electricity or if it is just some. And if they conduct, do they conduct in whatever position you place it in the circuit, or just certain ways?" You should have the students explore this issue, come up with a conclusion, and record their thinking in their science notebooks. I suspect that only certain samples of magnetite will conduct, and that those that do will do so only in certain locations. When the data are in, ask the students to talk in their groups to come up with a model (explanation) for the observed behaviors. Let the groups present their models and compare. Leave the conclusion hanging without resolution by authority (you). That"s the way science goes.

Then, when you get into series and parallel circuits, and you have two D-cells in series (more voltage; more power), casually ask your class if they think the magnetite will conduct in a circuit with two or three D-cells providing the power. I don"t know what will happen, but I"m thinking that maybe a few more pieces of magnetite might conduct. Then challenge students to modify, revise, or add to their models to explain what is going on. They should record their revised thinking in their notebooks, too.

Concerning the test, there should be no confusion. In your class there were no materials that stick to a magnet but do not conduct. Scientific evidence trumps what may be suggested as a "right" answer. You can tell your students that the answer sheet in the teacher guide says magnetite sticks but does not conduct. Ask them what they think of that. They should say, and rightly so, that the teacher guide is wrong. Part of scientific thinking is to trust evidence, be skeptical, build arguments to support your claims, and challenge assertions that don"t agree with observations.

You and your students are on a journey of discovery into the natural world. The FOSS teacher guide is just that—a guide. But we don"t always know what you will discover on that journey. That"s the joy of it. You came to a juncture in the path, ventured down it, and found something interesting—magnetite that conducts. You are on your own at these times. But you are not alone, you are there with your students. This is where you all have to consult with one another to figure out what to do. That"s really fun.

Thanks for the note. Sorry for the confusion, but I"m glad you made an interesting discovery. And in the future, when unanticipated things present themselves that you can"t figure out, don"t be shy about telling your students that you don"t get what"s going on exactly—try to turn the question back on the students, as I suggested above. It will be just the kind of challenge that will get some of your students really going. And once you get a feel for that kind of willful departure from the charted path in the teacher guide, you may find yourself looking for opportunities to tell the class, "I don"t get this. Can you help me figure this out?" Let me know how it all comes out.


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