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Hi. I am a new teacher who will be beginning a unit on photosynthesis with 7th graders. I am looking for a good "hook" or discrepant event to introduce the topic. We will be doing a btb and chromatography lab with out studies. Thanks!
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It's not only related to photosynthesis, but http://www.growingthenextgeneration.com/just-for-kids-games.html has some nice interactive games for students in a student friendly version. You could do this as a review or as a preview of what is to come and then debrief with them about what they learned. You would need internet access though and enough computers.
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If you want something discrepant do the following:
Ask students: Do plants need Oxygen to survive?
You need a dissolved oxygen test tab.
Place three sprigs of elodea in a mason jar filled with water.
Repeat the above.
Take the first jar and place it in a brown bag for 24 hours.
Place the other jar in daylight for 24 hours.
Test the Dissovled Oxygen of both containers.
The DO in the hidden jar will be close to zero. Plants use Oxygen during their respiration time and since the jar was without sunlight no photosynthesis occurred. Hence it used up all its DO.
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There are a couple of Page Keeley probes on this topic, too. You can access the book chapters at these two places:
Light and Dark
and this one is by Page Keeley, Francis Eberle, and Joyce Tugel
Plants in the Dark and Light
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Carolyn, thank you for the excellent suggestions about Page Keeley's probes; they are designed for teachers to identify misconceptions through discrepant events and enable teachers to learn how to interview students to assess their understanding and knowledge in clear cut ways.
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Adah: I also do that lab with the elodea sprigs. I love to see the kids expressions when I take out the test tube from the dark and they seem so puzzled with the color of the water. Then several "light bulbs" turn on and they figure out that plants also go through cellular respiration. This is something even adults don't realize that plants do. People usually associate plants with photosynthesis but they forget that plants need energy at night too....cellular respiration. After this discussion, many kids go "oh...." That lab is one of my favorite labs to do....very easy to set up.
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I have done that lab with a group of teachers (elementary and middle school as well) and they are surprised with that result. It is my favorite one as well. Thank you for reinforcing my suggestion.
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