Wednesday, August 11, 2010

Day 27 - Gotta Follow the Procedure...or Change Your Plans

Plant pigment chromatography worked so beautifully in Matendla. Well, it's not working here. To be fair, we don't have enough time in the morning to prepare before class, so we can't get tamalapaku leaves crushed with ethanol by a mortar and pestle. Instead, my mom tries to crush some badam (almond) leaves by hand. Yeah, that doesn't really get the chlorophyll out.

The experiment worked well in Matendla because we did a quick demo, then had the students get into (four large) groups and do it themselves. They got to play with it and do something with their hands, and they had lots of questions afterward.

Here, we can't find enough beakers, so the class has to sit for 20 minutes, watching the acetone slowly creep up the filter paper from 20 feet away while we try to explain the principles behind an experiment that is not showing the result it's supposed to.

We've learned our lesson. Instead of taking the second section of 10th class immediately afterward, we ask if we could have one period extra to prepare. Hurrying back to the lab, we make a change of plans. Who needs plant pigments? That would relate much better to bio, but these kids have never even seen paper chromatography. So we borrow some markers.

A quick test shows us that mixing red, green, and blue markers in a line along the bottom of the filter paper strip results in a very nice separation. We hunt through the cabinets one more time and find a couple of glasses to go along with the beakers. A poor washrag that has the misfortune of being nearby gets torn into 5 pieces to act as a cover for the beakers. We pick a couple of solvent systems and get some students to help us carry all the equipment back across the grounds and up the stairs to the school.

The second section of 10th gets a much better lesson. We call groups of 6 kids outside one group at a time, and demonstrate what they need to do. Then we hand them the scissors, filter paper, markers, tape, and beaker with solvent system (water, acetone + water, or ethanol + water), and send them off to a corner of the balcony to begin their test.

As we check the groups, we find that for some, the green color has disappeared and yellow has appeared! So in the spirit of science, we assign those groups a second task now that their first chromatograph has finished: try it again with just the green.

After everyone's marker pigments have separated out clearly enough, we return to the classroom to talk about the principles. We draw a little color-chalk diagram of each group's results on the board and compare them. We ask everyone, where did the yellow come from? And then we suggest that perhaps the green marker was actually made up of yellow and blue, and show the extra chromatograph to prove that this is indeed the case.

All in all, it's a pretty successful lesson. But the first section of 10th didn't get it. So we go back to their classroom after lunch (the teachers are very accommodating since this is a short-term project) and repeat the better version of paper chromatography with them.

Perhaps it's because we gave them freedom to work in groups, or perhaps because the experiment is really working, or simply because the teacher is not sitting at the back watching them, but the kids are much more enthusiastic this time around. One group even carries out a little experiment of their own: they try it with regular notebook paper.

Obviously it doesn't work, but they ask why in the discussion afterward, and we're able to explain about the qualities of filter paper that make capillary action work much better. But they're thinking about it themselves and trying things, and that was really the goal of this whole exercise. Science is not something you just learn and memorize from a textbook. Science is something you do, and think about, and keep on doing.

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