Tuesday, July 6, 2010

Day 3 - Science At Last!

Yes! Today I get to actually do some experiments! I'm starting with the one I know will work - the plant pigment chromatography based off what we did in AP Bio. I don't have ether, but Elizabeth bought us a bottle of acetone, which works fine.

I'm doing this with the entire 10th class at once during 4th period (just before lunch). They're usually divided into two sections, but I've got about 50 students here. I've been informed that the little red/green/yellow/blue patches on their shoulders are used for dividing them into groups, so we use them. The students sit either in circles on the floor or gathered around a couple of benches (desks), curious to see what's in the dark bottles I've brought with me.

I explain what the teachers have done so far - extracting the pigments from some leaves using a roll (mortar and pestle) and surgical spirit (which I think is isopropanol, since that's what it smells like) - and tell them what they will be doing. We cut filter paper into strips, mark the loading line with a pencil, and hand one piece to each group. I demo the experiment once, making sure that all of the windows are open so we don't breathe too much of those lovely acetone fumes, and then have them do it.

The solid green line travels up the filter paper, splitting (though not separating as much as I would like) into 3 visible bands of color. Yellow xanthophylls at the top, green chlorophylls in the middle, and faintly orange beta-carotene at the bottom. The pictures of this, unfortunately, are on my cell phone, and I can't get them to the computer :-(

Afterward, the students ask questions. "What is the acetone for?" "What is the spirit for?" I answer as best I can in Telugu, and the teachers fill in the science terms I don't know. I explain why plants have different pigments (to absorb other wavelengths of light), and why leaves appear green despite that (the amount and color of chlorophyll overpower the others).

It seems a success, and as we leave, the students are surprised to see that the lesson is in the very beginning of their very own 10th grade biological science book (though school's only been in for a week and they haven't gotten there yet). They ask if I'll be doing an experiment every day, and I say that I'll be trying to, though they won't all be for the 10th grade. Well, I will try, once I figure out which ones fit in the syllabus.

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