Wednesday, August 18, 2010

Day 28 - DNA, Electroplating, and Magnets, Oh My!

Today, we have scheduled a simple DNA extraction demonstration for the two sections of 10th class. There have been a few changes since I tried this in Matendla. Instead of onion, we're using a banana. The two reasons for this are as follows:
  1. The inside of a banana is pretty sterile. You don't really have to worry about dirt and things that will break up your DNA into pieces too short to spool.
  2. It's much much easier to mash a banana inside a ziploc bag than to find a mortar and pestle (a.k.a. a roll, which is used in cooking in India) and grind an onion with soap solution. Especially when the science lab is isolated from the rest of the school and you have no idea where all the teachers are because you're testing it out after school.
The DNA precipitates at the soap/ethanol border, and even allows itself to be spooled onto a clean pipet, but it's very gel-like. I suspect a high level of protein contamination. Maybe some pineapple juice would help next time? Ah well, the kids are asking why we used soap and why we used ethanol, etc., so it's all good. They're interested and curious.

Afterward, we take electroplating to the 8th graders, and to keep more of them occupied at any given time, we do magnetism as well. The 8th grade classes are located at one end of the second-floor labyrinth, and we would definitely not have found them were it not for our student guides/helpers who carried the materials all the way over.

There are two tables set up on the balcony outside, and we decide to take advantage of that. My mom sets up the electroplating materials on the right table, and I set up my magnets and iron filings on the left. This way, we can do two groups at once, keeping half of the 30-member class occupied at a time.

I begin by ascertaining how much they know about magnets. Opposite poles attract, like poles repel. A compass points north. They've got all that, but I figure it's useful to have a quick refresher, since lessons on science topics are so ridiculously spread out across the years in the curriculum.

So I move on the magnetic field, which I know they haven't yet covered. They don't need to know it yet, but it's a memorable demo. Place a magnetic field under a piece of cardboard (in this case, the lid of a box) containing iron filings (these are actually shavings taken from some iron/steel mill - I've sifted out the big, sharp pieces and kept only the fine iron dust). Nothing really happens. Give the box a few taps, and all of a sudden, the iron filings align themselves along the field lines, revealing a pattern.

Next up is induced magnetism, in which a non-magnetic piece of iron becomes a magnet itself when it is stuck to one end of the bar magnet. As soon as you pull the magnet off, the iron filings fall. The kids seem to enjoy playing with this one, and I sometimes have to take back the magnets and redistribute them so everyone in the group gets a chance to try.

After giving this spiel on magnetism 8 times, I think I've got it down pretty well. But my throat is getting tired of the constant talking. Time for some water and some rest before we head over to the junior college for dinner.

1 comment:

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