Day 48

Friday, November 7.

Physical Science: This was a bit of a hodge podge today. 2 classes played Chem Scrabble, a game invented by some bored study hall kids about 10 years ago. Basically they make words out of the atomic symbols. It’s a fun game, plus it subliminally gets them reading and figuring stuff out with the periodic table. A benefit for when that unit comes up later.

The odd class out read and worked on the “Particles in Motion” article that the other classes did a few weeks back.

Chemistry: We reviewed what temperature was all about, and then introduced the difference between this and thermal energy. For good measure, we also introduced the concept of heating (heat). We watched an episode of Eureka! to do this.

I do disagree with some of this video. What it calls heat, I call thermal energy: the total energy of all of the particles in a sample of matter. Heat is a process, one of the 3 methods of energy transfer (working and radiating are the others.) Heating is the trnasfer of energy when particles bounce off of each other.

From this we got back to talking about energy and states of matter. I posed a question that came up about Anders Celsius:

“How did he know when to mark off his thermometer? Doesn’t the mercury in his test tube keep expanding?”

So I thought maybe we should look into that finally. So we will on Monday.

Physics of Light: We finished up with our converging lens lab discussion. I thought it was important to tie in the relationships we saw in the Pre-Lab portion with our new data, specifically the image sizes. So, we looked at the geometry of the lens, and found that di/do = hi/ho, where we have the height of the image and the height of the object. This gives us the chance to see what do and di would have to be for a certain magnification.

So we used the thin lens equation to figure it out. Then I showed the kids how, if you have data for the lens, you could find do and di graphically. Basically, if you have the Converging Lens data, you can create a data set with the line: 1/di = 1/Mdo + 0, where M is the magnification you are looking for. Where the two lines cross, is the 1/do and 1/di that will give you the magnification you are looking for.


You can do the same thing by graphing 1/di = -1/Mdo + 0, but this is a little outside of what we have talked about so far, especially since it means you get a negative image distance…another day my friends.

I then gave the kids a lab challenge, instead of the typical post-lab write up: find the focal length and power of an unknown lens, and find do and di such that M=3. We will be doing this on Monday.


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