Day 40

Physical Science: After collecting the homework from Thursday, I introduced the lab we would be doing for the next two days. Since we just got done talking about mixtures, I decided we would do a mixture separation lab. Using Chromatography, we were going to look at whether or not wet erase markers are more attracted to polar mobile phases or stationary mobile phases.

Since the next thing we plan on getting into is properties of substances, I like doing a lab that introduces kids to a property of matter that they are probably not that familiar with. Plus the Chromatography technique is pretty interesting, and gives them lots of measurement practice as well.

Chemistry: Today was the final day of our Pressure Labs. Today we did Pressure v. Temperature. Here are a couple of images for you.

The problem we always have, year in and out, is that the seals are not that great, and the gas leaks out as it gets warmer. This leads to graphs with a slope of 0, and very little meaning. This year I had an idea to wet the rubber stopper slightly to help get a snug seal. then I had my in-school work experience student put it all together. The combination of the two, and we got awesome data.

There was one group that struggled though.

“Mr. Schwaller, our data looks weird. All the points are the same; same temp and pressure.”

“Well I see what the problem is.”

“What?”

“This,” and I slapped my hand down on the surface of the hotplate. After a few gasps, they realized that the hotplate was never plugged in, and it was nice and cool. Lesson of the day, make sure your stuff is plugged in, not just turned on.

Physics of Light: We started going over the Optics assignment from last week. While the diagrams are nicely done, there are some concerns of mine about their understanding of real images versus reproduction. This is certainly not nailed down yet. Some of that is recall since we did pinhole cameras so long ago, and some of it is our new found knowledge about aerial/real images.

There is an issue with the difference between light selection (pinhole cameras/reproductions) and light bending (real images). The pinhole camera only forms a reproduction because it takes away so many of the streams of light particles. When there are to many, the reproduction is blurry, as what we have are gagillions of versions of the reproduction overlapping to make one light blur. With the lens, we control and bend the light so that all of the light leaving a single point on the object, ends up at a single point where the image forms. This does NOT require light selection.

The lens allows us to utilize all of the light leaving an object to make the image. In fact, more light is better as it allows for a brighter image to form. As was stated in one presentation, “While more light gives a brighter image, since there are countless streams of particles hitting the entire surface of the lens, we can cover up most of the lens, almost like a making a pinhole in front of it, and the aerial image will still form. We just need some light to strike the lens, and we get the image. It’s just a question of how bright it will be.”

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