Day 41

Physical Science: Today kids collected data from the ink pen separation. It was a mad dash for them to get all of the measurements they needed. The data collection is one of the more complex that we do during the year, and really requires that each group has “all hands on deck.” Most groups got done by the end of the hour, but some had to come back during ELT (Extended Learning Time.)

Chemistry: Today we finally got to white board the results of our Pressure Labs. It was fun to see what the kids have been collecting and thinking over the last few days as they performed the lab. Kids who have been paying attention to the details of particle movement and behavior, get it pretty fast. Here are the white boards they prepared.

As you can see, I only have one group create the linear graph for Boyle’s Law. I am m ore interested in them understanding the inverse relationship than I am in having them be able to linearize it. The group that did this has two of my physics students, who saw an inverse graph earlier in the quarter. It provided them a good chance to explain this to small groups as we did “White Board in the Round” presentations.

At the end of the hour, started to see how we could use the data and their relationships to start creating a more quantitative analysis of gases and pressure. We ran out of time right around the point we developed “PV = k.”

Physics of Light: We picked up looking at ray diagrams for converging lenses, which we didn’t get to from yesterdays assignment. The last set of drawing have kids move an object from beyond 2F, at 2F, between 2F and F, and finally at F. After doing the drawings they are supposed to discuss the relative positions of the image, if it is inverted, its relative size, and if it is real or virtual.

After presenting solutions, we developed an agreed upon table of the above information. This was our qualitative analysis of object/image distances and object/image heights. It was at this point that we decided it was time to forgo the “theory” and see if our diagrams are in fact matching reality.

This is when I present them with our Converging Lens Pre-Lab. In order to test the above information, we would have to get a lens and figure out its focal length. Can’t you just get that off the box? Sure, but what fun is that?

The pre-lab is really a chance to check over some things, before we get carried away with the actual lab. First, do students understand the definition of focal length and the focal point? We discuss methods that they could use in order to get a rough idea of what this might be. Basically we need parallel light rays. Possible sources? Well, the best one around is the sun. Since the sun is so far away, the light rays traveling to us are diverging so little as they pass by us, they are essentially parallel. So if we held the lens up to the sun and found that little light dot where they focus to, we can get the focal length.

After that the pre-lab has them set up their lenses at some pre-determined object distances (figured out based on focal length of course.) This gives me a chance to assess if they understand how to take the measurements for the lab. Good data collection is necessary in order for the kids to get results in the actual lab. It also gives us a chance to see if our qualitative results match up with reality.

We talked about some of this, but the actual pre-lab is tomorrow.


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