Day 26

Physical Science: I spent the hour assessing their Circumference v. Diameter labs from yesterday. While I did this, they worked on analyzing some more complex graphs as a final review before their quiz. The Circumference labs were mostly okay. Students did a good job again of constructing graphs, and were even better at analyzing them.

The big issue came from writing their C-E-R conclusions. This was the first real investigation since we did the scientific method stuff a couple weeks back. There were some that were awesome, some that were well constructed but showed simple thinking in terms of analysis, and a few that simply decided not to do it.

It’s a work in progress. At least the main focus of the assignment went well.

Chemistry: We wrapped up by looking at the “Smelly Demo” today. Here are the few notes that came out of discussion:


It was interesting to hear what they thought happened. I was focused on two things: how does the particles from the liquid end up in the air, and what proof do we have that air moves? Obviously the smell particles moved, or we would not have been able to smell them. But students were not able to give evidence that air moves.

We also looked at evidence for a chemical or physical change. Students agreed that by definition, the odds of smelling peppermint if the oil had chemically reacted with something in the air, was minimal. So the peppermint particles must have turned to gas. Hmmm…

So then we did the “Double Beaker” activity: two beakers of the same fluid, same amounts, both get color dye added to them, and observe.

CIMG1684 CIMG1685

the kids made observations about what they saw, and then some inferences. They had to construct white boards again to explain what they saw, and then if there was any connection that they could make to the “Smelly Demo, then they should also include that information. On Wednesday, we will be completely figuring this thing out.

Physics of Light: We did a flash quiz today on refraction. If you’ve not heard of a “flash quiz” it’s pretty simple: kid work problems on small white boards, then when I call time, they have to show me (flash) their answers. I tell them its a quiz, but its not graded. I also go around the room and tell if they got the question right or not.


When they don’t, they automatically look to someone else and say, “What? What was the answer? What did I do wrong?” It gets them talking about Physics, and correcting themselves. Which is nice.

I asked a series of both quantitative questions and qualitative.

“If the mediums are air and water, if the light ray is incident in air at 35 degrees, what is the angle of refraction?

“Explain the light behavior you just calculated.”

“If we move the light ray further from the normal, sketch the light ray that you would get, relative to your last answer.”

After a while of checking their understanding, I switch to light rays entering from a medium with higher index of refraction to one that is lower. Then we increase the angles a little bit, then qualitatively look at what increasing the angle does to the angle of refraction in the “faster” medium. Then I hit them with:

“Calculate and sketch the angle of refraction if the ray is incident in water at angles of 48.7, 48.75, and 48.8 degrees. The first two get close to 90 degrees, and the last one gives them a domain error.

When they do the sketches, I also make them draw the reflected rays, forgot to mention that. They have to draw ALL of the light action at the boundary.

So with the “Domain Error” they get a reflected ray, but no refraction. We discuss this qualitatively, as they saw first hand that the refracted light ray was approaching 90 degrees, which would be parallel to the boundary. Basically we develop the concept of Total Internal Reflection.

Ss: “Wait, is that why we got the error on that one homework problem yesterday?”

Me: “Yes it is.”


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