Thurs Oct. 24, 2013
Chemistry 1 – We took a quiz on unit conversions. We’ve focused on the “domino” method to make these conversions. But, as I’m assessing the quizzes I’ve notice some students have gone back to previously learned methods, which I’m fine with, if it gets them to the correct final destination. It’s been my experience in the past that if students try to memorize when to multiply and divide they screw up 50% of the time. When I see this I will insist they set the problems up with the domino method.
Physics 1 – With the use of robots this year for constant velocity motion we haven’t used the Vernier Motion Detectors. Usually somewhere in the middle of the Constant Velocity Unit we would do the walking/graph matching activity with the motion detectors. I would usually use this to relate a position vs. time graph to a velocity vs. time graph for the first. The robots did a much better job of this. I still wanted the students to have the experience of the motion detectors so we used it more as a have fun/review activity.
Chemistry 2 – We continued to look at the data gathered from a titration between a strong acid and strong base. As expected the concentration of the H+ ion went down as NaOH was added. By looking at the graph above it looks as if there is a point when the concentration reaches 0.000 M. However, upon further analysis as we zoomed in on the data the concentration never actually gets to exactly zero. This contradicted our expectations that the H+ ion would completely “used up” upon addition of the OH- ions. I then took a sample of pure water and measured the H+ Molarity of that. It came out pretty close to 1E-7. So even in pure water, which we know is neutral there is H+ ions. This means there must be OH- ions as well to keep it neutral.