10/7/13 Weekly Reflection

      This week, we did more POGILs on bonds and did the actual lab work for a lab. The POGILs were on covalency, bond order and bond strength, and the one we did on Friday was the start of VSEPR (Valence Shell Electron Pair Repulsion) models. We used red balloons to mimic the electron domains of bonded electrons and we used white balloons to mimic the electron domains of lone electron pairs. The white balloons were larger than the red because the red were subject to stronger attractive forces between the nuclei of the atoms and the electrons in the bond. The first of the earlier two POGILs were looking at bond orders and bond energies and how they are connected. As the bond order increases, bond energy also increases. The second of those POGILs looked at bond length, calculated bond order and lewis dot bond order and how they interact and in what ways. This segued into resonance structures, which are multiple, equally valid representations for a molecule in which bonds could be in various different places. Lastly, we did a lab on the reaction between brass and nitric acid. We got to work with one of the seven strong acids! We observed the reaction and are now trying to use a diluted sample of the result to determine the mass percent of copper in those brass screws.
        This lab was slightly confusing, mostly because my group was assigned to do something different than I had written my lab report for (I wrote it for the calibration curve, not the visualization method) and, although I knew how to do it, it was unsettling. However, I understood the VSEPR models very well. I also understood the bond orders and bond energies relationships very well - they made a lot of sense, especially if you think of bonds as both chords of energy and relationships of attraction with electrons and nuclei at the same time.  The material in the second POGIL also made a lot of sense. I did my best to participate in the learning as much as I could and as well as I could. I love my table group which helps a lot (although I liked my last one as well). I still have a few questions about the lab, however. First, what determines how long the reaction takes? Is it merely the quantities of reactant, and the more reactant the longer the reaction takes? Also, I'm sure we covered this, but what determines the electronegativity of an element? Obviously there is the periodic trend, but what determines that? One of the pitfalls when thinking on the particle level is that you start thinking about everything in terms of the subatomic particles that make it up, so now I'm thinking of the keyboard as a remarkable dense and complicated - nay, fascinating -structure.