In my IB Chemistry class, my seniors were finishing up independent investigations for their Internal Assessment a few weeks ago when something cool happened. One of my students was using silver nitrate and potassium chromate for a titration. This is notable to the story here because the endpoint is marked by the formation of silver chromate as a precipitate, with a deep reddish color. I overhead the student showing his reaction to another student, with both of them commenting on the cool colors involved.
First, I would like to thank all those who commented on my last blog. For the record, I was wrong. Initially I looked at Linus Paulings early papers as he worked on electronegativity. Much of the work focused on connecting the concept to bond energy. There were some great comments posted to the blog. Probably one of the best was explaining how the concept of electronegativity presents a model for bonds. It is not an observable quantity. This really helped me explain it better to my students. As the commentor posted, all models have limitations. Second, the person commented that in Linus Pauling's General Chemistry book published in 1970 (Dover Publishing) that he does indeed talk about the differences in electronegativity to discuss a type of ionic and covalent character. I stand corrected.
This year in the midwest United States, winter has been a fickle friend. I haven’t seen the same amount of snow or ice as in recent years, but I still made sure I was prepared for it at our home. I went to my local big box hardware store in December and contemplated buying rock salt (NaCl), and NaCl/calcium chloride mixture, or just calcium chloride. Growing up my dad had switched entirely to calcium chloride because it was less damaging to the brick pavers leading to our porch and backyard. In fact, calcium chloride is generally much safer toward plants and soil than NaCl. Even though calcium chloride is much more expensive than rock salt (it was about twice the cost for 10 pounds more), that what’s I chose. Why?
The Biennial Conference on Chemical Education (BCCE) will be held at the University of Northern Colorado in Greeley, CO from July 31 through August 4, 2016. This is an excellent professional development opportunity for high school and college chemistry instructors. You still have time to submit an abstract to present. Presentations are generally 20 minutes in length.
In my high school chemistry class, a unit we cover is that of atomic structure. In particular, given an elements symbol, mass number, atomic number, and charge, the objective would be for the student to determine the atoms number of protons, neutrons, and electrons. I have several apps/program suggestions that can be useful for this purpose.
I’m a first year AP chemistry teacher. My emotions swing from fear of inadequacy to confusion in pacing to acute awareness of the number of years since college chemistry to desperation in grading 55 lab notebooks to exhaustion with inexperience. Honest truth: I'm studying. I'm studying a lot. Despite 14 years of chemistry teaching experience, I feel blindfolded again.
Most chemistry teachers somehow teach Lewis dot structures. These structures are the foundation for VSEPR theory, three dimensional models and ultimately how the structure allows us to predict what happens on a large scale. Here is the crazy part...there are a number of different "rules" that really do not make a whole lot of sense. Do a quick search...everyone has there own rules.
Technology is a word that can generate a great deal of debate in a chemistry classroom. I got into an interesting conversation with a teacher who is new to my school this year as she was moving into her classroom next to mine.