Week 2

This past week in AP Chemistry we focused on stoichiometry, the area of chemistry dealing with the ratios of atoms in chemical reactions, and the many applications it has in the real world. To help the class better understand the topic of stoichiometry, we "white-boarded" problems from various worksheets in class. This consists of each table group being assigned a single problem to work through quickly, but thoroughly and presenting their work to the class.

This approach to students doing practice problems offers multiple advantages over the standard way of having each student work through every problem on their own. First, a significant amount of time is saved by doing this simply because each student does less work. One might jump to the conclusion that saving this time would only sacrifice the students' understanding of the material, but this is not the case. This is because of the presentation of work. While students present their work, others are encouraged to double-check their classmates work, which requires thinking through the process of the problem and getting the required practice, while excluding the manual calculation of numbers which students gain little from. Working in groups also increases the efficiency of getting students through parts they may get stuck on or make a mistake. Instead of spending time trying to remember something that is not there, or looking for a mistake, students are quickly aided by their peers to get them through while reminding them what area they may need to review. Lastly, students have an added positive motivation to focus on their own problem as to not make a mistake for the rest of class to see.

This week has also changed the way that I think about the numbers and units given to me in any particular problem. Previously, I had considered all given information to be finite, single pieces of information that can help to find other information. I now know that given information used to find the solution to a problem is part of a large web of values relating to the problem that can always be traversed with the right conversion factors and aided by units (see figure below)(see URL below for stoichiometry summary and practice problems). The idea that units should be used as a guide was also reinforced as we did many multiple-step problems in which you could easily get lost in.

I have observed many connections between the material we covered during this last week and the weeks before that. During the summer we learned how to verify that a chemical equation is balanced and change coefficients if necessary to follow the law of conservation of mass and the idea that atoms themselves are not changes in chemical reactions. These same principles are present in the stoichiometry we covered this week. Without following the law of conservation of mass, many of our calculations regarding limiting and excess reagents would be impossible.

Stoichiometry summary and practice:
http://s-owl.cengage.com/ebooks/vining_owlbook_prototype/ebook/ch3/Sect3-3-c.html

The general molar web connecting each value