What's going on in class 9/18-10/1

IB Chemistry
Here are 2 videos that I recommended watching before class on Friday 9/20:

1. Crash Course Chemistry: Significant Figures: http://www.youtube.com/watch?v=hQpQ0hxVNTg
2. Rich Thornley's Uncertainties in Measurements: http://www.youtube.com/watch?v=XcaYc9xr9-k