Tuesday, March 18, 2008 - 4A

Collected RA 2.2 if students did not hand it in last time.

Handed back Distillation of Wood Lab Reports. Answered any questions on grading.

Handed back Boiling Point Lab. Reviewed the processes and phases for the plateaus (phase changes) and slopes (heating).

Showed students a diagram and sample set-up for the Heating and Cooling of an Unknown Substance Lab.

Described the data table, graph, and procedure. On the graph students need to identify the various phases and processes for each segment of the graph.

In addition to the data table and graph, students need to make the following observations and included them on the back of their graph:
1. At what temperature does the substance first seem to begin to melt?
2. At what temperature does the substance first seem to freeze?
3. When the substance begins to freeze, does it freeze at the bottom first or the top first?

Some thermometers were broken. I think this may be because I gave the students the thermometers embedded in the solid. If students wiggled the thermometers, perhaps they might break. Tomorrow when the other class does the lab, I will start with the liquid, have them freeze it, and then have them melt it.

Homework is to graph the data using the elements of a good graph (title showing variables being plotted, labels, units) as well as the processes and phases for each segment of the graph.