Monday, March 17, 2008 - 4B

Handed back Separation of Mixture Lab Reports.

Talked about the heating curve from the Boiling Point lab. Where there is a flat area (plateau) on the temperature (y-axis) vs time (x-axis), you have a phase change. Where the temperature is rising, you are heating the substance.

Drew the heating curve on the board, showed the plateaus and slopes, and filled it in with the process (heating water, boiling water), and the phase or phases for each section of the graph. Whenever the curve is flat, there is a phase change. When ever the curve slopes, the substance is changing temperature.

Gave students the background info for the Heating and Cooling of an Unknown Substance which we will do next class. Drew a diagram of the set-up, showed a sample data table, gave the steps in the procedure.
1. Set up as indicated in the diagram. Turn on the hot plate to high and take temperature measurements of both thermometers (water and substance) every half minute until the temperature of the substance is 95 deg C.
2. When the temperature of the substance reaches 95 deg C, quickly lift the test tube out of the water and turn it away from the hot water.
3. Continue to take temperature measurements every 30 seconds until the temperature of the substance reaches 40 deg C.
4. Plot Tw and Ts vs time using the elements of a good graph.
5. On the graph of Ts vs time, show the phases and processes for each section of the graph.
6. Show the melting point temperature and freezing point temperatures on the graph.

Handed back Distillation of Wood lab reports and answered any questions.

Handed out RA 2.2. Gave students 30 minutes in class to work on it.