Wednesday, March 12, 2008 - 4A

Reviewed Boiling Point Lab.

Sketched heating curve for water. The graph from the lab has three regions. The middle section with the steep slope (when the temperature is rising at a steady rate) is when you are heating the water. The graph then flattens at about 100 deg C. This flat section shows the boiling point of water. As you add energy, the temperature does not go up - instead the energy goes into changing liquid water into gas.

In this lab we started with ice water. There is a flat portion (adding energy with no temperature increase) when we started the lab which occurs when the energy goes into melting the ice. As long as you stir to maintain a consistent temperature, the temperature does not rise until all the ice is melted.

You can use the boiling point to help identify the substance. The boiling point is a characteristic property of the substance. You will do this in the sludge lab to help identify what the liquids are in your sludge.

Showed the Bill Nye video on Phase Changes. Students acted out "solid", "liquid", "gas", just as in the video.

Students spent the last 30 min working on Reading Assignment 2.2a. Many students finished and handed it in. For the rest, it is due on Tuesday March 18.