August 29, 2000
Inquiry Lesson: Charles's Law; V=kT
The instructor takes several balloons of different size, shape, and color and places them in a flask of liquid nitrogen.(only bring the balloon near the liquid, the cooling effect will begin, do not touch the balloon to the Nitrogen!) Wear appropriate safety goggles and gloves. Students will see the collapsed balloon in the flask, and then watch as it expands when removed. The students are told nothing about the contents of the balloon or the flask. The students then engage in discussion and propose different explanations for the phenomena. (Instructor will guide suggestions when needed.) Some students may guess that the balloon is made of a special material. Some students may believe that the gas in the balloon causes the deflation, or that the balloon leaks when it comes in contact with the contents of the flask. Some students could notice the steam around the flask and guess that temperature has an effect on the size of the balloon.
The students will then break into groups to perform individual experiments to test the explanations.
Examples of variables:
Composition of balloon
Composition of gas in balloon
Temperature of balloon
Composition of gas in flask
The students will design their own experimental procedure using a list of available material. They will compose a proposal and submit it for approval. The instructor will then review the procedures and make suggestions when needed. After the students have a chance to revise their proposals they begin their experiments.
The students will regroup after they complete the lab work and report to each other their findings. From the collected data each group will draw a conclusion and use experimental data to justify their answer.
The groups will then perform a measurement lab and compare the volume of a given gas to temperature. The class will then compile information and discuss the best way to illustrate their findings. They will create a graph using the collected data. The graph will show the direct relationship, V=kT, of volume and temperature. These graphs can also be used make predictions.
As a challenge the instructor can ask that the students try to find some common applications of this gas law. (i.e. hot air balloons)