Charles' Law states that the volume of a gas is directly proportional to the Kelvin temperature. Students will learn about this gas law by observing a demonstration, graphing sample data using a spreadsheet program, and practicing problems. This will be the first gas law studied by the students. Before this, students will have studied the general properties of gases in chemistry class. They will have had some practice graphing and substituting into formulas in their math classes. Many, if not most, will have had prior experience with spreadsheets. Following this lesson they will do a lesson on Boyle's Law in which they will generate their own data in lab and try different graphing solutions to discover the formula. Then both laws will be incorporated into the Ideal Gas Law.

See standards from Graphing Gases Unit.

Plotting graphs. Substitution into formulas as a method of problem solving.

Demonstration of Charles' Law: Stretch the mouth of a large balloon over the mouth of a large Erlenmeyer flask. Place the flask on a ring and wire gauze over a bunsen burner. As you heat the air in the flask, the balloon will expand. Graphing Exercise: This lesson encorporates practicing graphing in groups both by hand and on the computer using a spreadsheet. If students are accomplished graphers and very computer literate, the duplication may not be necessary. In the next lesson, all work is done on the computer.

Hand and computer graphs submitted by students. Problem sets done by students for homework.

1. Students observe demonstrations of Charles' Law, and note that as the temperature increases, the volume of the air in a balloon increases. 2. Student groups are given sample data. Groups calculate Kelvin temperatures and V/T, and plot Volume vs. Temperature. 3. Groups enter data on spreadsheet program in computer, and produce a similar graph by computer. 4. Class sharing and discussion to synthesize Charles' Law and develop formula. Teacher provides problem examples. 5. Students do problem set for homework.

A computer for each group of students. Spreadsheet program.