Apologia Chemistry: Module 12 Gas Laws Charles' Law or Gas Thermometer

The Chemistry class just began Module 12.  I like to start with labs, especially to teach gas laws.  I can refer back to their experience when we get to the math.  The class collected the Boyle's Law lab data, averaged the trials, and ran out of time.  Next class, we will finish the graph analysis with the graphing calculators.  The kids are going to make a Gas thermometer, using a side arm flask, graduated cylinder, beaker, stopper, thermometer, and a bucket of ice for a lab on Charles' Law.

Charles' Law is the relationship between temperature and volume.  In this lab, the kids are creating crude gas thermometers.  The first step is to start a boiling water bath using a larger beaker, 1000 mL. (Home Training Tools sells the equipment at fair prices.)  Fill a bucket with ice water.  The bucket must be large enough to submerge the side-arm or filter flask.  Next measure the actual volume of the flask by filling it with water and measuring the volume with a graduated cylinder.  Empty the flask.  The volume of water equals the volume of air the flask can hold.  Here is the procedure.  Stopper the flask, cover the side arm opening with one finger and submerge it in the water bath. Allow it to sit in the boiling water for about one minute.  Keep your finger on the arm of the flask, remove the flask from the hot water bath, and plunge the flask into the bucket of ice water, and remove your finger from the side arm once the flask is under water.  Note that some water entered the flask.  Measure the amount of water in a graduated cylinder.  The trapped gas in the flask compresses, allowing water to enter.  Record the temperatures of the boiling water bath and the ice water in the bucket. Repeat the process at least three times.

To graph the data, you have two points: hot and cold.  The initial temperature of the gas in the flask is the same as the temperature of the boiling water.  The corresponding volume is the volume of the flask.  The cold temperature is the temperature of the ice water in the bucket and its volume is the original volume minus the amount of water which entered the flask.  These two points can be graphed and an extension is to extrapolate to the temperature of absolute zero and zero volume.