Gas Laws
Goal
Chemistry Unit 7 States of Matter
C2.2c Explain changes in pressure, volume and temperature for gasses using the kinetic molecular model
Background
This lab can be done as a demo or classroom activity with each student participating or in pairs or groups. It involves all three pressures, temperature and volume. There are two methods that are dramatically different and lead to some open ended discussions. While the can is heating you can be discussing the various gas laws
Vocabulary
Boyles Law, Charles Law, Guy-Lusacs Law
Materials
Hot Plate, water, large empty aluminum ice tea cans ( non returnable ) 600-1000ml beaker, beaker tongs. If you want each student to complete the lab they can bring in their own can ( non returnable)
Procedure
Rinse out the cans and just put enough water in one or two that the bottom of the can is covered. Place on the hot plate on Hi. Fill the beaker full with water. When you see steam rolling out of the can pick it up with the beaker tongs around the bottom of the can. Turn the can over and carefully just touch the top of the water in the beaker. As the air cools and the volume decreases the water will be forced into the can, slowly lower the can into the beaker as the water continues to be forced into the can. You will be able to fill the can. Once filled lift the can hi above the beaker and let the water flow out of the can and back into the beaker.
For the next part this time tell the students to watch closely as this time it will go very fast, a fraction of a second. Reheat the can and fill the beaker with cold water. When the steam has had a time to flow out pick up the can, turn over and this time push it into the water quickly all the way. The can will implode !!
The questions are not just describe what happened and why ( gas laws ) but describe the difference between the two methods. Discussions can lead into submarines imploding, Arcamede’s principal and submarines and then why hot air balloon rise, Helium balloons getting smaller in winter when you take them outside the store.
This can be done as a demo but the students really enjoy doing it themselves after a teacher demo. Safety factors include the hotplate, hot cans and boiling water with steam. Lab can be done with pop cans but they will be non returnable and you’ll add a 10 cent cost to each demo.