Thursday, March 24, 2011

Gas Laws and Imploding Cans

Keeping it simple, but providing avenues for learning many concepts is important for both teachers and students.

One lab that I use in my chemistry course is the imploding cans lab to demonstrate gas laws, pressure and temperature relationships. 

Students provide two or three aluminum cans for this lab.
I use a hot plate for safety in my classroom.
Students add about 1-2 mL of water to an aluminum can and place it on a hot plate.
As the can heats up steam will realease out of the opening at the top of the can. 
I discuss why we add water to the can.  The steam is an indicator of when the can is hot enough anad demonstrates how molecules that are hot move rapidly and escape from the container.
When the can is hot enough the student will invert the can in to a trough of room temperature water.
When done properly the students will witness the imploding of the can.
Water will be drawn in to the can due to the low pressure vacuum created.

Discussion points:
  • pressure and temperature relationships
  • internal and external pressure on the walls of a container
  • kinetic molecular theory
  • decreasing pressure to create a vacuum
  • malleability of metals

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