Thermal Behavior of Gases
A small amount of shaving cream is placed in a beaker which is in turn placed on a platform that is connected to a vacuum pump. The platform is covered by a bell jar and the system evacuated. As the pressure decreases, the shaving cream's volume increases, due to the little air bubbles in the cream, to a large blob. When the air is let in, the blob collapses. The same can be shown with a balloon slightly inflated.
The compression igniter demonstrates the high temperature produced during adiabatic compressing of air by igniting paper cotton inside a transparent chamber. When the compression rod is rapidly pressed down, temperatures inside the compression chamber are elevated to ignition temperature of paper or cotton, which are about 450 degrees Celsius to 495 degrees Celsius.
- Insert a small piece (1cm2) of tissue paper or a few strands of cotton fiber using the steel loading rod to push the material to the bottom of the chamber.
- Insert the compression rod into the top of the glass compression chamber, and place the glass chamber inside the plastic pipe. Screw the cap onto the plastic safety pipe (standing perpendicular to the floor). With a quick, sharp stroke, push the rod down into the compression chamber.
Note: Do not push the rod all the way to the grip excessive force of the grip on the top of the glass chamber may break the chamber.
Click here to see a video of this demo.