ADIABAT

Animation of adiabatic processes

This animation shows a gas inside a box. The collisions are elastic. The gas can be adiabatically compressed or expanded by slowly moving one of the walls of the box. Free expansion can also be observed by suddenly moving a wall.

The total kinetic energy of the molecules is displayed at the top of the screen. When the gas is adiabatically compressed, the kinetic energy increases. When the gas is adiabatically expanded, the kinetic energy decreases. Under free expansion, the kinetic energy remains constant. The changes in kinetic energy are caused by collisions with a moving wall.

Note that when the gas is first compressed and then expanded, the kinetic energy does not return to its original value. This happens because the speed of the wall's movement is a sizable fraction of the average speed of the molecules, and the process is therefore not "quasi-static". If the speed of the wall were much smaller, the kinetic energy would return to its original value, but then, this animation would take much longer.

OpenGL Version

The program recognizes the following commands. The command may be executed by either clicking the button with the mouse (first column below) or by pressing a key (second column below). The mouse buttons may be removed from the screen by pressing the M key. Press M again to restore buttons.

The program recognizes the following commands:

compress C Compression. The left wall moves to the right until you press S or until the box has reached its minimum size.
expand E Expansion. The left wall moves to the left until you press S or until the box has reached its maximum size.
free F Free expansion. The left wall suddenly moves to the left so that the box has its maximum size.
stop S Stop compression or expansion. Wall stops moving.
quit Q Quit program.

DOS Version

The program recognizes the following commands:

C	Compression. The left wall moves to the right until you press S or until the box has reached its minimum size.
E	Expansion. The left wall moves to the left until you press S or until the box has reached its maximum size.
F	Free expansion. The left wall suddenly moves to the left so that the box has its maximum size.
S	Stop compression or expansion. Wall stops moving.
Q	Quit program.
?	Help. These commands are listed.

compress	C	Compression. The left wall moves to the right until you press S or until the box has reached its minimum size.
expand	E	Expansion. The left wall moves to the left until you press S or until the box has reached its maximum size.
free	F	Free expansion. The left wall suddenly moves to the left so that the box has its maximum size.
stop	S	Stop compression or expansion. Wall stops moving.
quit	Q	Quit program.