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To: betty boop

Gibbs free energy relates to systems at a constant pressure.

Helmotz free energy relates to systems at a constant volume.

Note that volume can change when systems at constant pressure change; this leads to work being done on or by the system. Pressure times volume has the units of energy (or work). The model is a piston moving through a cylinder; it can compress air or be pushed by steam or burning gasoline.

Systems at constant volume can do no outside work.


189 posted on 05/09/2005 11:44:08 AM PDT by Doctor Stochastic (Vegetabilisch = chaotisch is der Charakter der Modernen. - Friedrich Schlegel)
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To: Doctor Stochastic
Systems at constant volume can do no outside work.

Thanks Doc for clearing that up!

191 posted on 05/09/2005 12:03:47 PM PDT by betty boop (If everyone is thinking alike, then no one is thinking. -- Gen. George S. Patton)
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