Leidenfrost effect at thermodynamic equilibrium

AI Thread Summary
The discussion revolves around the thermodynamic equilibrium of a spherical drop of a pure substance floating on its vapor. The key finding is that at equilibrium, the pressure difference between the liquid drop (PL) and the vapor (PV) is given by the equation PL - PV = 3σ/a, where σ is the surface tension and a is the radius of the drop. The participant confirms that their calculations align with thermodynamic principles and emphasizes the need for detailed explanations when seeking validation of results. The conversation highlights the relationship between surface tension and pressure in the context of the Leidenfrost effect. Overall, the analysis reinforces the significance of surface tension in thermodynamic systems at equilibrium.
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Homework Statement


A spherical drop of a pure substance floats on top of the vapor of the same substance so the system vapor+drop is isolated. The drop has a surface tension σ. Show that at the thermodynamic equilibrium PL≠PV and calculate the difference.

Homework Equations


Three laws of thermodynamics

The Attempt at a Solution


I solved this one already but I would like to check my result. Following the three laws of thermodynamics and maximizing the entropy at the equilibrium yadda yadda yadda I got PL-PV=3σ/a, where a is the radius of the drop. The dimension of the result seems correct.
 
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Is there a question here? If the question is "Am I right?", you have to supply the "yadda, yadda, yadda" so that someone can check your work and point out possible mistakes.
 
kuruman said:
Is there a question here? If the question is "Am I right?", you have to supply the "yadda, yadda, yadda" so that someone can check your work and point out possible mistakes.

Ok...
For σ=0, Thermodynamic equilibrium says: PL=PV, but if we add a work therm for the liquid -σdS=-3σdV/a we get PL-PV=3σ/a.
 

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