Understanding of irreversibility

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Irreversibility in thermodynamics encompasses both macroscopic and microscopic perspectives. While macroscopic concepts like pressure and temperature relate to large numbers of molecules, the microscopic view involves the random movement of individual molecules, as seen in processes like gas expansion or ice melting. Reversibility is primarily a macroscopic idea, as it does not apply at the molecular level. All real processes exhibit some degree of irreversibility, highlighting the complexity of thermodynamic behavior. Understanding both viewpoints is essential for a comprehensive grasp of irreversibility in thermodynamics.
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The thermodynamic explanation of irreversibility - does it include the microscopic view of a process, i.e. the expansion of a ideal gas (the random movement of the molecules) or the melting of an ice cube?
Or is it only defined within the macroscopic world?
 
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erty said:
The thermodynamic explanation of irreversibility - does it include the microscopic view of a process, i.e. the expansion of a ideal gas (the random movement of the molecules) or the melting of an ice cube?
Or is it only defined within the macroscopic world?

It's defined in both:

http://en.wikipedia.org/wiki/Entropy

# 2.1 Macroscopic viewpoint (classical thermodynamics)
# 2.2 Microscopic viewpoint (statistical mechanics)
 
erty said:
The thermodynamic explanation of irreversibility - does it include the microscopic view of a process, i.e. the expansion of a ideal gas (the random movement of the molecules) or the melting of an ice cube?
Or is it only defined within the macroscopic world?
Irreversibility, of course, is the opposite of reversibility. A reversible process is one that can change direction with an infinitessimal change in conditions. In reality, all processes are somewhat irreversible. An example would be the expansion of a gas caused by applying a pressure to a container wall that was infinitessimally lower than the pressure of the gas. An infinitessimal increase in pressure will reverse the expansion and result in a compression of the gas.

In thermodynamics, reversibility is definitely a macroscopic concept. It has no meaning at the molecular level. Pressure and temperature are macroscopic concepts that relate to qualities of large numbers of molecules and are not defined at the molecular level.

AM
 
Andrew Mason said:
In thermodynamics, reversibility is definitely a macroscopic concept. It has no meaning at the molecular level. Pressure and temperature are macroscopic concepts that relate to qualities of large numbers of molecules and are not defined at the molecular level.
AM

Ok, thanks. Just had to be sure.
 
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