Understanding of irreversibility

  • Thread starter erty
  • Start date
26
0

Main Question or Discussion Point

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?
 

Answers and Replies

973
0
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)
 
Andrew Mason
Science Advisor
Homework Helper
7,540
317
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
 
26
0
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.
 

Related Threads for: Understanding of irreversibility

Replies
34
Views
3K
Replies
2
Views
10K
  • Last Post
Replies
1
Views
3K
Replies
0
Views
909
  • Last Post
Replies
1
Views
6K
Replies
2
Views
2K
Replies
6
Views
6K
  • Last Post
Replies
2
Views
984
Top