Understanding of irreversibility

  • Thread starter Thread starter erty
  • Start date Start date
  • Tags Tags
    Irreversibility
AI Thread Summary
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.
erty
Messages
26
Reaction score
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?
 
Physics news on Phys.org
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.
 
Thread 'Gauss' law seems to imply instantaneous electric field'

Thread 'Gauss' law seems to imply instantaneous electric field'

Imagine a charged sphere at the origin connected through an open switch to a vertical grounded wire. We wish to find an expression for the horizontal component of the electric field at a distance ##\mathbf{r}## from the sphere as it discharges. By using the Lorenz gauge condition: $$\nabla \cdot \mathbf{A} + \frac{1}{c^2}\frac{\partial \phi}{\partial t}=0\tag{1}$$ we find the following retarded solutions to the Maxwell equations If we assume that...
View full post »

Thread 'Do electron density waves accompany EM waves in coaxial cables?'

Maxwell’s equations imply the following wave equation for the electric field $$\nabla^2\mathbf{E}-\frac{1}{c^2}\frac{\partial^2\mathbf{E}}{\partial t^2} = \frac{1}{\varepsilon_0}\nabla\rho+\mu_0\frac{\partial\mathbf J}{\partial t}.\tag{1}$$ I wonder if eqn.##(1)## can be split into the following transverse part $$\nabla^2\mathbf{E}_T-\frac{1}{c^2}\frac{\partial^2\mathbf{E}_T}{\partial t^2} = \mu_0\frac{\partial\mathbf{J}_T}{\partial t}\tag{2}$$ and longitudinal part...
View full post »

Similar threads

I The relationship between reversible and irreversible processes
Replies
5
Views
2K
Understanding reversible and irreversible process
Replies
34
Views
5K
Chemistry A few questions on an irreversible adiabatic expansion of an ideal gas
Replies
1
Views
2K
I Irreversible adiabatic processes & entropy change (clarification needed)
Replies
22
Views
5K
Chemistry What does the differential of U mean in an irreversible process?
Replies
11
Views
2K
I Irreversible Isochoric Process in a Cycle
Replies
8
Views
3K
B Irreversible Process to Move Gas from State 1 to State 2
Replies
30
Views
2K
I About Reversible vs Irreversible Gas Compression and Expansion Work
Replies
4
Views
2K
B Loschmidt's paradox and free gas expansion
Replies
5
Views
1K
The exact formula for PV-work in an irreversible process
Replies
27
Views
9K

Hot Threads

Recent Insights

Back
Top