Path dependence - Question of Thermodynamics

In summary, the conversation discusses a solution to a problem involving two gases in a container separated by an adiabatic fixed wall, which is later changed to a diathermic mobile wall causing a change in equilibrium point. The solution involves dividing the process into two parts: an isochoric process and an isothermal one, but it is noted that pressure and temperature evolve simultaneously. The conversation then delves into the concept of path dependence and independence in thermodynamics, with state variables being independent and work and heat being dependent on the path taken to reach a state.
  • #1
gerardpc
8
0
I've read a solution of a problem, in which there are two different gases in a container, initally at equilibrium and separated by an adiabatic fix wall. At some time, this wall is changed by a diathermic mobile wall, so the equilibrium point changes. You have to find the final state of the gases, given the initial volumes, temperatures and pressions.

Then the solution says: we will divide the process in two parts: first an isochoric process and after that and isothermal one. But it is clear that pressure and temperature evolve at the same time.
I'm making a bit of a mess here: is it path dependent or indpendent? In a generic process, when is it path independent and when it is not? And why?
 
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  • #2
State variables, such as energy, entropy, enthalpy, free energy, temperature, pressure, volume, etc. are path independent.

The chief path-dependent quantities in thermodynamics are work and heat. They are not determined just by the state, but by the path taken to reach the state.
 

FAQ: Path dependence - Question of Thermodynamics

What is path dependence in the context of thermodynamics?

Path dependence in thermodynamics refers to the fact that the final state of a system is not only dependent on its initial state, but also on the path it took to get there. This means that the same initial and final states can be reached through different pathways, and the final state can be affected by the history of the system.

How does path dependence relate to the laws of thermodynamics?

The second law of thermodynamics, which states that the total entropy of a closed system tends to increase over time, is closely related to path dependence. This is because the entropy of a system is a measure of the disorder or randomness of its particles, and the pathway taken by the system can affect the final state's level of entropy.

What are some real-life examples of path dependence?

One common example of path dependence in thermodynamics is the hysteresis of magnetic materials. When a magnetic material is exposed to a magnetic field, it can become magnetized in a certain direction. However, when the magnetic field is removed, the material may not return to its original state, but instead retain some level of magnetism. This is due to the path dependence of the material's magnetization.

Is path dependence always a disadvantage in thermodynamics?

No, path dependence can actually be advantageous in certain situations. For example, in the human body, enzymes often follow specific pathways in biochemical reactions, which allows for more efficient and precise control of these reactions. In industry, path dependence can also be used to manipulate and control the final state of a system, such as in the production of alloys.

How can path dependence be overcome in thermodynamics?

In some cases, path dependence can be overcome by carefully designing or manipulating the system to follow a specific pathway. This can be done by controlling external factors such as temperature and pressure, or by introducing catalysts to guide the reaction. In other cases, path dependence may be unavoidable, and understanding and predicting its effects is essential for efficient and effective thermodynamic processes.

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