Constant pressure and constant volume?

Click For Summary

Discussion Overview

The discussion revolves around the possibility of a thermodynamic system existing under both constant volume and constant pressure simultaneously at a particular instant. Participants explore the implications of such conditions and the physical principles involved, including thermal expansion and ideal gas behavior.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant questions whether a thermodynamic system can be under both constant volume and constant pressure at the same time, expressing uncertainty about the validity of the question.
  • Another participant suggests that while it is possible, it is uncommon, noting that this would imply zero thermal expansion and referencing materials that exhibit this property.
  • A different viewpoint states that if both conditions are met, the system must also be at constant temperature.
  • One participant provides an example of a sealed gas canister, questioning whether it could be considered under constant pressure and volume, while seeking clarification on potential oversights in this reasoning.
  • A further response challenges the notion of simultaneous constant conditions, arguing that if "constant" refers to time, it leads to contradictions, suggesting that uniformity or a process rather than an instant may be more appropriate terms.

Areas of Agreement / Disagreement

Participants express differing views on the feasibility of a system existing under both conditions simultaneously, with some supporting the possibility while others challenge the coherence of the concept. The discussion remains unresolved with multiple competing perspectives.

Contextual Notes

Participants highlight the need for clarity in definitions, particularly regarding the terms "constant" and "instant," indicating that the discussion may depend on specific interpretations of these concepts.

Federer33
Messages
1
Reaction score
0
Can a thermodynamic system simultaneously exist under both constant volume and constant pressure at a particular instant. I mean , when the system is under constant pressure condition, can we impose constant volume on the system. Please clear my doubt. I don't know if it's a silly question, but eating my brain.
 
Physics news on Phys.org
It's possible, but pretty uncommon. Equivalently this says that the thermal expansion (∂V/∂T)P vanishes. If you Google "zero thermal expansion" you'll find a few articles where such a material has been created. Otherwise the only time the thermal expansion vanishes is at absolute zero.
 
Sure. It just means that you also have constant temperature.
 
Wouldn't a sealed uncooled canister of gas, such as a helium tank at a party store, be at a constant pressure and constant volume? Or is there something else to the problem I don't see?
 
Federer33 said:
Can a thermodynamic system simultaneously exist under both constant volume and constant pressure at a particular instant.
If by "constant" you mean constant in time, the specification underlined will make it a nonsense.
Either you mean "uniform" (that means no spatial variation) or you mean a process and not an instant.

A process with no change in pressure or volume may be possible, for a general system. Other parameters may change. For ideal gas you may have a system which variable number of particles.
 

Similar threads

Undergrad Pressurized containers: Stress distribution and large displacements
  • · Replies 69 ·
3
Replies
69
Views
5K
Undergrad Temp and Pressure measure of KE(average)
  • · Replies 6 ·
Replies
6
Views
2K
High School Pressure of captured air under water
  • · Replies 12 ·
Replies
12
Views
3K
Graduate Use internal pressure to compute work done by an expanding gas?
  • · Replies 15 ·
Replies
15
Views
3K
Graduate Constant pressure or isobaric expansion of gas
  • · Replies 14 ·
Replies
14
Views
6K
Zeroth Law of Thermodynamics
  • · Replies 5 ·
Replies
5
Views
2K
Graduate Fluid Mechanics: Constant Pressure and Incompressible flow
  • · Replies 5 ·
Replies
5
Views
2K
Graduate Does Fluid Dynamics Explain Pressure Gradients in a Frictionless Tube?
  • · Replies 48 ·
2
Replies
48
Views
6K
Chemistry Graph of several thermodynamic processes
  • · Replies 8 ·
Replies
8
Views
3K
Graduate Internal energy pressure dependence
  • · Replies 2 ·
Replies
2
Views
2K