Thermodynamics : Isothermal process

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Discussion Overview

The discussion revolves around the concept of isothermal processes in thermodynamics, particularly focusing on ideal gases. Participants explore the conditions under which an ideal gas maintains a constant temperature during an isothermal process, the implications of supplying heat, and the challenges of realizing idealized processes in practical scenarios.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant questions how an ideal gas maintains a constant temperature during an isothermal process and how heat supplied is converted to work done by the system, seeking a molecular perspective.
  • Another participant notes that idealized thermodynamic processes are difficult to achieve in practice, suggesting that an isothermal process is only approximated and typically requires a heat bath with slow changes.
  • A participant raises concerns about the interaction between the heat bath and the system, questioning the control over heat transfer and the potential for heat loss to the bath.
  • There is a discussion about the dependence of outcomes on other constraints, with a participant suggesting the exploration of reversible heat supply without constraints.
  • One participant asserts that some heat will always escape the system, emphasizing the need for experimental design to account for this loss.
  • Another participant reiterates that constraints are always present, and without prior knowledge of these constraints, the system's behavior may become unpredictable.

Areas of Agreement / Disagreement

Participants express various viewpoints on the nature of isothermal processes and the implications of supplying heat, indicating that multiple competing views remain and the discussion is unresolved.

Contextual Notes

Limitations include the assumptions about ideal gas behavior, the practical realization of isothermal processes, and the effects of heat loss to the environment, which are not fully addressed in the discussion.

Rohan95
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In principle, what happens when an ideal gas undergoes an isothermal process? How is the gas at a constant temperature; is it maintained at that temperature? If we supply heat to the standard ideal piston assembly, why, or rather how is the heat supplied completely converted to work done by the system? Trying to get bit of a molecular picture here.

Also, what happens if known amount of heat is supplied to ideal gas at known thermodynamic state?
 
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The idealized thermodynamic processes are not easy to realize in real life - in practice, an isothermal process is only approximated.
You are correct, you'd usually have to supply a heat bath, and make changes slowly.

What happens when a known amount of heat is supplied depends on the other constraints - you do this every time you boil water: you know how much heat you supply and you know the thermodynamic state at the start. You may want to look at a simplified situation - say you have a gas in a cylinder/pluger affair you've seen in your textbooks, and you input some heat Q. What happens?
 
1) If we supply a heat bath, then we can't control how it will interact with the system, can we? What if some of the heat that is supplied to the system goes to the heat bath?

2) I get that it will depend on other constraints (eg. type of process (constant pressure, constant volume, etc)), but I was wondering what might happen if I supply heat reversibly, without placing any constrains.
 
Last edited:
1. Some heat supplied to the system will always escape. The experiment design needs to account for this.
i.e. The system may be insulated, and the other state variables allowed to change.

2. There are always constraints... if you do not know, in advance, what the constraints are, then the system will behave unpredictably.
 

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