Free Expansion of Gas: Internal Energy & Work

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Discussion Overview

The discussion revolves around the free expansion of gas, specifically addressing the implications for internal energy and work done during the process. It touches on theoretical aspects of thermodynamics, particularly the first law, and the behavior of ideal versus real gases during adiabatic expansion.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant questions whether the change in internal energy is zero during free expansion, given that dQ=0 according to the first law of thermodynamics.
  • Another participant references a previous comment to clarify their understanding of the temperature behavior of gases during expansion.
  • It is noted that for an ideal gas, the temperature remains constant during free expansion, while for real gases, the temperature decreases due to particle interactions and potential energy changes.
  • A participant explains that the attractive interactions in real gases can lead to a decrease in temperature upon expansion, but also mentions that there are exceptions based on the inversion temperature of specific gases, such as helium.

Areas of Agreement / Disagreement

Participants express differing views on the behavior of internal energy and temperature during free expansion, particularly distinguishing between ideal and real gases. The discussion remains unresolved regarding the implications of these differences.

Contextual Notes

There are limitations in the discussion regarding the assumptions made about ideal versus real gases, as well as the conditions under which the inversion temperature applies. These factors contribute to the complexity of the topic.

Apashanka
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If a gas is suddenly allowed to expand freely and adibatically inside a container then from the first law of thermodynamics dQ=0,
My question is whether the change of internal energy would be 0 and if it then how would the work done be 0 (since accessible volume of the gas changes inside the container changes)??
Thqnks
 
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Apashanka said:
Thanks that's clear now but temp remains constt for ideal gas but for real gas it decrease ,can you please help me in clearing this concept
Thank you
For a real gas, you have to take into account the interaction between particles. In most cases, there is an overall attractive interaction (negative potential energy) which leads to a decrease in temperature when the gas expands and the attraction between the particle is globally lower because of the greater volume occupied. Note that this is not always true, as each gas has an inversion temperature above which the gas will heat upon expansion. This is already the case at room temperature and pressure for helium.
 
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