Is Pressure Directly Proportional to Temperature in Gases?

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Discussion Overview

The discussion centers around the relationship between pressure and temperature in gases, specifically whether pressure is directly proportional to temperature for a fixed volume of gas. Participants explore theoretical implications, definitions, and experimental observations related to this relationship.

Discussion Character

  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • Some participants reference a lecturer's notes stating that pressure (P) is proportional to temperature (t) for a fixed volume of gas, expressed as P = P0(1 + αt), with α approximately equal to 1/273.
  • Others affirm that P is indeed proportional to t under certain conditions, such as for ideal gases or at low pressures and reasonable temperatures.
  • One participant questions the formulation of the relationship, suggesting that if P is proportional to t, it should be expressed as P = αt rather than including a constant term.
  • Another participant seeks clarification on how α is derived as approximately 1/273, linking it to the definition of absolute zero.
  • There is a challenge regarding the validity of defining α in terms of absolute zero, indicating a need for further explanation.

Areas of Agreement / Disagreement

Participants express differing views on the formulation of the relationship between pressure and temperature, with some supporting the lecturer's notes while others question the implications and definitions involved. The discussion remains unresolved regarding the exact nature of the proportionality and the derivation of α.

Contextual Notes

Participants have not fully clarified the assumptions underlying the proportionality, nor have they resolved the mathematical implications of the relationship. The discussion also highlights potential dependencies on definitions of temperature scales.

hasan_researc
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My lecturer writes the following in his lecture notes:

" P [tex]\propto[/tex] t for a fixed volume of gas,
P = P0(1+[tex]\alpha[/tex]t)

Using the celsius scale of temperature, we find [tex]\alpha \cong[/tex] 1/273."

Is P really proportional to t?

How do we find [tex]\alpha \cong[/tex] 1/273 using the celsius temp scale?
 
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hasan_researc said:
My lecturer writes the following in his lecture notes:
" P [tex]\propto[/tex] t for a fixed volume of gas,
Correct

P = P0(1+[tex]\alpha[/tex]t)
Just another way of writing the above,

Is P really proportional to t?
Yes - for an ideal gas or at low pressure and reasonable temperatures.

How do we find [tex]\alpha \cong[/tex] 1/273 using the celsius temp scale?
Experimentally - it's the definition of absolute zero
 
If P [tex]\alpha[/tex] t for a fixed volume of gas, then should P not equal [tex]\alpha[/tex] t, instead of being equal to a constant P-nought times the sum of 1 and [tex]\alpha[/tex] t?
 
mgb_phys said:
Experimentally - it's the definition of absolute zero

How can it be the definition of absolute zero?
 

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