Gas pressure and temperature relation

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Discussion Overview

The discussion revolves around the relationship between gas pressure and temperature, exploring the underlying mechanisms that connect these two properties. Participants examine the effects of gas compression, molecular movement, and kinetic energy, with a focus on both theoretical and conceptual aspects.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • One participant questions the proportionality of gas pressure and temperature, suggesting that compression reduces molecular movement and raises the potential for friction, which may create heat.
  • Another participant clarifies that temperature relates to the collisions of gas molecules rather than friction, indicating that increased pressure leads to more frequent collisions and higher average kinetic energy, thus raising temperature.
  • A third participant states that higher temperatures result in faster molecular movement, which increases the force exerted by the molecules and consequently raises pressure.
  • A reference is provided to a previous discussion, where it is noted that pressure is related to the average velocity and momentum of gas molecules, linking it to kinetic energy and temperature.

Areas of Agreement / Disagreement

Participants express differing views on the role of friction in the relationship between pressure and temperature, with some emphasizing molecular collisions instead. The discussion remains unresolved regarding the initial question about the cooling effect observed when gases are compressed into liquids.

Contextual Notes

Some assumptions about molecular behavior and definitions of pressure and temperature are not explicitly stated, which may affect the clarity of the arguments presented.

dusty8683
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just trying to understand how/why these two are proportional. if you compress a gas all the atoms and/or molecules would have less room to move around. so does the friction between these moving objects create heat? and if when gasses are compressed they heat up... why then when they are compressed to a liquid are they extremely cold? any explanation would be helpful, even just a link that has an explanation would do. thanks
 
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dusty8683 said:
just trying to understand how/why these two are proportional. if you compress a gas all the atoms and/or molecules would have less room to move around. so does the friction between these moving objects create heat?

The temperature has nothing to do with friction, but just with colliding effects. The more pressure the less space between molecules, and then major probability of colliding each other, and then the more kinetic energy transferring, and then the more average kinetic energy, and then the more temperature, and then... :zzz:
 
The larger the temperature of a gas the faster the molecules will move (temperature is proportional to the average kinetic energy of the particles) and the larger the force they will excert, and the higher the pressure (pressure is the force excerted by the particles divided by the area).
 
See also https://www.physicsforums.com/showthread.php?t=39446

My answer there was:
Microscopically the force on a container wall with some (ideal) gas in it is proportional to the average velocity (determines the rate of collisions) and momentum (determines the 'impact' of the collisions) of the molecules constituting the gas.

As you might know, pressure is a force per area. Kinetic energy is half the product of momentum and velocity. So you can easily see that pressure is proportional to the average kinetic energy and thus the temperature...
 

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