Can Temperature Be Misleading in Energy Comparisons?

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Discussion Overview

The discussion revolves around the relationship between temperature, internal energy, and energy flow in thermodynamic systems. Participants explore whether temperature can be misleading when comparing energy states of different systems, particularly in the context of kinetic energy (KE) and potential energy (PE).

Discussion Character

  • Exploratory
  • Debate/contested
  • Technical explanation

Main Points Raised

  • Some participants question if a system with a higher temperature can have lower internal energy than a system with a lower temperature, suggesting that temperature is a measure of average translational KE, while internal energy includes all forms of KE and PE.
  • Others assert that energy can flow from an object with a higher temperature to one with a lower temperature, even if the latter has a higher internal energy, indicating that temperature difference dictates the direction of heat flow.
  • There is a discussion about the meaning of molecular potential energy (PE) in the context of gas compression, with some participants noting that inter-molecular forces can contribute to molecular PE.
  • One participant emphasizes that temperature is not solely a measurement of KE, providing an example comparing the internal energy of a large block of ice to that of a small candle flame.

Areas of Agreement / Disagreement

Participants express differing views on the relationship between temperature and internal energy, with some agreeing that temperature is a measure of KE while others argue it is more complex. The discussion remains unresolved regarding the implications of these relationships on energy flow.

Contextual Notes

Participants highlight the complexity of internal energy, which includes various forms of energy beyond translational KE, and the role of molecular interactions in determining potential energy. There are unresolved questions about the definitions and implications of these concepts.

Clara Chung
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1.If temperature is just a measurement of KE, can a system with higher temperature contains lower internal energy than a system with lower temperature?
2.Can energy flow from an object with higher temperature to an object with lower temperature even if the internal energy of the object with a lower temperature is higher?
3. It is said that the gas passing through compressor will result in decrease on its molecular PE, what does molecular PE refer to?
 
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Clara Chung said:
1.If temperature is just a measurement of KE, can a system with higher temperature contains lower internal energy than a system with lower temperature?
Yes. Temperature is a measure of the average translational KE of the molecules in the system. Internal energy is the sum of the KE (all modes, translational, rotational, vibrational) + the total PE of all molecules in the system. Internal energy is a function of the number of molecules and the average KE and PE of its molecules. Temperature is just a function of the average translational KE per molecule.
2.Can energy flow from an object with higher temperature to an object with lower temperature even if the internal energy of the object with a lower temperature is higher?
Yes. Temperature difference always determines the direction of heat flow.
3. It is said that the gas passing through compressor will result in decrease on its molecular PE, what does molecular PE refer to?
If there are inter-molecular attractive forces (such as in water), there will be molecular potential energy. A decrease in the average separation distance between molecules will reduce the average potential energy of the molecules.

AM
 
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Clara Chung said:
1.If temperature is just a measurement of KE, can a system with higher temperature contains lower internal energy than a system with lower temperature?
Temperature is not just a measurement of KE, though KE per degree of freedom is a close approximation under many conditions.

A huge block of ice contains more internal energy than a tiny candle flame.
2.Can energy flow from an object with higher temperature to an object with lower temperature even if the internal energy of the object with a lower temperature is higher?
Heat will flow from candle flame to ice block.
 
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jbriggs444 said:
Temperature is not just a measurement of KE, though KE per degree of freedom is a close approximation under many conditions.

A huge block of ice contains more internal energy than a tiny candle flame.

Heat will flow from candle flame to ice block.
I have figured out the questions. Thanks for all your help
 

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