Kinetic energy and heat energy of molecule?

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Discussion Overview

The discussion centers around the relationship between average kinetic energy and heat energy of gas molecules, exploring definitions and terminology used in thermodynamics. It involves theoretical considerations of energy forms and their implications in the context of ideal and non-ideal gases.

Discussion Character

  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant states that the average kinetic energy of a molecule is given by (f/2)kT, where f represents degrees of freedom, and questions whether average kinetic energy and heat energy are the same.
  • Another participant suggests that the textbook may be using imprecise language by referring to "heat energy" instead of "kinetic energy," noting that heat is not a state function.
  • A participant proposes that "thermal energy" might be a more appropriate term than "heat energy."
  • One participant reiterates the question of whether thermal energy and kinetic energy are the same, indicating that it depends on definitions.
  • Another participant mentions that for an ideal gas, total energy is equivalent to the kinetic energy of the molecules, while for non-ideal gases, potential energy may also contribute to total energy.

Areas of Agreement / Disagreement

Participants express differing views on the terminology used to describe energy forms, with no consensus reached on whether average kinetic energy and heat energy are equivalent.

Contextual Notes

The discussion highlights potential ambiguities in definitions of energy types and their implications in different gas models, without resolving these ambiguities.

Hardik Batra
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I know that .
Average kinetic energy of a molecule is (f/2)kT (for translational motion.where f=3 )

In my textbook given that...

If the degree of freedom of the gas molecule is f then the average heat energy of each molecule of the gas is = E(avg.) = (f/2)kT

which is same as the average kinetic energy.

Are the avg. kinetic energy and heat energy both are same or there is difference between them?
 
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I think the textbook may just be using slightly sloppy language, using "heat energy" for what should be "kinetic energy". As heat is not a state function, there is no "heat energy" function that can be associated with an equation of state. Heat is energy flow into or out of a system that is not work.
 
Thermal energy might have been a better choice of words.
 
256bits said:
Thermal energy might have been a better choice of words.

thermal Energy and kinetic energy of molecule is same?
 
Last edited:
Hardik Batra said:
thermal Energy and kinetic energy of molecule is same?

It depends on the definitions. I would prefer simply the phrase "total energy" of the material. For an ideal (perfect) gas the total energy is the same as the kinetic energy of the molecules, for a non-perfect gas, there can be potential energy contributions to the total energy.

Thermal energy is often just another word for "heat".
 

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