Do ideal gases at zero Kelvin have potential energy?
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asked Feb 20, 2014 at 13:17
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$\begingroup$ Ideal gas is just a theoretical term, all real gases solidify well above 0 K. By the way, 0 K is also just a theory, which says that at that point gas particles stop moving. So I guess that ideal gas at 0 K has no kinetic energy. $\endgroup$– WojciechCommented Feb 20, 2014 at 13:50
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$\begingroup$ Explain what do You mean by 'potential energy'? $\endgroup$– WojciechCommented Feb 20, 2014 at 14:22
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2$\begingroup$ There can not be "gas" at 0K. $\endgroup$– Olin LathropCommented Feb 20, 2014 at 14:23
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$\begingroup$ There is also a theory that at 0K the volume of substance shrinks to 0. $\endgroup$– WojciechCommented Feb 20, 2014 at 14:26
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1$\begingroup$ I don't think that mechanical energy is conserved in this case, to cool the substance down to 0K You literally remove all the energy it has. $\endgroup$– WojciechCommented Feb 20, 2014 at 14:28
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2 Answers
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There are many problems :
$1.$ As pointed out by Olin, gas cannot exist as a gas at $0 K$.
$2.$ In ideal gases, interaction between molecules are absent. Hence, there is no potential energy. Remember that Potential energy always has an additive arbitrary constant.
$3.$ As pointed by Wojciech, you would need (to take}energy to cool that down to $0 K$.
I could have just commented about my point but I do not have enough reputation to comment. :P
answered Feb 20, 2014 at 14:37
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The real question is "Can any substance at absolute zero have any potential energy?"
There is potential energy in a substance composed of molecules that contain covalent bonds. If the atoms of these molecules can form lower energy covalent bonds with other atoms in a chemical reaction, the difference in bond energies represents chemical potential energy in the original substance that is released in the chemical reaction. The energy released disperses out of the substance and into the surroundings.
It seems that this potential energy should be present in the substance "even if it had no kinetic energy" - which is a definition of a substance at absolute zero.
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$\begingroup$ Good first post, John. I have taken the liberty of adding some space to improve readability. $\endgroup$ Commented Jan 6, 2017 at 1:48
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$\begingroup$ Thanks for the review Sammy. The spacing does enhance readability. $\endgroup$ Commented Jan 6, 2017 at 17:39