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The absolute zero is the temperature at which basically even atoms stop moving ( of course I know the enthalpy and entropy version of this but that is not what we are concerned with). Everyone would agree that this temperature is practically impossible so this thing must have been reached theoretically. The Wikipedia thing says that it was done by extrapolating the ideal gas law
https://en.m.wikipedia.org/wiki/Absolute_zero
I want to know what exactly was done,like what do they mean by 'extrapolating' ?

My question is not a duplicate of :
Why is the absolute zero -273.15ºC?

Infact I want to ask how did we come to know that everything had to come to a stop at that particular temperature (meaning, the triple point thing won't be accepted) and also for that matter how did we know that everything would stop at some temperature ?

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    $\begingroup$ Things do not stop moving at absolute zero. This is one of the surprising counter intuitive things at the core of quantum mechanics. When you remove all the energy you can from an atom, the atom doesn't stay still. $\endgroup$ – mmesser314 Jan 18 '17 at 14:16
  • $\begingroup$ @mmesser314 can you tell me more about it ? Here if possible or just provide a link to some page that talks about it. I don't have chat room privileges yet $\endgroup$ – Raghav Jan 18 '17 at 14:31
  • $\begingroup$ mmesser314 is talking about zero-point energy. $\endgroup$ – Ruslan Jan 18 '17 at 14:45
  • $\begingroup$ @Ruslan thanks for the link. Probably now you will have to answer my question through a classical approach $\endgroup$ – Raghav Jan 18 '17 at 17:03
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Temperature is closely connected to the kinetic energy of particles that make up stuff, so the first thing that we must say is that heat is actaully a sum of kinetic and potential energy of these particles( i stand corrected, heat is the part of the energy that is transfered because of the temperature difference). This energy is stored in a chaotic motion of these particles and in a potential form due to intermolecular and interatomic forces that make up chemical bonds which hold stuff together. This has been proven experimentaly so we do know that heat is just this motion. Transfer of heat will happen if one body is at the higher temperature than some other body to which the energy is being transfered. In this context temperature tells as where the heat flow will go....experimentaly this has been proven. So we can imagine particles that move at higher rate exhibit higher temperature. If we now imagine particles that are totally at rest what is their temperature? Well, these particles have zero heat and zero ability to transfer heat, so this can be called the lowest temperature possible. This lowest temperature possible is also called absolute zero as you said. So we did not know thateverything stops at some temperature we knew that motion is related to temperature and that no motion means no heat transfer. It is only logical to call this no motion state absolute zero. If you than define some temperature scale you can put a number on this zero. Extrapolation is a procedure by which, by means of examination of part of some curve, we predict the behaviour of that curve in the range of values of variables that are not yet accesible. In this manner you can plot the curve for the pressure of the ideal gas against temperature and see where it gives zero pressure and conclude that it means zero motion, and by the logic mentioned above, zero heat transfer id est, by definition, zero temperature.

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  • $\begingroup$ I don't think heat of a system at a particular instant means anything $\endgroup$ – Raghav Jan 18 '17 at 14:20
  • $\begingroup$ I understood the extrapolation part thanks for that but I didn't quite understand the relation between 'heat', temperature and energies $\endgroup$ – Raghav Jan 18 '17 at 14:24
  • $\begingroup$ Heat is the net transfer of energy from one object to another object because the temperatures are different. Temperature is an indication of the average kinetic energy per molecule in a system, where the size of the system can be defined as a few nanomoles (so that there can be a distribution of temperatures in an object) or several moles (such as a uniform temperature object). $\endgroup$ – Bill N Jan 18 '17 at 14:29
  • $\begingroup$ @BillN I was told that the reason for people coming up with enthalpy was because Heat of a system didn't mean anything, change of heat meant. $\endgroup$ – Raghav Jan 18 '17 at 14:41
  • $\begingroup$ That's correct. Read my comment again. Heat is energy being transferred due to temperature difference. I never said there was heat in the system. $\endgroup$ – Bill N Jan 18 '17 at 17:39

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