Question

IF temperatures reached absolute zero? The particles will have negative entropy and molecules will start to overlap each other? Is this true??

Answer 1

You may find this article of interest: http://en.wikipedia.org/wiki/Bose_einstein_condensate

Answer 2

is this true?

Answer 3

temperatures never reach absolute zero

Answer 4

No. If T = 0 it simply means the entire system falls into its quantum ground state. The system will have an entropy of zero because there is only one possible microstate (the ground state). Molecules will not overlap, and in fact will not even stop moving -- there is still zero-point motion, which for systems of many fermions can be enormous.

There's no particular magic about T=0. For certain purposes, quite a lot of systems are routinely treated as if T= 0 for them. For example, when you talk about an atom being in the groud state, you are implicitly assuming T = 0 for that system. If you discuss the electrons in a metal and assume there are no electrons in the conduction band and no holes in the valence band, you are assuing T = 0. And so on. Indeed, any time you discuss a system in the ground quantum state, that system is implicitly at T = 0.

Where T = 0 becomes definitely unrealistic, as an assumption, is when you are talking about the translational behaviour or nearly free molecules, e.g. a macroscopic volume of a gas or liquid. In such a case, the spacing between quantum states becomes so teeny tiny that it is utterly impossible to keep the system in its ground state. Even the tiniest imaginable external perturbation -- an atom becomign ionized on the Moon by a cosmic ray, say -- will provide enough energy to make higher states accessible. Here, you cannot speak of a single quantum state, and T = 0 is a wholly unreasonable assumption.

Answer 5

Carl can you sum that up in a couple of sentences?

Answer 6

Basically, Carl's saying that T=0 is unreasonable because even the slightest radiation would put it out of T=0 and that even if T=0 were attained, then it would simply revert to the quantum ground state, that is, the state of lowest energy.

Answer 7

Are all of these true?

Answer 8

yes