3rd law of thermodynamics

[705961146]

Hi,
I am a little confused about the concept behind the third law of thermodynamics. Specifically, I am confused about when Dr. Lavelle wrote: "If a system can be prepared only in one way, then S=Kbln(W) = 0 and lim(T--> 0K) S = 0." I know that S=0 means that the substance is perfectly ordered (which is a hypothetical), but I don't understand how this is related to temperature and a system being prepared in only one way.
Thanks!

[Mathew Dinh]

Specifically, the 3rd law of thermodynamics is in relation to a perfect crystal at temperature 0 kelvin. Under those conditions, the entropy will be equal 0. When in relation to the system only being prepared in one way, you can interpret this from the s = k ln(W) meaning that W or the degeneracy only has one way to be orientated, therefore, only one way to prepare it as no other orientation or way will work.

[406003397]

This concept means that at 0K, a perfectly ordered system has only one possible microstate (W = 1), leading to (ln(1) = 0), thus the entropy (S) being zero, signifying complete order and no randomness in the arrangement of particles at the absolute zero temperature.