Third Law
The third law of thermodynamics is sometimes stated as follows:
The entropy of a perfect crystal at absolute zero is exactly equal to zero.At zero temperature the system must be in a state with the minimum thermal energy. This statement holds true if the perfect crystal has only one state with minimum energy. Entropy is related to the number of possible microstates according to S = kBln(Ω), where S is the entropy of the system, kB Boltzmann's constant, and Ω the number of microstates (e.g. possible configurations of atoms). At absolute zero there is only 1 microstate possible (Ω=1) and ln(1) = 0.
A more general form of the third law that applies to systems such as glasses that may have more than one minimum energy state:
The entropy of a system approaches a constant value as the temperature approaches zero.The constant value (not necessarily zero) is called the residual entropy of the system.
Read more about this topic: Laws Of Thermodynamics
Famous quotes containing the word law:
“Just as the constant increase of entropy is the basic law of the universe, so it is the basic law of life to be ever more highly structured and to struggle against entropy.”
—Václav Havel (b. 1936)
“The law is only one of several imperfect and more or less external ways of defending what is better in life against what is worse. By itself, the law can never create anything better.... Establishing respect for the law does not automatically ensure a better life for that, after all, is a job for people and not for laws and institutions.”
—Václav Havel (b. 1936)