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第138行： − + − 第三定律 − − The [[third law of thermodynamics]] is sometimes stated as follows: − − The third law of thermodynamics is sometimes stated as follows: − − :''The [[entropy]] of a perfect [[crystal]] of any pure substance approaches zero as the temperature approaches [[absolute zero]].'' − − The entropy of a perfect crystal of any pure substance approaches zero as the temperature approaches absolute 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 [[microstate (statistical mechanics)|state with minimum energy]]. Entropy is related to the number of possible microstates according to: − − 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: − − − − ::<math>S = k_{\mathrm B}\, \mathrm{ln}\, \Omega</math> − − − − − Where ''S'' is the entropy of the system, ''k''<sub>B</sub> [[Boltzmann constant|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 as all the atoms are identical for a pure substance and as a result all orders are identical as there is only one combination) and ln(1) = 0. − − Where S is the entropy of the system, k<sub>B</sub> 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 as all the atoms are identical for a pure substance and as a result all orders are identical as there is only one combination) and ln(1) = 0. − − − − A more general form of the third law that applies to a system such as a [[glass]] that may have more than one minimum microscopically distinct energy state, or may have a microscopically distinct state that is "frozen in" though not a strictly minimum energy state and not strictly speaking a state of thermodynamic equilibrium, at absolute zero temperature: − − A more general form of the third law that applies to a system such as a glass that'''<font color="#32CD32"> may have more than one minimum microscopically distinct energy state, or may have a microscopically distinct state that is "frozen in" though not a strictly minimum energy state and not strictly speaking a state of thermodynamic equilibrium,</font>''' at absolute zero temperature: − − :''The entropy of a system approaches a constant value as the temperature approaches zero.'' − − :''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. − − The constant value (not necessarily zero) is called the residual entropy of the system.
→Third law
'''<font color="#32CD32"> This information entropy difference defines how much additional microscopic physical information is needed to specify one of the macroscopically specified states, given the macroscopic specification of the other – often a conveniently chosen reference state which may be presupposed to exist rather than explicitly stated. A final condition of a natural process always contains microscopically specifiable effects which are not fully and exactly predictable from the macroscopic specification of the initial condition of the process. This is why entropy increases in natural processes – the increase tells how much extra microscopic information is needed to distinguish the final macroscopically specified state from the initial macroscopically specified state.</font>'''
'''<font color="#32CD32"> This information entropy difference defines how much additional microscopic physical information is needed to specify one of the macroscopically specified states, given the macroscopic specification of the other – often a conveniently chosen reference state which may be presupposed to exist rather than explicitly stated. A final condition of a natural process always contains microscopically specifiable effects which are not fully and exactly predictable from the macroscopic specification of the initial condition of the process. This is why entropy increases in natural processes – the increase tells how much extra microscopic information is needed to distinguish the final macroscopically specified state from the initial macroscopically specified state.</font>'''
==Third law==
==第三定律 Third law==
热力学第三定律可以表示为：
热力学第三定律可以表示为：
当温度接近绝对零度时，任何纯物质的完整晶体的熵接近零。
当温度接近绝对零度时，任何纯物质的完整晶体的熵接近零。
在零温时，系统必须处于热能最小的状态。如果完美晶体只有一种能量最小的状态，则该说法成立。熵与可能的微状态数有关:
在零温时，系统必须处于热能最小的状态。如果完美晶体只有一种能量最小的状态，则该说法成立。熵与可能的微状态数有关:
::<math>S = k_{\mathrm B}\, \mathrm{ln}\, \Omega</math>
::<math>S = k_{\mathrm B}\, \mathrm{ln}\, \Omega</math>
其中 s 是系统的熵，k<sub>B</sub>是玻尔兹曼常数，以及Ω是微状态数(例如:可能的原子结构)。在绝对零度下只有一种微状态(Ω=1，因为纯物质的所有原子都是相同的，所以所有阶数都是相同的，因为只有一个组合)和 ln (1)=0。
其中 s 是系统的熵，k<sub>B</sub>是玻尔兹曼常数，以及Ω是微状态数(例如:可能的原子结构)。在绝对零度下只有一种微状态(Ω=1，因为纯物质的所有原子都是相同的，所以所有阶数都是相同的，因为只有一个组合)和 ln (1)=0。
第三定律的一个更普遍的形式，适用于像玻璃这样的系统，'''<font color="#32CD32">可能有一个以上的微观上截然不同的能量状态，或可能有一个微观上截然不同的“冻结状态”，虽然不是一个严格意义上的的最低能量状态，也不是严格意义上的热力学平衡，</font>'''在绝对零度的温度下:
第三定律的一个更普遍的形式，适用于像玻璃这样的系统，'''<font color="#32CD32">可能有一个以上的微观上截然不同的能量状态，或可能有一个微观上截然不同的“冻结状态”，虽然不是一个严格意义上的的最低能量状态，也不是严格意义上的热力学平衡，</font>'''在绝对零度的温度下:
:''系统的熵随着温度接近绝对零度而接近一个恒定值。''
:''系统的熵随着温度接近绝对零度而接近一个恒定值。''
这个常数(不一定是零)被称为系统的余熵。
这个常数(不一定是零)被称为系统的余熵。