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The second law of thermodynamics states that the total entropy of an isolated system can never decrease over time, and is constant if and only if all processes are reversible. Isolated systems spontaneously evolve towards thermodynamic equilibrium, the state with maximum entropy.
The second law of thermodynamics states that the total entropy of an isolated system can never decrease over time, and is constant if and only if all processes are reversible. Isolated systems spontaneously evolve towards thermodynamic equilibrium, the state with maximum entropy.
'''热力学第二定律 Second Law Of Thermodynamics'''指出，孤立系统的总熵永远不会随着时间而减少，且当且仅当所有过程都是可逆时，总熵才恒定。孤立系统自发地到达到热力学平衡状态，此时为熵最大的状态。
The total entropy of a system and its surroundings can remain constant in ideal cases where the system is in thermodynamic equilibrium, or is undergoing a (fictive) reversible process. In all processes that occur, including spontaneous processes, the total entropy of the system and its surroundings increases and the process is irreversible in the thermodynamic sense. The increase in entropy accounts for the irreversibility of natural processes, and the asymmetry between future and past.
The total entropy of a system and its surroundings can remain constant in ideal cases where the system is in thermodynamic equilibrium, or is undergoing a (fictive) reversible process. In all processes that occur, including spontaneous processes, the total entropy of the system and its surroundings increases and the process is irreversible in the thermodynamic sense. The increase in entropy accounts for the irreversibility of natural processes, and the asymmetry between future and past.
系统及其周围环境的总熵在理想情况下可以保持不变，在这种情况下，系统处于热力学平衡状态，或者正在经历一个(虚拟的)可逆过程。在所有发生的过程中，包括自发过程，系统及其周围环境的总熵增加，这一过程在热力学意义上是不可逆的。熵的增加解释了自然过程的不可逆性，以及未来和过去之间的不对称性。
Historically, the second law was an empirical finding that was accepted as an axiom of thermodynamic theory. Statistical mechanics, classical or quantum, explains the microscopic origin of the law.
Historically, the second law was an empirical finding that was accepted as an axiom of thermodynamic theory. Statistical mechanics, classical or quantum, explains the microscopic origin of the law.
从历史上看，第二定律是一个经验性的发现，它被认为是热力学理论中的公理。经典统计力学、量子统计力学都可以解释这个定律的微观起源。
The second law has been expressed in many ways. Its first formulation is credited to the French scientist Sadi Carnot, who in 1824 showed that there is an upper limit to the efficiency of conversion of heat to work in a heat engine. This aspect of the second law is also known as Carnot's rule or limit.
The second law has been expressed in many ways. Its first formulation is credited to the French scientist Sadi Carnot, who in 1824 showed that there is an upper limit to the efficiency of conversion of heat to work in a heat engine. This aspect of the second law is also known as Carnot's rule or limit.
'''热力学第二定律 Second Law of Thermodynamics'''是热力学的四条基本定律之一，它表述了热力学过程的不可逆性——孤立系统自发地朝着热力学平衡方向（即最大熵状态）演化，另一种表述为：第二类永动机永不可能实现。
==Introduction引言==
[[File:Heat flow hot to cold.png|thumb|upright|Heat flow from hot water to cold water. 热量总是从热水流向冷水]]
The first law of thermodynamics provides the definition of the internal energy of a thermodynamic system, and expresses the law of conservation of energy. The second law is concerned with the direction of natural processes. It asserts that a natural process runs only in one sense, and is not reversible. For example, when a path for conduction and radiation is made available, heat always flows spontaneously from a hotter to a colder body. Such phenomena are accounted for in terms of entropy. If an isolated system is held initially in internal thermodynamic equilibrium by internal partitioning impermeable walls, and then some operation makes the walls more permeable, then the system spontaneously evolves to reach a final new internal thermodynamic equilibrium, and its total entropy, , increases.
The first law of thermodynamics provides the definition of the internal energy of a thermodynamic system, and expresses the law of conservation of energy. The second law is concerned with the direction of natural processes. It asserts that a natural process runs only in one sense, and is not reversible. For example, when a path for conduction and radiation is made available, heat always flows spontaneously from a hotter to a colder body. Such phenomena are accounted for in terms of entropy. If an isolated system is held initially in internal thermodynamic equilibrium by internal partitioning impermeable walls, and then some operation makes the walls more permeable, then the system spontaneously evolves to reach a final new internal thermodynamic equilibrium, and its total entropy, , increases.
'''热力学第一定律 First Law Of Thermodynamics''' 对热力学系统所涉及到的内能进行了定义，并体现了能量守恒定律。热力学第二定律与自然过程的方向有关。它设定自然过程只在一种意义上进行，且是不可逆的。例如，当有了传导和辐射的（传播）路径时，热量总是自发地从一个较热的物体流向一个较冷的物体。这种现象可以用熵来解释。若一个孤立系统最初在内部不可渗透的薄膜维持内部的热力学平衡，通过一些操作使得薄膜具有渗透性，则该系统可自发地演变，最终达到一个新的内部热力学平衡，其总熵增加。
--[[用户:趣木木|趣木木]]（[[用户讨论:趣木木|讨论]]） more permeable不知道是否需要译为更具有 impermeable wall是不可渗透 如果要使用比较级 是否应该再有一个 permeable
In a fictive reversible process, an infinitesimal increment in the entropy () of a system is defined to result from an infinitesimal transfer of heat () to a closed system (which allows the entry or exit of energy – but not transfer of matter) divided by the common temperature () of the system in equilibrium and the surroundings which supply the heat:
In a fictive reversible process, an infinitesimal increment in the entropy () of a system is defined to result from an infinitesimal transfer of heat () to a closed system (which allows the entry or exit of energy – but not transfer of matter) divided by the common temperature () of the system in equilibrium and the surroundings which supply the heat:
在设置的虚拟可逆过程中，系统熵的无穷小增量<math>dS</math>被定义为由无穷小的热量<math>δQ</math>传递到一个封闭系统(允许能量进入或出去，但不允许物质传递)除以平衡系统和提供热量的环境的共同温度 <math>T</math> :
(闭合系统，理想化的可逆过程) / math
: <math>\mathrm dS > \frac{\delta Q}{T_{surr}} \,\, \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\, \text {(closed system, actually possible, irreversible process封闭系统中理想状态下的可逆过程).}</math>
Different notations are used for infinitesimal amounts of heat () and infinitesimal amounts of entropy () because entropy is a function of state, while heat, like work, is not. For an actually possible infinitesimal process without exchange of mass with the surroundings, the second law requires that the increment in system entropy fulfills the inequality
Different notations are used for infinitesimal amounts of heat () and infinitesimal amounts of entropy () because entropy is a function of state, while heat, like work, is not. For an actually possible infinitesimal process without exchange of mass with the surroundings, the second law requires that the increment in system entropy fulfills the inequality
用不同的符号''δ''和''d''表示无穷小量的热量和无穷小量的熵 ，因为熵是状态函数，而热量和功一样不是状态函数。第二定律要求系统熵的增量满足不等式，对于实际上可能存在的不与环境发生质量交换的无穷小过程，系统熵增量满足不等式
: <math>\mathrm dS > \frac{\delta Q}{T_{surr}} \,\, \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\, \text {(closed system, actually possible, irreversible process 封闭系统中理想状态下的可逆过程).}</math>
: <math>\mathrm dS > \frac{\delta Q}{T_{surr}} \,\, \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\, \text {(closed system, actually possible, irreversible process).}</math>