更改

<math>W = \Delta \mathrm{KE}_{\rm system}+\Delta \mathrm{PE}_{\rm system}+\Delta U_{\rm system}</math>

<math>W = \Delta \mathrm{KE}_{\rm system}+\Delta \mathrm{PE}_{\rm system}+\Delta U_{\rm system}</math>

* When matter is transferred into a system, that masses' associated internal energy and potential energy are transferred with it.

* When matter is transferred into a system, that masses' associated internal energy and potential energy are transferred with it.<br>

A prime example of irreversibility is in the transfer of heat by conduction or radiation. It was known long before the discovery of the notion of entropy that when two bodies initially of different temperatures come into thermal connection, then heat always flows from the hotter body to the colder one.

A prime example of irreversibility is in the transfer of heat by conduction or radiation. It was known long before the discovery of the notion of entropy that when two bodies initially of different temperatures come into thermal connection, then heat always flows from the hotter body to the colder one.

The second law tells also about kinds of irreversibility other than heat transfer, for example those of friction and viscosity, and those of chemical reactions. The notion of entropy is needed to provide that wider scope of the law.

The second law tells also about kinds of irreversibility other than heat transfer, for example those of friction and viscosity, and those of chemical reactions. The notion of entropy is needed to provide that wider scope of the law.

 

According to the second law of thermodynamics, in a theoretical and fictive reversible heat transfer, an element of heat transferred, δQ, is the product of the temperature (T), both of the system and of the sources or destination of the heat, with the increment (dS) of the system's conjugate variable, its entropy (S)

According to the second law of thermodynamics, in a theoretical and fictive reversible heat transfer, an element of heat transferred, δQ, is the product of the temperature (T), both of the system and of the sources or destination of the heat, with the increment (dS) of the system's conjugate variable, its entropy (S)

根据热力学第二定律理论，在理论上和虚构的可逆传热中，传热元件 q 是系统和热源或热目的地的温度(t)与系统共轭变量 s 的增量(dS)的乘积

根据热力学第二定律，在理论上和假设的可逆传热中，传热元素δQ是系统和热源或热目的地的温度(t)与系统共轭变量熵（S）的增量(dS)的乘积

Entropy may also be viewed as a physical measure of the lack of physical information about the microscopic details of the motion and configuration of a system, when only the macroscopic states are known. This lack of information is often described as disorder on a microscopic or molecular scale. The law asserts that for two given macroscopically specified states of a system, there is a quantity called the difference of information entropy between them. 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.

Entropy may also be viewed as a physical measure of the lack of physical information about the microscopic details of the motion and configuration of a system, when only the macroscopic states are known. This lack of information is often described as disorder on a microscopic or molecular scale. The law asserts that for two given macroscopically specified states of a system, there is a quantity called the difference of information entropy between them. 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.

当只知道宏观状态时，熵也可以被看作是对系统运动和构型的微观细节缺乏物理信息的一种物理度量。这种信息的缺乏常常被描述为微观或分子尺度上的无序。该定律声称，对于一个系统的两个给定的宏观特定状态，它们之间存在一个被称为熵差的量。这种熵的差异定义了需要多少额外的微观物理信息来指定一个宏观指定的状态，给定另一个宏观指定-往往是一个方便选择的参考状态，可能预先假定存在，而不是明确说明。一个自然过程的最终条件总是包含着微观上特定的影响，从过程初始条件的宏观规定来看，这些影响是不能完全和准确地预测的。这就是为什么熵在自然过程中增加——熵的增加告诉我们需要多少额外的微观信息来区分最终的宏观指定状态和最初的宏观指定状态。

当只知道宏观状态时，熵也可以被看作是对系统运动和构型的微观细节有关的物理度量。这种细节通常在微观或分子尺度上被称为无序。该定律声称，对于一个系统的两个给定的宏观指定状态，它们之间存在一个被称为熵差的量。这种熵的差异定义了需要多少额外的微观物理信息来指定一个宏观指定状态，给定另一个宏观指定状态-通常是一个方便选择的参考状态，这可能是假定存在的，而不是明确陈述的。自然过程的最终条件始终包含着微观上特定的影响，而这些影响，从过程初始条件的宏观规定来看是无法被完全准确预测的。这就是为什么熵在自然过程中会增加——熵的增加告诉我们需要多少额外的微观信息来区分最终的宏观指定状态和最初的宏观指定状态。

==Third law==

==Third law==<br>

The [[third law of thermodynamics]] is sometimes stated as follows:

The [[third law of thermodynamics]] is sometimes stated as follows:

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]].''

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 [[microstate (statistical mechanics)|state with minimum energy]].  Entropy is related to the number of possible microstates according to:

==History==

==History==<br>

{{see also|Philosophy of thermal and statistical physics}}

{{see also|Philosophy of thermal and statistical physics}}