What we define as zero is the enthalpy of every element in its natural state at room temperature and ambient pressure.

我们将零点定义为每种元素,在室温和正常大气压下,在其自然状态下的焓。

麻省理工公开课 - 热力学与动力学课程节选

It tells you what kind of molecule it is andgives you twovariables that are state variables You could have the volume and the temperature.

告诉你它是哪种分子,还给你了两个状态变量,它们可以是体积或温度。

麻省理工公开课 - 热力学与动力学课程节选

Maybe you don't control thermostats in your dorm room, some of you do and some of you don't probably, and maybe it doesn't work very well so it might not be a good example, but imagine a perfect thermostat that you set for a temperature and then the temperature stays the same inside the room no matter what the temperature is outside.

可能你根本就不理卧室里的恒温器,有些人去调它,有些人就置之不理,可能它压根就是坏的,所以这个例子也许并不恰当,但你还是想象一个完美运行的恒温器,你设定温度后房间里的温度就保持不变,不管外面温度是多少

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This is going to be the connect, what connects the pressures and the temperature.

这就是联系初末，态压强和温度的关系式。

麻省理工公开课 - 热力学与动力学课程节选

So delta u is just equal to the work but we also know what happens T2 because the temperature is changing from T1 to T2.

所以Δu等于输出的功,但我们也知道它会发生,同时我们知道温度从T1变到。

麻省理工公开课 - 热力学与动力学课程节选

All right, so gamma, the gas is cooling so V2 is going to be less than it what would be if the temperature kept constant.

气体温度下降了,于是V2会比等温过程,降到相同压强时的体积要小。

麻省理工公开课 - 热力学与动力学课程节选