You know, if you want to measure the potential energy of something in a gravitational field, you have to define the zero somewhere, right, because it's arbitrary. You can set it anywhere you want. It's the same with enthalpy.

你知道，如果你想测量重力场,中某种东西的势能，你需要，在某处定义一个零点，对吧？,因为势能的值是任意的,你可以把它设定在。

麻省理工公开课 - 热力学与动力学课程节选

The absolute number that you assign to it is something that's arbitrary. You have to set what the zero is. And so there's a well-understood convention for what the zero is.

你指定给它的绝对值是有任意性的,你需要设定零点的位置,因此有一个经过充分研究的,关于设定零点的约定。

麻省理工公开课 - 热力学与动力学课程节选

pV So there is an arbitrary set point that needs to be defined, right? Because what you actually measure in the lab are changes in enthalpy, just like what you measure when you look at energy change of some sort, you measure the change in energy, right.

焓也是一样，焓是U加,所以需要定义一个任意的设定值,对吧？因为实际上你在实验室里,测得的是焓的改变,就像你在研究某种能量变化时，所测量的那样，你测量的是能量的改变，对吧。

麻省理工公开课 - 热力学与动力学课程节选