So what they do is, they're describing how these thermodynamic properties change, in terms of only state functions and state variables.

他们的作用是描述,随着状态函数和状态变量的变化，系统的热力性质如何变化。

麻省理工公开课 - 热力学与动力学课程节选

There's no change in them, and then we also looked at some at non-state functions, work and heat, and saw that those aren't zero going around a cycle. Of course you can do work in a cyclic process, and heat can be exchanged with the environment at the same time.

它们不会有变化，然后我们研究了,一些非态函数，功和热量，并看到,沿着循环行进一周的话,它们并不是零，当然你可以在,一个循环过程中做功，而同时热量可以在系统,与外界环境之间进行交换。

麻省理工公开课 - 热力学与动力学课程节选