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

Now to make that happen, it's not adiabatic, right. If I wanted to do that, I'd need a heating element or something to cool, so I could make that temperature change happen, right.

要实现这点，它就不会是绝热的，对吧，如果我想做到这点,我需要一个加热元件或什么制冷的东西,这样我才能让温度变化。

麻省理工公开课 - 热力学与动力学课程节选

Iron as an element is a solid. That's it's most stable state at room temperature and pressure, right, and so on. And then we can figure out heats of formation.

铁单质是固态,这是他在室温和常压下,最稳定的状态，然后我们,可以算出生成热，现在这个。

麻省理工公开课 - 热力学与动力学课程节选