Remember when we talked about star formation, we said that as a star ages, it becomes brighter, right?

还记得吗，我们讨论恒星形成的时候说过，恒星会随着年龄增长变得更亮，对吧？

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This is the negative heat of formation, right?

这里是负的生成热，对吧？

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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。

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So here, I'm going to have delta H, is just the sum for all the products of delta heat of formation right? Here I'm going to put together all the products. So this is a positive heat of formation.

所以这里△H就是所有生成物的,生成热的和,对吧？这里,我要把元素组合成所有这些,生成物，所以这里是正的生成热。

麻省理工公开课 - 热力学与动力学课程节选

But this is a compound, right, it has some non-zero heat of formation from the elements. So is water, right?

但这是种化合物，对吧？,它具有非零的生成热,水也是一样，对吧？

麻省理工公开课 - 热力学与动力学课程节选

So we're just subtracting, in effect, zero, right, from the enthalpy of the product, but of course it's important have that established because the heat of formation is something you could measure, right?

所以从效果上说，我们只是，从生成物的焓中减去了零，但，是确立这一点很重要,因为生成热是,你能测量的东西，对吧？

麻省理工公开课 - 热力学与动力学课程节选

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The flag formation is even clearer on the daily chart (right panel), lines g and h.

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