You could run the reaction, take solid iron gaseous oxygen, form iron oxide, measure the heat of formation of it, tabulate it.

你可以进行一个反应,用固态铁和氧气生成氧化铁，测量它的生成热，列成表格。

麻省理工公开课 - 热力学与动力学课程节选

Now in this particular reaction, I've got hydrogen gas, iron solid. Those already are elements in their most stable forms at room temperature and pressure.

特定的反应中，我有氢气,固态铁，这些都已经是,处于室温和常压下,最稳定的元素单质。

麻省理工公开课 - 热力学与动力学课程节选