Hydrogen gas it's in its most stable state, right at room temperature and pressure.

和常压下氢气是氢元素，最稳定的状态，这个小“0“

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