this happens spontaneously, you actually get energy out of the reaction as this happens.

这是自发的，当反应发生的时候,你会自发地放出能量。

麻省理工公开课 - 化学原理课程节选

Just to illustrate the kind of issues that we're up against here, let me just consider a few different chemical reactions, all of which happen spontaneously.

为了说明我们的观点,考虑一些，不同的化学反应，这些化学反应都是自发进行的。

麻省理工公开课 - 热力学与动力学课程节选

So here are some spontaneous chemical changes Here's one.

这有一些自发进行的化学反应,这一个。

麻省理工公开课 - 热力学与动力学课程节选