What's happening there? Well, the selection of reactants has been done judiciously to provide either heat or to provide something that's cool.

就会感到这东西，比如说变冷了，对吧？,这里发生了什么？这些反应物都是,被仔细的选出来的，能够提供热量或制冷。

麻省理工公开课 - 热力学与动力学课程节选