Chemistry
What Is the Difference Between Enthalpy and Entropy in Reactions?
Quick fact
A reaction can be endothermic (absorbs heat) and still be spontaneous if it increases entropy enough—for example, dissolving ammonium nitrate in water feels cold but proceeds readily because the ions spread out and create far more disorder.
Why this is interesting
Why do some reactions that absorb heat happen on their own, while some that release heat don't happen at all? The answer lies in the hidden tension between enthalpy and entropy.