Spontaneous Reactions and Enthelpy

[LordWillO]

Today in AP Chemistry we started learning about entropy and spontaneous reactions. Could someone explain on an undergraduate level (preferably not using calculus) how, if the universe has a fixed amount of mass and energy, that reactions can be spontaneous and create their own energy? Thanks!

 

[DrDu]

Reactions don't create energy. There is the first law of thermodynamics which says that energy is conserved. If a reaction is exothermic, heat is given off in the course of the reaction. However this type of energy was stored in the reactands. The products of the reaction have less energy.