Endothermic Reaction:A chemical reaction that absorbs heat from its surroundings. These reactions may not be spontaneous at low temperatures but can become so at high temperatures.
Exothermic Reaction:A chemical reaction that releases heat into its surroundings. These reactions are often spontaneous because they lower the system's overall energy state.
Equilibrium Constant (K):The ratio of concentrations of products over reactants when a reaction has reached equilibrium. For spontaneous processes, K > 1.