Final answer:
In chemistry, a spontaneous reaction occurs without the continual input of energy and moves to a more stable state, releasing free energy. Non-spontaneous reactions do not favor the formation of products at the given set of conditions. The direction of spontaneous reactions is determined by factors such as ΔH and ΔS.
Step-by-step explanation:
In chemistry, a spontaneous reaction is one that occurs without the continual input of energy from an external source. It is a reaction that has a natural tendency to occur and moves to a more stable state, releasing free energy. On the other hand, a non-spontaneous reaction does not favor the formation of products under the given set of conditions. It may be endothermic, accompanied by a decrease in entropy, or both.
For example, if a reaction A → B is spontaneous, it means that it occurs on its own, releasing free energy. However, if we reverse the reaction to B → A under the same conditions, it would not occur spontaneously. The direction of spontaneous reactions is determined by factors such as the change in enthalpy (ΔH) and the change in entropy (ΔS).