Final answer:
An increase in temperature makes certain reactions spontaneous in exothermic reactions.
Step-by-step explanation:
In the context of reactions, an increase in temperature makes certain reactions spontaneous in exothermic reactions. Exothermic reactions release heat into the surroundings, causing the temperature to increase. When the temperature increases, the reaction rate also increases, making the reaction more likely to occur. This is because the increase in temperature provides the reactant molecules with more kinetic energy, allowing them to overcome the activation energy barrier.