Chemistry Regents Practice Test 2026 – Complete Prep Resource

An endothermic reaction is characterized by the absorption of heat from the surroundings, resulting in a decrease in the temperature of the immediate environment. This process requires energy input, which is typically in the form of heat. When molecules undergo an endothermic transition, they absorb energy to break bonds or to facilitate a change in state—such as melting or vaporization.

In contrast, a reaction that produces light and sound typically describes combustion or other exothermic processes where energy is released, so that cannot define an endothermic reaction. Additionally, a reaction that releases heat into the surroundings clearly represents an exothermic reaction, which is the opposite of endothermic. Finally, a spontaneous reaction may or may not be endothermic; spontaneity is determined by factors like entropy and enthalpy changes, rather than whether heat is absorbed or released. Therefore, the correct definition of an endothermic reaction is indeed the absorption of heat from its surroundings.