Which term describes a chemical reaction that requires energy input?

The term that describes a chemical reaction requiring energy input is "endergonic." In an endergonic reaction, the total energy of products is greater than that of the reactants, indicating that energy has been absorbed from the surroundings to drive the reaction forward. This energy input is necessary for breaking chemical bonds or allowing new ones to form, facilitating the conversion of reactants to products.

Contrasting terms include exothermic, which refers specifically to reactions that release energy, typically in the form of heat, into the surroundings. Enthalpic relates to heat content but doesn’t specifically convey the concept of energy being absorbed. Exergonic, on the other hand, describes reactions that release energy, making them spontaneous rather than requiring energy input. Thus, endergonic is the correct choice as it captures the essence of reactions needing external energy to proceed.