What type of reaction requires the addition of energy or heat to the reactants?

An endothermic reaction is characterized by the absorption of energy, typically in the form of heat, from its surroundings. This type of reaction requires energy input to proceed, which often results in a decrease in temperature of the surrounding environment. Common examples of endothermic processes include photosynthesis and the melting of ice. In these cases, the reactants need energy to break bonds and initiate the conversion into products.

In contrast, exothermic reactions release energy, which can often raise the surrounding temperature. Combustion reactions are a specific type of exothermic reaction that involves the burning of a substance, resulting in the release of heat and light. Redox reactions entail the transfer of electrons between substances and can include both endothermic and exothermic processes, depending on the specific reaction being described. Therefore, the correct response is that an endothermic reaction requires the addition of energy or heat to the reactants to take place.