What distinguishes an endothermic reaction from an exothermic reaction?

An endothermic reaction is characterized by the absorption of heat from the surroundings, which means that the system takes in energy in the form of heat. This absorption leads to a decrease in the temperature of the surroundings, as energy is drawn away. In contrast, exothermic reactions release heat to the surroundings, causing an increase in temperature. The distinction between these two types of reactions is fundamental in thermochemistry, highlighting how energy changes influence chemical processes.

The differentiation is based on the net energy change during the course of the reaction: endothermic processes require energy input, thereby consuming heat, whereas exothermic processes produce energy in the form of heat when bonds are formed during the reaction. Thus, the understanding of these concepts is essential for predicting how a reaction will behave and for practical applications in energy management in chemical systems.