What is the principle that states that energy cannot be created or destroyed?

The principle that states that energy cannot be created or destroyed is known as the Law of Conservation of Energy. This law emphasizes that in any isolated system, the total amount of energy remains constant over time. Instead of being lost or gained, energy can only change from one form to another—for example, from kinetic energy to potential energy or from chemical energy to thermal energy. This concept is fundamental in understanding various processes in chemistry and physics, where energy transformations are involved, such as in chemical reactions, mechanical work, and heat transfers.

The other concepts relate to energy and matter but differ in their focus. For instance, the Law of Thermodynamics encompasses a broader set of principles governing energy changes, including heat and work in systems, rather than just stating that energy cannot be created or destroyed. Similarly, the Law of Conservation of Mass pertains to the principle that mass is conserved in a chemical reaction, meaning that the mass of reactants equals the mass of products. Lastly, the Law of Energy Transfer typically describes how energy moves between systems rather than affirming the unchangeable nature of energy's total amount within a closed system. Thus, the Law of Conservation of Energy specifically captures the essence of the idea presented in the question.