What is another term used to describe the first law of thermodynamics?

The first law of thermodynamics is fundamentally about the conservation of energy, which means that energy cannot be created or destroyed but can only be transformed from one form to another. This law underscores the principle that the total energy in a closed system remains constant over time.

Referring to the law of energy conservation as another term for the first law of thermodynamics emphasizes this exact idea. It highlights that while energy can change forms—such as from kinetic to potential energy or from thermal energy to mechanical energy—the total amount of energy within that closed system will not change. This principle is crucial in various scientific fields, particularly physics and engineering, as it governs how energy systems operate, ensuring that the input and the output energy quantities can always be accounted for.

The other terms listed do not accurately reflect the concept of the first law of thermodynamics: conservation of mass pertains to mass not being created or destroyed, the law of increasing entropy relates more to the second law of thermodynamics, and the principle of equilibrium addresses a state where forces or changes are balanced, rather than energy conservation directly.