What does the first law of thermodynamics state?

The first law of thermodynamics is often expressed as the principle of conservation of energy, which means that in an isolated system, the total energy remains constant. This fundamental concept states that energy cannot be created or destroyed; it can only change forms, such as from kinetic energy to potential energy or into heat during various processes.

When this law is applied, it implies that any energy added to a system must either increase the internal energy of that system or be converted into work done by the system on its surroundings. This understanding is crucial in various applications, from engineering to natural sciences, as it provides a framework for analyzing energy interactions and transformations.

The other statements do not align with the core principles outlined in the first law of thermodynamics. While energy transformations can lead to heat production, the law itself encompasses all forms of energy rather than limiting energy transformations to heat alone. Additionally, the assertion regarding entropy relates to the second law of thermodynamics, which addresses the direction of energy transfer and the tendency of systems toward increased disorder, not the conservation of energy. Thus, the declaration of constant energy in an isolated system captures the essence of the first law.