Which law of thermodynamics involves the conservation of energy?

The First Law of Thermodynamics is the principle that embodies the concept of conservation of energy, stating that energy cannot be created or destroyed, only transformed from one form to another. This law mathematically expresses that the change in internal energy of a system equals the heat added to the system minus the work done by the system on its surroundings.

In practical terms, the First Law emphasizes that in any thermodynamic process, the total energy of an isolated system remains constant. This foundational principle is key to understanding how energy flows and converts in various systems, whether in engines, refrigerators, or biological organisms.

The Second Law of Thermodynamics, in contrast, deals with the direction of processes and the concept of entropy, indicating that energy transformations are not 100% efficient and tend to move towards a state of greater disorder. The Third Law focuses on systems approaching absolute zero and describes the behavior of entropy at that limit, while Fourier's Law pertains specifically to heat conduction and does not address the broad concept of energy conservation directly.