With respect to the first law of thermodynamics, which of the following statements is the most relevant?
The first law of thermodynamics is a version of the law of conservation of energy, adapted for thermodynamic systems.
The law of conservation of energy states that the total energy in an isolated system is constant. An isolated system does not exchange particles and energy with the surrounding space. In an isolated system, energy can be converted from one form to another but it can neither be created nor destroyed.