Final answer:
Cooking an egg until both yolk and white are firm involves the irreversible, spontaneous process of converting liquid egg white and yolk into solids, driven by changes in enthalpy and entropy, particularly with proteins like albumin solidifying above 373 K.
Step-by-step explanation:
When cooking eggs, it is important to ensure that both the yolk and white are firm. An egg is a heterogeneous mixture consisting of different substances, including proteins like albumin that undergo physical changes when heated. The liquid egg white consists mainly of albumin, which when boiled, transforms from a compact, ordered structure into a disorganized solid due to the breaking of hydrogen bonds, a process requiring an input of energy. This transformation is indicated by a positive change in enthalpy (AH>0) and entropy (AS > 0), making it a spontaneous process at temperatures greater than 373 K. Consequently, this leads to a negative Gibbs Free Energy (AG < 0), indicating that the conversion of a raw egg to a hard-boiled egg is irreversible and spontaneous above such temperatures.