What condition occurs when two objects in contact do not change state?

Thermal equilibrium is the condition that arises when two objects in contact have no net heat exchange between them, meaning they are at the same temperature. When two objects reach thermal equilibrium, their thermal states become stable, and they do not undergo any temperature change, as any heat energy transferred from one object is completely compensated by the other. This is an important concept in thermodynamics, as it helps define temperature and serves as a fundamental principle for the laws of heat transfer.

In contrast, mechanical equilibrium relates to objects that are at rest or moving at constant velocity and not experiencing net forces acting on them, while chemical equilibrium describes a state where the concentrations of reactants and products remain constant over time in a reversible reaction. Dynamic equilibrium refers to systems where processes occur continuously but with no net change in the system's macroscopic properties. These concepts are vital in understanding various processes in physical chemistry but do not pertain specifically to the thermal state of objects in contact.