Question

what is the definition of thermal equilibrium tendency of particles to spread out when the kinetic energy increases state in which all parts of a system are at the same temperature sum of the kinetic energies of all the particles that make up an object transfer of thermal energy by direct contact of two objects or portions of matter

Explanation:

Thermal equilibrium is a fundamental concept in thermodynamics. When all parts of a system are at the same temperature, there is no net heat transfer between them. This is the key characteristic of thermal equilibrium. The other options describe different concepts: the tendency of particles to spread out relates to diffusion (not thermal equilibrium), the sum of kinetic energies is related to internal energy (not the definition of thermal equilibrium), and the transfer of thermal energy by direct contact is conduction (a mechanism of heat transfer, not the definition of thermal equilibrium).

Answer:

state in which all parts of a system are at the same temperature