Thermodynamic Equilibrium

Definition

Thermodynamic equilibrium is a state in which the macroscopic properties of a system, such as temperature, pressure, and chemical composition, do not change over time. It is a fundamental concept in thermodynamics that underpins the study of energy transformations, work, heat, and the behavior of systems.

5 Must Know Facts For Your Next Test

1. In thermodynamic equilibrium, the system is in a state of maximum entropy, and no spontaneous changes occur.
2. Thermodynamic equilibrium is a necessary condition for the application of the First Law of Thermodynamics, which relates the changes in internal energy, work, and heat.
3. Thermodynamic processes, such as adiabatic, isothermal, and isobaric processes, are defined by the system's path between different states of thermodynamic equilibrium.
4. The concept of thermodynamic equilibrium is crucial in understanding the efficiency of heat engines and the limitations imposed by the Second Law of Thermodynamics.
5. Entropy, a measure of disorder or randomness, increases in a spontaneous process and is maximized at thermodynamic equilibrium.

Review Questions

• Explain how the concept of thermodynamic equilibrium is related to the First Law of Thermodynamics.
  • The First Law of Thermodynamics states that the change in a system's internal energy is equal to the sum of the work done on the system and the heat added to the system. This law is only valid when the system is in a state of thermodynamic equilibrium, where the macroscopic properties of the system do not change over time. Thermodynamic equilibrium ensures that the system can be described by well-defined state variables, such as temperature, pressure, and volume, which are necessary for the application of the First Law.
• Describe the relationship between thermodynamic equilibrium and the concept of entropy.
  • Entropy is a measure of the disorder or randomness of a system. At thermodynamic equilibrium, the system is in a state of maximum entropy, meaning that the system has reached the most probable distribution of its microscopic states. This is because in a state of thermodynamic equilibrium, the system has reached a stable configuration where no spontaneous changes occur, and the system's macroscopic properties remain constant. The increase in entropy during a spontaneous process is a driving force towards thermodynamic equilibrium, as the system seeks to maximize its entropy.
• Analyze how the concept of thermodynamic equilibrium is used to define different thermodynamic processes, such as adiabatic, isothermal, and isobaric processes.
  • Thermodynamic processes are defined by the path a system takes between different states of thermodynamic equilibrium. In an adiabatic process, the system undergoes a change in state without any heat transfer with the surroundings, and the system remains in thermodynamic equilibrium throughout the process. In an isothermal process, the system's temperature remains constant, and the system is in thermodynamic equilibrium. In an isobaric process, the system's pressure remains constant, and the system is in thermodynamic equilibrium. The concept of thermodynamic equilibrium is essential in understanding the constraints and limitations of these different thermodynamic processes, which are fundamental to the study of heat engines and the efficiency of energy transformations.

Related terms

Thermal Equilibrium: A state in which two or more objects or systems have the same temperature, and no net transfer of thermal energy occurs between them.

Mechanical Equilibrium: A state in which the net force and net torque acting on a system are zero, and the system is at rest or in uniform motion.

Chemical Equilibrium: A state in which the forward and reverse rates of a chemical reaction are equal, and the concentrations of reactants and products remain constant over time.