Free Energy

Definition

Free energy is a thermodynamic quantity that represents the maximum amount of work that can be extracted from a system at a constant temperature and pressure. It is a measure of the useful energy available in a system, taking into account both the energy and the entropy of the system.

5 Must Know Facts For Your Next Test

1. Free energy is a measure of the maximum amount of work that can be extracted from a system while it is in thermodynamic equilibrium with its surroundings.
2. The Second Law of Thermodynamics states that the entropy of an isolated system not in equilibrium will tend to increase over time, approaching a maximum value at equilibrium.
3. Spontaneous processes in a system occur when the change in free energy is negative, indicating that the process will release energy and increase the entropy of the universe.
4. The change in free energy is the sum of the change in enthalpy (heat) and the change in entropy multiplied by the absolute temperature.
5. Free energy is an important concept in understanding chemical reactions, biological processes, and the behavior of physical systems.

Review Questions

• Explain how the Second Law of Thermodynamics relates to the concept of free energy.
  • The Second Law of Thermodynamics states that the entropy of an isolated system not in equilibrium will tend to increase over time, approaching a maximum value at equilibrium. This means that the spontaneous processes in a system occur when the change in free energy is negative, indicating that the process will release energy and increase the entropy of the universe. The change in free energy is the sum of the change in enthalpy (heat) and the change in entropy multiplied by the absolute temperature. Therefore, the Second Law of Thermodynamics is directly related to the concept of free energy, as it governs the direction and spontaneity of processes in a system.
• Describe the differences between Gibbs free energy and Helmholtz free energy, and explain how they are used in different contexts.
  • Gibbs free energy and Helmholtz free energy are both measures of the total useful work that can be extracted from a system, but they differ in the variables they hold constant. Gibbs free energy is a measure of the total useful work that can be extracted from a system at constant temperature and pressure, while Helmholtz free energy is a measure of the total useful work that can be extracted from a system at constant volume and temperature. Gibbs free energy is typically used in the context of chemical reactions and biological processes, where the system is often at constant temperature and pressure. Helmholtz free energy, on the other hand, is more commonly used in the context of physical systems, where the volume of the system is held constant.
• Analyze the role of free energy in understanding the behavior of physical and chemical systems, and explain how it can be used to predict the spontaneity and direction of processes.
  • Free energy is a fundamental concept in understanding the behavior of physical and chemical systems. The change in free energy of a system determines the spontaneity and direction of processes. Spontaneous processes occur when the change in free energy is negative, indicating that the process will release energy and increase the entropy of the universe. This is a direct consequence of the Second Law of Thermodynamics, which states that the entropy of an isolated system not in equilibrium will tend to increase over time. By calculating the change in free energy for a given process, we can predict whether the process will occur spontaneously and the amount of work that can be extracted from the system. This knowledge is essential in fields such as chemistry, biology, and materials science, where understanding the behavior of systems is crucial for designing and optimizing processes, reactions, and materials.

Related terms

Gibbs Free Energy: Gibbs free energy is a measure of the total useful work that can be extracted from a system at constant temperature and pressure. It combines the internal energy, pressure-volume work, and entropy of the system.

Helmholtz Free Energy: Helmholtz free energy is a measure of the total useful work that can be extracted from a system at constant volume and temperature. It combines the internal energy and entropy of the system.

Entropy:

Entropy is a measure of the disorder or randomness in a system. It represents the amount of energy in a system that is not available for useful work.