Gibbs free energy

Gibbs Free Energy

The Gibbs free energy (pronounced: /ɡɪbz friː ˈɛnərdʒi/), also known as Gibbs energy or Gibbs function, is a thermodynamic potential that measures the maximum reversible work that a system can perform at constant temperature and pressure. It is named after Josiah Willard Gibbs, the American scientist who first proposed it in the 1870s.

Etymology

The term "Gibbs free energy" is derived from the name of its proposer, Josiah Willard Gibbs. The word "free" in the term refers to the energy in a system that is available to do work, i.e., free for use. The term "energy" comes from the Greek word "energeia", which means activity or operation.

Definition

The Gibbs free energy (G) is defined as:

G = H - TS

where:

• H is the enthalpy of the system,
• T is the absolute temperature (measured in Kelvin), and
• S is the entropy of the system.

Applications

The Gibbs free energy is used to determine whether a process will occur spontaneously. If the change in Gibbs free energy (ΔG) is negative, the process is spontaneous. If ΔG is positive, the process is non-spontaneous. If ΔG is zero, the system is in equilibrium.

Related Terms

• Thermodynamics
• Enthalpy
• Entropy
• Spontaneous process
• Non-spontaneous process
• Equilibrium

See Also

• Laws of thermodynamics
• Chemical thermodynamics
• Statistical thermodynamics

External links

• Medical encyclopedia article on Gibbs free energy
• Wikipedia's article - Gibbs free energy

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