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Related Concept Videos

Gibbs Free Energy02:39

Gibbs Free Energy

34.6K
One of the challenges of using the second law of thermodynamics to determine if a process is spontaneous is that it requires measurements of the entropy change for the system and the entropy change for the surroundings. An alternative approach involving a new thermodynamic property defined in terms of system properties only was introduced in the late nineteenth century by American mathematician Josiah Willard Gibbs. This new property is called the Gibbs free energy (G) (or simply the free...
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Gibbs Free Energy and Thermodynamic Favorability02:23

Gibbs Free Energy and Thermodynamic Favorability

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The spontaneity of a process depends upon the temperature of the system. Phase transitions, for example, will proceed spontaneously in one direction or the other depending upon the temperature of the substance in question. Likewise, some chemical reactions can also exhibit temperature-dependent spontaneities. To illustrate this concept, the equation relating free energy change to the enthalpy and entropy changes for the process is considered:
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Free Energy Changes for Nonstandard States03:25

Free Energy Changes for Nonstandard States

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The free energy change for a process taking place with reactants and products present under nonstandard conditions (pressures other than 1 bar; concentrations other than 1 M) is related to the standard free energy change according to this equation:
 
where R is the gas constant (8.314 J/K·mol), T is the absolute temperature in kelvin, and Q is the reaction quotient. This equation may be used to predict the spontaneity of a process under any given set of conditions.
Reaction Quotient...
11.7K
Free Energy and Equilibrium00:55

Free Energy and Equilibrium

6.7K
The free energy change for a process may be viewed as a measure of its driving force. A negative value for ΔG represents a driving force for the process in the forward direction, while a positive value represents a driving force for the process in the reverse direction. When ΔG is zero, the forward and reverse driving forces are equal, and the process occurs in both directions at the same rate (the system is at equilibrium).
The reaction quotient, Q, is a convenient measure of the...
6.7K
An Introduction to Free Energy01:05

An Introduction to Free Energy

9.0K
How can we compare the energy that releases from one reaction to that of another reaction? We use a measurement of free energy to quantitate these energy transfers. Scientists call this free energy Gibbs free energy (abbreviated with the letter G) after Josiah Willard Gibbs, the scientist who developed the measurement. According to the second law of thermodynamics, all energy transfers involve losing some energy in an unusable form such as heat, resulting in entropy. Gibbs free energy...
9.0K
Calculating Standard Free Energy Changes02:49

Calculating Standard Free Energy Changes

22.3K
The free energy change for a reaction that occurs under the standard conditions of 1 bar pressure and at 298 K is called the standard free energy change. Since free energy is a state function, its value depends only on the conditions of the initial and final states of the system. A convenient and common approach to the calculation of free energy changes for physical and chemical reactions is by use of widely available compilations of standard state thermodynamic data. One method involves the...
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Related Experiment Video

Updated: Sep 22, 2025

An Analog Macroscopic Technique for Studying Molecular Hydrodynamic Processes in Dense Gases and Liquids
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A free energy principle for generic quantum systems.

Chris Fields1, Karl Friston2, James F Glazebrook3

  • 123 Rue des Lavandières, 11160, Caunes Minervois, France.

Progress in Biophysics and Molecular Biology
|May 26, 2022
PubMed
Summary

The Free Energy Principle (FEP) is reformulated in quantum information theory, showing quantum systems act as agents minimizing prediction error. This suggests biological systems utilize quantum coherence for computation and communication.

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Area of Science:

  • Theoretical Physics
  • Quantum Information Theory
  • Computational Neuroscience

Background:

  • The Free Energy Principle (FEP) posits that systems minimize variational free energy, an upper bound on surprisal, acting as Bayesian prediction error.
  • This principle offers a unified framework for understanding self-evidencing behaviors in dynamical systems.

Purpose of the Study:

  • To reformulate the Free Energy Principle within a quantum information theory framework.
  • To explore the implications of this reformulation for understanding agents and their interaction with uncertain environments.
  • To investigate the connection between the quantum FEP and fundamental principles like Unitarity.

Main Methods:

  • Reformulation of the FEP in spacetime-background free, scale-free quantum information theory.
  • Analysis of generic quantum systems as observers and agents.
  • Investigation of Bayesian prediction error minimization under quantum contextuality.

Main Results:

  • Quantum systems can be viewed as agents minimizing Bayesian prediction error in uncertain, contextuality-laden environments.
  • The quantum-theoretic FEP is shown to be asymptotically equivalent to the Principle of Unitarity.
  • Biological systems may leverage quantum coherence as a computational and communication resource.

Conclusions:

  • The quantum reformulation of the FEP provides a novel perspective on agency and information processing.
  • Quantum coherence is proposed as a key resource for biological computation and communication.
  • Future research should focus on quantum resources for communication and context-switch detection.