Thermodynamic giveaway energy

نوشته شده در موضوع تولید انرژی رایگان در 16 نوامبر 2016


  • Property databases

Specific feverishness capacity 
c={displaystyle c=}

T{displaystyle T}
S{displaystyle prejudiced S}
N{displaystyle N}
T{displaystyle prejudiced T}

β=−{displaystyle beta =-}

1{displaystyle 1}
V{displaystyle prejudiced V}
V{displaystyle V}
p{displaystyle prejudiced p}

Thermal expansion 
α={displaystyle alpha =}

1{displaystyle 1}
V{displaystyle prejudiced V}
V{displaystyle V}
T{displaystyle prejudiced T}

  • Internal energy
    U(S,V){displaystyle U(S,V)}
  • Enthalpy
    H(S,p)=U+pV{displaystyle H(S,p)=U+pV}
  • Helmholtz giveaway energy
    A(T,V)=U−TS{displaystyle A(T,V)=U-TS}
  • Gibbs giveaway energy
    G(T,p)=H−TS{displaystyle G(T,p)=H-TS}


The thermodynamic giveaway energy is a volume of work that a thermodynamic complement can perform. The judgment is useful in a thermodynamics of chemical or thermal processes in engineering and science. The giveaway appetite is a inner appetite of a complement reduction a volume of appetite that can't be used to perform work. This obsolete appetite is given by a entropy of a complement double by a feverishness of a system.

Like a inner energy, a giveaway appetite is a thermodynamic state function. Energy is a generalization of giveaway energy, given appetite is a ability to do work that is indeed giveaway energy.


Free appetite is that apportionment of any first-law appetite that is accessible to perform thermodynamic work; i.e., work mediated by thermal energy. Free appetite is theme to irrevocable detriment in a march of such work.[1] Since first-law appetite is always conserved, it is transparent that giveaway appetite is an expendable, second-law kind of appetite that can perform work within calculable amounts of time. Several giveaway appetite functions competence be formulated formed on complement criteria. Free appetite functions are Legendre transformations of a inner energy. For processes involving a complement during constant vigour p and feverishness T, a Gibbs giveaway appetite is a many useful because, in further to subsuming any entropy change due merely to heat, it does a same for a p dV work indispensable to “make space for additional molecules” constructed by several processes. (Hence a application to solution-phase chemists, including biochemists.) The Helmholtz giveaway appetite has a special fanciful significance given it is proportional to a logarithm of a assign duty for a authorized garb in statistical mechanics. (Hence a application to physicists; and to gas-phase chemists and engineers, who do not wish to omit p dV work.)

The historically progressing Helmholtz giveaway appetite is tangible as A = UTS, where U is a inner energy, T is a comprehensive temperature, and S is a entropy. Its change is equal to a volume of reversible work finished on, or convenient from, a complement during consistent T. Thus a sequence “work content”, and a nomination A from Arbeit, a German word for work. Since it creates no anxiety to any quantities concerned in work (such as p and V), a Helmholtz duty is totally general: a mitigation is a extent volume of work that can be finished by a system, and it can boost during many by a volume of work finished on a system.

The Gibbs giveaway appetite is given by G = HTS, where H is a enthalpy. (H = U + pV, where p is a vigour and V is a volume.)

Historically, these appetite terms have been used inconsistently. In physics, free energy many mostly refers to a Helmholtz giveaway energy, denoted by A, while in chemistry, free energy many mostly refers to a Gibbs giveaway energy. Since both fields use both functions, a concede has been suggested, regulating A to imply a Helmholtz duty and G for a Gibbs function. While A is elite by IUPAC, G is infrequently still in use, and a scold giveaway appetite duty is mostly substantial in manuscripts and presentations.

Meaning of “free”[edit]

In a 18th and 19th centuries, a speculation of heat, i.e., that feverishness is a form of appetite carrying propinquity to vibratory motion, was commencement to succeed both a caloric theory, i.e., that feverishness is a fluid, and a 4 member theory, in that feverishness was a lightest of a 4 elements. In a identical manner, during these years, feverishness was commencement to be renowned into opposite sequence categories, such as “free heat”, “combined heat”, “radiant heat”, specific heat, feverishness capacity, “absolute heat”, “latent caloric”, “free” or “perceptible” caloric (calorique sensible), among others.

In 1780, for example, Laplace and Lavoisier stated: “In general, one can change a initial supposition into a second by changing a difference ‘free heat, sum heat, and feverishness released’ into ‘vis viva, detriment of vis viva, and boost of vis viva.’” In this manner, a sum mass of caloric in a body, called absolute heat, was regarded as a reduction of dual components; a giveaway or obvious caloric could impact a thermometer, since a other component, a implicit caloric, could not.[2] The use of a difference “latent heat” pragmatic a likeness to implicit feverishness in a some-more common sense; it was regarded as chemically firm to a molecules of a body. In a adiabatic application of a gas, a comprehensive feverishness remained consistent though a celebrated arise in feverishness pragmatic that some implicit caloric had turn “free” or perceptible.

During a early 19th century, a judgment of obvious or giveaway caloric began to be referred to as “free heat” or feverishness set free. In 1824, for example, a French physicist Sadi Carnot, in his famous “Reflections on a Motive Power of Fire”, speaks of quantities of feverishness ‘absorbed or set free’ in opposite transformations. In 1882, a German physicist and physiologist Hermann von Helmholtz coined a word ‘free energy’ for a countenance ETS, in that a change in F (or G) determines a volume of appetite ‘free’ for work underneath a given conditions.[3]:235

Thus, in normal use, a tenure “free” was trustworthy to Gibbs giveaway energy, i.e., for systems during consistent vigour and temperature, or to Helmholtz giveaway energy, i.e., for systems during consistent volume and temperature, to meant ‘available in a form of useful work.’[4] With anxiety to a Gibbs giveaway energy, we supplement a gift that it is a appetite giveaway for non-volume work.[5]:77-79

An augmenting series of books and biography articles do not embody a connection “free”, referring to G as simply Gibbs appetite (and further for a Helmholtz energy). This is a outcome of a 1988 IUPAC assembly to set one terminologies for a ubiquitous systematic community, in that a verb ‘free’ was presumably banished.[6][7][8] This standard, however, has not nonetheless been zodiacally adopted, and many published articles and books still embody a detailed ‘free’.[citation needed]


The initial utility of these functions is limited to conditions where certain variables (T, and V or external p) are hold constant, nonetheless they also have fanciful significance in deriving Maxwell relations. Work other than p dV competence be added, e.g., for electrochemical cells, or f dx work in effervescent materials and in flesh contraction. Other forms of work that contingency infrequently be deliberate are stress-strain, magnetic, as in adiabatic demagnetization used in a proceed to comprehensive zero, and work due to electric polarization. These are described by tensors.

In many cases of seductiveness there are inner degrees of leisure and processes, such as chemical reactions and proviso transitions, that emanate entropy. Even for comparable “bulk” materials, a giveaway appetite functions count on a (often suppressed) composition, as do all scold thermodynamic potentials (extensive functions), including a inner energy.

Natural variables
Internal energy
U{displaystyle U}
(TdS−pdV+∑idNi){displaystyle int (T{text{d}}S-p{text{d}}V+sum _{i}mu _{i}{text{d}}N_{i})}
S,V,{Ni}{displaystyle S,V,{N_{i}}}
Helmholtz giveaway energy
F{displaystyle F}
U−TS{displaystyle U-TS}
T,V,{Ni}{displaystyle T,V,{N_{i}}}
H{displaystyle H}
U+pV{displaystyle U+pV}
S,p,{Ni}{displaystyle S,p,{N_{i}}}
Gibbs giveaway energy
G{displaystyle G}
U+pV−TS{displaystyle U+pV-TS}
T,p,{Ni}{displaystyle T,p,{N_{i}}}
Landau Potential (Grand potential)
Ω{displaystyle Omega }, ΦG{displaystyle Phi _{text{G}}}
U−TS−{displaystyle U-TS-}i{displaystyle sum _{i},}μiNi{displaystyle mu _{i}N_{i}}
T,V,{μi}{displaystyle T,V,{mu _{i}}}

Ni is a series of molecules (alternatively, moles) of form i in a system. If these quantities do not appear, it is unfit to report compositional changes. The differentials for reversible processes are (assuming customarily pV work):

dF=−pdV−SdT+∑idNi{displaystyle dF=-p,dV-S,dT+sum _{i}mu _{i},dN_{i},}
dG=Vdp−SdT+∑idNi{displaystyle dG=V,dp-S,dT+sum _{i}mu _{i},dN_{i},}

where μi is a chemical intensity for a ith member in a system. The second propinquity is generally useful during consistent T and p, conditions that are easy to grasp experimentally, and that approximately impersonate vital creatures.

(dG)T,p=∑idNi{displaystyle (dG)_{T,p}=sum _{i}mu _{i},dN_{i},}

Any mitigation in a Gibbs duty of a complement is a top extent for any isothermal, isobaric work that can be prisoner in a surroundings, or it competence simply be dissipated, appearing as T times a comparable boost in a entropy of a complement and/or a surrounding.

An instance is aspect giveaway energy, a volume of boost of giveaway appetite when a area of aspect increases by any section area.

The trail constituent Monte Carlo routine is a numerical proceed for last a values of giveaway energies, formed on quantum dynamical principles.


The apportion called “free energy” is a some-more modernized and accurate deputy for a old-fashioned tenure affinity, that was used by chemists in prior years to report a force that caused chemical reactions. The tenure affinity, as used in chemical relation, dates behind to during slightest a time of Albertus Magnus in 1250.[citation needed]

From a 1998 text Modern Thermodynamics[9] by Nobel Laureate and chemistry highbrow Ilya Prigogine we find: “As suit was explained by a Newtonian judgment of force, chemists wanted a identical judgment of ‘driving force’ for chemical change. Why do chemical reactions occur, and because do they stop during certain points? Chemists called a ‘force’ that caused chemical reactions affinity, though it lacked a transparent definition.”

During a whole 18th century, a widespread perspective with courtesy to feverishness and light was that put onward by Isaac Newton, called a Newtonian hypothesis, that states that light and feverishness are forms of matter captivated or detered by other forms of matter, with army comparable to inclination or to chemical affinity.

In a 19th century, a French chemist Marcellin Berthelot and a Danish chemist Julius Thomsen had attempted to quantify affinity regulating heats of reaction. In 1875, after quantifying a heats of greeting for a vast series of compounds, Berthelot due a principle of extent work, in that all chemical changes occurring though involvement of outward appetite tend toward a prolongation of bodies or of a complement of bodies that acquit heat.

In further to this, in 1780 Antoine Lavoisier and Pierre-Simon Laplace laid a foundations of thermochemistry by display that a feverishness given out in a greeting is equal to a feverishness engrossed in a retreat reaction. They also investigated a specific feverishness and implicit feverishness of a series of substances, and amounts of feverishness given out in combustion. In a identical manner, in 1840 Swiss chemist Germain Hess formulated a element that a expansion of feverishness in a greeting is a same either a routine is achieved in one-step routine or in a series of stages. This is famous as Hess’ law. With a appearance of a automatic speculation of feverishness in a early 19th century, Hess’s law came to be noticed as a effect of a law of charge of energy.

Based on these and other ideas, Berthelot and Thomsen, as good as others, deliberate a feverishness given out in a arrangement of a devalue as a magnitude of a affinity, or a work finished by a chemical forces. This view, however, was not wholly correct. In 1847, a English physicist James Joule showed that he could lift a feverishness of H2O by branch a paddle circle in it, so display that feverishness and automatic work were comparable or proportional to any other, i.e., approximately, dWdQ. This matter came to be famous as a automatic comparable of feverishness and was a preceding form of a initial law of thermodynamics.

By 1865, a German physicist Rudolf Clausius had shown that this balance element indispensable amendment. That is, one can use a feverishness subsequent from a explosion greeting in a spark furnace to boil water, and use this feverishness to burn steam, and afterwards use a extended high-pressure appetite of a vaporized steam to pull a piston. Thus, we competence naively reason that one can wholly modify a initial explosion feverishness of a chemical greeting into a work of pulling a piston. Clausius showed, however, that we contingency take into comment a work that a molecules of a operative body, i.e., a H2O molecules in a cylinder, do on any other as they pass or renovate from one step of or state of a engine cycle to a next, e.g., from (P1,V1) to (P2,V2). Clausius creatively called this a “transformation content” of a body, and afterwards after altered a name to entropy. Thus, a feverishness used to renovate a operative physique of molecules from one state to a subsequent can't be used to do outmost work, e.g., to pull a piston. Clausius tangible this transformation heat as dQ = T dS.

In 1873, Willard Gibbs published A Method of Geometrical Representation of a Thermodynamic Properties of Substances by Means of Surfaces, in that he introduced a rough outline of a beliefs of his new equation means to envision or guess a tendencies of several healthy processes to occur when bodies or systems are brought into contact. By study a interactions of comparable substances in contact, i.e., bodies, being in combination partial solid, partial liquid, and partial vapor, and by regulating a three-dimensional volume-entropy-internal appetite graph, Gibbs was means to establish 3 states of equilibrium, i.e., “necessarily stable”, “neutral”, and “unstable”, and either or not changes will ensue. In 1876, Gibbs built on this horizon by introducing a judgment of chemical intensity so to take into comment chemical reactions and states of bodies that are chemically opposite from any other. In his possess words, to promulgate his formula in 1873, Gibbs states:

In this description, as used by Gibbs, ε refers to a inner appetite of a body, η refers to a entropy of a body, and ν is a volume of a body.

Hence, in 1882, after a introduction of these arguments by Clausius and Gibbs, a German scientist Hermann von Helmholtz stated, in antithesis to Berthelot and Thomas’ supposition that chemical affinity is a magnitude of a feverishness of greeting of chemical greeting as formed on a element of maximal work, that affinity is not a feverishness given out in a arrangement of a devalue though rather it is a largest apportion of work that can be gained when a greeting is carried out in a reversible manner, e.g., electrical work in a reversible cell. The extent work is so regarded as a mitigation of a free, or available, appetite of a complement (Gibbs giveaway appetite G during T = constant, P = consistent or Helmholtz giveaway appetite F during T = constant, V = constant), while a feverishness given out is customarily a magnitude of a mitigation of a sum appetite of a complement (Internal energy). Thus, G or F is a volume of appetite “free” for work underneath a given conditions.

Up until this point, a ubiquitous perspective had been such that: “all chemical reactions expostulate a complement to a state of balance in that a affinities of a reactions vanish”. Over a subsequent 60 years, a tenure affinity came to be transposed with a tenure giveaway energy. According to chemistry historian Henry Leicester, a successful 1923 text Thermodynamics and a Free Energy of Chemical Reactions by Gilbert N. Lewis and Merle Randall led to a deputy of a tenure “affinity” by a tenure “free energy” in most of a English-speaking world.

See also[edit]

  • Exergy
  • Second law of thermodynamics
  • Superconductivity
  • Merle Randall


  1. ^ Stoner, Clinton D. (2000). Inquiries into a Nature of Free Energy and Entropy in Respect to Biochemical Thermodynamics. Entropy Vol. 2.
  2. ^ Mendoza, E. (1988). Clapeyron, E.; Carnot, R., eds. Reflections on a Motive Power of Fire – and other Papers on a Second Law of Thermodynamics. Dover Publications, Inc. ISBN 0-486-44641-7. 
  3. ^ Baierlein, Ralph (2003). Thermal Physics. Cambridge University Press. ISBN 0-521-65838-1. 
  4. ^ Perrot, Pierre (1998). A to Z of Thermodynamics. Oxford University Press. ISBN 0-19-856552-6. 
  5. ^ Reiss, Howard (1965). Methods of Thermodynamics. Dover Publications. ISBN 0-486-69445-3. 
  6. ^ International Union of Pure and Applied Chemistry Commission on Atmospheric Chemistry, J. G. (1990). “Glossary of Atmospheric Chemistry Terms (Recommendations 1990)” (PDF). Pure Appl. Chem. 62 (11): 2167–2219. doi:10.1351/pac199062112167. Retrieved 2006-12-28. 
  7. ^ International Union of Pure and Applied Chemistry Commission on Physicochemical Symbols Terminology and Units (1993). Quantities, Units and Symbols in Physical Chemistry (2nd Edition) (PDF). Oxford: Blackwell Scientific Publications. p. 48. ISBN 0-632-03583-8. Retrieved 2006-12-28. 
  8. ^ International Union of Pure and Applied Chemistry Commission on Quantities and Units in Clinical Chemistry, H. P.; International Federation of Clinical Chemistry Committee on Quantities and Units (1996). “Glossary of Terms in Quantities and Units in Clinical Chemistry (IUPAC-IFCC Recommendations 1996)” (PDF). Pure Appl. Chem. 68 (4): 957–1000. doi:10.1351/pac199668040957. Retrieved 2006-12-28.  Cite uses deprecated parameter |coauthors= (help)
  9. ^ Kondepudi, Dilip; Prigogine, Ilya (1998). Modern Thermodynamics. John Wiley Sons Ltd. ISBN 978-0-471-97394-2.  Chapter 4, Section 1, Paragraph 2 (page 103)

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