Thermodynamics

Thermodynamics (Greek: thermos = heat and dynamis = power) is the physics of heat, work, enthalpy, and entropy changes in relation to the spontaneity of processes. In origins, thermodynamics is the study of engines. Prior to 1698, with the invention of the Savery Engine, horses were used to "power" pulleys, attached to buckets, which lifted water out of flooded salt mines in England. In the years to follow, more variations of steam engines were built; as the Newcomen Engine, and later the Watt Engine. In time, these early engines would eventually be utilized in place of horses. Thus, each engine began to be associated with a certain amount of "horse power" depending upon how many horses it had replaced! The main problem with these first engines was that they were slow and clumsy, converting less than 2% of the input fuel into useful work. In other words, large quantities of coal (or wood) had to be burned to yield only a small fraction of work output. Hence the need for a new science of engine dynamics was born.

History

Most cite Sadi Carnot?s 1824 paper Reflections on the Motive Power of Fire as the starting point for thermodynamics as a modern science. Carnot defined "motive power" to be the expression of the useful effect that a motor is capable of producing. Herein, Carnot introduced us to the first modern day definition of "work": weight lifted through a height. The desire to understand, via formulation, this useful effect in relation to "work" is at the core of all modern day thermodynamics.

Related Topics:
Sadi Carnot?s - Work

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The name "thermodynamics", however, did not arrive until some twenty-five years later when in 1849, the British mathematician and physicist William Thomson (Lord Kelvin) coined the term ?thermodynamics' in a paper on the efficiency of steam engines. In 1850, the famed mathematical physicist Rudolf Clausius originated and defined the term enthalpy H to be the total heat content of the system, stemming from the Greek word ?enthalpein? meaning to warm, and defined the term entropy S to be the heat lost or turned into waste, stemming from the Greek word ?entrepein? meaning to turn.

Related Topics:
William Thomson - Rudolf Clausius

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In association with Clausius, in 1871, a Scottish mathematician and physicist James Maxwell formulated a new branch of thermodynamics called Statistical Thermodynamics, which functions to analyze large numbers of particles at equilibrium, i.e. systems where no changes are occurring, such that only their average properties as temperature T, pressure P, and volume V become important.

Related Topics:
James Maxwell - Equilibrium

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Soon thereafter, in 1875, the Austrian physicist Ludwig Boltzmann formulated a precise connection between entropy S and molecular motion:

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:S=k*log ,

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being defined in terms of the number of possible states such motion could occupy, where k is the Boltzmann's constant. The following year, 1876, was a seminal point in the development of human thought. During this essential period, chemical engineer Willard Gibbs, the first person in America to be awarded a PhD in engineering (Yale), published an obscure 300-pg paper titled: On the Equilibrium of Heterogeneous Substances, wherein he formulated one grand equality, the Gibbs free energy equation, which gives a measure the amount of "useful work" attainable in reacting systems:

Related Topics:
Boltzmann's constant - Willard Gibbs - Gibbs free energy

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:Delta G = Delta H - T Delta S ,

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Building on these foundations, those as Lars Onsager, Erwin Schrodinger, and Ilya Prigogine, and others, functioned to bring these engine ?concepts? into the thoroughfare of almost every modern-day branch of science.

Related Topics:
Lars Onsager - Erwin Schrodinger - Ilya Prigogine

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