This is a branch of physics that is concerned with temperature and heat and how they relate to energy and work. The four laws of thermodynamics govern the behaviour of these quantities irrespective of the composition or specific properties of the material or system in question. Thermodynamics is applied in different branches of science and engineering such as physical chemistry, mechanical engineering, and chemical engineering.
The need to increase the efficiency of early steam engines led to the development of thermodynamics. This is seen in the work of French physicist, Nicolas Léonard Sadi Carnot (1824), who believed France could win the Napoleonic war by increasing the efficiency of the steam engines. The first concise definition of thermodynamics was first formulated by Lord Kelvin, a Scots-Irish physicist in 1854. It states that “Thermo-dynamics is the subject of the relation of heat to forces acting between contiguous parts of bodies, and the relation of heat to electrical agency.”
Thermodynamics as a scientific study began in 1650 when Otto von Guericke designed the world’s first vacuum pump and demonstrated it using his Magdeburg hemispheres. In 1656, English chemist and physicist Robert Boyle who had learned of Guericke’s design collaborated with English scientist Robert Hook to build an air pump. Boyle and Hook noticed a relationship between pressure, temperature, and volume; Boyle then formulated Boyle’s law which states that there is an inverse relationship between pressure and volume.
Denis Papin, an associate of Boyle, built a steam digester in 1679 based on the principles of Boyle’s law. The steam digester was a closed vessel with a tight-fitting lid that confined steam until a high pressure was generated. A steam release valve was included in later designs to prevent an explosion. In 1697, Thomas Savery built the first engine, based on Papin’s design. This was followed by Thomas Newcomen in 1712.
Professor Joseph Black of the University of Glasgow developed the fundamental concepts of heat capacity and latent heat and these were necessary for the development of thermodynamics. Black and James Watt, an instrument maker performed several experiments together but the idea for an external condenser was conceived by Watt and this resulted in an increase in steam engine efficiency.
The first book on thermodynamics was written by William Rankine in 1859. The 1850s also witnessed the emergence of the first and second laws of thermodynamics by William Rankine, William Thomson, and Rudolf Clausius. The foundations of statistical thermodynamics were laid by James Clerk Maxwell, Ludwig Boltzmann, Max Planck, Rudolf Clausius, and J. Willard Gibbs.
Branches of Thermodynamics
1. Classical Thermodynamics:
This describes the state of thermodynamic systems at near equilibrium that uses macroscopic, measurable properties. It uses the laws of thermodynamics to model the exchange of energy, work, and heat.
2. Chemical Thermodynamics:
This is the study of the interrelation of energy with chemical reactions or with a physical change of state within the confines of the laws of thermodynamics.
3. Statistical Thermodynamics:
Also called statistical mechanics, it relates to the microscopic properties of individual atoms and molecules to the macroscopic, bulk properties of materials that can be observed on the human scale, classical thermodynamics as a natural result of statistics, classical mechanics, and quantum theory at the microscopic level.
4. Equilibrium Thermodynamics:
This is the systematic study of the transfer of matter and energy in systems as they pass from one state of thermodynamic equilibrium to another.
Laws of Thermodynamics
- First Law of Thermodynamics:“The internal energy of an isolated system is constant.” This law expresses the principle of conservation of energy that states that energy can be changed from one form to another but can neither be destroyed nor created.
- Second Law of Thermodynamics:“Heat cannot spontaneously flow from a colder location to a hotter location.” This expresses the universal principle of decay observable in nature. It observes that given the time differences in temperature, pressure and chemical potential even out in an isolated system.
- Third Law of Thermodynamics:“As a system approaches absolute zero, all processes cease and the entropy of the system approaches a minimum value.” This is a statistical law of nature concerning entropy and the impossibility of reaching absolute zero temperature.
- Zeroth Law of Thermodynamics:“If two systems are each in thermal equilibrium with a third, they are also in thermal equilibrium with each other.” This implies that thermal equilibrium is an equivalence relation on the set of thermodynamic systems under consideration.
Modern Application of Thermodynamics
The second law of thermodynamics applies to every type of heat engine cycle and has led to the progress made in modern day vehicles. This law is also applied in refrigerators and heat pumps using the reversed Carnot Cycle. Removing heat from food in a refrigerator does not happen automatically, there has to be a supply of external work through the compressor for the heat to be released to a higher temperature atmosphere.
This same law applies in air conditioners and heat pumps. An air conditioner removes hot air from a room while keeping the room at a lower temperature and releases the hot air into the atmosphere. A heat pump supplies a room with hot air absorbed from the atmosphere during cooler seasons.
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