Thermodynamics

by Adarsh S.M(2016-2019)

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Thermodynamics, Science of the relationship between heat ,work,temperature and energy. In broad terms, thermodynamics deals with the transfer of energy from one place to another and from one form to another. The key concept is that heat is a form of energy corresponding to a definite amount of mechanical work.

Heat was not formally recognized as a form of energy until about 1798, when Count Rumford (Sir Benjamin Thomson), a British military engineer, noticed that limitless amounts of heat could be generated in the boring of cannon barrels and that the amount of heat generated is proportional to the work done in turning a blunt boring tool. Rumford’s observation of the proportionality between heat generated and work done lies at the foundation of thermodynamics. Another pioneer was the French military engineer Sadi Carnot, who introduced the concept of the heat-engine cycle and the principle of reversibility  in 1824. Carnot’s work concerned the limitations on the maximum amount of work that can be obtained from a steam engine operating with a high-temperature heat transfer as its driving force. Later that century, these ideas were developed by Rudolf Clausius, a German mathematician and physicist, into the first and second laws of thermodynamics, respectively.

 

 

Statistical mechanics

Statistical mechanics is a branch of theoretical physics that uses probability theory to study the average behaviour of a mechanical system whose exact state is uncertain.^{[1][2][3][note 1]}

Statistical mechanics is commonly used to explain the thermodynamic behaviour of large systems. This branch of statistical mechanics, which treats and extends classical thermodynamics, is known as statistical thermodynamics or equilibrium statistical mechanics. Microscopic mechanical laws do not contain concepts such as temperature, heat, or entropy; however, statistical mechanics shows how these concepts arise from the natural uncertainty about the state of a system when that system is prepared in practice. The benefit of using statistical mechanics is that it provides exact methods to connect thermodynamic quantities (such as heat capacity) to microscopic behaviour, whereas, in classical thermodynamics, the only available option would be to just measure and tabulate such quantities for various materials. Statistical mechanics also makes it possible to extend the laws of thermodynamics to cases which are not considered in classical thermodynamics, such as microscopic systems and other mechanical systems with few degrees of freedom.

Statistical mechanics also finds use outside equilibrium. An important subbranch known as non-equilibrium statistical mechanics deals with the issue of microscopically modelling the speed of irreversible processes that are driven by imbalances. Examples of such processes include chemical reactions or flows of particles and heat. Unlike with equilibrium, there is no exact formalism that applies to non-equilibrium statistical mechanics in general, and so this branch of statistical mechanics remains an active area of theoretical research.

Are there new states of matter at ultrahigh temperatures and densities?

by Abhijith.A.D(2016-2019)

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Under extreme energetic conditions, matter undergoes a series of transitions, and atoms break down into their smallest constituent parts. Those parts are elementary particles called quarks and leptons, which as far as we know cannot be subdivided into smaller parts. Quarks are extremely sociable and are never observed in nature alone. Rather, they combine with other quarks to form protons and neutrons (three quarks per proton) that further combine with leptons (such as electrons) to form whole atoms. The hydrogen atom, for example, is made up of an electron orbiting a single proton. Atoms, in turn, bind to other atoms to form molecules, such as H₂O. As temperatures increase, molecules transform from a solid such as ice, to a liquid such as water, to a gas such as steam.

{Add a little heat, and molecules can be easily transformed from solids into liquids and then gases. But what happens at extreme temperatures? Does matter break down into a soup of subatomic particles—called a quark-gluon plasma—and then into energy? }

That’s all predictable, known science, but at temperatures and densities billions of times greater than those on Earth, it’s possible that the elementary parts of atoms may come completely unglued from one another, forming a plasma of quarks and the energy that binds quarks together. Physicists are trying to create this state of matter, a quark-gluon plasma, at a particle collider on Long Island. At still higher temperatures and pressures, far beyond those scientists can create in a laboratory, the plasma may transmute into a new form of matter or energy. Such phase transitions may reveal new forces of nature.

These new forces would be added to the three forces that are already known to regulate the behavior of quarks. The so-called strong force is the primary agent that binds these particles together. The second atomic force, called the weak force, can transform one type of quark into another (there are six different “flavors” of quark—up, down, charm, strange, top, and bottom). The final atomic force, electromagnetism, binds electrically charged particles such as protons and electrons together. As its name implies, the strong force is by far the most muscular of the three, more than 100 times as powerful as electromagnetism and 10,000 times stronger than the weak force. Particle physicists suspect the three forces are different manifestations of a single energy field in much the same way that electricity and magnetism are different facets of an electromagnetic field. In fact, physicists have already shown the underlying unity between electromagnetism and the weak force.

Some unified field theories suggest that in the ultrahot primordial universe just after the Big Bang, the strong, weak, electromagnetic, and other forces were one, then unraveled as the cosmos expanded and cooled. The possibility that a unification of forces occurred in the newborn universe is a prime reason particle physicists are taking such a keen interest in astronomy and why astronomers are turning to particle physics for clues about how these forces may have played a role in the birth of the universe. For unification of forces to occur, there must be a new class of supermassive particles called gauge bosons. If they exist, they will allow quarks to change into other particles, causing the protons that lie at the heart of every atom to decay. And if physicists prove protons can decay, the finding will verify the existence of new forces.