Made by, Vasava vipul [ ]

Thermodynamics Thermodynamics is the science of energy conversion involving heat and other forms of energy, most notably mechanical work. It studies and interrelates the macroscopic variables (temperature, volume and pressure). A thermodynamic system (a physical system) is a precisely defined macroscopic region of the universe that is studied.

Branches of Thermodynamics Classical thermodynamics is the description of the states of thermodynamical systems at near-equilibrium, using macroscopic, empirical properties directly measurable in the laboratory. It is used to model exchanges of energy, work and heat based on the laws of thermodynamics. Statistical mechanics (or statistical thermodynamics) gives thermodynamics a molecular interpretation. This field relates the microscopic properties of individual atoms and molecules to the macroscopic or bulk properties of materials that can be observed in everyday life, thereby explaining thermodynamics as a natural result of statistics and mechanics (classical and quantum) at the microscopic level. Chemical thermodynamics is the study of the interrelation of energy with chemical reactions. Biological thermodynamics is the study of energy transformation in the biological systems.

Equilibrium and non-equilibrium thermodynamics The word equilibrium implies a state of balance. In an equilibrium state there are no unbalanced potentials, or driving forces, within the system. Equilibrium thermodynamics is the systematic study of transformations of matter and energy in systems as they approach equilibrium. Most systems found in nature are not in thermodynamic equilibrium because they are not in stationary states, and are continuously and discontinuously subject to flux of matter and energy to and from other systems. Non-equilibrium thermodynamics deals with such systems.

Thermodynamic system. Thermodynamic parameters A thermodynamic system (a physical system) is a precisely defined macroscopic region of the universe that is studied. A thermodynamic system is characterized and defined by a set of thermodynamic parameters An intensive property (parameter) is a physical property of a system that does not depend on the system size or the amount of material in the system extensive property (parameter) is one that is additive for independent, noninteracting subsystems. It is directly proportional to the amount of material in the system.

Thermodynamic system All space in the universe outside the thermodynamic system is known as the surroundings (the environment, or a reservoir). A system is separated from its surroundings by a boundary which may be notional or real, but which by convention delimits a finite volume. Systems are distinguished depending on the kinds of interaction they undergo and the types of energy they exchange with the surrounding environment.

Thermodynamic systems Isolated systems are completely isolated from their environment. They do not exchange heat, work or matter with their environment. An example of an isolated system is a completely insulated rigid container, such as a completely insulated gas cylinder.

Thermodynamic systems Closed systems are able to exchange energy (heat and work) but not matter with their environment. A greenhouse is an example of a closed system exchanging heat but not work with its environment. Whether a system exchanges heat, work or both is usually thought of as a property of its boundary.

Thermodynamic systems Open systems may exchange any form of energy as well as matter with their environment. A boundary allowing matter exchange is called permeable. The ocean would be an example of an open system.

Internal energy Internal energy is defined as the energy associated with the random, disordered motion of molecules. It is separated in scale from the macroscopic ordered energy associated with moving objects; it refers to the invisible microscopic energy on the atomic and molecular scale. The internal energy is the total energy contained in a thermodynamic system. It is the energy necessary to create the system, but excludes the energy associated with a move as a whole, or due to external force fields. Internal energy has two major components, kinetic energy and potential energy. For an ideal monoatomic gas, this is just the translational kinetic energy of the linear motion of the "hard sphere" type atoms. However, for polyatomic gases there is rotational and vibrational kinetic energy as well.

System Work When work is done by a thermodynamic system, it is ususlly a gas that is doing the work. The work done by a gas at constant pressure is: For non-constant pressure, the work can be visualized as the area under the pressure-volume curve which represents the process taking place. The more general expression for work done is:

Heat Transfer Heat is energy transferred from one body or thermodynamic system to another due to thermal contact when the systems are at different temperatures. Heat Conduction Conduction is heat transfer by means of molecular agitation within a material without any motion of the material as a whole. For heat transfer between two plane surfaces, such as heat loss through the wall of a house, the rate of conduction heat transfer is:

First law of thermodynamics The first law of thermodynamics is the application of the conservation of energy principle to heat and thermodynamic processes: Heat added to the thermodynamic system goes to change the internal energy and to do the work by the system.

First law of thermodynamics The internal energy of a system can be changed by heating the system or by doing work on it. If the system is isolated, its internal energy cannot change.

Entropy as a Measure of the Multiplicity of a System The probability of finding a system in a given state depends upon the multiplicity of that state. That is to say, it is proportional to the number of ways you can produce that state. Here a "state" is defined by some measurable property which would allow you to distinguish it from other states. Entropy: where k is Boltzmann's constant, W is the number of microstates The k is included as part of the historical definition of entropy and gives the units J/K in the SI system of units. The logarithm is used to make the defined entropy of reasonable size. The multiplicity for ordinary collections of matter are on the order of Avogadro's number, so using the logarithm of the multiplicity is convenient.

Entropy in Terms of Heat and Temperature A the change in entropy can be described as the heat added per unit temperature ΔS = Q/T where S is the change in entropy, Q is the heat flow into or out of a system, and T is the absolute temperature in degrees Kelvin (K). This is often a sufficient definition of entropy if you don't need to know about the microscopic details. It can be integrated to calculate the change in entropy during a part of an engine cycle. The concept of entropy (S) gives us a more quantitative way to describe the tendency for energy to flow in a particular direction.

Entropy Entropy: a state variable whose change is defined for a reversible process at T where Q is the heat absorbed. Entropy: a measure of the amount of energy which is unavailable to do work. Entropy:a measure of the disorder of a system. Entropy: a measure of the multiplicity of a system.

Enthalpy Enthalpy is a thermodynamic potential. It is a state function since it is defined in terms of three other precisely definable state variables, and it is an extensive quantity. Enthalpy is a measure of the total energy of a thermodynamic system. It includes the internal energy U, which is the energy required to create a system, and the amount of energy required to make room for it by displacing its environment and establishing its volume V and pressure P. H = U + PV It is somewhat parallel to the first law of thermodynamics for a constant pressure system Q = ΔU + PΔV, since in this case Q=ΔH

The second law of thermodynamics Clausius statement The second law of thermodynamics describes the flow of energy in nature in processes which are irreversible. The second law of thermodynamics may be expressed in many specific ways. Second Law and Refrigerator It is not possible for heat to flow from a colder body to a warmer body without any work having been done to accomplish this flow. Energy will not flow spontaneously from a low temperature object to a higher temperature object. This precludes a perfect refrigerator. The statements about refrigerators apply to air conditioners and heat pumps, which embody the same principles.

Kelvin-Planck statement Second Law and Heat Engine It is impossible to extract an amount of heat from a hot reservoir and use it all to do work. Some amount of heat must be exhausted to a cold reservoir. It meams that the efficiency of a heat engine cycle is never 100%. This precludes a perfect heat engine.

Thank you