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adiabatic process – A process in which there is no heat transfer. (Q = 0, where Q represents heat)
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allotropic transformation – A transition from one solid phase to another.
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calorie – The amount of heat required to raise 1 g of water from 14.5°C to 15.5°C.
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closed system – No mass flow through control surface.
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control mass – No mass can escape or enter through the control surface. It contains the same amount of matter at all times; may be abbreviated with CM.
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control surface – May be abbreviated with CS.
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control volume – A system enclosed within a control surface. The volume remains constant, but the mass within it may change over time. contains the matter and devices inside a control surface. Everything external to the control volume is the surroundings, with the separation given by the control surface. The surface may be open or closed to mass flows, and it may have flows of energy in terms of heat transfer and work across it. The boundaries may be movable or stationary; may be abbreviated with CV.
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hygroscopic – Absorbing or attracting moisture from the air.
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ideal process – A quasi-equilibrium process.
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isentropic process – A constant-entropy process.
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isobaric process – A constant-pressure process. Sometimes called isopiestic.
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isochoric process – A constant-volume process.
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isotherm – See isothermal surface.
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isothermal process – A constant-temperature process.
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isothermal surface – A surface of constant temperature.
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nonequilibrium process – The system of which a nonequilibrium process occurs can only be described 1.) before a process occurs and 2.) after the process is completed and equilibrium is restored. Each state through which the system passes or the rate at which the process occurs is unable to be specified. Although, certain overall effects that occur during the process may be described. For example, if a number of weights on a piston were all removed at once and the piston rapidly rised until it hit the stops. This would be a nonequilibrium process, and the system would not be in equilibrium at any time during this change of state. In contrast to quasi-equilibrium process.
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open system – Involves mass flow through control surface.
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point function – Quantity that depends only on the state and is independent of the path. This is in contrast to a path function, which is dependent on the path.
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quasi-equilibrium process – A process in which the deviation from thermodynamic equilibrium is infinitesimal, and all the states the system passes through during a quasi-equilibrium process may be considered equilibrium states. Many actual process closely approach a quasi-equilibrium process and may be so treated with essentially no error.
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reversibility – The phenomenon of undergoing reversible change.
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simple compressible substance – A substance whose surface effects, magnetic effects, and electrical effects are insignificant when dealing with the substances; but changes in volume, such as those associated with the expansion of a gas in a cylinder, are very important.
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simple compressible system – A system consisting of a simple compressible substance.
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state – For a substance that exists at certain properties, a state can define the substance at specific values of those properties. For example one state may be for the substance existing at T1 and P1, another state may be for the substance existing at T2 and P2.
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steam – Is water vapor.
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thermal equilibrium – When the temperature is the same throughout the entirety of a system.
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thermodynamic equilibrium – When a system is in equilibrium regarding all possible changes of state. (i.e. same temperature throughout, same pressure throughout, etc. etc.)
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triple point – For three phases, vapor, liquid, and solid, it is the state or point in which all three phases may be in equilibrium, or exist together. (picture), also see Gibbs Phase Rule
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water vapor – Is steam.
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