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1: Definitions, 2: Examples , 3:Remarks/Properties, 4: Short Questions & Answers
1. System - Environment
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- A thermodynamic system is defined as a quantity of matter or a region in space that is of interest. The mass or region outside the system is called the surroundings, and the surface that separates the system and the surroundings is called the boundary.
- A thermodynamic system is an area (or volume) in space upon which study is concentrated. Everything outside the system is called surrounding. A system is separated from the surrounding with the help of a boundary. A boundary has zero thickness so it does not contain any matter
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- if we are studying a car engine, the burning gasoline inside the cylinder of the engine is the thermodynamic system; the piston, exhaust system, radiator, and air outside form the surroundings of the system
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How do you classify thermodynamic system?Thermodynamic systems can be classified as open, closed, and isolated systems on the basis of the possible transfer of heat and matter to the environment. An open system is a system that freely allows the exchange of energy and matter with its environment.
2. Quasi-Static-Process
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In thermodynamics, a quasi-static process (also known as a quasi-equilibrium process; from the Latin quasi, meaning ‘as if’[1]), is a thermodynamic process that happens slowly enough for the system to remain in internal physical (but not necessarily chemical) thermodynamic equilibrium.
Wikipedia
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An example of this is quasi-static expansion of a mixture of hydrogen and oxygen gas, where the volume of the system changes so slowly that the pressure remains uniform throughout the system at each instant of time during the process.[2] Such an idealized process is a succession of physical equilibrium states, characterized by infinite slowness.[3]
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Only in a quasi-static thermodynamic process can we exactly define intensive quantities (such as pressure, temperature, specific volume, specific entropy) of the system at every instant during the whole process; otherwise, since no internal equilibrium is established, different parts of the system would have different values of these quantities so a single value per quantity may not be sufficient to represent the whole system. In other words, when an equation for a change in a state function contains P or T, it implies a quasi-static process.
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