Extensive Property

3 Key excerpts on "Extensive Property"

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  eBook - PDF

  Fundamentals of Chemical Engineering Thermodynamics, SI Edition

  • Kevin Dahm, Donald Visco(Authors)
  • 2014(Publication Date)
  • Cengage Learning EMEA

    (Publisher)

  Conversely, the mass and volume of water are examples of extensive properties; they are directly proportional to the number of moles of water present. Examples 4-2 and 4-3 will give an illustration of two very different paths from the same initial state to the same final state. Specific internal energy is an example of an intensive property, which is discussed further in the next section. The word “extensive” shares a root with the word “extend.” You might say that as the amount of a material extends (gets larger) the extensive proper-ties change, but the intensive properties do not. Copyright 2015 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. 55 C H A P T E R 2 The Physical Properties of Pure Compounds The distinction between intensive and extensive properties is important, because intensive properties are fundamental and repeatable properties of a mate-rial, while extensive properties only can be used to describe a particular sample of a material. For example, if told “the mass of the water is 1 kg,” the value of 1 kg is an Extensive Property that is applicable only to that particular sample of water. But “the density of water at T 5 323.15 K and P 5 0.1 MPa is 988 kg/m 3 ” is an intensive property and is valid for any system or process involving water at that T and P . The relationship among the temperature, pressure, and density of pure liquid water is illustrated in Table 2-2. Notice that, if any two of these properties are known, there is only one value the third can have, and it can be determined from the table.

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  eBook - ePub

  Engineering Thermodynamics with Worked Examples

  • Nihal E Wijeysundera(Author)
  • 2016(Publication Date)
  • WSPC

    (Publisher)

  intensive property is independent of the mass of a system. Pressure and temperature are examples of intensive properties. It is clear that the magnitude of an intensive property may vary spatially within a system, especially under dynamic conditions. We then speak of intensive property gradients within a system. For example, the pressure of a gas contained in a vertical cylinder varies due to the action of gravity.

  1.3.2Extensive properties

  The value of an Extensive Property depends on the quantity of matter in the system. Mass and volume are examples of extensive properties. The value of an Extensive Property of a composite system may be obtained by adding the values of the property of the constituent sub-systems.

  1.4State of a System

  The state of a system is characterized or described by the values of its properties. The minimum number of independent properties that are needed to uniquely identify the state depends on the complexity of the system. For simple thermodynamic systems two independent properties are sufficient to completely describe its state, for example temperature and pressure.

  1.5Some Basic Properties of Systems

  In the following sections we review a few familiar thermodynamic properties that we have encountered in basic physics courses. These are pressure, temperature and density.

  1.5.1Pressure

  Pressure is defined as the normal force per unit area exerted by a system on the boundary. In order to define the pressure at a location inside the system we consider the force, δF on one side of a small imaginary surface of area δA at the location. The pressure is given by, P = δF/δA . The pressure distribution in a system in an equilibrium state is assumed to be uniform. However, we need to remember that gravity will cause an increase in pressure from the top of the system to its bottom even under equilibrium conditions. In many applications this pressure variation due to gravity can be neglected.

  Many techniques are available for the measurement of pressure. The more common pressure-measuring instruments include liquid manometers, Bourdon-tube pressure gages and pressure transducers. These instruments, in general, measure the gage pressure, which is the difference in pressure between a fluid and the surrounding atmosphere. The absolute pressure of the fluid is obtained from the relation

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  eBook - ePub

  Science: Image in Action

  Proceedings of the 7th International Workshop on Data Analysis in Astronomy "Livio Scarsi and Vito DiGesù"

  • Bertrand Zavidovique, Giosue' Lo Bosco(Authors)
  • 2011(Publication Date)
  • WSPC

    (Publisher)

  There are various definitions of the latter. Some authors define it as a quantity which scales with mass, others as a quantity which scales with the quantity of matter; some other refer to additivity. Let us adopt the most general definition, since is the only one suitable for generalizations to arbitrary space-time metrics or to arbitrary spaces: Given a system P T and given the quantities defining it, by extensive quantity we mean any quantity E whose value is given by the volume integral of function (x i), called density, of E in the point x i. Note that in the definiens above, volume plays the fundamental role: it is, by definition, the extensive reference quantity ; it is extensive, homogeneous and isotropical thanks to the homogeneity and isotropy of space-time. Having this definition in mind, the “additivity property” often used to define extensive quantities (which would be a better choice in a quantum domain) acquires a rigorous and general meaning: if we considered the system P T as if it were subdivided into n sub-systems, in the sense of volume (n sub-volumes), the value of E would be given by the “sum” of the n values of E within the n sub-systems (by the additivity of integrals). The mass of a system is a paradigmatic example of extensive quantity, since it can be thought of as the volume integral of the mass density

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