1.2    SCOPE AND PERSPECTIVES:   The grandest abstract of thermodynamics is the universe which is defined to be all there is, all that exists in a physical sense. The universe, being infinitely vast, much more than is applicable to engineering. Physical events of importance to human life occur in vanishingly small spaces in the universe. The impossibility of dealing with the entirety of the universe mandates a system approach.

Local changes occur with inconsequential effect universally. Thus it makes sense, in the study of thermodynamics, to focus on part of the mass which occupies part of the space. The property changes of this mass, named the system, are of primary importance. All mass of the universe that is not system mass belongs to the surroundings.
massuniverse + masssystem = masssurroundings
massuniverse + masssystem = masssurroundings

The construct, "universe equals system plus surroundings," has promise provided it can be refined. The system, the focus of interest, will be a finite mass (with its space attached inherently) but how will it be selected. It must be selected relative to its event, to the particulars of what happened. Event brings the consideration, time, into the thinking.



1.2   MEASUREMENT AND PROPERTIES:  
Measurement, the driving force of science, is the process of making matter and events quantitative. Whatever characteristic of a system that can be measured has the possibility of being named a property. Whatever cannot be measured is not a property. Measurement is property oriented, results in a number which has units. As a rule, numbers have units. Students at this level generally have adequate experience with ideas of measurement and property. The brief discussion below is focused on the needs of classical engineering thermodynamics, limited to simple, compressible substances with minor exceptions.

MEASURABLE AND NON-MEASURABLE PROPERTIES:  While the idea measurable properties (or primary, in some texts) might seems obvious, the fact that there are properties, physical characteristics of matter, which can be made quantitative but which cannot be measured. Non-measurable (or secondary) properties are made quantitative in relation to other properties that are measurable. There are subtle differences among types of properties but there are many steps of learning that can be accomplished with just a little of the sublty. Measurement itself has become a science. But limited to primary properties - that's all that can be measured. But before that, lets talk primary properties.

Qualifiers for properties of matter include the following distinctions and contrasts:
  • ENUMERATIVE or NATURAL:  numbers: plain counting. Dimensions and units are useful. Sometimes natural or enumerative numbers are ascribed units the don't have as 6 persons (3hr/person...)
  • GEOMETRIC:   two and three dimensional reasoning, mensuration
  • SPATIAL:  time is the independent variable of position and velocity.
  • TEMPORAL:  
  • MATERIAL:
  • EQUILIBRIUM:
  • MEASURABLE:  Measurement is the power of science and science begins in a meager way with only what can be measured. Mesaurement can be direct or indirect. (eratosthenes).
  • NON-MEASURABLE: realm of thermodynamics
  • MECHANICAL:
  • PRIMARY AND SECONDARY
    The distinction of primary measurements is that they basically are independent of inner detail of the matter. Primary properties are basic, those for which successful measurement devices are available including: mass, volume, length, density, pressure, temperature and others.
  • THERMODYNAMIC PROPERTIES OF SIMPLE COMPRESSIBLE SUBSTANCES MEASURABLE:
  • THERMODYNAMIC NONMEASURABLE:
  • INTRINSIC - EXTRINSIC
  • EXTENSIVE - INTENSIVE (or specific)
  • EXTENSIVE versus INTENSIVE:
    Properties with extent: mass (m), volume (L3), kinetic energy [E], potential energy [E], internal energy [E], enthalpy [E] and entropy [E/O].
    Properties made by division by system mass: kinetic energy (e=E/m), potential energy (e=E/m), internal energy (e=E/m), enthalpy (e=E/m) and entropy (e/mO).


  • PROPERTIES OF MECHANICS: BODY, (PARTICLE) AND RIGID BODY.  

    NAME SYMBOL [dimensions]
    mass: m ~ [m]
    time: t ~ [t]
    position:(#) P ~ [L]
    velocity:(#) V ~ [L/t]
    momentum:(#) mV ~ [m L/t]
    angular momentum:(#) r x (mV) ~ [m L2/t]
    center of mass:(#) rcm ~[L]
    radius of gyration:(#) rcm ~[L]
    (#), requiring a vector origin and basis


    PROPERTIES OF THERMODYNAMICS FOR A PURE SIMPLE COMPRESSIBLE SUBSTANCES:  Thermodynamics is the study of matter, its phases, states and events that occur to it as a consequence of equilibration, or energy interaction with the surroundings. Conditions of existance (undisturbed, static or equilibrium) are categorized as state. Transformations from some initial state to a final, ie, changes of state are explained in terms of heat and/or work. There is a great amount of terminology, nuances, qualifications and disagreements among thermodynamicists about a great amount of thermo. Typically texts spread their talk about subtle terms over 300 pages. Here we do it in 2 pages.

    Physical characteristics of systems include spatial relationships and material properties. Position, velocity, and other spatial characteristice are generally not considered properties because they are independent of the matter of the system. Logically, the first system characteristics established were not thought of so much as properties but as geometry (meaning earth measurement). After each years flood of the Nile, ancient Egyptian engineers re-located boundaries of property, measured acreage to estimate productivity and general value of irregular land acreages, and so on. The studies were basic, about geometric "properties" of squares, triangles... and sometime later circles. These simple, disciplined efforts constituted the begining, the foundation of scientific accomplishment and process engineers use today.


    P A nearly complete list, symbols listed first - we use the symbols more often than the words.
    NAME SYMBOL [dimensions]
    mass:m ~ [m]
    volume:V ~ [L3]
    specific volume: v = v(T,p) ≡ V/m [L3/m]
    density: ρ = ρ(T,p) ≡ m/V (or 1/v [m/L3])
    pressure: p ~ [F/L2]
    temperature: T ~ [0]
    specific internal energy u = u(T,v) ≡ U/m ~ [E/m]
    specific enthalpy h = h(T,p) (≡ u + pv) = H/m ~ [E/m]
    specific entropy s = s(T,v) and s = s(T,p) ~ [E/(m0)]
    Internal Energy, Enthalpy and Entropy as mU, mH, and mS, respectively

    IN GENERAL   Each property consists of i) a name and technical description and ii) at least one measurement process whereby measurements taken thereafter are statistically the same unique number (or three, or nine numbers... depending upon the property). Thus a property is more than a number or numbers and the same set of numbers must be obtained (subject to measurement accuracy) by different measurement processes. For example, the distance between two parked automobiles might be measured by use of a tape measure by say, a sheriff. And that distance, measured from a vehicle on the moon, would be the same number.

    With regard to numbers, physical properties are tensors. Each distinct physical property is ultimately described numerically by one number (the property being a scalar), or by 3 numbers (that property being a vector with the numbers determined relative to a space and time coordinate reference) or 9... numbers. .

    Tensors are classed by rank as rank zero, rank one, two or some larger integer. There are (3)RANK , that is three raised to the "rank" numbers, and appropriated dinensions, vector basis and so, associated with a physical tensor or system properties. The "numbers" of physical properties must be established by some measurement process.

    RANK NUMBERS NAME EXAMPLES
    0 (3)0 scalar pressure, mass, density,
    length...
    1 (3)1 vector position, velocity, momentum,
    area. {But not force. Force is a
    vector but not a property}.
    2 (3)2 tensor moment of inertial and material stress
















    HISTORICAL MEASUREMENTS:   To read further about measurement, review historic accounts of efforts by these persons, which in groups or as indivuduals, measured physical properties relevant to the engineering they accomplished and today.

    Texts like this one are necessarly just words and ideas. The point being made here is that measurement and physical reality is what engineering is about. In addition to those named above, there have been very many more scientists and engineers who by property identification and measurement advanced our technical competences.