
The ten "fundamental quantities" of thermodynamics, according to the 1914 views of American physicist Percy Bridgman. [3]

The ten "fundamental quantities" of thermodynamics, according to the 1914 views of American physicist Percy Bridgman. [3]

In science, quantity, from the Latin quantus “how much”, refers to the measurement of something, in relation to that which can be expressed numerically in units. [1]

Quantifiable
The three step process for a subject becoming a “science”, according to the William Jenson categorization scheme (see: etymology), is for the “theoretical” stage to transform into the “quantification” stage, which then transforms into the “modern” stage, which in the case of transformation of thermochemistry (1783) to science of modern chemical thermodynamics (1923) took about 140-years. [5]

Nonquantifiable

See main: Proxmire affair

In 1975, American politician William Proxmire, after hearing of the $84K NSF grant awarded to American psychologists Ellen Berscheid and Elaine Walster to study on romantic love, dubbed love a non-quantifiable subject matter, as follows: [6]

“No one can argue that falling in love is a science. The impact of love is a very subjective, nonquantifiable subject matter. Love is simply a mystery.”

In 1969, Walster and Berscheid, in their Interpersonal Attraction, reflected on this: [7]

“It is odd that the notion that attraction, particularly such intense forms as romantic love, are simply ‘non-quantifiable’ has lingered to the present day. It seems especially strange when we consider that each of us, every day and in a variety of ways, manages to quantify our attraction to others and measure their attraction to us.”

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Five principle quantities
The five “principle quantities” in thermodynamics, according to the 1878 views of Scottish physicist James Maxwell, are the energy U, entropy S, volume V, temperature T, and pressure P of a body. [2] Quantities can be either “intensive”, defined uniquely per point in space, or “extensive”, proportional to the dimension of the system.


The 7 base units and 26 derived units of the quantities of the SI unit system. [4]

The 7 base units and 26 derived units of the quantities of the SI unit system. [4]

Ten fundamental quantities
The ten "fundamental quantities" in thermodynamics, according to the 1914 views of American physicist Percy Bridgman, are pressure p, temperature τ, volume v, entropy s, heat Q, work W, internal energy E, total heat H (enthalpy), Gibbs potential Z (Gibbs free energy), and Helmholtz potential ψ (Helmholtz free energy), as shown adjacent.

Units | Base and derived
All thermodynamic quantities are measured in "units" of which there are 7 base units and 26 derived units (shown adjacent). [4] Historically, in 1960, in aims to unify scientific calculations throughout the world, French scientists developed the International System (SI) of units, using the three basic metric (meter-based) units of mass (kg), length (m), time (s), in addition to the four newer units temperature (K), mole (mol), current (A), and light intensity (cd). The first five SI units (kg, m, s, K, mol) are fairly simple units, whereas the latter two, i.e. current (A), measured in force per distance, and light (cd), being the measure of photon emission from a typical candle, are somewhat more complicated to understand.

One of the more conceptually difficult derived units to understand is the unit interrelationship involved in the measurement of the mechanical equivalent of heat (J), which involves two derived SI units, work and heat, and one base SI unit, temperature.

Quotes
The following are related quotes:

“Elegant intellects which despise the theory of quantity are but half developed.”
— Alfred Whitehead (c.1910), cited by Alfred Lotka in Elements of Physical Biology (pg. 100)

See also
● Characteristic function notation table
● SI unit genius

References
1. Quantity (definition) – Merriam-Webster Collegiate Dictionary, 2000.
2. (a) Maxwell, James C. (1878). “Tait’s ‘Thermodynamics’ (I)”, (pgs. 257-59). Nature, Jan. 31.
(b) Maxwell, James C. (1878). “Tait’s ‘Thermodynamics’ (II)”, (pgs. 278-81). Nature, Feb. 07.
3. Bridgman, P.W. (1914). "A Complete Collection of Thermodynamic Formulas" (abstract). Phys. Rev. 3 (4): 273–281.
4. SI base and derived units – Physics.Nist.gov.
5. Jensen, William B. (2005). “The Quantification of 20th-Century Chemical Thermodynamics: a Tribute to Thermodynamics and the Free Energy of Chemical Substances” (pdf), Lecture given at Boston Society Symposium on Classic 20th-Century Chemistry Textbooks, 230th meeting of the ACS, Washington, DC, Aug 29.
6. Solomon, Robert C. (1981). Love: Emotion, Myth, & Metaphor (pg. 93). Prometheus Books, 1990.
7. (a) Walster, Elaine and Berscheid, Ellen. (1969). Interpersonal Attraction (pg. 5). Addison-Wesley.
(b) Solomon, Robert C. (1981). Love: Emotion, Myth, & Metaphor (pg. 94). Prometheus Books, 1990.