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chemistry (mass of one atom divided by the atomic mass constant, 1 Da) Bodenstein number: Bo or Bd = / = Max Bodenstein: chemistry (residence-time distribution; similar to the axial mass transfer Peclet number) [2] Damköhler numbers: Da =
Mean lifetime: τ: Average time for a particle of a substance to decay s T: intensive Molar concentration: C: Amount of substance per unit volume mol⋅m −3: L −3 N: intensive Molar energy: J/mol: Amount of energy present in a system per unit amount of substance J/mol L 2 M T −2 N −1: intensive Molar entropy: S° Entropy per unit amount ...
In engineering and science, dimensional analysis is the analysis of the relationships between different physical quantities by identifying their base quantities (such as length, mass, time, and electric current) and units of measurement (such as metres and grams) and tracking these dimensions as calculations or comparisons are performed.
These include the Boltzmann constant, which gives the correspondence of the dimension temperature to the dimension of energy per degree of freedom, and the Avogadro constant, which gives the correspondence of the dimension of amount of substance with the dimension of count of entities (the latter formally regarded in the SI as being dimensionless).
Theoretical chemistry requires quantities from core physics, such as time, volume, temperature, and pressure.But the highly quantitative nature of physical chemistry, in a more specialized way than core physics, uses molar amounts of substance rather than simply counting numbers; this leads to the specialized definitions in this article.
Physics relies on dimensionless numbers like the Reynolds number in fluid dynamics, [6] the fine-structure constant in quantum mechanics, [7] and the Lorentz factor in relativity. [8] In chemistry , state properties and ratios such as mole fractions concentration ratios are dimensionless.
In physics, natural unit systems are measurement systems for which selected physical constants have been set to 1 through nondimensionalization of physical units.For example, the speed of light c may be set to 1, and it may then be omitted, equating mass and energy directly E = m rather than using c as a conversion factor in the typical mass–energy equivalence equation E = mc 2.
Dimension symbol; second: s time "The second, symbol s, is the SI unit of time. It is defined by taking the fixed numerical value of the caesium frequency, ∆ν Cs, the unperturbed ground-state hyperfine transition frequency of the caesium 133 atom, to be 9 192 631 770 when expressed in the unit Hz, which is equal to s −1." [1]