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Extended data list for water

Important constants and conversion factors


Values for some useful physical constants and units
Constant Value
Absolute zero
temperature; zero kelvin (0 K, exactly)
Amp (A)
electric current; one A = one C ˣ s-1 = 6.241 5094 ˣ 1018 e- ˣ s-1
Ångström (Å; A.U.) (not an SI unit)
length; one Å = 0.1 nm (exactly)
Angular velocity (ω, radians per second)
ω = 2 π ˣ frequency
Standard atmosphere (that is, 1 atm)

101.325 kPa (exactly) =1.013 25 bar (exactly) = 760 Torr (exactly)
= 1.033 23 kgF ˣ cm-2 = 760.001 mm Hg (0 °C) equivalent to 10.3629 m H2O (25 °C)

Standard pressure is now defined as 100 kPa exactly.

Atomic mass of 12C 12 g ˣ mol-1 (exactly)
Atomic mass unit (u, amu) = Dalton (Da) 12C atom/12 = 1.660 538 921 ˣ 10-27 kg [934]
Atomic unit of action = reduced Planck's constant
Atomic unit of charge = elementary charge
Atomic unit of energy = Hartree
Atomic unit of force = Eh/a0 8.238 722 78 ˣ 10-8 N (under revision)
Atomic unit of length = Bohr radius
Atomic unit of mass = electron rest mass
Atomic unit of pressure = Eh/a03 2.942 101 31 ˣ 1013 Pa [934] (under revision)
Atomic unit of temperature = Eh/kB 3.157 775 04 ˣ105 K [934] (under revision)
Atomic unit of time = h/Eh 2.418 884 326 502 ˣ 10-17 s [934] (under revision)
Avogadro constant (NA)
6.022 140 82 ˣ 1023 mol-1 [2395] (under revision)
Avogadro number
dimensionless; 6.022 140 82 ˣ 1023 [2395] (under revision)
Bar (not an SI unit) pressure; 1 bar = 100,000 Pa (exactly) =14.695 9487 7551 psi
Barrel (bbl, oil volume; not an SI unit) = 42 US gallons = 158.987 294 928 L (exactly)
Barn (b) cross-sectional area; 1 b = 100 fm2 = 10-28 m2
Barye (Ba) (not an SI unit) pressure; 1 Ba = 0.1 Pa (exactly)
Becquerel (Bq)
unit of radioactivity; = one nuclear disintegration ˣ s-1, 1 Bq = 27.0270  pCi
Billion
number; 1000,000,000
Boltzmann constant (kB)
1.380 648 8 ˣ 10-23 J ˣ K-1 [934] (under revision)
Bohr radius (a0, atomic unit of length)
0.529 177 210 92 ˣ 10-10 m [934] (under revision)
British Thermal unit (BTU) (not an SI unit)
heat energy; 1 BTU = 1.054 35 kJ
calorie (cal, obsolete)
energy; one cal = 4.1868 J (exactly)
Calorie (nutrition only, Cal)
energy; one Cal = 1 kcal = 4.1868 kJ (exactly)
Candela (cd)
luminous intensity; a lit candle emits light of ~ 1 cd
Celsius zero point (0 °C exactly)

273.15 K (exactly; one degree Celsius has the same size as one kelvin);

Standard temperature is now defined as 273.15 K exactly.

Charge density

1 C m-2 = 6.241 5094 e- nm-2

1 e- nm-2 = 0.1602177 C m-2

Coulomb (C)
electric charge; = NA/F electrons = 6.241 5094 ˣ 1018 e-
Cubic foot (customary unit)

volume; = 0.028 316 846 592 m3 = 28.316 846 592 L (exactly)

1 m3 = 35.314 666 7215 cubic feet

Curie (Ci)
unit of radioactivity; 3.7 ˣ 1010 Bq (exactly)
Dalton (Da)
mass; = atomic mass unit, 12C atom/12 = 1.660 538 921 ˣ 10-27 kg [934]
Day (d)
time: 86,400 seconds (exactly)
Debye (D)
3.335 640 95 ˣ 10-30 C ˣ m (= -0.208 194 35 e- ˣ Å)
Degree (°)
angle; 1° = π/180 rad (a circle equivalent to 360° = 2π rad )
Dyne (dyn) (not an SI unit)
force; 1 dyn = 10-5 N
e (base for natural logarithms)
Electromagnetic radiation
100 cm-1 equivalent to 105 nm equivalent to 1.197 kJ ˣ mol-1 equivalent to ~ 3 THz
Electron volt (eV)

energy; 1.602 176 565 ˣ 10-19 J (96.485 336 5 kJ ˣ mol-1) [934]

1 eV equivalent to  8,065.544 29  cm-1 equivalent to 241.798 9348 THz (equivalent to 1,239.841 93 nm)

1 eV equivalent to 11,604.5193 K

Electron mass (me, atomic unit of mass)
9.109 382 91 ˣ 10-31 kg [934] (under revision)
Electrostatic constant (ke) = coulomb force constant
ke=1/(4πε0) = c2 ˣ !0-7 H ˣ m-1 =  8.987 551 787 368 1764 ˣ 109 N ˣ m2 ˣ C-2 (exactly)
Elementary charge (e, atomic unit of charge)
(-ve) 1.602 176 565 ˣ 10-19 C [934] (under revision)
Erg (erg) (not an SI unit)
energy; 1 erg = 10-7 J
Electrostatic unit of charge (esu) (not an SI unit)
electrical charge; 1 esu = 1 statC = dyn1/2 ˣ cm = cm3/2 ˣ g1/2 ˣ s-1 = 3.335 641×10-10 C. = 2.081 944 ˣ 1011 e-
Fahrenheit temperature scale (°F, customary unit)

(Fahrenheit temperature) = (Kelvin temperature) ˣ 9⁄5 − 459.67
(Kelvin temperature) = (Fahrenheit temperature + 459.67) ˣ 5⁄9

(Fahrenheit temperature) = (Celsius temperature) ˣ 9⁄5 + 32
(Celsius temperature) = (Fahrenheit temperature - 32) ˣ 5⁄9

One degree Fahrenheit has the same size as 5/9 kelvin or 5/9 °C

Farad (F) capacitance, = C/V = s4 ˣ A2 ˣ m-2 ˣ kg-1
Faraday electrical charge: 96,485.3365 C equivalent to one mole of electrons [934]
Faraday constant 96,485.3365 C ˣ mol-1 (96,485.3365 J ˣ V-1 ˣ mol-1) [934]
Foot (ft, ') (not an SI unit) length; 30.48 cm (exactly)
Foot candle (fc) (not an SI unit) illuminance; 1 fc = lm ˣ ft-2 (1 fc ~ 10.763 91 lux)
Gallon (liquid volume; not an SI unit))

Imperial (UK) = 4.546 09 L (exactly)

US                = 3.785 411 784 L (exactly)

Gas constant, molar; R

(R = kB ˣ NA)

R = 8.314 4621 J ˣ mol-1 ˣ K-1 [934] (= 0.082 057 46 L ˣ atm ˣ mol-1 ˣ K-1)
RT, Gas constant ˣ temperature (25 °C)
2.478957 kJ ˣ mol-1
Gauss (G) (not an SI unit) magnetic flux density; 1 G = 1 Mx ˣ cm-2 = 10-4 T
Giga anna (Ga, Gyr) (not an SI unit)
time passed; 1000,000,000 years ago
Gram molecule mass; relative molecular mass (molecular weight) in grams = mol
1.618 033 988 749 894 848 204 586 834 365 638 117 720 309 179 ...
Acceleration due to gravity (g, standard)
9.806 65 m s-2 (exactly) (~ 32.1740 ft s-2 )
Hartree (Eh, atomic unit of energy)

4.359 744 34 ˣ 10-18 J [934] (under revision)

Henry (H)

inductance; 1 H = 1 V ˣ s ˣ A-1 = kg ˣ m2 ˣ s-2 ˣ A-2

Hertz (Hz)

frequency (ν), cycles per second: = 1 s-1 (see also terahertz)

Inch (in, ") (not an SI unit)

length; 2.54 cm (exactly)

Joule (J)

energy; one J = one kg ˣ m2 ˣ s-2; J = h ˣ ν ; J ˣ mol-1 = h ˣ ν ˣ NA

Kelvin (K)

The fraction 1/273.16 of the thermodynamic temperature of the triple point of water; (Absolute zero, 0 K = −273.15 °C or −459.67 °F).

1 K = 0.086 217 38 meV = 0.695 cm1 ( equivalent to 8.318 7129 J mol-1)

Kilocalorie (kcal, thermochemical)
one kcal = 4.1840 kJ (exactly)
Kilogram (kg)
SI base unit of mass
Kilogram-force (kgF)
force; 1 kgF = 9.806 65 N (exactly)
Kilowatt hour (kWh)
work (= energy); 1 kWh = 3.6 MJ (exactly)
Light year length; one light year = 9,460,730,472,580.8 km (exactly)
Liter, (L) volume; one L = 10-3 m3 (exactly)
Loge(10)
Loschmidt constant (STP) (= P NA/RT)
2.651 6462 ˣ 1025 molecules of ideal gas m-3 (= 44.615 036 mol m-3)
Lumen, (lm) luminous flux; one lm = one cd ˣ sr
Luminance, (Lv) one Lv = one cd ˣ m-2
Lux, (lx) illuminance; 1 lx = 1 cd ˣ sr ˣ m-2
Mega anna (Ma, Myr) (not an SI unit)
time passed; 1,000,000 years ago
Maxwell (Mx) (not an SI unit) magnetic flux; 1 Mx = 1 G cm2 = 10-8 Wb
Meter (m) length; see speed of light below
Micron (µ) length: = 1 µm
Mile (international, not an SI unit) length: 1,609.344 m (exactly)
mm-Hg (not an SI unit)
pressure; 133.322 387 415 Pa (exactly) (1 mm-Hg ~ 1 Torr)
Molal concentration (m)
1 m = 1 mol ˣ (kg solvent)-1 (see for conversion to molarity)
Molality , standard (m°)
m° = 1 mol ˣ (kg solvent)-1
Molar concentration (M)
1 mol ˣ (L solution)-1 = 103 mol ˣ m-3 (see for conversion to molality)
Molar volume of ideal gas (STP) = R ˣ 273.15/100,000 m3 ˣ mol-1 = 22.710 953 L ˣ mol-1 (22.414 L ˣ mol-1 at 101.325 kPa)
Mole (mol) amount; an Avogadro number of items
Mya (not an SI unit) time passed; 1000,000 years ago
Nernst constant, = RT/F 25.692576 mV (25 °C); Loge(10) ˣ RT/F = 0.059 159 243 V (25 °C)
Newton (N) force; N = 1 kg ˣ m ˣ s-2
Oersted (Oe) magnetic field; 1 Oe equivalent to (103/4π) ˣ A ˣ m-1
Ohm (Ω) electric resistance; = V/A, 1 Ω = 1 kg ˣ m2 ˣ s-3 ˣ A-2
Osmole (Osm) (not an SI unit) amount; number of moles of solute that contribute to the osmotic pressure of a solution. Ideally, 1 mole of NaCl in 1 Kg water is 2 Osm Kg-1 water
Pascal (Pa) pressure, 1 Pa = 1 N ˣ m-2 = 1 kg ˣ m-1 ˣ s-2
Parts per billion (ppb) At this site, ppb = parts per 1000,000,000

Permeability

= H ˣ m-1

Permeability of a vacuum (µ0)

(Magnetic constant)

4π ˣ 10-7 N ˣ A-2 = 4π ˣ 10-7 T2 ˣ m3 ˣ J-1 (exactly)

= 1.256 637 061 435 917 295 µH ˣ m-1N ˣ A-2) [934]

Permittivity

= F ˣ m-1

Permittivity of a vacuum (ε0)

(Electric constant)

= (μ0 c2)-1 in units C2 ˣ J-1 ˣ m-1 (exactly)

= 8.854 187 817 620 389 850 536 563 031 710 pF ˣ m-1

Π (= circle circumference/diameter)
Planck constant (h)

6.626 069 83 × 10-34 J ˣ s (under revision); energy (J) = h ˣ ν

Reduced Planck constant (h/2π = ħ = atomic unit of action)
1.054 571 726 ˣ 10-34 J ˣ s (under revision); energy (J) =ħ ˣ ω
Pint (liquid volume)

Imperial (UK) = 0.568 261 25 L (exactly)

US                = 0.473 176 473 L (exactly)

Poise (P) (not an SI unit)
dynamic viscosity; one P = one dyne ˣ s ˣ cm-2 = 0.1 N ˣ m-2 ˣ s = 0.1 Pa ˣ s

Pound (lb) (avoirdupois, US and UK) (not an SI unit)

mass = 0.453 592 37 kg (exactly)
Pound weight (lbf) (not an SI unit)
force = 4.448222 N
Proton charge
(+ve) 1.602 176 565 ˣ 10-19 C (under revision)
Proton gyromagnetic ratio (γP)
γP = 2.67515255 ˣ 108 rad ˣ s-1 ˣ T-1
psi (pounds weight per square inch; customary unit)
pressure; 1 psi = 6,894.757 293 168 Pa
Radian (rad)

angle; 360°/2π = 57.295 779 513 082 320 876 798 154 814 105 170 3°

One revolution = 360° = 2π ˣ rad °

Siemens (S) electric conductance; =A/V, 1 S = 1/Ω = 1 s3 ˣ A2 ˣ kg-1 ˣ m-2
Speed of light in a vacuum, (c)
299,792,458 m ˣ s-1 (exactly, also defines the meter) [934]
Standard temperature and pressure, for gasses (STP)

100 kPa, 273.15 K (exactly) IUPAC

Statcoulomb (statC)

electrical charge; see esu

Standard state        (thermodynamic)

varies as stated, but often; pressure, 100 kPa; temperature, 25.00 °C

Standard temperature and pressure, for gasses (STP)

100 kPa, 273.15 K (exactly) IUPAC

Steradian (sr)

the solid angle of the surface from the center of a sphere;

4π sr = entire surface of a sphere radius r

Stokes (St) (not an SI unit)
kinematic viscosity; 1 St = 1 cm2 ˣ s-1 = 10-4 m2 ˣ s-1
Tesla
magnetic field strength; = Wb ˣ m-2 ; 1 Wb = 1 kg ˣ s-2 ˣ A-1
Terahertz (THz)

frequency in cycles per second:one THz = 1012 s-1 = 2π ˣ 1012 radian ˣ s-1 = one ps-1 equivalent to 33.355 640 952 cm-1 equivalent to 299.792 458 µm (exactly)

equivalent to 0.004 135 667 516 eV equivalent to 399.031 27 J ˣ mol-1

Thermal energy (kT at 25 °C)
2.478 957 kJ ˣ mol-1; 4.116405 J ˣ 10-21 ˣ molecule-1
Ton (metric ton) (tonne, t) mass; = 103 kg (1 Mg)
Ton (UK; long ton)

mass; = 2,240 lb avoirdupois, UK; = 1016.046 908 80 kg (exactly)

Ton (US; short ton)

mass; = 2,000 lb avoirdupois, US; = 907.184 740 kg (exactly)

Torr (not an SI unit) pressure; one Torr = 101325⁄760 Pa (exactly; ~133.322 368 4211  Pa ).
Trillion
number; 1000,000,000,000
Units; metric prefixes

deci- d 10-1;centi- c 10-2; milli- m 10-3; micro- µ 10-6; nano- n 10-9; pico- p 10-12; femto- f 10-15; atto- a 10-18; zepto- z 10-21; yocto- y 10-24

deca- da 101; hecto- h 102; kilo- k 103; mega- M 106; giga- G 109; tera- T 1012; peta- P 1015; exa- E 1018; zetta- Z 1021; yotta- Y 1024

Volt (V) amps ˣ ohms (A ˣ Ω), power/current (W/A), energy/amount of charge (J/C) one V = one kg ˣ m2 ˣ s-3 ˣ A-1
Wavelength (nm)

one nm = 107/wavenumber (cm-1)

(electromagnetic; one nm equivalent to 3.335 640 95 attosecond)

Wavenumber (m-1) (=1/wavelength)

one m-1 = 109/wavelength (nm), one m-1 equivalent to 0.119 626 57 J ˣ mol-1

(one cm-1 equivalent to 0.029 979 2458 THz exactly)

Wavenumber, wavelength. frequency conversions

The electromagnetic spectrum

Watt (W)

power; one W = one J ˣ s-1 = one kg ˣ m2 ˣ s-3

Weber (Wb)

magnetic flux; = T ˣ m2 ; 1 Wb = 1 kg ˣ m2 ˣ s-2 ˣ A-1

Year (a, yr)

One Gregorian year = 365.2425 days = 31,556,952 seconds

One Julian year = 365.25 days = 31,557,600 seconds

One mean Tropical year = 365.2422 days = 31,556,926 seconds

 

Note that the SI unit definitions are under review for change soon; for example, the kelvin may be redefined in terms of an exactly defined value for the Boltzmann constant and the kilogram may be defined in terms of its energy content [1031].

 

 

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This page was established in 2007 and last updated by Martin Chaplin on 20 October, 2017


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