List of physicochemical data concerning water

Water Properties (including heavy water data)

 

Property	Data
Area, surface covered	19.0 Å2 molecule-1 (monolayer [795]) 9.6 - 10.2 Å2molecule-1(single molecule; calculated from dimensions) 8.84 Å2molecule-1(single molecule; basal plane of hexagonal ice)
Atmospheric content	19.66 g kg-1 (25 °C, 101.325 kPa, relative humidity = 100)
Bond energy, average at 0 K	H2O, 0.5 (H-O-H   O+2H), 458.9 kJ mol bond -1
	D2O, 0.5 (D-O-D   O+2D), 466.4 kJ mol bond -1
Boiling point, 101.325 kPa	H2O: 100.0 °C c1 373.1243 K (99.9743 °C), see [88]
	D2O: 101.42 °C [70]
	T2O: 101.51 °C [745]
	H217O: 100.08 °C [745]
	H218O: 100.15 °C [745]
	D218O: 101.54 °C [745]
	HDO: 100.74 °C [745]
	HTO: 100.8 °C [745]
Bulk modulus (=1/κT, isothermal elasticity)	H2O: 2.174 GPa (2.174 nN nm-2, 25 °C); 8.9 GPa (ice 1h, -20 °C, [717])
	D2O: 2.100 GPa (2.100 nN nm-2, 25 °C)
CAS registry number	H2O: 7732-18-5, (H2O is also known as protium oxide)
	D2O: 7789-20-0 , (D2O is also known as deuterium oxide)
	T2O: 14940-65-9 , (T2O is also known as tritium oxide)
Chemical potential (μ)	see Gibbs energy of formation
Chemical potential, temperature coefficient (dμ/dT) [987] = negative molar entropy (-S)	H2O (gas): -188.7 J mol-1 K-1 (25 °C) H2O (liquid): -69.9 J mol-1 K-1 (25 °C) H2O (solid): -44.8 J mol-1 K-1 (25 °C)
Chemical potential, pressure coefficient (dμ/dP) [987] = molar volume	H2O (gas): 24460 J mol-1 MPa-1 (25 °C) H2O (liquid): 18.07 J mol-1 MPa-1 (25 °C) H2O (solid): 19.73 J mol-1 MPa-1 (25 °C)
Cohesive energy density	2.2973 kJ cm-3 = 2.2973 GPa (= (ΔHvap-RT)/VM) (25 °C)
Internal cohesive pressure	168 MPa (25 °C),   (= 3.04 kJ mol-1, 25 °C) [1279]
Compressibility, adiabatic (κS)	H2O: 0.4477 GPa-1 (25 °C) [620], 0.5086 GPa-1 (0 °C) Ice Ih: 0.1142 GPa-1 (0 °C) (IAPWS)
	D2O: 0.4625 GPa-1 (25 °C) [620]
Compressibility, critical (=PcVc/RTc)	H2O: 0.2294
	D2O: 0.2277
Compressibility, isothermal (κT), κT = -(1/V)(δV/δP)T = <(ΔV)2>/(kBTV) [1373b]	H2O: 0.4599 GPa-1 (25 °C) [507] Ice Ih: 0.1178 GPa-1 (0 °C) (IAPWS); 0.069 GPa-1 (-20 °C), [561] gas: 10.03 MPa-1 (100 °C, 101.325 kPa) [540]
	D2O: 0.4763 GPa-1 (25 °C) [507]
Compressibility, isothermal (κT), minimum	H2O: 0.4415 GPa-1 at 46.5 °C, calculated from [399]
	D2O: 0.4489 GPa-1 at 49.9 °C, calculated from [1454]
Compressibility, change with pressure	-0.1152 GPa-1 (25 °C) [1599]
Conductivity, electrolytic (IAPWS)	0.05501 μS cm-1 (25 °C, [737])h, 1.2 μS cm-1 (22 °C, degassed; [711]) Ice Ih: ~0.06 μS cm-1 (-20 °C) [717] (mainly from surface defects)
Conductivity, thermal	H2O: 0.610 W m-1 K-1 (25 °C) [IAPWS]; 0.606 502 308 W m-1 K-1 (25 °C, 0.1 MPa [IAPWS] from formula) Ice Ih: 2.4 W m-1 K-1 (-20 °C) [717] gas: 0.025 W m-1 K-1 (100 °C, 101.325 kPa) [540]
	D2O: 0.595 W m-1 K-1 (25 °C) [IAPWS]
Conductivity, thermal; maximum	H2O: 0.686 W m-1 K-1 at 133 °C, calculated from [1453]
	D2O: 0.636 W m-1 K-1at 113 °C, calculated from [1453]
Critical point	H2O: 647.096 K,c1 22.064 MPa, 322 kg m-3 (IAPWS)g
	D2O: 643.847 K, 21.671 MPa, 356 kg m-3 (IAPWS) g
	T2O: 641.657 K, 21.385 MPa, 376 kg m-3 [830] g
Critical point, second	H2O: no generally accepted value, for example, ~217 K, ~340 MPa, ~1130 kg m-3 [419 ]; ~188 K, ~230 MPa, ~1100 kg m-3 [432 ]; ~182 K, ~195 MPa [580 ]; 145-175 K, ~200 MPa [999 ]; 223 K, ~50 MPa [1685 ]
	D2O: ~-78 °C, ~230 MPa, ~1220 kg m-3 [450]; ~-86 °C, ~211 MPa [580]
Cryoscopic constant	1.8597 K kg mol-1
Density	a	997.05 kg m-3 (25.0 °C, 101.325 kPa)  [67, 112], 997.047 013 kg m-3 (25 °C, 0.1 MPa [IAPWS] from formula)
	H2O	2260 kg m-3 (liquid, ~1500 K, 57 GPa) [1218 ]
	H218O	1110.64 kg m-3 (20.0 °C) [745]
	HDO	1050.7 kg m-3 (25.0 °C) [1857]
	D2O	1104.36 kg m-3 (25.0 °C) [620]
	D218O	1216.22 kg m-3 (20.0 °C) [745]
Density of ice at melting pointa	H2O: 916.72 kg m-3 (0 °C, 101.325 kPa) (IAPWS)
	D2O: 1017.5 kg m-3 (3.82 °C)
Density of liquid water at melting point [70]	H2O: 999.84 kg m-3 (0 °C, 101.325 kPa)
	D2O: 1105.46 kg m-3 (3.813 °C)
Density of gas at boiling point	H2O: 0.5976 kg m-3 (100 °C, 101.325 kPa) [540]
Density maximum (and molar volume) attemperature of maximum density [67, 112]	a	999.97495 kg m-3e	3.984 °C
	H2O	999.972 kg m-3, 29.91 Å3 mol-1 999.975 kg m-3 ( IAPWS formula)	3.984 °C  3.978 °C ( IAPWS)
	D2O	1105.3 kg m-3, 30.07 Å3 mol-1	11.185 °C
	T2O	1215.01 kg m-3, 30.10 Å3 mol-1	13.403 °C
	H218O	1112.49 kg m-3, 29.87 Å3 mol-1	4.211 °C
	D218O	1216.88 kg m-3, 30.06 Å3 mol-1	11.438 °C
Dielectric constant  (more details)	H2O: 87.9 (0 °C), 78.4 (25 °C; 78.375 218 [ IAPWS] from formula at 0.1 MPa), 55.6 (100 °C) [63] 104.3 (supercooled liquid, 240 K, IAPWS) Ice Ih: 99 (-20 °C) 171 (-120 °C) [717] gas: 1.0059 (100 °C, 101.325 kPa) [540]
	D2O: 78.06 (25 °C) [808] D2O Ice Ih: 104 (-20 °C) [717]
Dielectric, change with pressure	37.88 GPa-1 (25 °C) [1599]
Dielectric relaxation	H2O: 9.55 x 10-12 s (20 °C) [8] H2O Ice Ih: ~2 x 10-5 s (0 °C)
	D2O: 12.3 x 10-12 s (20 °C) [8]
Diffusion coefficient	H2O: 0.2299 Å2 ps-1 (25 °C) [1933], 0.0187 Å2 ps-1 (-31 °C) [62]; 6 x 10-8 Å2 ps-1 (ice 1h, -20 °C) [717] ~10-8 Å2 ps-1 (amorphous water, ~160 K) [334]
	D2O: 0.2109 Å2 ps-1 (25 °C) [8]
	H218O: 0.266 Å2 ps-1 [745]
	HDO: 0.234 Å2 ps-1 [745]
	HTO: 0.244 Å2 ps-1 [745]
Diffusivity, thermal    ()	H2O: 14.6 Å2 ps-1 (25 °C) Ice Ih: 84.3 Å2 ps-1 (0 °C)
	D2O: 12.7 Å2 ps-1 (25 °C)
Dipole moment (average), μ  z	2.95±0.2 D (liquid, 27 °C) [129], 1.85498 D (gas, 6.1875×10-30 C m) [IAPWS], 3.09 D (ice) [238]
	1.8517 D (HDO gas, [IAPWS])
Displacement, root mean square	~0.07 mm s-1 [1577a]
Ebullioscopic constant	0.5129 K kg mol-1
Electron affinity [563 ]	-16 kJ mol-1 (-0.17 eV) (25 °C)l HOMO-LUMO gap, 659 kJ mol-1 (6.83 eV) (25 °C)
Elemental composition a	Hydrogen (all isotopes), 11.1903 % w/w Oxygen (all isotopes), 88.8097 % w/w
Energy, internal (U) [540]	1.8883 kJ mol-1 (25 °C, 101.325 kPa) Ice Ih: -6.007 kJ mol-1 (0 °C, 101.325 kPa) (IAPWS) gas: 45.15 kJ mol-1 (100 °C, 101.325 kPa) [540]
Enthalpy (H = U + PV) [67]	1.8909 kJ mol-1 (25 °C) Ice Ih: -6.005 J mol-1 (0 °C, 101.325 kPa) (IAPWS) gas: 48.20 kJ mol-1 (100 °C, 101.325 kPa) [540]
Enthalpy of formation, ΔHf, [808]	H2O: -285.85 kJ mol-1 (25 °C)
	D2O: -294.6 kJ mol-1 (25 °C)
Enthalpy of vaporization (liquid)	H2O: 45.051 kJ mol-1 (0 °C) [906], 40.657 kJ mol-1 (100 °C) [61]  46.567 kJ mol-1 (240 K) [906]
	D2O: 45.988 (3.82 °C), 41.521 kJ mol-1 (101.42 °C), calculated from [1453]
Enthalpy of fusion	6.00678 kJ mol-1 (0 °C, 101.325 kPa) [1385]  6.354 kJ mol-1 (81.6 °C, 2150 MPa, ice VI) [535]
	H218O: 6.029 kJ mol-1 (0.31 °C) [1710]
	D2O: 6.132 kJ mol-1 (3.68 °C) [2000] D216O: 6.315 kJ mol-1 (3.82 °C) [1710]
	HD16O: 6.227 kJ mol-1 (2.04 °C) [1710]
Enthalpy of sublimation (ice Ih)	51.059 kJ mol-1 (0 °C), 51.139 kJ mol-1 (240 K) [906]
Entropy (S)	63.45 J mol-1 K-1 (Absolute entropy at triple point) [869 ] 6.6177 J mol-1 K-1 (25 °C) [67]  Ice Ih: -21.99 J mol-1 K-1 (0 °C) (IAPWS) Ice Ih: 3.408 J mol-1 K-1 (0 K) [1832] ~ RLn(3/2) gas: 132.5 J mol-1 K-1 (100 °C, 101.325 kPa) [540]
Entropy, molar	see Chemical potential, temperature coefficient (dμ/dT)
Entropy of fusion	H2O: 22.00 J mol-1 K-1 (0 °C) [8]
	D2O: 22.15 J mol-1 K-1 (3.68 °C) [2000]
Entropy of vaporization [8]	108.951 J mol-1 K-1 (100 °C)
Expansion coefficient (α), αP = (1/V)(δV/δT)P = <(ΔV)(ΔS)>P/(kB2T) [1373b]	H2O: 0.000000 °C-1 (3.984 °C), 0.000253 °C-1 (25 °C) [68] Ice Ih: 0.0001598 °C-1 (0 °C, 101.325 kPa) (IAPWS); 0.000053 °C-1 (-20 °C) [717]
	D2O: 0.0001722 °C-1 (25 °C) [620]
Fragile to strong liquid transition	~220 K [1200]
Gas constant (R95)	461.51805 J kg-1 K-1 (IAPWS)
Gibbs energy (G = U - TS + PV), all referenced to triple point	-82.157 J mol-1 (25 °C, 101.325 kPa) [540] Ice Ih: 1.826 J mol-1 (0 °C, 101.325 kPa) (IAPWS) gas: -1239 J mol-1 (100 °C, 101.325 kPa) [540]
Gibbs energy of formation, ΔGf,    = Chemical potential (μ)	H2O (liquid): -237.18 kJ mol-1 (25 °C) [987] H2O (gas): -228.59 kJ mol-1 (25 °C) [987] H2O (solid): -236.59 kJ mol-1 (25 °C) [987]
	HDO (liquid): -241.86 kJ mol-1 (25 °C) [988 ] HDO (gas): -233.11 kJ mol-1 (25 °C) [988]
	D2O (liquid): -243.44 kJ mol-1 (25 °C) [988] D2O (gas): -234.54 kJ mol-1 (25 °C) [988]
Glass transition temperature	136 K (this has been subject to dispute [312])
Heat capacity ratio (γ=CP/CV)	H2O (gas) 1.3368 (100 °C, 101.325 kPa) [540]
Helmholtz energy (A = U - TS) [540]	-83.989 J mol-1 (25 °C, 101.325 kPa) Ice Ih: -0.166 J mol-1 (0 °C, 101.325 kPa) (IAPWS) gas: -4293 J mol-1 (100 °C, 101.325 kPa)
Hydrogen bond	Donor, Σα 1.17 [666]; compare CHCl3, 0.15; CH3OH, 0.43 Acceptor, Σβ; 0.47 [666]; compare (C2H5)2O, 0.41; CH3OH, 0.47
	Donor number (DN), 18.0 [456]; compare CH3CN 14.1; CH3OH, 19.0 Acceptor number (AN), 54.8 [456]; compare C6H6 8.2; CH3OH, 41.3
Ionic dissociation constant,    [H+][OH-]/[H2O] (25 °C) [808]	H2O: 1.821 x 10-16 mol l-1 (25 °C) [808] H2O Ice Ih: 3.8 x 10-22 mol l-1 (-10 °C) [1831]
	D2O: 3.54 x 10-17 mol l-1 (25 °C) [808] D2O: Ice Ih: 1.9 x 10-23 mol l-1(-10 °C) [1831]
	T2O: ~1.1 x 10-17 mol l-1 (25 °C) [808]
Ionization in liquid water, ΔG (25 °C)	2H2O   H3O+ + OH-   79.907 kJ mol-1 j
	2D2O   D 3O+ + OD-   84.88 kJ mol-1 j
Ionization potential	H2O: gas; 1216 kJ mol-1 (12.61 eV) [381a] H2O: liquid; 1018 kJ mol-1 (10.56 eV) [381a] H2O: ice; 1061 kJ mol-1 (11.00 eV) [381a]
	D2O: 1219 kJ mol-1 (12.64 eV) [381b]
Ionization rate (25 °C)	H2O   H+ + OH-           2.59x10-5 L mol-1 s-1 H+ + OH-   H2O           1.43x1011 L2 mol-2 s-1
Limits of stability for liquid water	Lowest temperature, -22 °C at 207.5 MPa Lowest pressure, 611.657 Pa at 0.01 °C Lowest density, 0.322 g cm-3 at 373.946 °C, 22.064 MPa Highest temperature, 373.946 °C, >22.064 MPa Highest pressure, ~12 GPa at 373.946 °C Highest density, ~1.7 g cm-3 at 373.946 °C, ~12 GPa
Magnetic susceptibility [670 ]	-1.64x10-10 m3 mol-1 (25 °C), -1.63x10-10 m3 mol-1 (0 °C)
Mass spectrum	H2O+ (1.0), OH+ (0.32), H+ (0.26), O+ (0.07), O2+ (0.002), H2+ (0.001) (ionization cross sections at 200 eV relative to H2O+, [1456 ])
Melting, contraction on	H2O: 1.634 cm3 mol -1
	D2O: 1.567 cm3 mol -1
Melting point, 101.325 kPa [70, 88]	H2O: 0.00 °C c2, 273.152519 K (IAPWS)
	D2O: 3.82 °C
	T2O: 4.49 °C
	H218O: 273.43 K [829 ]
Melting point, pressure coefficient	-74.293 mK MPa-1 (0 °C) [1385]
Molality b	H2O: 55.508472 mol kg -1
	D2O: 49.931324 mol kg -1
Molar concentration b	H2O: 55.345 mol L-1 (25 °C)
	HOD: 55.244 mol L-1 (25 °C, but maximum possible is 27.3 mol L-1) [1857]
	D2O: 55.142 mol L-1 (25 °C)
Molar isotopic composition a, m     H 1.007 825 032 07 g mol-1 D 2.014 101 777 85 g mol-1 T 3.016 049 2777 g mol-1 16O 15.994 914 619 56 g mol-1 17O 16.999 131 50 g mol-1 18O 17.999 1604 g mol-1 Molar masses may be calculated	H216O	99.7317 %	18.01056469 g mol-1
	H217O	0.0372 %	19.01478156 g mol-1
	H218O	0.199983 %	20.0148105 g mol-1
	HD16O	0.031069 %	19.01684143 g mol-1
	HD17O	0.0000116 %	20.02105831 g mol-1
	HD18O	0.0000623 %	21.0210872 g mol-1
	D216O	0.0000026 %	20.02311818 g mol-1
	HT16O	variable trace f	20.01878892 g mol-1
	T216O	0 %	22.02701316 g mol-1
Molar mass  b	H2O: 18.015268 g mol-1
	D2O: 20.027508 g mol-1
Molar volume (gas, STP)	0.022199 m3 mol-1 (0 °C, 101.325 kPa)
Molecular dimensions	O-H bond length (liquid, ab initio), 0.991 Å [90] O-H bond length (liquid, by diffraction) 0.990 Å [1884] O-H bond length (solid ice Ih, -20 °C) , 0.985 Å [717]
	H-O-H bond angle (liquid, ab initio), 105.5° [90] H-O-H bond angle (solid ice Ih, -20 °C), 106.6°±1.5° [717]
	O-H bond dissociation energy, 492.2148 kJ mol-1 [350]
	O-D bond length (liquid), 0.970 Å [91], 0.985 Å [1884]
	D-O-D bond angle (liquid), 106° [91]
Molecular mass	H2O: b 2.9915051 x 10-23 g molecule-1
	H216O: 2.9907243 x 10-23 g molecule-1
	D216O: 3.3249166 x 10-23 g molecule-1
Moment of inertia (axes through centers of mass)	H2O: 1.0220 x 10-40 g cm2 x; 2.9376 x 10-40 g cm2 y; 1.9187 x 10-40 g cm2 z [8]
	HDO: 1.2092 x 10-40 g cm2 x; 4.2715 x 10-40 g cm2 y; 3.0654 x 10-40 g cm2 z [8] (z and x axes rotated around y axis by 21.09°)
	D2O: 1.8384 x 10-40 g cm2 x; 5.6698 x 10-40 g cm2 y; 3.8340 x 10-40 g cm2 z [8]
NMR chemical shift, proton	H2O liquid: 4.82 ppm H2O ice: ~7 ppm H2O gas: 0.56 ppm, relative to methane [850] 4.766 ppm for HDO in D2O (25 °C, a triplet [609]; relative to sodium 2,2-dimethyl-2-silapentane-5-sulfonate, DSS)
NMR chemical shift, 17O	H2O liquid: 287.5 ppm (300 K, relative to O8+) [886 ] H2O gas: 323.6 ppm (300 K, relative to O8+) [886] D 2O liquid: 3.08 ppm (relative to H2O)
Nuclear shielding constants (27 °C), [740]	1H σ(l) 25.79 ppm (44.0 ppm parallel to O—H bond; 16.6 ppm perpendicular to O—H bond, [430]); gas to liquid shift, δ = σ(l) - σ(g) = -4.26 ppm 17O σ(l) 287.5 ppm; gas to liquid shift, δ = σ(l) - σ(g) = -36.1 ppm
Octupole moment, 25 °C [452 ]	-1.754 D Å2 xxz; -0.554 D Å2 yyz; -1.981 D Å2 zzz
Octupole moment, (alternative)	linear (Ω0) -1.34 D Å2; cubic (Ω2) 1.15 D Å2; SSDQO1 [1731 ]Ω
Optical permittivity (ε∞) [296 K, 1563]	H2O: 2.34
	H218O: 2.28
	D2O: 2.29
Other systematic names for water	Oxidane (IUPAC)
Packing density (volume, O···O 2.82Å, 4 °C)	0.3925
pD	D2O: 7.43 (25 °C) (based on [70])
pHD	HDO: 7.266 (25 °C)
pH	H2O: 6.9976 (25 °C; [H3O]+=[OH]- = 1.0054x10-7 mol L-1; [IAPWS])
Piezoscopic constant (= R/Vm)	H2O: 0.4602 MPa K-1 (25 °C)
	D2O: 0.4585 MPa K-1(25 °C)
	T2O: 0.4580 MPa K-1 (25 °C)
pKa	H2O: 15.738 (25 °C) [IAPWS]
	D2O: 16.610 (25 °C) (based on [70])
pKw	H2O: 13.995 (25 °C) [IAPWS]
	D2O: 14.87 (25 °C) [70]
Polarity/dipolarity, π [666]	1.09
Polarizability, ()	1.62x10-40 F m2
Polarizability volume ,	1.470 Å3; 1.5284 Å3 x; 1.4146 Å3 y; 1.4679Å3 z [736] 1.457 Å3 (electronic), 0.037 Å3 (static) [IAPWS]
Prandtl Number       (= kinematic viscosity / thermal diffusivity)	H2O: 6.12 (25 °C)
	D2O: 7.81 (25 °C)
Quadrupole moment, Q, 25 °C	-4.27 D Å xx; -7.99 D Å yy; -5.94 D Å zz (calc., liquid H2O [453])
Quadrupole moment (alternative)	linear (Θ0) 0.28 D Å; square (Θ2) 2.13 D Å; SSDQO1 [1731 ]Ω
Redox: water oxidation Redox: water reduction	2H2O   O2(g) + 4H+ + 4e-          -E° = -1.229 V (25 °C, pH 0) 2H2O + 2e-   H 2(g) + 2OH-         E° = -0.8277 V (25 °C, pH 14)
Refractive index	H2O: 1.33286 (25 °C, λ = 589.26 nm) [310]  Ice Ih: ηO 1.3091; ηE 1.3105 (-3.6 °C, λ = 589 nm) [717]
	D2O:1.32828 (20 °C, λ = 589 nm) [795]
Refractive index, real n and imaginary partsk	H2O: n 1.306169; k 0.300352153 (25 °C, v, 3404.795 cm-1) [942]
	D2O: n 1.342528; k 0.279696327 (25 °C, v, 2503.923 cm-1) [942]
Resistance, electrical	18.18 MΩ cm (25 °C, ultrapure water [737])h, 0.8 MΩ cm (22 °C, degassed; [711])
Shear modulus (adiabatic elasticity)	H2O: 2.44 GPa (2.44 nN nm-2, 25 °C) [1326 ]
	D2O: 2.50 GPa (2.50 nN nm-2, 25 °C) [1326]
Specific heat capacity, CP = (δH/δT)P = T(δS/δT)P = <(ΔS)2>/kB[1373b]	H2O: 75.338 J mol-1 K-1; 4.1819 kJ kg-1 K-1, 4.1696 MJ m-3 K-1 (25 °C, 101.325 kPa, calculated from [1154 ]), 4.181 446 18 kJ kg-1 K-1 (25 °C, 0.1 MPa [IAPWS] from formula) H2O: 89.22 J mol-1 K-1 (240 K) [906] Ice Ih: 37.77 J mol-1 K-1 (0 °C) (IAPWS), 22.10 J mol-1 K-1 (150 K) [906] gas: 37.47 J mol-1 K-1 (100 °C, 101.325 kPa) [540]
	D2O: 84.67 J mol-1 K-1 ; 4.228 kJ kg-1 K-1, 4.669 MJ m-3 K-1 (25 °C, calculated from [620])
Specific heat capacity minimum, CP,min	H2O: 75.27 J mol-1 K-1 at 36 °C, calculated from [1453]
	D2O: 82.58 J mol-1 K-1 at 61 °C, calculated from [2000]
Specific heat capacity, Cv = (∂U/∂T)v	H2O: 74.539 J mol-1 K-1 (25 °C) [67] gas: 28.03 J mol-1 K-1 (100 °C, 101.325 kPa) [540]
	D2O: 84.42 J mol-1 K-1 (25 °C) [620]
Speed of sound	H2O: 1496.7 m s-1 (25 °C) [620], 1496.699 22 m s-1 (25 °C, 0.1 MPa [IAPWS] from formula); 'fast' sound ~3200 m s-1 [1151] Ice Ih: 3837.9 m s-1 (0 °C) [1812] gas: 472.2 m s-1 (100 °C, 101.325 kPa) [540]
	D2O: 1399.2 m s-1 (25 °C)
Speed of sound, maximum	H2O: 1555.4 m s-1 at 74.0 °C, calculated from [921]
	D2O: 1461.0 m s-1 at 75.6 °C, calculated from [1454]
Standard state of water	unity (exactly, as pure solvent); unit molal (as solute)
Surface entropy (= -dγ/dT)	H2O: 0.1542 mJ m-2 K-1 (25 °C) (calculated from IAPWS)
Surface enthalpy (surface energy)	H2O: 0.1179 J m-2 (25 °C) (= γ -T dγ/dT; calculated from IAPWS)
Surface tension (change with pressure)	H2O: 6.96 Å (25 °C) (calculated from [1279] and IAPWS)
Surface tension ()	H2O: 0.07198 N m-1(25 °C; 0.07198 J m-2) [IAPWS]
	HDO: 0.07193 N m-1 (25 °C; 0.07193 J m-2)
	D2O: 0.07187 N m-1 (25 °C; 0.07187 J m-2) [IAPWS]
Triple point	H2O: 0.01 °C exactly (273.16 K exactly) by definitiond for VSMOWa, 611.657 Pa, 0.99978 g cm-3 [536] Isotopically pure 1H216O: 0.0087 °C [565]
	D2O: 3.80 °C, 660.096 Pa, 1.1056 g cm-3 [IAPWS]
	H217O: 0.21 °C [745]
	H218O: 0.31 °C [717]
	D216O: 3.82 °C [1710]
	D218O: 4.13 °C [745]
	HD16O: 2.04 °C [1710]
	HTO: 2.4 °C [745]
	T2O: 4.49 °C [716], 662.9 Pa [830]
Vapor pressure	H2O: 3.165 kPa (25 °C) [808]; 611.657 Pa (273.16 K, M.Pt.) [906] H2O: 37.667 Pa (240 K) [906] Ice Ih: 611.657 Pa (273.16 K), 27.272 Pa (240 K) [906]
	D2O: 2.734 kPa (25 °C) [808]; 659.893 Pa (276.95 K, M.Pt.) [1790]
	T2O: 2.639 kPa (25 °C) [808]; 662.388 Pa (277.64 K, M.Pt.) [1790]
Velocity, root mean square	~640 m s-1 [1577a]
Viscosity, dynamic	H2O: 0.8909 mPa s (25 °C, 101.325 kPa) [IAPWS], 0.889 996 774 mPa s (25 °C, 0.1 MPa [IAPWS] from formula); 1.0016 mPa s (20 °C, 101.325 kPa) [745] gas: 0.0123 mPa s (100 °C, 101.325 kPa) [540]
	D2O: 1.095 mPa s (25 °C) [IAPWS]; 1.2467 mPa s (20 °C) [745]
	H218O: 1.0564 mPa s (20 °C) [745]
	D218O: 1.3050 mPa s (20 °C) [745]
	HDO: 1.1248 mPa s (20 °C) [745]
	T2O: 1.40 mPa s (estimated, 20 °C) [73]
Viscosity, kinematic	H2O: 0.008935 stoke; 0.8935 x 10-6 m2 s-1 (25 °C)
	D2O: 0.009915 stoke; 0.9915 x 10-6 m2 s-1 (25 °C)
Viscosity, bulk (volume viscosity)	2.47 mPa s (25 °C) [1703]
Viscosity, temperature coefficient	0.0199 mPa s K -1 (25 °C) [304]
Van der Waals gas constants [70] k	a = 0.5536 Pa (m3 mol-1)2 b = 3.049 x 10-5 m3 mol-1
Volume, molar, 101.325 kPa, see also chemical potential, pressure coefficient (dμ/dP)	H2O: 18.0182 cm3 (0 °C) 18.0685 cm3 (25 °C) [1006]; 19.66 cm3 (iceIh, 0 °C); 0.030143 m3 (gas, 100 °C)
	H2O: 50.6 Å3 molecule-1 from the van der Waals gas 'b' constant
	H217O: 18.0556 cm3 (25 °C) [1006]
	H218O: 18.0428 cm3 (25 °C) [1006]
	HDO: 18.101 cm3 (25 °C) [1857]
	D2O: 18.1331 cm3 (25 °C) [1006]
	D217O: 18.1297 cm3 (25 °C) [1006]
	D218O: 18.1263 cm3 (25 °C) [1006]
	T2O: 18.1549 cm3 (25 °C) [1006]
Volume, intrinsic H2O	11.01 Å3
Volume, molecular H2O at 101.325 kPa	29.92 Å3 (0 °C ); 32.53 Å3 (ice Ih, -20 °C, [717]); 50.05 nm3 (gas, 100 °C)
Volume, van der Waals	14.6 Å3 molecule-1 (liquid)
Zero point energy (calculated from gaseous vibrations) [8]	H2O: 55.44 kJ mol-1
	HDO: 48.24 kJ mol-1
	D2O: 40.54 kJ mol-1