Science & Engineering

Water Properties

Physical and thermodynamic properties of water — density, viscosity, specific heat, phase transitions.

Molecular

FormulaH₂O
Molar mass18.015 g/mol
Bond angle104.5°
O–H bond length0.9584 Å

Thermal

Melting point (1 atm)0.00 °C (273.15 K)
Boiling point (1 atm)99.974 °C (373.12 K)
Triple point0.01 °C @ 611.657 Pa
Critical point374 °C @ 22.064 MPa
Heat capacity (liquid, 25 °C)4181.3 J/(kg·K)
Heat of fusion334 kJ/kg
Heat of vaporization2257 kJ/kg (at 100 °C)
Thermal conductivity0.598 W/(m·K) at 20 °C

Density (liquid)

TemperatureDensity (kg/m³)
0 °C999.84
4 °C999.97 (max)
10 °C999.70
20 °C998.21
25 °C997.05
50 °C988.04
100 °C958.37

Viscosity

TemperatureDynamic (mPa·s)Kinematic (mm²/s)
0 °C1.7931.793
20 °C1.0021.004
40 °C0.6530.658
80 °C0.3550.365

Other

Surface tension (20 °C)72.8 mN/m
Refractive index (589 nm)1.333
Dielectric constant (20 °C)80.1
Dissociation constant pKw14.0 at 25 °C
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