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Physical properties of water
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properties listed below:
To calculate relative humidity from dry-bulb and wet-bulb temepratures,
general
vapour pressure
vapour pressure calc&graph
water vapour diffusion
density
try our Relative Humidity Calculator
| quantity | value |
| density (T=293 K) | 998 kg/m3 |
| surface tension (T=293 K) | 0.073 N/m |
| viscosity (T=293 K) | 1.00 x 10-3 Pa s |
| specific heat (T=293…373 K) | 4180 J kg-1 K-1 |
| heat conductivity (T=293 K) | 0.60 W m-1 K-1 |
| melting heat | 3.34 x 105 J/kg |
| evaporation heat | 22.6 x 105 J/kg |
| critical temperature | 647 K |
| critical pressure | 22.1 x 106 Pa |
| speed of sound (T=293 K) | 1480 m/s |
relative permittivity  r (T=298 K) |
80 |
| index of refraction (relative to air) |
1.31 (ice; 589 nm; T=273 K; p=p0) 1.34 (water; 430-490 nm; T=293 K; p=p0) 1.33 (water; 590-690 nm; T=293 K; p=p0) |
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saturation vapour pressure (SVP) [top]
The curve below is calculated with the following empirical equation, with temperature T in Kelvin [K] and saturation vapour pressure psat in Pascal [Pa]:
[Source: Perry's Chemical Engineers' Handbook, 1997]
Another useful empirical relation, with only three parameters is:
(NB: now T is in Celcius! [ = {Kelvin} - 273.15])
[Source: Monteith and Unsworth, 1990; some parameters slightly adjusted ]
This equation has a small error for T>80oC.
The following simple SVP-calculator uses the latter equation:
diffusion coefficient of water vapour in air (online calculator) [top]
The diffusion coefficient (also called diffusivity) of water vapour molecules in air can be described by:
T: temperature, Celcius scale [C]; Dv: diffusion coefficient [m2/s].Error: <0.1x10-6 m2/s; validity range: 0-45oC.
[Source: linear fit on values given by Gates, 1980, Appendix 3]
density of liquid water (online calculator) [top]
The density of water as a function of temperature can be described by:
T: temperature, Celcius scale [C]; 
w: density [kg/m3]. Note that at 3.98oC water has its highest density.Error: <0.1 kg/m3; validity range: 0-30oC.
[Source: parabolic fit on values from Weast, 1986; page F-10]
Holsoft (c) 2001
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