# Water - Thermophysical Properties

## Thermal properties of water - density, freezing temperature, boiling temperature, latent heat of melting, latent heat of evaporation, critical temperature and more

Thermodynamic properties of water:

- Boiling temperature (at 101.325 kPa): 99.974 °C = 211.953 °F
- Bulk modulus elasticity: 2.15 x 10
^{9}Pa or N/m^{2} - Critical temperature: 373.946 °C = 705.103 °F
- Critical pressure: 217.7 atm = 220.6 bar = 22.06 MPa (MN/m
^{2}) = 3200 psi (=lb_{f}/in^{2}) - Critical density: 0.322 g/cm
^{3}= 0.62478 slug/ft^{3}= 20.1018 lb_{m}/ft^{3} - Ionization constant, pKw (at 25°C): 13.995
- Latent heat of melting: 334 kJ/kg = 144 Btu(IT)/lb
- Latent heat of evaporation(at 100°C): 40.657 kJ/mol = 2030 kJ/kg = 872.7 Btu(IT)/lb
- Maximum density (at 4
^{o}C): 999.975 kg/m^{3 }= 1.9403 slug/ft^{3}= 9.71086 lb_{m}/gal(US) ^{ }Melting temperature (at 101.325 kPa): 0 °C = 32°F- Molar mass: 18.01527 g/mol
- pH (at 25°C): 6.9976
- Specific heat (C
_{p}) water (at 15°C/60°F): 4.187 kJ/kgK = 1.001 Btu(IT)/(lb_{m}°F) or kcal/(kg K) - Specific heat ice: 2.108 kJ/kgK = 0.5035 Btu(IT)/(lb
_{m}°F) or kcal/(kg K) - Specific heat water vapor: 1.996 kJ/kgK =0.4767 Btu(IT)/(lb
_{m}°F) or kcal/(kg K) - Specific Weight (at 4
^{o}C): 9.806 kN/m^{3 }= 62.43 lb_{f}/ft^{3} - Thermal expansion from 4
^{o}C to 100^{o}C: 4.2x10^{-2 }(Note! - volumetric temperature expansion of water is not linear with temperature)^{} - Triple point pressure: 0.00604 atm = 0.00612 bar = 611.657 Pa = 0.08871 psi (=lb
_{f}/in^{2}) - Triple point temperature: 0.01 °C = 32.02 °F

See also thermodynamic properties of heavy water, D_{2}O

Follow the links below to get values for the listed **properties of liquid water** at varying** pressure** and **temperature**:

- Boiling points at high pressure
- Boiling points at vacuum pressure
- Density, specific weight and thermal expansion coefficient
- Dynamic and kinematic viscosity
- Enthalpy and entropy
- Heat of vaporization
- Ionization Constant, pK
_{w}, of normal and heavy water - Melting points at high pressure
- Saturation pressure
- Specific gravity
- Specific heat (heat capacity)
- Specific volume
- Thermal conductivity

For each topic, there are figures and tables showing the variations in properties with temperature. Calculators giving the properties at specified temperatures are also available. All properties are given in both SI and imperial units.

The **Prandtl Number** is a dimensionless number approximating the ratio of *momentum diffusivity (kinematic viscosity)* to *thermal diffusivity*. It is often used in heat transfer and free and forced convection calculations. It depends on the fluid properties, and for water it varies with temperature as shown below:

Temperature - t -(^{o}C) | Prandtl no. |
---|---|

0.01 | 13.67 |

10 | 9.47 |

20 | 7.01 |

30 | 5.43 |

40 | 4.34 |

50 | 3.56 |

60 | 2.99 |

70 | 2.56 |

80 | 2.23 |

90 | 1.96 |

100 | 1.75 |

120 | 1.45 |

140 | 1.25 |

160 | 1.09 |

180 | 0.98 |

200 | 0.92 |

220 | 0.88 |

240 | 0.87 |

260 | 0.87 |

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