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Up to 99.63 °C (the boiling point of water at 0.1 MPa), at this pressure water exists as a liquid. Above that, it exists as water vapor. Note that the boiling point of 100.0 °C is at a pressure of 0.101325 MPa (1 atm ), which is the average atmospheric pressure.
Water has a very high specific heat capacity of 4184 J/(kg·K) at 20 °C (4182 J/(kg·K) at 25 °C)—the second-highest among all the heteroatomic species (after ammonia), as well as a high heat of vaporization (40.65 kJ/mol or 2268 kJ/kg at the normal boiling point), both of which are a result of the extensive hydrogen bonding between its ...
In spite of the fact that the decreed definition of the gram specified water at 0 °C (32 °F)—a highly reproducible temperature—the scientists chose to redefine the standard and to perform their measurements at the temperature of highest water density, which was measured at the time as 4 °C (39 °F). [126]
Density (g cm-3) Boiling point (°C) K b (°C⋅kg/mol) Freezing point (°C) ... Water: 100.00 0.512 0.00 ... [25] Tetrahydrofuran: 66.0 [26]
Thus pKw D 2 O = p[OD −] + p[D +] = 7.44 + 7.44 = 14.87 (25.0 °C), and the p[D +] of neutral heavy water at 25.0 °C is 7.44. The pD of heavy water is generally measured using pH electrodes giving a pH (apparent) value, or pHa, and at various temperatures a true acidic pD can be estimated from the directly pH meter measured pHa, such that ...
Density at 20 °C relative to 20 °C water Density at 25 °C relative to 25 °C water Freezing temperature, °C 10 °C 20 °C 25 °C 30 °C 0.0: 0.0: 0.0: 0.99973:
As a guide, the saturated vapour pressure at 121 °C is 200 kPa, 150 °C is 470 kPa, and 200 °C is 1550 kPa. The critical point is 21.7 MPa at a temperature of 374 °C, above which water is supercritical rather than superheated. Above about 300 °C, water starts to behave as a near-critical liquid, and physical properties such as density start ...
A Assuming an altitude of 194 metres above mean sea level (the worldwide median altitude of human habitation), an indoor temperature of 23 °C, a dewpoint of 9 °C (40.85% relative humidity), and 760 mmHg sea level–corrected barometric pressure (molar water vapor content = 1.16%).