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The boiling point of water is the temperature at which the saturated vapor pressure equals the ambient pressure. Water supercooled below its normal freezing point has a higher vapor pressure than that of ice at the same temperature and is, thus, unstable. Calculations of the (saturation) vapor pressure of water are commonly used in meteorology.
e * is the saturation water vapor pressure T is the absolute air temperature in kelvins T st is the steam-point (i.e. boiling point at 1 atm.) temperature (373.15 K) e * st is e * at the steam-point pressure (1 atm = 1013.25 hPa) Similarly, the correlation for the saturation water vapor pressure over ice is:
Although the relation between vapor pressure and temperature is non-linear, the chart uses a logarithmic vertical axis to produce slightly curved lines, so one chart can graph many liquids. A nearly straight line is obtained when the logarithm of the vapor pressure is plotted against 1/(T + 230) [ 8 ] where T is the temperature in degrees Celsius.
where temperature T is in degrees Celsius (°C) and saturation vapor pressure P is in kilopascals (kPa). According to Monteith and Unsworth, "Values of saturation vapour pressure from Tetens' formula are within 1 Pa of exact values up to 35 °C." Murray (1967) provides Tetens' equation for temperatures below 0 °C: [3]
Values are given in terms of temperature necessary to reach the specified pressure. Valid results within the quoted ranges from most equations are included in the table for comparison. A conversion factor is included into the original first coefficients of the equations to provide the pressure in pascals (CR2: 5.006, SMI: -0.875).
English: Plot of water vapor pressure p in Torr (mmHg) and hPa versus Temperature T in degrees Celsius. Note that the vapor pressure equals atmospheric pressure (760 Torr) at the boiling temperature of water. Produced by Yannick Trottier in 2006. Extended by Dr. Schorsch (talk) 10:32, 25 April 2021 (UTC).
Printable version; In other projects ... The Antoine equation is a class of semi-empirical correlations describing the relation between vapor pressure and temperature ...
The red line on the chart to the right is the maximum concentration of water vapor expected for a given temperature. The water vapor concentration increases significantly as the temperature rises, approaching 100% (steam, pure water vapor) at 100 °C. However the difference in densities between air and water vapor would still exist (0.598 vs. 1 ...