Why does boiling point change with pressure?
Boiling occurs when vapor pressure equals external pressure. Lower external pressure (like at high altitudes) means less heat is needed to reach that vapor pressure.
Calculator
Enter your values
Standard sea level pressure is 1 atm.
Results
Boiling Point
100.00 C
Fahrenheit
212.00 F
Kelvin
373.15 K
Phase Change Analysis
Pressure effects on boiling point
Pressure Context
Input Pressure:1 atm
Standard Pressure:1.0 atm
Difference:0.00 atm
Cooking Implications
Standard range. Cooking times should be close to standard recipes.
Thermodynamic Insight
The boiling point is the temperature where the vapor pressure of the liquid equals the external pressure. Lower external pressure requires less kinetic energy (lower temperature) for molecules to escape into the gas phase.
How to Use
Step-by-step instructions
- 1Enter the atmospheric pressure in atm.
- 2The calculator will estimate the boiling point of water.
Clausius-Clapeyron Equation
Describes the relationship between pressure and temperature for a phase change. This calculator estimates the boiling point of water based on external pressure.
ln(P2/P1) = (-DeltaHvap/R)(1/T2 - 1/T1)Variables:
PPressureTTemperature (Kelvin)DeltaHvapEnthalpy of vaporizationExample
High Altitude (0.8 atm)
Inputs:
Pressure:0.8 atm
Steps:
- 1.Standard BP: 100 C at 1 atm
- 2.Lower pressure reduces boiling point.
- 3.Result is about 93.6 C
Result:
93.6 C