Boiling Point Calculator

What is Boiling Point?

The boiling point of a substance is the temperature at which its vapor pressure equals the surrounding atmospheric pressure, causing the liquid to change into gas. At this temperature, bubbles of vapor form within the liquid and rise to the surface. The boiling point is a fundamental physical property that varies depending on the substance and the ambient pressure.

For water at sea level (1 atm or 101.325 kPa), the boiling point is 100 °C (212 °F). However, at higher altitudes where atmospheric pressure is lower, water boils at a lower temperature. This is why cooking times and methods often need adjustment at high elevations. Our boiling point calculator helps you determine the exact boiling temperature for any substance at any pressure.

The Clausius-Clapeyron Equation

The boiling point calculator uses the Clausius-Clapeyron relation, a fundamental thermodynamic equation that describes the phase transition between liquid and gas phases. The equation is:

$$ln(\frac{P_1}{P_2}) = -\frac{\Delta H}{R} \times (\frac{1}{T_1} - \frac{1}{T_2})$$

Where:

• $P_1$ is the reference pressure (usually 1 atm)
• $P_2$ is the target pressure
• $T_1$ is the boiling point at reference pressure
• $T_2$ is the boiling point at target pressure
• $\Delta H$ is the latent heat of vaporization (J/mol)
• $R$ is the universal gas constant (8.314 J/(K·mol))

By rearranging the equation, we can solve for the unknown boiling point $T_2$:

$$T_2 = \frac{1}{\frac{1}{T_1} + \frac{R}{\Delta H} \cdot ln(\frac{P_1}{P_2})}$$

How to Use the Boiling Point Calculator

Using our calculator is straightforward. Select a substance from the dropdown menu to automatically load its reference boiling point and heat of vaporization. The calculator uses 1 atm (101325 Pa) as the reference pressure. Enter the target pressure in your preferred unit, and the calculator instantly computes the boiling point at that pressure.

For advanced users, check the "Show heat of vaporization" box to view and adjust the $\Delta H$ value. You can also select "Custom" from the substance list to enter your own reference boiling point and heat of vaporization for substances not in the predefined list.

Boiling Points of Common Substances at 1 atm

Explore related topics with the Boiling Point at Altitude Calculator, the Boiling Point Elevation Calculator, and the Vapor Pressure Deficit Calculator.