Boiling Point Calculator

Find how a liquid's boiling point shifts when pressure changes.

How the Math Works

The Boiling Point Calculator uses the Clausius-Clapeyron equation, which describes how the boiling point of a substance changes with pressure. The formula 1/T₂ = 1/T₁ − (R/ΔH)·ln(P₂/P₁) mathematically relates two boiling points (T₁ and T₂) and their corresponding pressures (P₁ and P₂). Here, R is the universal gas constant (8.314 J/mol·K), ΔH is the enthalpy of vaporization (energy required to transition from liquid to gas), and ln is the natural logarithm. By rearranging the equation, users can solve for any missing variable when given the others, enabling precise predictions of boiling points under different pressure conditions. This relationship assumes constant ΔH and ideal gas behavior, making it widely applicable for common substances.

Practical Applications

To apply this calculation, first gather known values: the initial boiling point (T₁) and pressure (P₁) for the substance, such as water at standard atmospheric pressure (100°C, 1 atm), and the new pressure (P₂) of interest, like in a pressure cooker or at high altitude. Input these into the calculator along with ΔH for the substance (e.g., 40.7 kJ/mol for water). The tool then computes T₂, allowing engineers to design systems like distillation columns, chemists to optimize reactions, or chefs to adjust cooking times for different elevations. For instance, at 0.75 atm (common in mountainous regions), water’s boiling point drops to ~90°C, which directly impacts food preparation and industrial processes.

Day-to-Day Use

This calculator simplifies everyday tasks where pressure affects boiling points. For home cooks, it explains why recipes at high altitudes require longer cooking times, as lower atmospheric pressure reduces water’s boiling point, slowing heat transfer. Gardeners might use it to understand how altitude affects irrigation systems or greenhouse pressures. Even in HVAC maintenance, knowing how pressure changes affect refrigerants’ boiling points helps technicians service air conditioners efficiently. Additionally, pressure cookers rely on elevated pressure to increase boiling points, cooking food faster—a principle easily quantified with this tool. By demystifying the science behind pressure-temperature relationships, users gain practical insights for cooking, outdoor activities, and home maintenance.

Worked example

Water at 80 kPa → boils near 366 K (≈93 °C).

FAQ