Enthalpy Calculator

Enthalpy is a thermodynamic state function defined as internal energy plus pressure multiplied by volume. It is especially convenient for processes at constant pressure because, when only pressure-volume work occurs, the enthalpy change equals the heat transferred to the system. This calculator combines three transparent contributions: sensible heat from a temperature change, latent heat associated with a specified phase change, and the change in pressure-volume flow work between the initial and final states. Sensible heat is calculated as mass times specific heat capacity times final temperature minus initial temperature. A positive temperature difference produces a positive contribution, while cooling produces a negative one. Celsius temperature differences have the same numerical size as kelvin differences, so the entered Celsius values can be used directly in this term. The model assumes the supplied specific heat remains constant across the interval. For wide temperature ranges, integrating a temperature-dependent heat capacity gives a more accurate result. Latent heat is mass multiplied by the entered latent heat per gram. Enter zero when no phase transition occurs. Use a positive value for energy absorbed during melting, vaporization, or sublimation under this calculator's sign convention. For freezing or condensation, represent released latent heat separately when interpreting the process, because the field accepts a non-negative material magnitude. The pressure-volume contribution is final pressure times final volume minus initial pressure times initial volume. Liter-atmospheres are converted using 101.325 joules per liter-atmosphere. This is a general educational energy balance, not a full property database or equation-of-state solver. Real enthalpy changes can depend on temperature-dependent heat capacities, nonideal gas behavior, mixing, reaction extent, reference states, pressure-dependent phase properties, and additional forms of work. For a chemical reaction, use tabulated standard enthalpies of formation or measured reaction data unless the simplified terms entered here fully describe the process. Ensure mass and specific heat use the matching gram basis, and keep pressure and volume paired for each state. The component breakdown makes assumptions visible and helps with heating, cooling, idealized phase-change, and introductory thermodynamics exercises.