How this calculator works
For isolated mixing, total body enthalpy is conserved. Each body may have constant specific heat or piecewise heat capacities separated by two latent-heat jumps. The solver searches for a common temperature and handles partial transitions on a temperature plateau. If several bodies share a plateau, one common transition fraction is a bookkeeping convention; individual phase fractions are not uniquely determined by total energy. Coffee-cup mode includes solution and calorimeter heat uptake, taking reaction heat as their negative. No environmental loss, extra reaction work or phase changes in the solution are included.
Formula
No phases: Tf = sum(mi ci Ti)/sum(mi ci). With phases: sum[Hi(Tf) - Hi(Ti)] = 0, adding mi Li for each completed transition. Coffee cup: qreaction = -(msolution c + Ccal)(Tf - Ti); deltaH = qreaction/nreactant.
Worked example
Two 1 kg bodies with c = 1000 J/(kg K), initially 300 K and 400 K, equilibrate at 350 K and exchange 50000 J. In a coffee cup, 0.1 kg of solution with c = 4186 warming by 10 K absorbs 4186 J; reaction of 0.1 mol then has deltaH = -41860 J/mol if calorimeter heat capacity is negligible.
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Frequently asked questions
How do I enter a melting plateau?
Use a phase-change row and its transition temperature and latent heat. If the initial temperature equals that transition, choose whether the initial material is fully in the lower or upper phase.
Can the final state contain two phases?
Yes. At a transition, progress gives the fraction of the available latent-heat jump completed. A zero or one fraction is a pure endpoint.
Is reaction enthalpy per mole of reaction?
The coffee-cup result is per mole of the entered reacting solute. Apply stoichiometric scaling before comparing it with a differently normalized reaction.