Heat Balance With Phase Change — the NEET Physics formula with its derivation, variables, validity constraints and worked solver.
Heat Balance With Phase Change This formula applies to calorimetry problems where heat exchange occurs between substances and at least one substance undergoes a phase transition (e.g., melting ice). Apply the principle of conservation of energy: Heat Lost = Heat Gained. Calculate heat lost by the hot component: Q lost = m s c s (T s - T f) . Calculate total heat gained: Q gained = Q water + Q ice, melt + Q cal . Set up the balance equation: Q lost = (m w c w + C cal ) (T f - T w) + m i L f + m i c w (T f - 0) . Solve for the unknown variable (usually T f ) by rearranging the terms. The final temperature (T f) must be physically achievable given the initial conditions. Masses (m) and specific heat capacities (c) must be positive. The heat lost by the hot component must equal the total heat gained by the cold components. Forgetting to include the heat absorbed by the calorimeter ( C cal ). Confusing the latent heat of fusion ( L f ) with the specific heat capacity ( c ). Assuming the final temperature must be 0°C, ignoring the heat gained by the melted ice.