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Calorimetry is the measurement of heat exchange. The fundamental relation $Q = mc\Delta T$ connects heat, mass, specific heat, and temperature change. Water's specific heat (4186 J/kg/K = 1 cal/g/K) is the highest among common substances, making it an excellent coolant and temperature buffer.

The principle of calorimetry (conservation of energy in isolated systems): heat lost = heat gained. For mixing problems without phase changes, the final temperature is a weighted average: $T_f = \sum m_i c_i T_i / \sum m_i c_i$.

Phase changes require latent heat ($Q = mL$) at constant temperature. Water's latent heats: $L_f = 80$ cal/g (fusion, 0 degrees C), $L_v = 540$ cal/g (vaporization, 100 degrees C). For mixing problems involving phase changes, always work step-by-step: (1) calculate total heat available, (2) calculate heat needed for each phase change, (3) check which changes complete, (4) find equilibrium temperature with remaining heat. The critical trap: never assume all ice melts or all steam condenses — always verify.