word_count: 180

delta_H(T2) = delta_H(T1) + delta_Cp(T2 - T1). delta_Cp = sum(Cp products) - sum(Cp reactants). This relates reaction enthalpy at different temperatures. Similarly: delta_U(T2) = delta_U(T1) + delta_Cv(T2 - T1). Physical meaning: if delta_Cp > 0 (products have higher heat capacity), the reaction becomes more endothermic (or less exothermic) with increasing temperature. If delta_Cp < 0, the reaction becomes more exothermic with increasing temperature. If delta_Cp = 0, enthalpy is temperature-independent. Application: calculating delta_H at non-standard temperatures when standard data is given at 298 K. The equation assumes Cp is constant over the temperature range (valid for small delta_T). For large ranges, integration with Cp as a function of T is needed (rarely required for JEE). Also applies to entropy: delta_S(T2) = delta_S(T1) + delta_Cp ln(T2/T1).