Thermodynamics | Class 11 Physics Notes

11.6 Specific heat capacity

Specific heat capacity (s) is defined as the amount of heat required to raise the temperature of 1 kg of a substance by 1 K. It is given by s = (1/m) × (ΔQ/ΔT), where m is the mass and ΔQ is the heat supplied to change the temperature by ΔT. Heat capacity depends on the nature of the substance and temperature. Molar specific heat capacity (C) is defined similarly per mole of substance: C = (1/μ) × (ΔQ/ΔT), where μ is the number of moles. For solids, the law of equipartition of energy predicts C ≈ 3R (R is universal gas constant), which generally agrees with experimental values at room temperature. The specific heat capacity of water varies slightly with temperature, as shown in Fig. 11.5. The old unit of heat, calorie, is defined as the heat required to raise 1 g of water from 14.5°C to 15.5°C, equal to 4.186 J. For gases, specific heats at constant volume (Cv) and constant pressure (Cp) differ, related by Cp - Cv = R for ideal gases. This section provides fundamental understanding of heat capacity and its measurement.

📊 Diagram: Table 11.1 Specific and molar heat capacities of some solids at room temperature and atmospheric pressure; Fig. 11.5 Variation of specific heat capacity of water with temperature.

🔗 Connection: This section connects to thermodynamic state variables and equations of state, as heat capacities relate to energy changes in different states.

Table on page 6 (7×3)

Table on page 16 (5×5)