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#Dulong-Petit

2 public questions tagged with this topic.

Zeroth Law Thermal Equilibrium and Quasi-static

What characteristic of a solid’s molecular structure leads to a molar specific heat capacity of approximately 3R ?

**Zeroth law of thermodynamics** if two systems A and B each in thermal equilibrium with third C, then A and B in equilibrium with each other, defines temperature as property that is same for systems in thermal equilibrium, basis for thermometer, temperature scale, thermal equilibrium means no net heat flow, same temperature. In solids, each atom vibrates with 3 degrees of freedom, contributing 3 k_B T (kinetic and potential) per atom. For a mole, this totals 3 R T , so C = (Δ U)/(Δ T) = 3R , due to vibrational motion. Using first law ΔU = Q - W, W = ∫ P

Ref: NCERT > Physics Book > Thermodynamics > Zeroth Law Thermal Equilibrium and Quasi-static

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Isobaric and Isothermal Processes Work Calculation

Why does the specific heat capacity of a solid generally agree with 3R at ordinary temperatures?

**Isobaric process** constant pressure, work W = P ΔV = P(V₂ - V₁) = n R ΔT, for expansion ΔV positive W positive, for compression negative, heat Q = n C_p ΔT, ΔU = n C_v ΔT. Isothermal process constant temperature ΔU=0, work W = n R T ln(V₂/V₁) = n R T ln(P₁/P₂), Q = W, heat absorbed equals work done. The law of equipartition predicts that each atom in a solid has 3 degrees of freedom (vibrational), contributing (3)/(2) k_B T kinetic and potential energy per atom. For a mole, U = 3 R T , so C = (Δ U)/(Δ T) =

Ref: NCERT > Physics Book > Thermodynamics > Isobaric and Isothermal Processes Work Calculation

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