= Heat capacity at constant pressure
{title2=$C_p=(\partial H/\partial T)_p$}
= Constant-pressure heat capacity
{synonym}
For a fixed-composition <closed system>, the <heat capacity> at fixed <pressure> is $C_p=(\partial H/\partial T)_p$, with <enthalpy> $H$. Under the <quasistatic process> assumptions in <heat capacity>, only <pressure>-<volume (thermodynamics)> <work> is permitted, so $dp=0$ gives $\delta Q=dH=C_p\,dT$. Thus supplied <heat> is $Q=\Delta H$, or $Q=C_p\Delta T$ within a single <thermodynamic phase> when $C_p$ is constant. For an <ideal gas>, the expansion <work> explains why this exceeds the required <heat> at fixed <volume (thermodynamics)> for the same <temperature> increase. Its per-unit-<mass> counterpart is <specific heat capacity at constant pressure>.
Back to article page
