What is meant by heat capacity at constant pressure?

Click For Summary
SUMMARY

Heat capacity at constant pressure, denoted as \(C_p\), is a fundamental thermodynamic property defined by the equation \(C_p=\left(\frac{\partial H}{\partial T}\right)_P\), where \(H\) represents the molar enthalpy of a material. This property does not depend on whether the pressure is constant externally or internally, as thermodynamics assumes equilibrium where internal and external pressures are equal. Even in irreversible processes with non-uniform internal pressure and temperature, the local definition of heat capacity remains valid.

PREREQUISITES
  • Understanding of thermodynamic principles
  • Familiarity with molar enthalpy concepts
  • Knowledge of the relationship between pressure and temperature in physical systems
  • Basic grasp of irreversible processes in thermodynamics
NEXT STEPS
  • Study the derivation and applications of the heat capacity equations in thermodynamics
  • Explore the differences between heat capacities at constant pressure (\(C_p\)) and constant volume (\(C_v\))
  • Investigate the implications of irreversible processes on thermodynamic properties
  • Learn about the role of enthalpy in chemical reactions and phase changes
USEFUL FOR

Students and professionals in chemistry and physics, particularly those studying thermodynamics, material science, and engineering applications involving heat transfer and energy systems.

Fermion70
Messages
1
Reaction score
0
Generally in chemistry and physics, we learned that a material has a heat capacity at constant pressure. However, I am confused at whether this refers to a constant external pressure or a constant system internal pressure?

Thanks.
 
Last edited:
Science news on Phys.org
Hello half integer spin, :welcome:

Thermodynamics is about equilibrium. Internal pressure and external pressure are supposed to be equal.
 
To elaborate on what BvU said, heat capacity is a physical property of a material, and does not depend on the process being applied to the material. Heat capacity per mole at constant pressure is defined as $$C_p=\left(\frac{\partial H}{\partial T}\right)_P$$
where H is the molar enthalpy of the material. If a process is irreversible so that the internal pressure and temperature of the material are not uniform, this equation still applies locally.
 

Similar threads

Undergrad Questions about my Understanding of Thermodynamics and Statistical Mechanics
  • · Replies 2 ·
Replies
2
Views
3K
Undergrad Enthalpy change in a flow process
  • · Replies 2 ·
Replies
2
Views
2K
Undergrad How to understand experiment to measure heat capacity of solid?
  • · Replies 1 ·
Replies
1
Views
2K
High School Gas cylinder at constant pressure being exposed to atmosphere, how?
  • · Replies 8 ·
Replies
8
Views
2K
Undergrad Cannot understand formula for molar heat capacities of an ideal gas
  • · Replies 22 ·
Replies
22
Views
3K
Undergrad Help understanding "Heat capacity"
  • · Replies 28 ·
Replies
28
Views
3K
Undergrad Entropy and Heat Capacity Relation
  • · Replies 2 ·
Replies
2
Views
2K
Undergrad Ideal working gas for a Stirling engine
  • · Replies 1 ·
Replies
1
Views
3K
Undergrad Heat capacity for a real gas using the ideal gas (zero pressure) equation
  • · Replies 32 ·
2
Replies
32
Views
4K
Undergrad Effects on Engine Overheating and Pressure Dynamics
  • · Replies 4 ·
Replies
4
Views
2K