What is the Difference Between Enthalpy and Internal Energy?
🆚 Go to Comparative Table 🆚The main difference between enthalpy and internal energy lies in the factors they consider. Here's a comparison of the two concepts:
- Enthalpy (H): Enthalpy is a measure of the total heat energy absorbed or released in a thermodynamic system, accounting for the pressure-volume work of the system. It is defined as U + pV, where U is the internal energy, p is the pressure, and V is the volume. Enthalpy is used for constant pressure systems.
- Internal Energy (U): Internal energy refers to the sum of the potential and kinetic energies in a system. It is the heat energy of the system at constant volume. Internal energy is used for constant volume processes.
In summary, enthalpy accounts for the pressure-volume work of a system, while internal energy only considers the heat energy of the system at constant volume.
On this pageWhat is the Difference Between Enthalpy and Internal Energy? Comparative Table: Enthalpy vs Internal Energy
Comparative Table: Enthalpy vs Internal Energy
Here is a table summarizing the differences between enthalpy and internal energy:
| Property | Enthalpy (H) | Internal Energy (U) |
|---|---|---|
| Definition | Enthalpy is the sum of internal energy and the product of pressure-volume work. | Internal energy is the sum of potential energy and kinetic energy within a system. It represents the total energy of the system. |
| State Function | Yes, enthalpy is a state function. | Yes, internal energy is a state function. |
| Energy Types | Enthalpy combines internal energy and energy due to the volume of the system. | Internal energy can be either potential energy or kinetic energy. |
| Dependence on Temperature | Enthalpy increases with temperature. The change in enthalpy is equal to the energy supplied as heat at constant pressure (dH = dQp). | Internal energy increases with temperature, as the kinetic energy of particles in a system rises when the temperature goes up. |
| Determining Changes | The change in enthalpy (∆H) can be calculated by finding the difference between the final enthalpy (Hf) and the initial enthalpy (Hi). | The change in internal energy (∆U) can be evaluated by measuring the heat transfer (q) at constant volume using the equation ∆U = q – w. |
In summary, enthalpy and internal energy are both essential concepts in thermodynamics, each providing unique insights into the energy dynamics of a system. Enthalpy is particularly useful for understanding heat exchange and work during chemical reactions, whereas internal energy provides a broader understanding of the total energy within a system.
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