Here’s a explanation:
Internal Energy (U)
- It is the total energy inside a system.
- Includes the energy of molecules moving, vibrating, and the energy in chemical bonds.
- It depends only on the state of the system, not on how it got there.
Enthalpy (H)
- It is the energy of the system plus the energy needed to push the surroundings away when the system expands.
- It is useful for reactions that happen at constant pressure because it tells us the heat absorbed or released.
Key Difference
- Internal energy is just the energy inside.
- Enthalpy is internal energy plus the extra energy to make space for the system.