Enthalpy is a thermodynamic quantity that represents the total heat content of a system when the pressure is constant. It combines the system’s internal energy with the energy needed to displace its surroundings due to pressure and volume.
In simple terms:
- Enthalpy accounts for all the energy required to form the system and to make room for it in the environment.
- It is especially useful for understanding heat flow in chemical reactions, phase changes, and heat exchange processes.
Why it matters:
- In many real-world processes (like reactions in open containers), pressure remains constant, making enthalpy the appropriate measure for energy changes.
- Changes in enthalpy (∆H) tell us whether a process is endothermic (absorbs heat) or exothermic (releases heat).
For example:
- When water boils at constant pressure, the heat added increases its enthalpy without raising its temperature.
Enthalpy is a central concept in thermodynamics, chemistry, and engineering for tracking energy transfer during processes.