Definition:
Enthalpy (H) = Internal Energy (U) + Pressure (P) x Volume (V)
Key Points:
* Total Energy: Enthalpy encompasses all forms of energy within a system, including internal energy, pressure-volume work, and potential energy due to its position in a gravitational field.
* State Function: Enthalpy is a state function, meaning it depends only on the current state of the system and not on the path taken to reach that state.
* Extensive Property: Enthalpy is an extensive property, meaning it is proportional to the amount of substance present.
* Enthalpy Change: The change in enthalpy (ΔH) represents the heat absorbed or released during a process at constant pressure.
* Applications: Enthalpy is crucial in understanding chemical reactions, phase changes, and other thermodynamic processes.
Examples:
* Combustion: The burning of fuel releases heat, indicating a decrease in enthalpy.
* Melting: The melting of ice requires energy input, resulting in an increase in enthalpy.
Units:
Enthalpy is typically measured in joules (J) or kilojoules (kJ).
Importance:
Enthalpy is a fundamental concept in thermodynamics, providing insights into energy transformations and the feasibility of chemical reactions. It helps us understand the energy balance of systems and predict the direction of spontaneous processes.