Internal Energy and Enthalpy The internal energy of a system is a measure of the total energy of its components, including both kinetic and potential energy....
The internal energy of a system is a measure of the total energy of its components, including both kinetic and potential energy. It is a state function, meaning its value depends only on the current state of the system, not on how it got there. The internal energy of a system can be changed by performing work, changing the system's temperature, or adding or removing energy.
The change in internal energy is equal to the amount of work done on the system. This is because work done on a system will transfer energy to or from the system, and this energy change will be reflected in the internal energy.
Similarly, the change in internal energy is equal to the change in heat added to the system. This is because heat added to a system will increase its internal energy, and this change in internal energy will be equal to the amount of energy transferred as heat.
The internal energy of a system is an extensive property, meaning its value depends on the amount of the system. This means that the internal energy of a system can be changed by adding or removing energy from the system, regardless of where in the system the energy is added or removed.
The internal energy is often used in conjunction with the enthalpy, which is an internal energy change at constant pressure. Enthalpy is a more useful property in many applications because it takes into account the change in pressure.
Internal energy and enthalpy are closely related. They are connected by the first law of thermodynamics, which states that the total energy of an isolated system is constant. This means that the internal energy of a system can only change if work is done on or by the system, and that the enthalpy of a system can only change if heat is added or removed from the system