Internal energy

Definition

Internal energy is the total energy contained within a thermodynamic system, arising from the kinetic and potential energies of its molecules. It is a state function and depends only on the current state of the system.

5 Must Know Facts For Your Next Test

1. Internal energy can be changed by adding or removing heat, and by doing work on or by the system.
2. The First Law of Thermodynamics states that the change in internal energy is equal to the heat added to the system minus the work done by the system: $\Delta U = Q - W$.
3. Internal energy is independent of path, meaning it only depends on the initial and final states of a process.
4. In an ideal gas, internal energy is primarily a function of temperature, as potential energy between particles is negligible.
5. Internal energy cannot be measured directly; instead, changes in internal energy are determined through calorimetry or other methods.

Review Questions

• What equation represents the change in internal energy according to the First Law of Thermodynamics?
• How does internal energy differ between an ideal gas and a real gas?
• Why is internal energy considered a state function?

Related terms

First Law of Thermodynamics:

A law stating that energy cannot be created or destroyed, only transferred or transformed. Mathematically expressed as $\Delta U = Q - W$.

Heat (Q): Energy transferred between systems or objects due to a temperature difference.

Work (W): Energy transfer resulting from force acting over a distance, often represented as $W = P \Delta V$ for thermodynamic processes.