The internal energy of a system is the energy contained within a system. The internal energy can be calculated using the first law of thermodynamics, which states that energy cannot be created or destroyed.

The internal energy of an ideal gas can be calculated using the ideal gas law. For example, if a gas has 100 kJ of internal energy when it occupies 1 m3, then it will also have 100 kJ of internal energy when it occupies 2 m3. The internal energy does not change as the volume changes.

When heat is added to or taken from an object, its temperature increases or decreases. This change in temperature represents a change in kinetic and potential energies. However, this does not mean that there has been an overall increase or decrease in total system energy — only that it has changed form.

Last modified: October 11, 2022