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Internal energy
Intermediate
Total microscopic energy of a system.
U is the sum of microscopic kinetic and potential energies. For an ideal gas it depends only on temperature: U = (f/2)nRT.
1 mol of a monatomic gas at 300 K: 3.7 kJ.
U is a state function.
In more detail
Internal energy is the total energy of the molecules of a system, including their kinetic and potential energies. For an ideal gas it depends only on temperature.
Real-world uses
- Engines convert changes in internal energy into work.
- Heating a gas increases its internal energy.
- A heated metal block stores more internal energy because its atoms vibrate more strongly.
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Frequently asked questions
Is internal energy the same as heat?
No. Internal energy is a property of the system, while heat is energy transferred.
What determines it for an ideal gas?
Only temperature, because molecules do not interact.
Is internal energy the same as temperature?
No. Internal energy is the total energy of all particles, which also depends on how many particles there are.
Related topics in Heat & Thermodynamics
Charles's law · Ideal gas equation · Avogadro's number · First law of thermodynamics · Isothermal process · Adiabatic process