Thermodynamics adds a new quantity, called internal energy, into the fold; it’s the energy possessed by the system itself. Getty Images. If we add heat to the system, its internal energy increases.

For an Ideal Gas, the internal energy is only a function of the gas temperature and is a measure of the mean translational kinetic energy of the gas atoms. These atoms have three translational degrees ...

In hotter objects, the particles have more internal energy and vibrate faster. Human bodies, hot coffees, stoves or hobs. Ice particles vibrate slower, but still have energy.