What is the inversion temperature in terms of the Joule-Thomson coefficient?

The inversion temperature is defined as the specific temperature at which the Joule-Thomson coefficient changes sign. The Joule-Thomson coefficient measures the change in temperature of a real gas when it expands at constant enthalpy. For most gases at room temperature and above, the gas cools upon expansion, yielding a negative Joule-Thomson coefficient. However, at the inversion temperature, this behavior reverses: the gas begins to heat upon expansion, indicating a positive Joule-Thomson coefficient.

Understanding this concept involves recognizing that the values of the Joule-Thomson coefficient provide insight into the thermodynamic behavior of gases under specific conditions. Gases that cool upon expansion below the inversion temperature transition to those that heat upon expansion above it. Therefore, the inversion temperature is critical for applications in gas liquefaction and cryogenics, where understanding the cooling and heating behaviors of gases is essential.

The other choices do not accurately reflect the definition of inversion temperature within the context of thermodynamic processes involving the Joule-Thomson effect.