升华焓

[latex]\Delta H_{text{sub}} = \Delta H_{text{fus}} + \Delta H_{text{vap}}[/latex] 是热化学基本原理赫斯定热求和定律的直接应用。+ \Delta H_{text{vap}}[/latex] 是赫斯定热求和定律的直接应用，它是热化学的基本原理。该定律指出，只要初始状态和最终状态相同，化学或物理过程中的总焓变化都是相同的，而与所采取的途径无关。在这里，初始状态是固相，最终状态是气相。我们可以想象从固态到气态的两种路径：直接的一步路径（升华）或两步路径（将固态熔化为液态，然后将液态汽化为气态）。

The enthalpy change for the direct path is the enthalpy of sublimation, [latex]\Delta H_{\text{sub}}[/latex]. The enthalpy change for the two-step path is the sum of the enthalpy of fusion ([latex]\Delta H_{\text{fus}}[/latex], for the solid-to-liquid transition) and the enthalpy of vaporization ([latex]\Delta H_{\text{vap}}[/latex], for the liquid-to-gas transition). Since the initial and final states are identical for both pathways, Hess’s Law dictates that their total enthalpy changes must be equal. This principle is incredibly useful because it allows for the calculation of an unknown enthalpy change from known values. For instance, if the enthalpies of fusion and vaporization are experimentally easier to measure than the enthalpy of sublimation, the latter can be calculated accurately. This data is crucial for chemical engineers and physicists in designing processes and modeling physical phenomena where sublimation is a key factor, such as in material deposition, 低温， 和 天体物理学.