What defines the region beyond which volatile compounds like water could condense into ices in the spinning disk?

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The structure of the primordial solar nebula, flattened into a disk, established natural temperature gradients across its radius. Close to the forming Sun, temperatures were too high for anything but refractory materials like metals and silicates to condense, leading to the rocky terrestrial planets (Mercury, Venus, Earth, Mars). Further away, beyond a critical point, temperatures dropped sufficiently low for volatile compounds, such as water, methane, and ammonia, to freeze into solid ices. This boundary is referred to as the 'frost line' or 'snow line.' The presence of these abundant ices beyond this line provided significantly more solid building material, enabling the outer cores to rapidly accumulate mass and eventually gravitationally capture the remaining light gases to form the gas and ice giants.