Linked from
The 22 pages that link to Thermal diffusivity, each with the reason it gives.
Heat transferRelated: It sets the pace of temperature change inside materials.
Heat equationRelated: It sets the coefficient controlling the rate of smoothing in the equation.
Thermal conductionRelated: It predicts how rapidly conduction smooths temperature differences.
Thermal massRelated: It governs how quickly stored heat moves through a thermal mass.
Boiled eggRelated: It helps explain why a large egg takes longer to heat through than a small one.
Frying panRelated: It helps explain why pan materials differ in how evenly they heat.