Sublimation is regarded as a chemical change but the slaking lime is considered a physical change.

Sublimation and slaking lime represent different processes with distinct characteristics, leading to the differentiation in how they are categorized in terms of chemical or physical changes.

Sublimation:

Sublimation is the process where a substance transitions directly from the solid phase to the gas phase without passing through the liquid phase.
It involves the breaking and reforming of intermolecular bonds within the substance.
Sublimation is considered a chemical change because it involves a change in the chemical composition of the substance. The bonds between molecules are broken and reformed in a different arrangement.
Examples of substances that undergo sublimation include solid carbon dioxide (dry ice) and solid iodine.
Slaking Lime:

Slaking lime, or the process of slaking, refers to the reaction of quicklime (calcium oxide) with water to produce hydrated lime (calcium hydroxide).
The chemical equation for the slaking of lime is: CaO (s) + H2O (l) → Ca(OH)2 (aq).
Slaking lime is typically considered a physical change rather than a chemical change. This is because the reaction involves a change in state and the formation of a new phase of the substance (from solid to aqueous solution) without any alteration in its chemical composition.
While the process involves the release of heat and changes the physical properties of the lime, the chemical composition remains the same.
In summary, while both sublimation and slaking lime involve changes in the state or phase of matter, they differ in whether they involve alterations in chemical composition. Sublimation entails a change in chemical composition and is thus regarded as a chemical change, whereas slaking lime involves a change in physical state but retains the same chemical composition, therefore categorized as a physical change.