Question

Explain why sublimation is regarded as a physical change but the slaking of lime is considered as a chemical change

Concise Chemistry For Class Ix By Dr S.P Singh Chapter 5-Physical And Chemical Changes

Answer 1

Thanks for asking the question.
Sublimation is a physical change because it is simple conversion of  one state of matter into the other that is solid to gas. The nature and type of the substance remains the same.
However slaking of lime is a chemical change because the previous chemical changes into a new substance which has entirely different chemical properties that is Ca(OH)2.
Hope it helps. 

Answer 2

Answer:

sublimation is regarded as the physical change because it can return back to its original substance and slaking of lime is a chemical change it cannot return back.