Question

how do you know that melting ice is a physical change

Answer 1

We can know that melting ice is a physical change as it can be reversed, there is no change in mass and no change in chemical properties of the liquid . 

Answer 2

In a chemical reaction there is formation of a new substance and the reactions are most often irreversible. Melting of ice is rather a physical change than a chemical change as it is just the transition of water into its various forms. There is no new substance formed and water can be freezed again to make ice. That is it is reversible also.

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