Which of these is an indication that a chemical reaction has occurred?

select all that apply:

melting of a substance

boiling of a substance

formation of a new gas

formation of a precipitate

a new smell is given off

heat is released

Formation of a new gas

Formation of a precipitate

A new smell is given off

Heat is released

Explanation: A chemical reaction exhibits the following characteristics: formation of new substance, heat emission is an exothermic process which is due to chemical reactions

Precipitate formation occurs when insoluble substances are formed in an ionic compound solution.

And smells or odor are caused by the production of new substances.

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