Which is not proof that a chemical change has occurred?

the substance melts

the color changes

a precipitate forms

bubbles are produced

Answer: the substance melts

Explanation:

A physical reaction is defined as the reaction in which a change in shape, size takes place. No new substance gets formed in these reactions.

A chemical reaction is defined as the reaction in which a change in chemical composition takes place. A new substance is formed in these reactions.

Characteristics of chemical reaction:

1. Change in color

2. formation of precipitate

3. Energy is lost or absorbed

4. A gas or bubbles are produced

When a substance melts, no new compound gets formed and no change in chemical composition takes place, thus is a physical change.