Answer: the substance melts
Step-by-step 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.