In one experiment, magnesium metal melts. In a second experiment, magnesium metal ignites as it combines with oxygen. Classify the change in each experiment as chemical or physical. Explain your reasoning.

magnesium metal melts = physical change

magnesium metal ignites = chemical change

Explanation:

Physical changes are those in which the identity of the subtance remains unaltered. No new compounds are formed. They involve generally changes in agreggation states of matter: solid, liquid or gas. The first experiment, in which magnesium metal melts is a physical change because it only changes the state of matter, from solid to liquid, but it is still magnesium metal.

Conversely, chemical changes involve atoms combinations to form new compounds. The second experiment, in which magnesium metal ignites, is a chemical change. After the change, magnesium metal is no longer the metal but a metal oxide.