When substances change into new substances, the process must involve:

a physical change

a chemical change

heat being produced

heat being absorbed

A chemical change ...

Answer is a chemical change.

As a result of a chemical reaction, a substance is changed into new substances which involves a chemical change.

During a chemical reaction, atoms of a molecule within a substance are rearranged into different combinations by combining with the atoms of another substance to form new substances.

An example of a chemical change is the composition of sodium chloride (salt) where the atoms of sodium and chlorine combine and rearrange themselves to form salt.