Answer:
A chemical reaction
Step-by-step explanation:
In a physical change the chemical composition of a matter stays the same. One example is a change in state of matter. Consider water, you can heat it to vapour and cool it to form ice but you can get the exact same mass and colour after any physical change happens.
To form a two or more substance an internal arrangement of atoms must happen. For that chemical change should occur as only in chemical reactions atoms are rearrange to form new substances.