Answer: compounds
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 or compound is formed in these reactions.

Compound is a pure substance which is made from atoms of different elements combined together in a fixed ratio by mass. It can be decomposed into simpler constituents using chemical reactions. Example: water
Isotopes, alpha and beta particles are formed in nuclear reactions.