What is similar between reactants and roducts in a chemical reaction?

Answer 1

In a chemical reaction, reactants and products are different substances, but they're made up of the same atoms. The law of conservation of matter says that matter cannot be created or destroyed. So, the matter that makes up the reactants (what you have before the reaction) is the same matter that makes up the products (what you get at the end of the reaction.) It's just a different arrangement of the same atoms. It's like making a LEGO sculpture, then taking it apart and using the exact same Legos to make a completely different sculpture.