How does a chemical reaction change from start to finish?

A physical Change, such as a state changing or dissolving, does not create a new substance, but a chemical change does. In a chemical reaction the atoms and molecules that interact with each other are called reactants. In a chemical change reaction the atoms and molecules produced by the reaction are called products. only the atoms present in the reactants can end up in the products. No new atoms are created and no atoms are destroyed. Reactants contact each other, bonds between atoms in the reactants are broken, and atoms rearrange and form new bonds to make new products.