Answer the question...
The law of conservation of mass/matter states that mass/matter cannot be created or destroyed in chemical or physical changes.
The law of conservation of mass, which states that in a closed system, mass is neither created nor destroyed, it can only change form. This means that in a chemical reaction that takes place in a closed system, the mass of the reactants equals the mass of the products.
The Law of conservation of Energy applies to mass as mass is a form of energy, E=mc2.
If matter were destroyed, then it would not be conserved. "Conservation" means that the amount of mass doesn't change.
You are confusing the law of conservation of matter/mass with the law of conservation of energy. The law of conservation of matter/mass states that in a closed system matter is neither created nor destroyed. During a chemical reaction matter is rearranged, it doesn't change forms (energy can change forms). The atoms in the products are the same atoms that were in the reactants.
There is the law of conservation of mass, and the law of conservation of energy. All three state: (Mass/Matter/Energy) cannot be created or destroyed, simply transferred.
Law of Conservation of Mass (aka Law of Conservation of Matter)
Law of Conservation of mass(atomic mass). As mass can be considered relative to energy, therefore Law of Conservation is also correct but Law of conservation of mass is is much more accurate because here mass is a much more accurate term that is required here. Here, since, we are balancing molecules, then we require atomic or molecular mass.
the law of conservation of matter (or mass)
The law of conservation of mass. We now know that technically it's not quite true, but it's so close that the difference cannot be detected on the most sensitive balances we have.
matter can not be created or distroyed
There is no law of concervation of mass anymore, it is the law of conservations of energy (since mass can be converted into pure energy, thank you Albert).