Why must the law of conservation of energy include mass?
The law of conservation of mass/matter, also known as law of mass/matter conservation (or the Lomonosov-Lavoisier law), states that the mass of a closed system of substances will remain constant, regardless of the processes acting inside the system. An equivalent statement is that matter changes form, but cannot be created nor destroyed. This implies that for any chemical process in a closed system, the mass of the reactants must equal the mass of the products. In chemistry, so long as no nuclear reactions take place, a special form the conservation of mass also holds in regard to the conservation of the mass (and number of atoms) of each chemical element. In most basic chemical reactions and equations, atoms of no element may be created or destroyed. They must only come out exactly as found in the reactant side of an equation, with a different location in regard to their new chemical formula, as may be found on the product side of an equation. The conservation of mass is widely used i
