Antoine L. Lavoisier, a French scientist, established the theory of Law of Conservation of Mass. The law of conservation of mass states, “Mass can neither be created nor destroyed in a chemical reaction”.
All matters in the universe exist in three states. There are two ways of classification of matter.
According to physical state as solid, liquid or gas.
According to its composition as element, compound or mixture.
According to this law mass of an isolated system will remain constant over time. This means when mass is enclosed in a system and none is allowed in or out, its quantity will never change. That is mass will be conserved, and hence this is called Law of Conservation of Mass.
This means total mass of products is always equal to the total mass of reactants. As there is no loss of mass of substances, i.e. mass is conserved, that’* why Lavoisier called this the law of conservation of mass.
