Citation:
The principle of conservation of mass states that in any closed system subjected to no external forces, the mass is constant irrespective of its changes in form; in other words, matter cannot be created nor destroyed.
This law states that a chemical compound always contains exactly the same proportion of elements by mass.
A process that leads to the transformation of one set of chemical substances to another.
A physical system which does not exchange any matter with its surroundings, and isn't subject to any force whose source is external to the system.