How can the statement you can't get something for nothing relate to the law of the conservation of mass?

The statement "you can't get something for nothing" relates to the law of conservation of mass by emphasizing that matter cannot be created or destroyed in a closed system; it can only change forms. This means that every reaction or process requires an equivalent amount of mass to be present before and after the event. Thus, any gain in one area must be balanced by an equal loss elsewhere, reflecting the principle that all resources and energy must come from existing matter.