This is the law of mass conservation.
A scientific law is based on many repeated correct experiments.
a phenomenon of nature that has been proven to invariably
Antoine Lavoiser proposed the use of symbols and formulas in naming elements.
His experiments were based on quantitative data, not qualitative. Also, he was extremely accurate which was not the case for his predecessors. This allowed him to then develop the Law of Conservation of Mass.
Lavoisier conducted a number of experiments that were based on the assumption that matter can neither be created nor destroyed and validated it through the experiments. This led to the formulation of the Law of Conservation of Mass (or Matter).
a scientist
Lavoiser
Antonie Lavoiser Joseph Priestly Antonie Lavoiser Joseph Priestly
Scientific laws are based on scientific experiments, scientific conclusions after exhaustive tests, and they are also based on formerly scientific discoveries and experiments. Scientific evidence without a conclusive proof may be a false evidence. Scientific evidence doesn't exist. Science is not based on evidences, but on real results originated from a theory. Results are solid, palpable, real and cannot be doubted.
Lavoiser rejected the phlogiston theory!
Law
the law is that mass is not real