We explain what the law of conservation of matter or Lomonosov-Lavoisier Law is. History, background and examples.
Law of conservation of matter
The law of conservation of matter, also known as law of conservation of mass or just like Lomonosov-Lavoisier law (in honor of the scientists who postulated it), is a principle of chemistry that states that matter is neither created nor destroyed during a chemical reactionit just transforms.
This means that the quantities of the masses involved in a given reaction must be constant, that is, the quantity of reactants consumed is equal to the quantity of products formed, even if they have been transformed into each other.
This fundamental principle of natural sciences was postulated by two scientists simultaneously and independently: the Russian Mikhail Lomonosov in 1748 and the Frenchman Antoine Lavoisier in 1785. It is striking that this occurred before the discovery of the atom and the postulation of the atomic theory. , with which it is much easier to explain and illustrate the phenomenon.
The exception to the rule is nuclear reactions.in which it is possible to convert mass into energy and vice versa.
Along with the equivalence between mass and energy, the law of conservation of matter was key to the understanding of contemporary chemistry.
See also: Exothermic reaction
Background of the Law of Conservation of Matter
The chemistry of those years understood reaction processes in a very different way than today, in some cases going so far as to affirm the opposite of what this law states.
In the 17th century Robert Boyle experimented by weighing metals before and after letting them rust.. This scientist attributed the change in the weight of these metals to the gain of matter, ignoring that the metal oxide that was formed came from the reaction of the metal with the oxygen in the air.
Discovery of the Law of Conservation of Matter
The experiences that led Lavoisier to the discovery of this principle have to do with one of the main interests of chemistry at the time: combustion. By heating various metals, the Frenchman realized that they gained mass when calcined if they were left exposed to air, but that their mass remained identical if they were in closed containers.
Thus, he deduced that that extra amount of mass came from somewhere. He then proposed his theory that the mass was not created, but taken from the air. Therefore, under controlled conditions, the amount of mass of the reactants before the chemical process and the amount of mass afterwards can be measured, which must necessarily be identical, even if the nature of the products is no longer identical.
Example of the Law of Conservation of Matter
A perfect example of this law is the combustion of hydrocarbonsin which the fuel can be seen burning and “disappearing”, when in reality it will have been transformed into invisible gases and water.
For example, by burning methane (CH4) we will have the following reaction, whose products will be water and invisible gases, but with an identical number of atoms as the reactants:
