What is the law of conservation of matter?

Law of conservation of matter

To talk and describe important aspects of the law of conservation of matter, it is very important to remember what the term matter means . We understand matter as everything that occupies a place in space which can be perceived or measured by means of different methods. In modern physics, matter includes any entity, field, or discontinuity that translates into a perceptible phenomenon that has continuity through space-time , that has a speed that is equal to or less than the speed of light, and that can be associated with a certain energy .

Law of conservation of matter

What is the law of conservation of matter?

The law of conservation of matter postulates that the amount of matter that exists before and after a transformation takes place will always be the same, it is also called as the law of conservation of mass or Lomonosov-Lavoisier law .

  • What does the conservation law consist of?
  • History
  • Who proposed it
  • Statement of the conservation law
  • Lavoisier’s contributions
  • Formula
  • Experiments
  • Conservation law applications
  • Importance
  • Examples

What does the conservation law consist of?

The law that was later modified by Einstein into the law of conservation of mass energy consists of a description of the fact that the total mass and the energy in a system remain constant . This amendment incorporates the fact that mass and energy can be converted from one to the other. However, the law of conservation of mass is still a useful concept in chemistry , since the energy produced or consumed in a typical chemical reaction represents a minimal amount of mass .

Therefore, chemical reactions such as the rearrangement of atoms and bonds can be visualized , while the number of atoms involved in a reaction remains unchanged. This assumption allows us to represent a chemical reaction as a balanced equation , in which the number of moles of any element involved is the same on both sides of the equation.


In the year 1745, Mikhail Lomonosov was the one who enunciated the law of the conservation of matter and he did it in the following way: he said that in an ordinary chemical reaction where the mass remains unchanged, in other words that the mass that is present in the reactants is equal to the mass present in the products. In that same year, and completely independently, the chemist Antoine Lavoisier proposed that “matter is neither created nor destroyed, it only transforms . ” This is the reason why the conservation of matter is known as law Lavoisier-Lomonósov .

Who proposed it

The ancient Greeks first proposed the idea that the total amount of matter in the universe is constant. However, it was Antoine Lavoisier who described the law of conservation of mass or the principle of conservation of mass / matter as a fundamental principle of physics in the year 1789 . This fundamental principle is considered to have been postulated by two scientists simultaneously and independently: the Russian Mikhail Lomonosov in 1748 and the French Antoine Lavoisier in 1785.

Statement of the conservation law

The statement of the law of conservation of matter says that: “In a chemical reaction the mass remains constant . ” Another way of enunciating this law would be: “in a chemical reaction, matter is neither created nor destroyed but is transformed while remaining constant . 

Lavoisier’s contributions

Some important contributions of Lavoisier were the following:

  • He is considered as the father and founder of modern chemistry .
  • He carried out the first quantitative chemical experiments .
  • He showed that in a chemical reaction the amount of matter that participates in it is the same from the beginning of the reaction until it ends.
  • He discovered hydrogen and explained the process of combustion .
  • He helped introduce the metric system , gave rise to the first periodic table, and contributed to the establishment of the nomenclature of modern chemistry.
  • He established the law of conservation of mass .
  • He discovered that water was a compound of hydrogen and oxygen .
  • He wrote the first chemistry book called the Elementary Treatise on Chemistry .


The formula used for the law of conservation of matter is the following:

E = mc 2


  • E : is the amount of energy a body has
  • m : is the mass that a body has
  • v : speed of light in vacuum (300,000 km / sec).


To check the law we will need a commercial bag of popcorn , its mass must be measured with a scale . Then place them in the microwave and when they are ready, their mass is measured again with the packaging closed . The mass before and after said experiment must be the same, this because a physical and chemical change occurred within our system .

bottle is filled with two or three fingers of vinegar . A large spoonful of sodium bicarbonate is placed in a balloon without air and the mouth of the balloon is tied with the spout of the bottle, without the content falling inside. Everything is taken to the balance and weighed. Then, we lift the balloon in such a way that the bicarbonate falls inside and we wait for it to join with the vinegar and fizz . We weigh again and compare with the previous weight. In the second weighing, the bicarbonate is apparently gone, but the weight is exactly the same .

Conservation law applications

The applications of the law of conservation of matter can be observed for example when we prepare a fruit juice , when cement for a house is prepared , when the photosynthesis process occurs , in the oxidation of a fruit, when preparing salad of fruits, etc.


The law of conservation of matter is of fundamental importance, since it allows us to extract specific components from a certain type of raw material without having to discard the rest; It is also important, because it allows us to obtain pure elements, which we could not achieve if matter were destroyed.


Some examples of the law of conservation of matter are:

  • A perfect example of this law is the combustion of hydrocarbons , in which fuel can be seen to burn and “disappear” , but in reality it is transformed into invisible gases and released energy.
  • When you boil a Kilogram of water long enough to be consumed, you will get a Kilogram of steam .
  • Loading a vehicle with 20 Kilograms of fuel , after having started the engine for a while and it consumes all the fuel, the car will weigh 20 Kilograms less, but in the atmosphere there will be 20 Kilograms more of gases produced by combustion .

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