Law of Conservation of Matter or Law of conservation of mass or Law of conservation of matter Or known as the (Lavoisier-Lomonosov) law, it is a law that states the following when any chemical reaction occurs, the masses of the reactants are equal to the masses of the materials resulting from the reaction, and it is mentioned that any mass in a closed system will remain constant no matter what happens inside the system.

This law states that matter in a closed system cannot be created or destroyed, only that it can be rearranged. That any chemical process in a closed system must have the mass of the reactants equal to the mass of the products after the end of the process.

In view of the constant controversy over the terms mass and matter, the law of survival of mass remains valid only for approximation in classical physics, while it cannot be relied upon in relativity and quantum physics, while the laws of energy and momentum remain valid.

The concept of conservation of mass is widely used in many fields such as chemistry, mechanics, and fluid dynamics. Historically, the law of conservation of mass in chemical reactions was independently proven by Mikhail Lomonosov and later rediscovered by Antoine Lavoisier in the late 18th century. The formulation of this law was of crucial importance in the advancement of alchemy and the modern natural chemical sciences.

The law of conservation of mass is roughly correct and is part of a series of assumptions stemming from classical mechanics. The law must be modified to comply with the laws of quantum mechanics and special relativity under the principle of mass-energy equivalence, which states that energy and mass form one conserved quantity. For extremely high-energy systems, the law of conservation of mass does not apply alone, as in the case of nuclear reactions and particle-antiparticle annihilation in particle physics.

In addition, the block is generally not preserved on open systems. As in allowing different forms of matter and energy to exit or enter a system. However, unless there is radioactivity or nuclear reactions, the amount of energy leaving (or entering) these systems, such as heat, mechanical work, or electromagnetic radiation, is so small that it cannot be measured as a decrease (or increase) in mass the system.

For systems surrounded by large gravitational fields, general relativity must be taken into account, as the conservation of energy and mass becomes a more complex concept, subject to different definitions, and the conservation of mass or energy does not apply strictly and simply as it does in special relativity.

Drafting the law and its examples[عدل]

The law of conservation of mass in classical mechanics can only be formulated when the energy scales associated with an isolated system are much less than mc2, where (m) is the mass of the typical body in the system, measured in the frame of reference where the body is at rest, and (c) is the velocity the light.

The law can be formulated mathematically in the fields of fluid mechanics and continuum mechanics, as mass conservation is usually expressed using the continuity equation, in its differential form as follows

• 
  $\displaystyle \frac \partial \rho \partial t+\nabla \cdot (\rho \mathbf v )=0,$

  

where (rho) is the density (mass per unit volume), t is the time, ∇ is the divergence operator, and (in v) is the flow velocity. Here is the interpretation of the continuity equation for mass: For a given closed surface in the system, the change in mass with respect to time enclosed by the surface is equal to the amount of mass that crosses the surface, positive when matter enters and negative when matter exits. For a fully isolated system, this condition means that the total mass (or M), that is, the sum of the masses of all components of the system, does not change with time, which is expressed by the following mathematical equation:

${\displaystyle \frac \textdM\textdt=\frac \textd\textdt\int \rho \textdV=0}$

where dV is the differential that defines the integral over the entire volume of the system.

The continuity equation for mass is part of Euler’s equations of fluid dynamics. Many other convection and diffusion equations describe the conservation and flow of mass and matter in a given system.

In chemistry, the amount of reactants and products in a chemical reaction is calculated, which is known as stoichiometry, based on the principle of conservation of mass. The principle states that during a chemical reaction, the total mass of the reactants is equal to the total mass of the products. For example, in the following interaction:

CH4 + 2O2 → CO2 + 2H2O

One molecule of methane (CH4) and two molecules of oxygen ((O2) convert into one molecule of carbon dioxide (CO2) and two molecules of water (H2O). The number of molecules produced by the reaction can be derived from the principle of conservation of mass, since in the initial state there are four atoms hydrogen, four oxygen atoms, and one carbon atom (and also in the final case), so the number of water molecules produced must be equal to two for each molecule of carbon dioxide produced.

Many engineering problems are solved by following the time distribution of mass for a given system, this method is known as mass balance.

A historical perspective[عدل]

An important idea in ancient Greek philosophy was that “nothing comes from nothing,” so what is now has always been: new matter cannot be created from nothing. There is an explicit statement of this principle, along with the additional principle that nothing can perish into nothingness, in the saying of Empedocles (c. 4th century BC): “It is impossible for anything to come from nothing, and nothing that is non-existent can be brought about or heard.” Completely.”^[1]

Another principle of memorization was mentioned by Epicurus around the third century BC, in which he described the nature of the universe, as it states that “the sum of things has always been as it is now, and it will continue forever.”^[2]

Jain philosophy, an immoral philosophy, based on the teachings of Mahavira (6th century BC), states that the universe and its components such as matter cannot be created or destroyed. The Jain manuscript Tatvartha Sutra (2nd century AD) states that matter is permanent, but that its forms vary through creation and mortality. The principle of Nasr al-Din al-Tusi (about the thirteenth century AD) stipulated the principle of preserving matter. He wrote that “the physical body cannot completely disappear. It only changes its shape, state, composition, color and other properties and turns into a different substance, complex or simple.”^[3][4][5]

discoveries in chemistry[عدل]

By the 18th century, the principle of conservation of mass during chemical reactions was in wide use and was an important assumption during experiments, even before it was formally defined, as exemplified by the works of Joseph Black, Henry Cavendish, and Jane Ray. This principle was first identified by Mikhail Lomonosov in 1756. He had demonstrated it through several experiments and had discussed it before in 1774 in his correspondence with Leonhart Euler, although his claims on the subject were sometimes contested. Antoine Lavoisier later performed a more thorough series of experiments, expressing his conclusion in 1773 and making famous the principle of conservation of mass. Proofs of this principle replaced outdated theories, such as the phlogiston theory which claimed that mass can be gained or lost in combustion and heat processes.^[6][7][8][9]

Conservation of mass has been a mysterious principle for thousands of years due to the effect of buoyancy in the Earth’s atmosphere on the weight of gases. For example, a piece of wood weighs less after it has been burned; This seemed to indicate the disappearance, transformation or loss of some of their mass. This claim was not disproved until careful experiments were carried out which allowed chemical reactions such as rust to occur in sealed glass ampoules; It was found that the chemical reaction did not change the weight of the closed incubator and its contents. It was not possible to measure the weight of gases with balances until the invention of the vacuum pump in the 17th century.

History[عدل]

The first to refer to the law of conservation of mass is the Andalusian Muslim scholar Abu al-Qasim Maslama bin Ahmad al-Majriti, in his book “The Rank of the Wise.”^[10]

See also[عدل]

• energy survival
• Save momentum

Reference[عدل]

• Physical chemistry portal
• Chemistry portal
• Science portal
• Physics portal

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