One of the fundamental laws of nature.In any material system (isolated system) isolated from the surroundings, no matter what changes or processes occur, its total mass remains unchanged.French chemist in the 18th centuryLavoisierIt was overthrown experimentallyPhlogiston theoryAfter that, this law was recognized.In the early 20th century, high-speed movement was foundMass of objectFollowMovement speedHowever, it is found that the material object and the field can be transformed each other, so the quality of the field should be considered according to the relationship between quality and energy.The development of the concept of mass has led to new development of the principle of mass conservation. The two laws of mass conservation and energy conservation are combined into a conservation law through the mass energy relationship, namely the law of mass and energy conservation (hereinafter referred to as the law of conservation of mass and energy)Law of conservation of mass and energy）。
The law of conservation of matter means that matter can neither disappear nor produce, and can only be transformed from one kind of matter to another.According to the law of conservation of matter, matter will not be created out of thin air, but will be transformed from one form to another.
In a chemical reaction, the total mass of each substance before participating in the reaction is equal to the total mass of each substance generated after the reaction.This law is called law of conservation of mass.In any isolated system, no matter what changes or processes occur, the total mass remains unchanged.In other words, any change, including chemical reaction and nuclear reaction, can not eliminate substances, but only change the original form or structure of substances, so this law is also calledLaw of indestructibility of matter。Later, it evolved into one of the basic laws commonly existing in nature.
The process of chemical reaction is the process in which the atoms of various substances (reactants) participating in the reaction recombine to form other substances.In the chemical reaction, the type, number and mass of atoms have not changed before and after the reaction.
Dr. Einstein has a formula: energy=mass × speed of lighttwo。Here, the mass is completely destroyed and transformed into energy.Can we say that when we open the time tunnel, our space will exchange material energy with another space. If a person passes through the time tunnel to another space, the other space will throw a lot of energy into this space.
Simple solution of the law of conservation of mass
One of the fundamental laws of nature.In any material system (isolated system) isolated from the surroundings, no matter what changes or processes occur, its total mass remains unchanged.In the 18th century, after French chemist Lavoisier experimentally overturned the phlogiston theory, this law was recognized.Since the beginning of the 20th century, it has been found that the mass of high-speed moving objects changes with their speed, and that objects and fields can be transformed each other, so the mass of fields should be considered according to the mass energy relationship.The development of the concept of mass has led to new development of the principle of mass conservation. The two laws of mass conservation and energy conservation are combined into a conservation law through the mass energy relationship, that is, the law of mass and energy conservation.(short forLaw of conservation of mass and energy）
Law of conservation of mass
Announce
edit
concept
The law of conservation of mass means that the change in the mass of a system is always equal to the difference between the input and output mass of the system.The law of conservation of mass is one of the fundamental laws universally existing in nature.It shows that the mass will not be created or destroyed, but will only be transferred from one substance to another, and the total amount will remain unchanged.
specific
The law of conservation of mass includes——
Mass conservation of physical change
In physical changes, no matter how the shape, state and position of the object change, the mass contained remains unchanged;When an object is divided into several parts, the sum of the masses of each part is equal to the mass of the original object.When the object accelerates or decelerates, the dynamic mass will change, but the static mass will remain constant.
Mass conservation of chemical reaction
Since there is no atomic change in chemical reaction, the mass is always conserved (whether it is dynamic or static mass).The conservation of mass in chemical reaction includes the conservation of atom, charge and element.
Mass conservation of nuclear reaction
The nuclear reaction has atomic changes, so the static mass is nonconservative, with mass loss, and obeys the mass energy equation, which is also the theoretical principle of nuclear weapons.However, in the theory of relativity, the dynamic mass of nuclear reactions is also conserved.
explain
Announce
edit
stayChemical reaction processThe type of atoms has not changed before and after the reaction,atomThe number of atoms did not increase or decrease, nor did the mass of atoms change.Therefore, the total mass of each substance before and after the chemical reaction must be equal.
① "Certain invariance" in chemical change: the atomic type, atomic number, atomic mass, element type, element mass and the total mass of each substance before and after reaction must remain unchanged;
② "Certain change" in chemical change: the molecular type and material type must change;
③ "Possible change" in chemical change: the number of molecules may change, and the valence of elements may change.
verification
Announce
edit
At the beginning of the 20th century, German and British chemists carried out experiments with high accuracy to obtain more accurate experimental results. The mass change before and after the reaction was less than 1/10 million, which was within the allowable range of experimental error. Therefore, the law of mass conservation was based on rigorous scientific experiments.The law of conservation of mass is the total mass of all substances participating in the chemical reaction, which is equal to the total mass of all substances generated after the reaction.For example, putNailsPut onCopper sulfate solutionIn (blue), when the reaction is over (there will be obvious reaction phenomenon), the mass of the remaining material will be strictly equal to the sum of the mass of the iron nail and the mass of the copper sulfate solution.Experiments show that the mass of the object hasInvariance。No matter how divided or dissolved, the quality remains unchanged.The mass remains unchanged in any chemical reaction.The sum of the mass of carbon before combustion and the mass of oxygen consumed in the air during combustion is exactly equal to the mass of substances generated after combustion.
Scheme I: with fine sand at the bottomConical flaskMouth, put a match bigWhite phosphorus。Install a glass tube on the rubber stopper of the conical bottle mouth, fasten a small balloon on its upper end, and make the lower end of the glass tube contact with white phosphorus.Place the conical flask and glass tubeTray balanceUpper useWeightsBalance.Then, remove the conical flask.Place the glass tube on the rubber stopAlcohol lampAfter the flame burns to red heat, quickly plug the conical flask with a rubber stopper and ignite it with white phosphorus.After the conical flask cools down, put it on the tray balance again and observe whether the balance is balanced.
The experimental phenomenon is that white phosphorus burns and emits yellow light, and produces a large amount of white smoke and heat, and the balance is balanced.This is related tophosphorusSame combustion.
matters needing attention
1. Use of white phosphorus and its precautions: white phosphorus is a highly toxic substance that is prone to spontaneous combustion. It is usually stored in water, and white phosphorus cutting is also carried out in water.To take white phosphorus, tweezers should be used instead of hands. The water on the surface can be sucked up with filter paper. There are often phosphorus particles on the things that have been touched, and they cannot be placed randomly. The white phosphorus particles and filter paper that have absorbed the water on the surface of white phosphorus must be burned to ensure safety.
2. Function of balloon: the purpose of tying balloon is to prevent the bottle stopper from being flushed out due to the combustion of white phosphorus and the release of a large amount of heat due to gas expansion.When the gas in the bottle expands, the balloon is blown up. When it cools, the balloon retracts into the bottle for protection.
3. Error analysis: when igniting white phosphorus, it is necessary to take out the glass tube on the rubber stopper, burn it on the alcohol lamp flame until it is red hot, and then use the rubber stopper to tightly plug the conical flask. This operation will cause the imbalance of the tray balance during the experiment due to the expansion of the air in the conical flask due to heat and the escape of white smoke generated by the combustion of white phosphorus.
Scheme II: Add 30mL dilute solution into 100mL beakercopper sulphateSolution, usingSandpaperGrind several iron nails clean, put the beaker containing copper sulfate solution and iron nails together on the tray balance for weighing, and record the weighed mass mone。
Immerse iron nails in copper sulfate solution and observe the experimental phenomenon.When the color of solution changes after reaction for a period of time, put the beaker containing copper sulfate solution and iron nails on the tray balance to weigh, and record the weighed mass mtwo。Compare the quality before and after reaction.The law of conservation of mass, that is, in a chemical reaction, the sum of all substances participating in the reaction is equal to the sum of all substances generated after the reaction.Micro explanation: before and after the chemical reaction, the type, number and mass of atoms remain unchanged.
Range
Announce
edit
① The law of conservation of mass is applicable to all chemical changes, including most physical changes;
② The law of conservation of mass reveals the conservation of mass rather than other aspects.The volume of the object is not necessarily conserved;
③ In the law of conservation of mass, "what participates in the reaction" is not the simple addition of the mass of each substance, but the part of the mass that actually participates in the reaction, and some of the reactants may not participate in the reaction;
④ Deduction of the law of conservation of mass: in chemical reaction, the total mass of each substance before reaction is equal to the total mass of each substance after reaction.
development
Announce
edit
In 1756, Russian chemist Lomonosov puttinWhen calcined in a closed container, the tin changes to whiteTin oxideHowever, the total mass of the container and the substance in the container has not changed before and after calcination.After repeated experiments, the same results were obtained, so he thought that the mass of matter was conserved in chemical changes.But this discovery did not attract scientists' attention at that time. It was not until French Lavoisier did the same experiment in 1777 and got the same conclusion that this law was recognized.However, to accurately prove or deny this conclusion, extremely accurate experimental results are required, and the tools and technologies of the Lavoisier era (less than 0.2% of the mass change can not be detected) can meet the strict requirements.Because this is the most basic problem, some people constantly improve the experimental technology to solve it.In 1908, the German chemist Landolt and the British chemist Manley conducted experiments with extremely high accuracy. The container and reactant used were about 1000g in mass, the difference between the mass before and after the reaction was less than 0.0001g, and the change in mass was less than 1/10 million.This difference is within the experimental error range, so scientists unanimously recognized this law.
Since there is no atomic change in chemical reaction, the mass is always conserved (whetherDynamic massstillStatic mass）。according toDaltonOfAtomismThe chemical reaction is just the rearrangement of atoms in the substance. The type and number of atoms before and after the reaction remain unchanged, and each atom has a fixed mass, so the total mass before and after the reaction remains unchanged.Specifically, the number of elements in a substance in a chemical reaction is the same whether before or after the reaction.Mass conservation in chemical reaction includes atomic conservationCharge conservation、Conservation of elementsAnd so on.
In any isolated material system（Isolated system）It is one of the fundamental laws of nature that the total mass remains unchanged regardless of any change or process.In the 18th century, French chemist Lavoisier overthrew experimentallyPhlogiston theoryAfter that, this law was recognized.Since the beginning of the 20th century, it has been found that the mass of high-speed moving objects changes with their speed, and that objects and fields can be transformed into each other, so we shouldMass energy relationConsider the mass of the field.The development of the concept of mass has also led to the new development of the principle of mass conservation. The two laws of mass conservation and energy conservation are combined into a conservation law through the mass energy relationship, that is, the law of mass and energy conservation (in physics).
application area
Announce
edit
Physical applications
In physics, mass conservation is mainly used to solve thermal problems and function conversion,
Chemical application
In chemistry, the conservation of mass is mainly used to balance the equation and calculate the quantity of chemical elements, which mainly follows the following rules.
Six unchanged:
Macro: 1. The total mass of the substance before and after the reaction remains unchanged;2. The types of elements remain unchanged;3. The total mass of corresponding atoms of each element remains unchanged;
Microscopy: 4. The type of atom remains unchanged;5. The number of atoms remains unchanged;6. The mass of the atom remains unchanged.
Two definite changes:
Macroscopic: change of substance type.
Microscopy: the particle composition of matter must change.
Two possible changes:
Macro: The chemical valence of elements may change.
Microscopic: The total number of molecules may change.
Comprehensive application
(1) According to the law of conservation of mass: the types and numbers of elements before and after chemical reaction are equalreactantorProductOfchemical formula。
(2) The mass of a reactant or product is known according toChemical equationThe mass ratio of various substances in can be used to calculate the mass of products or reactants.
Application examples
Comprehensive application of mass conservation law and chemical equation:
(1) According to the law of conservation of mass, the total mass of the substances participating in the chemical reaction is equal to the total mass of the substances generated after the reaction.This law can be used to explain the mass change of substances before and after the reaction and to determine the mass of a reactant or product by using the mass difference.
(2) According to the law of conservation of mass, the type and mass of elements before and after chemical reaction remain unchanged, from which the constituent elements of reactants or products can be inferred.
(3) According to the law of conservation of mass: the types of elements before and after the chemical reaction are equal to the number of atoms, the chemical formula of reactants or products is deduced.
(4) Given the mass of a reactant or product, the mass of the product or product can be calculated according to the mass ratio of each substance in the chemical equation[1]。
influence
Announce
edit
sinceEinstein(Einstein) proposedSpecial relativityAnd mass energy relation formulaE=mc²Later, it shows that the substance can be transformed intoradiant energyRadiant energy can be transformed into matter.How does this conclusion affect the application of the law of conservation of mass in chemistry?The experimental results show that 1000gNitroglycerinThe energy released after explosion is 8.0 × 10sixJ。According to the formula of mass energy relationship, the mass generating these energies is 8.9 × 10-8g，Compared with the original 1000g, the difference is too small to be measured by experimental technology.From a practical point of view, the law of conservation of mass is completely correct.
Since the 20th century, people have found thatNuclear fissionThe energy produced far exceeds the most violent chemical reaction.1000gUranium 235As a result of fission, the released energy is 8.23 × 10sixteenJ，The mass equivalent to these radiant energies is 0.914g, and the mass change has reached one thousandth compared with the original 1000g.So people have a new understanding of the law of conservation of mass.Before the 20th century, scientists recognized two independent basic laws: the law of conservation of mass and the law of conservation of energy.Scientists combine these two laws into one and call it the law of conservation of mass and energy.
1756 Russian M5. Romonosov first measured the mass relationship of the substances in the chemical reaction, burning tin in a closed container, and the mass did not change before and after the reaction, so he came to the conclusion that "the mass of all substances participating in the reaction is often equal to the mass of all reaction products." In 1774, A-50. Lavoisier repeated similar experiments and reached the same conclusion.
Since the scales used in the times of Romonosov and Lavoisi were not precise enough, many scientists later proved this law with more accurate methods.For example, in the middle of the 19th century, Belgian analytical chemist J-S.StahlusesilverandiodinepreparationSilver iodideThe difference between the quality of silver iodide and the total quality of iodine and silver is only 0.002%.At the end of the 19th century, H.H. Landolt once again proved the correctness of this law with a very precise balance.
In the 20th century, Einstein deduced the special theory of relativity. He pointed out that the mass of matter is proportional to its energy, which can be expressed by the formula:E=mc²，WhereEIs energy,mIs the mass, speed of lightc=299792.458km/s (generally 300000km/s).It shows that matter can be transformed into radiant energy, and radiant energy can also be transformed into matter.This phenomenon does not mean that matter will be destroyed, but that the static mass of matter will be transformed into another form of motion.(The law of conservation and the law of conservation of energy are collectively called the law of conservation of mass and energy.
Discoverer
Announce
edit
Khair Vasilievich Romonosov (1711.11.19-1765.4.15), a Russian encyclopedic scientist, linguist, philosopher and poet, is known as Peter the Great in the history of Russian science.The rudiment of "the law of conservation of mass" (the law of indestructibility of matter) is proposed.Romonosov was born into a fisherman's family in Arkhangelsk. Romonosov is the first academician of the Russian Academy of Sciences. He is also an academician of the Swedish Academy of Sciences and the Italian Academy of Sciences in Bologna.He founded Russia's first chemical laboratory and the first university, Moscow Romonosov State University.
