The essence of the chemical reaction. The law of conservation of mass substances (chemistry)

Chemistry is the science of substances, their structure, properties and their transformation, resulting from chemical reactions, in the foundation of which chemical laws are laid. All general chemistry is based on 4 basic laws, many of which were discovered by Russian scientists. But in this article we will talk about the law of conservation of the mass of substances, which is part of the basic laws of chemistry.

The law of conservation of mass of matter will be considered in detail. The article will describe the history of the discovery of the law, its essence and components.

The law of conservation of mass of matter (chemistry): formulation

The mass of substances entering into a chemical reaction is equal to the mass of the substances formed as a result of it.

But back to history. More than 20 centuries ago, the ancient Greek philosopher Democritus suggested that all matter is an invisible particle. веке химик английского происхождения Роберт Бойль выдвинул теорию: вся материя построена из мельчайших частиц вещества. And only in the XVII century, a chemist of English origin Robert Boyle put forward a theory: all matter is built of the smallest particles of matter. Boyle conducted experiments with metal, heating it on fire. He weighed the vessels before heating and after and noticed that the weight increased. Burning the same wood gave the opposite effect - ash weighed less wood.

New story

The law of conservation of the mass of substances (chemistry) was provided to the scientific association in 1748. MV. Lomonosov, and in 1756 was witnessed by an experimental method. The Russian scientist brought evidence. If we heat sealed capsules with tin and weigh the capsules before heating, and then after, the law of conservation of the mass of matter (chemistry) will be evident. The formulation expressed by the scientist Lomonosov is very similar to the modern one. The Russian naturalist made an undeniable contribution to the development of atomic-molecular learning. He combined the law of conservation of mass substances (chemistry) with the law of conservation of energy. The current teaching has confirmed these beliefs. And only thirty years later, in 1789, the naturalist Lavoisier of France confirmed the theory of Lomonosov. But this was only an assumption. It became law in the twentieth century (the beginning), after 10 years of research by the German scientist G. Landolt.

Examples of experiments

Consider experiments that can confirm the law of conservation of mass substances (chemistry). Examples:

1. Put the red phosphorus in the vessel, cover it tightly with a stopper and weigh it. Heat on low heat. The formation of white smoke (phosphorus oxide) indicates that a chemical reaction has occurred. We weigh again and make sure that the weight of the vessel with the received substance has not changed. The reaction equation is 4P + 3O2 = 2P2O3.
2. We take two vessels of Landolt. In one of them, carefully, in order not to mix, we pour reagents of lead nitrate and potassium iodide. In another vessel we place potassium thiocyanate and ferric chloride. Vessels tightly closed. The scales should be balanced. Mix the contents of each vessel. In one, a yellow precipitate is formed-lead iodide, in the other, ferrous thiocyanate is obtained in a dark red color. With the formation of new substances, the balance retained its balance.
3. We light the candle and put it in a container. Hermetically close this container. We bring the scales into balance. When the air is exhausted in the tank, the candle goes out, the process of chemical reaction is over. The balance will be balanced, so the weight of the reagents and the weight of the substances formed are the same.
4. We will carry out one more experiment and consider, for example, the law of conservation of a mass of substances (chemistry). The formula of calcium chloride is CaCl2, and the sulfate acid is H2SO4. When these substances interact, a white precipitate is formed - calcium sulfate (CaSO4), and hydrochloric acid (HCl). For the experience, we need a balance and a vessel of Landolt. Very carefully pour calcium chloride and sulphate acid into the vessel, without mixing them, tightly close the stopper. Weigh on the scales. Then mix the reagents and observe that a white precipitate is precipitated (calcium sulfate). This indicates that a chemical reaction has occurred. We again weigh the vessel. Weight remained the same. The equation of this reaction will look like this: CaCl2 + H2SO4 = CaSO4 + 2HCl.

Basic

The main goal of the chemical reaction is to destroy molecules in certain substances and subsequently form new molecules of matter. In this case, the number of atoms of each substance before interaction and after remains unchanged. When new substances are formed, energy is released, and when they decay with its absorption, then there is an energy effect that manifests itself in the form of absorption or release of heat. During the chemical reaction, the molecules of the starting materials are reagents, break down into atoms, from which chemical reaction products are then produced. The atoms themselves remain unchanged.

The reaction can last for centuries, and can occur rapidly. In the manufacture of chemical products, one must know the rate of the course of a chemical reaction, with absorption or release of temperature, it passes, what pressure is needed, the number of reagents and catalysts. Catalysts - a small substance by weight, not involved in the chemical reaction, but significantly affecting its speed.

How to make chemical equations

Knowing the law of conservation of the mass of substances (chemistry), one can understand how to formulate chemical equations correctly.

1. It is required to know the formulas of reagents entering into a chemical reaction, and the formulas of the products that resulted in it.
2. On the left, formulas of reagents are written, between which a "+" sign is placed, and on the right - formulas of the resulting products with a "+" sign between them. Between the formulas of the reagents and the resulting products, the symbol "=" or arrow is placed.
3. The number of atoms of all components of the reagents should be equal to the number of product atoms. Therefore, the coefficients that are put before the formulas are calculated.
4. It is forbidden to move formulas from the left side of the equation to the right one or change them by places.

The meaning of the

The law of conservation of a mass of substances (chemistry) has enabled an interesting subject to develop as a science. We will find out why.

• The great importance of the law of conservation of the mass of substances in chemistry is that chemical calculations for industry are made on its basis. Suppose you need to get 9 kg of copper sulphide. We know that the reaction of copper and sulfur occurs in mass ratios of 2: 1. According to this law, with the chemical reaction of copper with a mass of 1 kg and sulfur of 2 kg, copper sulphide with a mass of 3 kg is obtained. Since we need to obtain copper sulphide with a mass of 9 kg, that is, 3 times more, then the reagents will need 3 times more. That is 6 kg of copper and 3 kg of sulfur.
• The ability to make the right chemical equations.

Conclusion

After reading this article, there should not be any questions about the essence of this law of the history of its discovery, to which, by the way, our well-known compatriot, M.V. Lomonosov. Which again confirms how great the strength of the science of science. It also became clear the significance of the discovery of this law and its meaning. And those who did not understand how to make chemical equations in school, after reading the articles should learn or remember how to do it.