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Lesson methods

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Mathematics - plotting graphs, converting formulas, calculations. Interdisciplinary communication Chemistry - electrolytic dissociation, electrolysis

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The main stages of the lesson Organizational moment Updating knowledge. Brainstorming Motivation. Demonstration experience Problem statement Encouraging dialogue. Finding and solving the problem Demonstration experiment. Integration into the field of chemistry. Leading dialogue Systematization and generalization of knowledge Search for information on the Internet Consolidation of knowledge Homework

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Answer the questions Into what groups are all substances divided by the conductivity of electric current? Give examples of the best conductors of electric current. What particles cause current in metals? Does the electrical conductivity of a metal change when it is heated? Will the electrical conductivity of a metal change if it is melted? What liquids do you know that conduct electricity, other than molten metals?

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Questions for research How does the resistance of the electrolyte depend on the temperature, the geometric parameters of the electrolyte? Why does pure water not conduct, but salt solution conducts electricity? What causes electric current in a salt solution?

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Conductive liquids Electrolytes Salt solutions Alkali solutions Acid solutions

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When oppositely charged electrodes are lowered into a solution of copper sulphate, a directed movement of ions occurs. Copper sulfate in an aqueous solution dissociates into copper ions and an acid residue.

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The process of release on the electrodes of the substances that make up the electrolyte, when an electric current flows through its solution (or melt), is called electrolysis Electrolysis has a wide technical application. Where is electrolysis used? This question must be answered using the Internet.

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What determines the mass of the substance released on the electrode? Electrolytic dissociation - the splitting of molecules into positive and negative ions under the action of a solvent. When ions of different signs approach each other, their recombination (combination) into one molecule is possible

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Michael Faraday - the great English scientist, the creator of the general doctrine of electromagnetic phenomena Michael Faraday in 1833 experimentally established the law of electrolysis. He introduced the now generally accepted terms: electrode, cathode, anode, electrolyte, electrolysis.

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Complete test tasks I. Indicate the wrong answer 1. Liquids can be dielectrics, conductors, semiconductors. 2. All fluids are electrolytes. 3. Solutions of salts, alkalis, acids and molten salts with electrical conductivity are called electrolytes. II. Electrolytic dissociation is called... III. Recombination is called ... IV. Electrolysis is called ... 1. the process of separating the substances that make up the electrolyte on the electrodes. 2. association of ions of different signs into neutral molecules. 3. the formation of positive and negative ions during the dissolution of substances in a liquid. V. With an increase in the temperature of the electrolyte, its electrical conductivity ... 1. increases. 2. decreases. 3. does not change.

Electrolytes Conductors of electric current are not only metals and semiconductors. Electric current conduct solutions of many substances in water. As experience shows, pure water does not conduct electric current, that is, there are no free carriers of electric charges in it. Do not conduct electric current and crystals of table salt, sodium chloride. Conductors of electric current are not only metals and semiconductors. Electric current conduct solutions of many substances in water. As experience shows, pure water does not conduct electric current, that is, there are no free carriers of electric charges in it. Do not conduct electric current and crystals of table salt, sodium chloride. However, sodium chloride solution is a good conductor of electric current. However, sodium chloride solution is a good conductor of electric current. Solutions of salts, acids and bases that can conduct electricity are called electrolytes. Solutions of salts, acids and bases that can conduct electricity are called electrolytes.


Electrolysis The passage of an electric current through an electrolyte is necessarily accompanied by the release of a substance in a solid or gaseous state on the surface of the electrodes. The release of matter on the electrodes shows that in electrolytes, electric charges are carried by charged atoms of matter - ions. This process is called electrolysis. The passage of electric current through the electrolyte is necessarily accompanied by the release of a substance in a solid or gaseous state on the surface of the electrodes. The release of matter on the electrodes shows that in electrolytes, electric charges are carried by charged atoms of matter - ions. This process is called electrolysis.


The law of electrolysis Michael Faraday, based on experiments with various electrolytes, found that during electrolysis, the mass m of the substance released on the electrode is proportional to the charge q or current I passed through the electrolyte and the time t of current passage: Michael Faraday, based on experiments with various electrolytes, found that during electrolysis the mass m of the substance released on the electrode is proportional to the charge q passed through the electrolyte or the current strength I and the time t of the current passage: m=kq= kIt. This equation is called the law of electrolysis. The coefficient k, which depends on the released substance, is called the electrochemical equivalent of the substance. This equation is called the law of electrolysis. The coefficient k, which depends on the released substance, is called the electrochemical equivalent of the substance.


Conductivity of electrolytes The conductivity of liquid electrolytes is explained by the fact that when dissolved in water, neutral molecules of salts, acids and bases decompose into negative and positive ions. The conductivity of liquid electrolytes is explained by the fact that when dissolved in water, neutral molecules of salts, acids and bases decompose into negative and positive ions. In an electric field, ions move and create an electric current. In an electric field, ions move and create an electric current.






Aggregate state of electrolytes There are not only liquid, but also solid electrolytes. Glass is an example of a solid electrolyte. Glass contains positive and negative ions. In the solid state, glass does not conduct electricity, since ions cannot move in a solid. There are not only liquid, but also solid electrolytes. Glass is an example of a solid electrolyte. Glass contains positive and negative ions. In the solid state, glass does not conduct electricity, since ions cannot move in a solid. When the glass is heated, the ions get the opportunity to move under the action of an electric field and the glass becomes a conductor. When the glass is heated, the ions get the opportunity to move under the action of an electric field and the glass becomes a conductor.


The use of electrolysis The phenomenon of electrolysis is used in practice to obtain many metals from a solution of salts. The phenomenon of electrolysis is used in practice to obtain many metals from a salt solution. With the help of electrolysis, for protection against oxidation or for decoration, various objects and machine parts are coated with thin layers of metals such as chromium, nickel, silver, gold. With the help of electrolysis, for protection against oxidation or for decoration, various objects and machine parts are coated with thin layers of metals such as chromium, nickel, silver, gold.


According to electrical properties, all liquids can be divided into 2 groups:

LIQUIDS

CONDUCTIVE

NON-CONDUCTIVE

These include distilled water, alcohol, mineral oil

These include solutions (most often aqueous) and melts of salts, acids and bases.


Electrolytic dissociation

Electrolytic dissociation is the breakdown of electrolyte molecules into positive and negative ions.

The degree of dissociation is the proportion of molecules that have decayed into ions in a solute. Depends on:

  • temperature
  • solution concentration
  • electrical properties of the solvent

With increasing temperature, the degree of dissociation increases and, consequently, the concentration of positively and negatively charged ions increases.


Ion recombination

Along with dissociation in the electrolyte, the process of reduction of ions into neutral molecules can occur simultaneously. Ions of different signs, upon meeting, can again unite into neutral molecules - recombine .

Under constant conditions in the solution is established dynamic balance, at which the number of molecules that decay into ions per second is equal to the number of pairs of ions that recombine into neutral molecules in the same time.


Ionic conduction

Charge carriers in aqueous solutions or electrolyte melts are positively and negatively charged ions.

If a vessel with an electrolyte solution is included in an electrical circuit, then negative ions will begin to move towards the positive electrode - the anode, and positive - towards the negative - cathode. As a result, an electric current will be established. Since the charge transfer in aqueous solutions or electrolyte melts is carried out by ions, this conductivity is called ionic .


Electrolysis

With ionic conductivity, the passage of current is associated with the transfer of matter. On the electrodes, substances that make up electrolytes are released. At the anode, negative ions donate their extra electrons (in chemistry, this is called an oxidative reaction), and at the cathode, positive ions receive the missing electrons (reduction reaction). The process of release of a substance at the electrode, associated with redox reactions, is called electrolysis .


Application of electrolysis

Electrolysis is widely used in engineering for various purposes. Electrolytically cover the surface of one metal with a thin layer of another ( nickel plating, chrome plating, copper plating etc.). This durable coating protects the surface from corrosion.

If good peeling of the electrolytic coating is ensured from the surface on which the metal is deposited (this is achieved, for example, by applying graphite to the surface), then a copy can be obtained from the relief surface.

The process of obtaining peelable coatings - electrotype- was developed by the Russian scientist B. S. Jacobi (1801-1874), who in 1836 applied this method to make hollow figures for St. Isaac's Cathedral in St. Petersburg.

Another way to use electrolysis is to obtain pure metal from impurities. Electrolysis is used to make printed circuit boards for various digital devices.


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  • Physics. Grade 10: textbook. for general education institutions: basic and profile. levels / G. Ya. Myakishev, B. B. Bukhovtsev, N. N. Sotsky
  • http://class-fizika.narod.ru/10_12.htm
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  • http://rza.org.ua/glossary/image-246.html(picture)
  • http://www.electrofaq.com/ETMbook/CONDUCT/CON5A.HTM(picture)
  • http://lib.convdocs.org/docs/index-280240.html(picture)