Physics presentation on the topic "electric current in liquids". Presentation on the topic "electric current in liquids" What determines the mass of the substance allocated on the electrode

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

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Conductive liquids Electrolytes Salt solutions Alkali solutions Acid solutions

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When immersed in solution blue vitriol oppositely charged electrodes, 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.

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The purpose of the lesson using the presentation is the formation of the concepts of “electrolytes, electrical dissociation, degree of dissociation”; consideration of the phenomenon of electrolysis, the derivation of Faraday's law; application of electrolysis in engineering.

Lesson topic: “ Electricity in liquids."

The purpose of the lesson:

1. A) Introduce the definition of concepts:

electrolytes;

electrical dissociation;

Degree of dissociation.

B) Consider the phenomenon of electrolysis. Faraday's law.

2. Development of observation, broadening one's horizons.

3. Raising interest in the subject being studied.

Equipment: multimedia projector, computer, interactive board, presentation (Appendix 1).

Type of lesson: lesson learning new material.

During the classes

I. Actualization of knowledge (message of the topic, purpose and objectives of the lesson). (Slide 2, 3)

II. Learning new material.

A) Questions:

1) What bodies are conductors of electric current?

2) What is the conductivity of liquid metals?

In solutions and melts of electrolytes (salts, acids and alkalis), charge transfer under the action of an electric field is carried out by “+” and “-” ions that move in opposite directions.

Electrolytes are substances whose solutions and melts have ionic conductivity. (Slide 4)

Question: Why does a solid polar dielectric become a conductor of electric current when dissolved in water? (Slide 5)

In order to answer this question, consider the process of dissolving CuCl 2 in water.

(Explanation: In such a crystal, + Cu ions and - Cl ions are located at the nodes of a simple cubic lattice.

When a CuCl 2 crystal is immersed in water, the negative OH poles of the water molecules begin to be attracted by the Coulomb forces to the positive Cu ions, and the water molecules turn to the negative Cl ions with their positive pole H.

Overcoming the forces of attraction between Cu + and Cl - ions, the electric field of polar water molecules separates ions from the surface of the crystal)

Conclusion: free carriers appear in the solution - Cu + and Cl -, which are surrounded by polar water molecules.

This phenomenon is called electrical dissociation (from the Latin word - separation). (Slide 6)

electrical dissociation- splitting of electrolyte molecules into positive and negative ions under the action of a solvent.

Question: On what parameters does the solubility of a substance depend? (from temperature)

Degree of dissociation- the ratio of the number of molecules dissociated into ions to the total number of molecules of a given substance.

Recombination- the process of combining ions of different signs into neutral molecules.

B) With ionic conductivity, the passage of current is associated with the transfer of matter. On the electrodes, substances that make up electrolytes are released. (Slide 7)

When an external electric field is created in the electrolyte, a directed movement of ions occurs. Copper chloride in aqueous solution dissociates into copper and chloride ions.

“+” copper ions (cations) are attracted to the “-” electrode (cathode), and “-” chlorine ions (anions) are attracted to the “+” electrode (anode).

Having reached the cathode, copper ions are neutralized by excess electrons that are on the cathode - as a result, neutral copper atoms are formed, which are deposited on the cathode.

Chlorine ions give off one excess electron at the anode, turning into neutral chlorine atoms, combining in pairs chlorine atoms form a chlorine molecule, which are released at the anode in the form of gas bubbles.

The process of release of a substance on the electrodes associated with a redox reaction - called electrolysis. (Slide 8)

(The phenomenon of electrolysis was discovered in 1800 by the English physicists W. Nichols and A. Carlyle)

What determines the mass of the substance released on the electrodes in a certain time?

The law of electrolysis (Faraday's law). (Slide 9). (Student's message)

Research in the field of electricity, magnetism, magnetooptics, electrochemistry. discovered the phenomenon of electromagnetic induction and established its laws. Experiments on the passage of current through solutions of acids, salts and alkalis were the result of the discovery of the laws of electrolysis (Faraday's laws). Introduced the concept of a field and used the term "magnetic field". For the first time he received chlorine in a liquid state, then hydrogen sulfide, carbon dioxide, ammonia and nitrogen dioxide. . He laid the foundation for research on natural rubber. He showed the possibility of photochemical chlorination of ethylene. Introduced the concept of dielectric permittivity. Faraday's name entered the system of electrical units as a unit of electrical capacitance.

Questions? (Slide 10)

1. How to find the mass of the substance released on the electrodes?

2. How to find the mass of one ion?

3. How to find the number of ions?

4. How to find the charge of one ion? (n - valency)

The mass of the substance released on the electrode during the passage of an electric current is directly proportional to the current strength and time. (This statement was received in 1833 by the English physicist Michael Faraday and is called Faraday's law).

K is the electrochemical equivalent of a substance (depends on the molar mass of the substance “M” and valence “n”)

Phys. the meaning of k is numerically equal to the mass of the substance released on the electrode when a charge of 1 C passes through the electrolyte.

N a *e=F is the Faraday constant. (Slide 12)

The physical meaning of F is numerically equal to the charge that must be passed through the electrolyte solution in order to isolate 1 mol of a monovalent substance on the electrode.

IN) The use of electrolysis in technology (student's communication). (Slide 13)

1. Electroplating - decorative or anti-corrosion coating metal products a thin layer of another metal (nickel plating, chromium plating, copper plating, gilding).
2. Galvanoplasty - electrolytic production of metal copies, embossed objects. In this way, figures were made for St. Isaac's Cathedral in St. Petersburg.
3. Electrometallurgy-obtaining pure metals in the electrolysis of molten ores (Al, Na, Mg, Be).
4. Refining of metals - purification of metals from impurities. (Slide 14-17)

G) Behavior of the lesson.

1. What substances are called electrolytes?

2. Define:

electrical dissociation;

degree of dissociation;

recombination.

3. What process is called electrolysis? Who opened it and when?

4. Formulate Faraday's law?

5. Physical meaning of the electrochemical equivalent of matter and Faraday's constant.

Homework: §§ 122-123, ex. 20 (4, 5). (Slide 18)

Bibliography

1. Educational electronic edition“Interactive physics course for grades 7-11”, “Physicon”, 2004

2. “Open Physics 1.1”, LLC “Physicon”, 1996-2001, edited by MIPT Professor S.M. Cosell.

3. “Library of electronic visual aids. Physics grades 7-11”, GU RC EMTO, “Cyril and Methodius”, 2003

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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 electricity and crystals 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 a substance on the electrodes shows that in electrolytes electric charges carry charged atoms of a substance - 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 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. Various objects and machine parts are coated with electrolysis for protection against oxidation or for decoration. thin layers 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.