Option 1. Equipment: A test tube with water and an alcohol lamp.
To demonstrate the poor thermal conductivity of the liquid, water is poured into a test tube ¾ of its volume. Holding the test tube in your hands at a slight angle over the flame of the spirit lamp, heat the water at the open end (Fig. 130). They show that the water here quickly boils, but at the bottom of the large heating is not felt.
Rice. 130 Fig. 2.105 Fig. 131
Option 1... Equipment: two test tubes, two stoppers, two rods, two balls, spirit lamp, tripod, suspension.
Poor thermal conductivity of air is demonstrated using two identical test tubes, closed with stoppers, through which short rods are passed. Steel balls are attached to the ends of the rods with plasticine or paraffin (Fig. 131). The test tubes above the spirit lamp are placed so that convection occurs in one of them, and the thermal conductivity of air in the other. Notice that in one test tube, the ball quickly falls off the rod.
Option 2. See fig. 2.105
Option 1. Equipment: device for demonstrating convection of liquid, potassium permanganate, spirit lamp, tripod.
The device, which is a closed glass tube (Fig. 132), is fixed in the tripod leg. (It is better to hang up than to clamp the tube at the bottom, because in the latter case, the glass is more likely to break.) The tube is filled with water through the upper opening of either elbow so that there are no air bubbles along the entire closed path inside the tube.
When performing the experiment, crystals of potassium permanganate are placed in a spoon with a grid and lowered into the knee (you can simultaneously lower two spoons with crystals of potassium permanganate in both knees). Then an alcohol lamp is brought to the bottom of this knee and convection is observed.
Rice. 132 Fig. 133
Option 1. Equipment: spirit lamp, matches, kite, metal point.
To demonstrate the convection of gas, a paper snake is made, which rotates in a stream of rising hot air coming from an alcohol lamp or an electric stove (Fig. 133). (When installing the snake on the tip, do not pierce the paper.)
Option 1. Equipment: heat sink, open demonstration manometer, table lamp (or electric stove).
The heat receiver, connected by a tube with a demonstration pressure gauge (see Fig. 123), is fixed in a tripod opposite the emitter. As a radiating body, you can take an electric stove, a vessel with hot water, etc. A heat collector is brought to it from the side with the dark side and the readings of the manometer are monitored for 1-2 minutes.
Then the heat receiver is turned with a shiny surface to the lamp located at the same distance from the heat receiver, and during the same time the manometer reading is monitored. Make a conclusion.
In the second series of experiments, the incandescence of the lamp (or the distance to the radiator) is reduced and the change in the manometer readings is observed again under the same conditions. Make a conclusion.
Option 2. See Fig. 2.99; 2.101.
Question. In which case, the change in the readings of the liquid pressure gauge
faster if the heat exchanger and heat sink are facing each other with shiny surfaces or if they are facing each other with blackened surfaces?
Rice. 123 Fig. 2.101 Fig. 2.99
This lesson discusses the concept of thermal conductivity.
Thermal conductivity is one of the types of heat transfer and is associated with the transfer of internal energy from more heated parts of the body (bodies) to less heated ones, which is carried out by chaotically moving body particles.
Each of us encounters thermal conductivity when inadvertently grasps the iron handle of a frying pan on the stove. Poor thermal conductivity of the air makes it possible to insulate the apartment for the winter with the help of double frames. And there are many such examples. Therefore, thermal conductivity is one of the most important physical thermal phenomena that we will study.
In the last lesson, we found out that heat transfer (Fig. 1) is of three types: thermal conductivity, convection and radiation(fig. 2). In this lesson, we will take a closer look at the first type of heat transfer, namely thermal conductivity.
Rice. 1. Heat transfer
Rice. 2 Types of heat transfer
Thermal conductivity is characteristic of substances in all three states of aggregation: solid, liquid and gaseous (Fig. 3).
Rice. 3. Thermal conductivity is inherent in all states of aggregation
In this case, solids (metals) have the highest thermal conductivity (Fig. 4a), and the lowest - gases (Fig. 4b).
Rice. 4 Coefficients of thermal conductivity of various substances
Thermal conductivity is associated with the internal structure of bodies and depends on the arrangement of molecules, their movement and interaction with each other (Fig. 5).
Rice. 5. Connection of thermal conductivity with the internal structure of bodies
It is important to note that with heat conduction, no matter is transferred, but energy is transferred from particle to particle or from one body to another during their direct contact. Let us formulate, in fact, the definition of thermal conductivity.
Definition.Thermal conductivity is a phenomenon in which energy is transferred from one part of the body to another through the collision of particles or through direct contact of two bodies.
Rice. 6. Illustration of the definition of thermal conductivity
Studies of this phenomenon were carried out mainly empirically. The first experiments to study this phenomenon were apparently carried out by Galileo Galilei (Fig. 7).
Rice. 7. Galileo Galilei (1564-1642)
The essence of his experiments was simple: Galileo placed various bodies near his thermoscope (Fig. 8) and observed the change in temperature. Subsequently, he drew conclusions: whether the body conducts heat well or not.
Fig 8. Galileo's thermoscope
Definition.Heat conduction process- This is the process of transferring energy from one particle to another located in close proximity to each other (Fig. 9).
Rice. 9. Thermal conduction process
In metals, thermal conductivity is higher, since the particles are located close to each other (Fig. 10).
Rice. 10. Thermal conductivity in metals
In liquids, the molecules, although closely spaced, are quite well isolated (Fig. 11).
Rice. 11. Thermal conductivity in liquids
Gases have the lowest thermal conductivity: molecules are located far from each other, and in order to transfer energy, they need to collide, so the process of energy transfer is rather slow (Fig. 12).
Rice. 12. Thermal conductivity in gases
Consider an experiment that clearly demonstrates the thermal conductivity of metals.
An aluminum rod is horizontally fixed to the tripod. Wooden toothpicks are vertically fixed on the rod at regular intervals with the help of wax. A candle is brought to the edge of the rod (Fig. 13).
Since the edge of the rod heats up, and aluminum, like any other metals, has a fairly good thermal conductivity, the rod gradually heats up. When the heat reaches the point where the toothpick is attached to the rod, the stearin melts - and the toothpick falls off.
Rice. 13. Demonstration of experience
We see that in this experiment there is no transfer of matter, therefore, thermal conductivity is observed.
We have considered the phenomenon of thermal conductivity, and in conclusion I would like to recall an important fact: there are no particles - there is no thermal conductivity.
In the next lesson, we will take a closer look at another type of heat transfer - convection.
Bibliography
Homework
When studying natural sciences in a modern school, the clarity of the educational material is of great importance. Visibility makes it possible to quickly and deeper assimilate the topic being studied, helps to understand difficult issues, and increases interest in the subject. Digital laboratories are new, modern equipment for carrying out a variety of school research in the natural sciences. With their help, you can carry out work, both included in the school curriculum, and completely new research. The use of laboratories significantly increases visibility, both in the course of the work itself and in the processing of results thanks to the new measuring instruments included in the physics laboratory kit (sensors of force, distance, pressure, temperature, current, voltage, illumination, sound, magnetic field, etc.) ). The equipment of the digital laboratory is universal, it can be included in a variety of experimental installations, save time for students and teachers, encourages students to be creative, making it possible to easily change measurement parameters. In addition, the video analysis program allows you to obtain data from video fragments, which allows you to use as examples and quantitatively explore real life situations filmed by the students themselves and fragments of educational and popular videos.
To use the preview of presentations, create yourself a Google account (account) and log into it: https://accounts.google.com
The only path leading to knowledge is activity. Bernard Show.
Methodological development of a demonstration experiment on the subject of physics "The amount of heat and heat capacity"
The purpose of this development: to show the possibilities of using the "Digital Laboratory" in the educational process. Show the possibility of measuring the specific heat of a substance
This development can be used when explaining new material, during laboratory work, for conducting classes outside of school hours.
Composition of the digital laboratory TriLink measuring interface Digital sensors for physics
Hardware screen and multimedia projector tripods (2 pcs.) Test tubes (2 pcs.) Water, alcohol temperature sensor 0-100 ° C (2 pcs.) Metal cylinders (2 pcs.) Spirit lamps (2 pcs.) Beaker calorimeter hot water
Experience: Difference in heat capacity of water and alcohol Heating two cylinders in boiling water, one cylinder is lowered with a melting spoon into a test tube with water, and the second into a test tube with alcohol at room temperature. After lowering the cylinders into the test tubes, it is required, holding the top of the test tube, to quickly insert the sensor, fix the sensor body on a steel sheet and start stirring the liquid in the test tube by rotating the test tube around the sensor.
We are at work
Using the digital lab in physics lessons
Thank you for your attention!!!
MUNICIPAL BUDGETARY EDUCATIONAL INSTITUTION
SECONDARY EDUCATIONAL SCHOOL №7 PORONAYSKA
Methodical development of a demonstration experiment
on the subject of physics
"The amount of heat and heat capacity"
For students in grade 8
MBOU Secondary School No. 7, Poronaysk
Poronaysk
2014
1. Introduction
2.The main part
3. Conclusion
4. Technical support
1. Introduction
I have been teaching physics in grades 7-11 of the Poronaysk secondary school since 1994. To instill interest in my subject, I believe a demonstration experiment is necessary, which is an integral organic part of high school physics.
Demonstration experiments form previously accumulated preliminary ideas, which by the beginning of the study of physics are not correct for everyone. Throughout the course of physics, these experiments replenish and broaden the horizons of students. They give rise to correct initial ideas about new physical phenomena and processes, reveal patterns, introduce research methods, show the structure and operation of new devices and installations. The demonstration experiment serves as a source of knowledge, develops the skills and abilities of students.
The experiment is of particular importance in the early stages of education, that is, in grades 7-8, when students first begin to study physics. I think it's better to see once than hear a hundred times.
2.The main part
The purpose of this development: to show the possibilities of using the "Digital Laboratory" in the educational process. Consider the use of the laboratory "Archimedes" in the study of the topic "Thermal phenomena" in grade 8:
Demonstration. Heat quantity and heat capacity
Demonstration purposeshow the possibility of measuring the specific heat of a substance
During the demonstration, the elements of knowledge "amount of heat", "specific heat capacity of a substance" are introduced. For the formation of ideas about the specific heat capacity as a physical quantity that can be measured, it is proposed to carry out a number of simple experiments.
Before conducting a series of experiments on the concept of heat capacity, students are encouraged to talk about the history of the introduction of the concept of “heat capacity of a body” at a time when “amount of heat” was perceived as the amount of invisible and weightless liquid “caloric”, and temperature was a measure of the level of liquid in the body. The "heat capacity of a body" was considered a coefficient of proportionality between the temperature and the amount of "caloric" flowing in the body. The greater the capacity of the vessel, the less the change in the liquid poured in it, the greater the heat capacity of the body - the less the change in the temperature level in it.
However, it turned out that with the same mass of bodies from different substances, with the same amount of heat received from another body, their temperature changes in different ways. Therefore, the concept of specific heat capacity of a substance was introduced, and the "heat capacity of a body" was calculated as the product of body mass by the specific heat capacity of the substance from which it is made.
According to modern concepts, the amount of heat Q is the change in the internal energy of the body in conditions when the body does not perform work. Heat capacity C is the coefficient of proportionality between the amount of heat received or given away by the body and the change in its temperature.
To estimate the heat capacity of a substance in comparison with another (water), the same amount of energy is given to the same mass of a substance (water and alcohol) and the temperature change that was caused by the addition of this energy is recorded.
Experience: Difference in heat capacity of water and alcohol
The conclusion that the heat capacity of water is greater than the heat capacity of alcohol can be made by showing that obtaining the same amount of heat heats alcohol by a greater number of degrees.
Heating two cylinders in boiling water, one bar is lowered with a melting spoon into a test tube with water, and the other into a test tube with alcohol at room temperature.
After putting the cylinders into the test tubes, it is required, holding the top of the test tube, to quickly insert the sensor, fix the sensor body on a steel sheet and start stirring the liquid in the test tube by rotating the test tube around the sensor. The graph shows a drop in the temperature of the sensor below room temperature due to the evaporation of the liquid at the tip of the sensor, then a surge to a maximum value due to heating of the water and the sensor's sensitive element near the hot cylinder, and then reaching a stationary value due to stirring of the liquid in the test tube. As you can see, the observed change in temperature does not reach the required difference corresponding to the difference in heat capacities (by about a factor of 2).
To approach the required values, it is recommended to conduct an experiment with cylinders heated to a temperature not higher than 80 0 C, since alcohol boils at 87 0 C. The exact numerical value of the initial temperature of the cylinders is unimportant, as long as it is approximately the same.
3. Conclusion
4. Technical support
screen and multimedia projector
5.List of used literature
Sections: Physics
The purpose of the work is a generalization of experimental tasks carried out by 8th grade students at home when studying various types of heat transfer.
Tasks:
I. Experiments on thermal conductivity.
In order to better understand the essence of the phenomenon of thermal conductivity, it is necessary to explain the following phenomena:
a) Why do metal objects seem colder than wood at the same temperature?
Answer: Wood has poor thermal conductivity, so when we touch a wooden object, only a small part of the body at hand heats up. Metal, on the other hand, has good thermal conductivity, so a much larger area heats up on contact with the hand. This results in more heat dissipation from the hand and cooling.
b) Why are the handles of taps and hot water tanks made of wood or plastic?
Answer: wood and plastic have poor thermal conductivity.
v) Does ordinary or porous bricks provide better thermal insulation for the building?
Answer: Porous bricks contain air in their pores, which has poor thermal conductivity, therefore, it provides better thermal insulation for the building.
G) is air used as a building material?
Answer: Yes, it is used, because foam materials, porous bricks, glass wool contain air that has poor thermal conductivity.
e) depending on the volume of the foam pores, its density is different. Does the thermal conductivity of the foam depend on its density?
Answer: The lower the density of the foam, the more pores that air, which has poor thermal conductivity, occupies. Consequently, the lower the density of the foam, the lower its thermal conductivity.
g) Why insert double frames?
h) Why do birds often freeze on the fly?
Answer: In frost, the birds sit huddled up, which creates an air shell around their body. During flight, the air from the bird's body changes all the time, taking away heat.
II. Convection experiments.
In addition to these experimental tasks, the following questions were answered:
a) Why does it blow from a tightly closed window in cold weather?
Answer: Glass has a lower temperature than the room temperature. The air near the glass cools down and sinks down as denser, then heats up near the battery and moves around the room again. This movement of air is felt near the window.
b) where is it better to provide for the location of the window?
Answer: it is better to place the window in the upper part of the window. Warm air is lighter, it is located in the upper part of the room, it will be replaced by colder air from the street. With this arrangement of the vents, the room will be ventilated more quickly.
v) when is the draft in the pipe better - in winter or in summer?
Answer: the draft will be better in winter, when the difference between the temperature of the air heated in the pipe and the outside will be greater, then the pressure difference at the top and bottom of the pipe will be more significant.
G) What role does convection play in heating water in a kettle?
Answer: heated layers of water, as lighter ones, rise up, giving way to cold ones. Thus, due to the movement of convection flows, all the water in the kettle is heated.
e) Why does the lampshade or ceiling turn black above the incandescent lamps?
Answer: Convection air currents rise from incandescent lamps, carrying away dust particles, which then settle on the lampshade or ceiling.
e) Why do aspen leaves sway even in calm weather?
Answer: Compared to other trees, aspen leaves are long and thin cuttings. There are vertical convection currents above the ground even in calm weather. Due to its structure, aspen leaves are sensitive to any, even minor, fluctuations in the air.
g) Can you save ice cream with a fan?
Answer: No, you can't, because the air flow coming from the fan will constantly carry away the cold air that forms around the ice cream, thereby speeding up the air exchange process, and the ice cream will melt faster.
h) what natural phenomena occur due to convection?
Answer: winds blowing in the earth's atmosphere; the existence of warm and cold sea currents, mountain building processes.
III. Radiation experiments.
To understand this phenomenon, the following questions were answered:
a) Why does the snow melt faster in the city than outside the city?
Answer: snow in the city is dirtier, so it absorbs energy better and melts
b) in which of the two vessels will water boil faster in light or smoked?
Answer: Smoked, because this surface will better absorb energy.
v) Why is the thermos flask made mirrored?
Answer: to exclude heating by radiant energy.
IV. Helpful hints.
Conclusion.
The phenomena that we constantly encounter in everyday life were studied not only in the classroom, but also at home, where students could demonstrate them to their parents. These experiments, questions helped to better understand the topic "Types of heat transfer". Analysis of the results allowed us to offer "Useful Advice" It should be noted that all experimental work must be carried out very carefully, in compliance with safety measures.
Literature.
The text of the work is placed without images and formulas.
The full version of the work is available in the "Work files" tab in PDF format
1. Introduction.
The project was developed in accordance with the standard of secondary general education in physics. When writing this project, the study of thermal phenomena, their use in everyday life and technology were considered. In addition to theoretical material, much attention is paid to research work - these are experiments that answer the questions "In what ways can the internal energy of the body be changed?" the surface heats up more ”; search and processing of information, photographs. Time of work on the project: 1 - 1.5 months. Project objectives: * practical implementation of the knowledge of heat phenomena available to schoolchildren; * formation of skills for independent research activities; * development of cognitive interests; * development of logical and technical thinking ; * development of abilities for independent acquisition of new knowledge in physics in accordance with vital needs and interests;
2. The main part.
2.1. Theoretical part
In life, we really encounter thermal phenomena on a daily basis. However, we do not always think that these phenomena can be explained if we know physics well. In physics lessons, we got acquainted with the ways of changing internal energy: heat transfer and performing work on the body or the body itself. When two bodies with different temperatures come into contact, energy is transferred from a body with a higher temperature to a body with a lower temperature. This process will continue until the temperatures of the bodies equalize (thermal equilibrium occurs). In this case, no mechanical work is performed. The process of changing internal energy without doing work on the body or on the body itself is called heat transfer or heat transfer. With heat transfer, energy is always transferred from a warmer body to a less heated one. The reverse process never occurs spontaneously (by itself), i.e. heat exchange is irreversible. Heat transfer determines or accompanies many processes in nature: the evolution of stars and planets, meteorological processes on the Earth's surface, etc. Types of heat transfer: heat conduction, convection, radiation.
Thermal conductivity the phenomenon of energy transfer from more heated parts of the body to less heated ones is called as a result of thermal motion and interaction of particles that make up the body.
Metals have the highest thermal conductivity - they have it hundreds of times more than water. The exceptions are mercury and lead, but even here the thermal conductivity is ten times greater than that of water.
When a metal spoke was lowered into a glass of hot water, very soon the end of the spoke also became hot. Consequently, internal energy, like any kind of energy, can be transferred from one body to another. Internal energy can be transferred from one part of the body to another. So, for example, if one end of a nail is heated in a flame, then its other end, which is in the hand, will gradually heat up and burn the hand.
2.2. The practical part.
Let us study this phenomenon by doing a series of experiments with solids, liquid and gas.
Experience number 1
They took various objects: one aluminum spoon, another wooden, the third - plastic, the fourth - from a stainless alloy, and the fifth - silver. Attached paper clips to each spoon with drops of honey. We put the spoons in a glass of hot water so that the handles with paper clips stick out from it in different directions. The spoons will heat up, and as it warms up, the honey will melt and the staples will fall off.
Of course, the spoons must be the same shape and size. Where heating occurs faster, that metal conducts heat better, is more heat conductive. For this experiment, I took a glass of boiling water and four types of spoons: aluminum, silver, plastic and stainless. I dipped them one by one into a glass and timed the time: how many minutes it would take to heat up. That's what I did:
Conclusion: spoons made of wood and plastic take longer to heat up than spoons made of metal, which means that metals have good thermal conductivity.
Experience number 2
Let's bring the end of a wooden stick into the fire. It will ignite. The other end of the stick outside will be cold. This means that wood has poor thermal conductivity.
We bring the end of a thin glass rod to the flame of the spirit lamp. After a while, it will heat up, but the other end will remain cold. Consequently, glass also has poor thermal conductivity.
If we heat the end of a metal rod in a flame, then very soon the entire rod will be very hot. We will no longer be able to hold it in our hands.
This means that metals conduct heat well, that is, they have high thermal conductivity. On the staff-ve go-ri-zon-tal-but-crepe-flax ster-zhen. On the rod, through one-on-one holes, ver-ti-cal-but-fastened with wax-like metal nails.
A candle is placed to the edge of the rod. Since the edge of the rod is on-gray-wa-et-sya, then in-ste-pen-no-ster-zhen pro-gre-va-et-sya. When the heat reaches the place where the studs are fastened from the rod, the ste-a-rin will melt, and the carnation will fall. We see that in this experience there is no pe-re-no-sa matter, co-answer-vet-but, na-blu-da-em-sya warm-lo-pro-water ness.
Experience number 3
Different metals have different thermal conductivity. In the physics study there is a device with which we can make sure that different metals have different thermal conductivity. However, at home, we were able to verify this with the help of a homemade device.
A device for displaying various thermal conductivity of solids.
We have manufactured a device for displaying different thermal conductivity of solids. To do this, they used an empty can of aluminum foil, two rubber rings (homemade), three pieces of wire made of aluminum, copper and iron, tiles, hot water, 3 figurines of men with their hands raised up, cut out of paper.
The procedure for manufacturing the device:
bend the wire in the shape of the letter "G";
strengthen them on the outside of the can with rubber rings;
hang paper men from the horizontal parts of the wire sections (using molten paraffin or plasticine).
Checking the operation of the device... Pour hot water into a jar (if necessary, heat a jar of water on an electric stove) and watch which figure falls first, second, third.
Results. The first figure will fall, fixed on a copper wire, the second - on aluminum, the third - on steel.
Conclusion. Different solids have different thermal conductivity.
The thermal conductivity of different substances is different.
Experience number 4
Let us now consider the thermal conductivity of liquids. Take a test tube with water and begin to heat its upper part. The water at the surface will soon boil, and at the bottom of the test tube, during this time it will only heat up. This means that the thermal conductivity of liquids is low.
Experience number 5
Let us investigate the thermal conductivity of gases. Put a dry test tube on your finger and heat it upside down in the flame of an alcohol lamp. In this case, the finger will not feel warm for a long time. This is due to the fact that the distance between gas molecules is even greater than that of liquids and solids. Consequently, the thermal conductivity of gases is even less.
Wool, hair, bird feathers, paper, snow and other porous bodies have poor thermal conductivity.
This is due to the fact that there is air between the fibers of these substances. And air is a poor heat conductor.
So green grass is preserved under the snow, winter crops are preserved from freezing.
Experience number 6
He fluffed up a small ball of cotton wool and wrapped it around the bulb of the thermometer. Now he held the thermometer at a certain distance from the flame and noticed how the temperature had risen. Then the same ball of cotton wool squeezed and tightly wrapped it around the bulb of the thermometer and brought it back to the lamp. In the second case, the mercury will rise much faster. This means that compressed cotton wool conducts heat much better!
The lowest thermal conductivity is possessed by vacuum (space freed from air). This is explained by the fact that thermal conductivity is the transfer of energy from one part of the body to another, which occurs during the interaction of molecules or other particles. In a space where there are no particles, thermal conductivity cannot be carried out.
3. Conclusion.
Different substances have different thermal conductivity.
Solids (metals) have high thermal conductivity, less - liquids, and poor - gases.
We can use the thermal conductivity of various substances in everyday life, technology and nature.
The phenomenon of thermal conductivity is inherent in all substances, regardless of what state of aggregation they are in.
Now, without difficulty, I can answer and explain from a physical point of view the questions:
1.Why do birds fluff their feathers in cold weather?
(There is air between the feathers, and air is a poor conductor of heat).
2. Why does woolen clothes better keep the cold out than synthetic ones?
(There is air between the hairs, which does not conduct heat well).
3. Why do cats sleep curled up in a ball in winter, when the weather is cold? (Curling up into a ball, they reduce the surface area that gives off heat.)
4. Why are the handles of soldering irons, irons, pans, pots made of wood or plastic? (Wood and plastic have poor thermal conductivity, so when we heat metal objects, we will not burn our hands by holding on to a wooden or plastic handle).
5. Why are the bushes of thermophilic plants and bushes covered with sawdust for the winter?
(Sawdust is a poor conductor of heat. Therefore, the plants are covered with sawdust so that they do not freeze).
6. Which boots better protect against frost: tight or loose?
(Spacious, since the air does not conduct heat well, it is another layer in the boot that retains heat).
4. List of used literature.
Printed editions:
1.A.V. Peryshkin Physics Grade 8 -M: Bustard, 2012.
2.M.I.Bludov Conversations on physics part 1 -M: Enlightenment 1984.
Internet resources:
1.http: //class-fizika.narod.ru/8_3.htm
2.http: //ru.wikipedia.org/wiki/%D0%A2%D0%B5%D0%BF%D0%BB%D0%BE%D0%BF%D1%80%D0%BE%D0%B2 % D0% BE% D0% B4% D0% BD% D0% BE% D1% 81% D1% 82% D1% 8C
