Thermal movement. Brownian motion

All molecules of any substance move continuously and randomly (chaotically).

The movement of molecules in different bodies happens in different ways.
Gas molecules move randomly at high speeds (hundreds of m/s) throughout the entire volume of gas. When they collide, they bounce off each other, changing the magnitude and direction of the velocities.
Liquid molecules oscillate around equilibrium positions (since they are located almost close to each other) and relatively rarely jump from one equilibrium position to another. The movement of molecules in liquids is less free than in gases, but more free than in solids.
In solids, particles vibrate around an equilibrium position.
With increasing temperature, the speed of particles increases, therefore the chaotic movement of particles is usually called thermal.

BROWNIAN MOTION

Proof thermal movement molecules.
Brownian motion was discovered by the English botanist Robert Brown (1773-1858)

If you spray liquid on the surface tiny grains any substance
then they will move continuously.

These Brownian particles move under the influence of impacts from liquid molecules. Because The thermal motion of molecules is a continuous and random movement, then the speed of movement of Brownian particles will randomly change in magnitude and direction.
Brownian motion is eternal and never stops.

LOOK AT THE BOOKSHELF!

HOME LABORATORY WORK

1. Take three glasses. Pour boiling water into the first, warm water into the second and cold water into the third.
Add a pinch of granulated tea to each glass. What did you notice?

2. Take an empty plastic bottle, after having cooled it, lower the neck into a glass of water and clasp the bottle with your palms, but do not press. Observe for a few minutes.

3. Place an inverted cork soaked in water on the neck of the same, but newly cooled bottle and also clasp it with warm palms. Observe for a few minutes.

4. Pour water into a shallow plate to a height of 1 - 1.5 cm, place it upside down and preheated hot water cup. Observe for a few minutes.

I'm waiting for a report explaining what I saw. Who is first?

TEMPERATURE

A quantity that characterizes the thermal state of a body or, in other words, a measure of the “heating” of a body.
The higher the temperature of a body, the greater the average energy of its atoms and molecules.

Devices used to measure temperature are called thermometers.

The principle of temperature measurement.

Temperature is not directly measured! The measured value is temperature dependent!
In modern liquid thermometers, this is the volume of alcohol or mercury (in Galileo’s thermoscope, this is the volume of gas). The thermometer measures your own temperature! And, if we want to measure the temperature of some other body using a thermometer, we must wait some time until the temperatures of the body and the thermometer are equal, i.e. thermal equilibrium will occur between the thermometer and the body.
This is the law of thermal equilibrium:
For any group of isolated bodies, after some time the temperatures become the same,
those. a state of thermal equilibrium occurs

...

DO A TEST AT HOME

Take three bowls of water: one with very hot water, another with moderately warm water, and the third with very cold water. Now lower it for a moment left hand into a bowl with hot water, and the right one with cold water. After a couple of minutes, remove your hands from the hot and cold water and place them in a bowl of warm water. Now ask each hand what will it “tell” you about the temperature of the water?

THERMOMETER - DO IT YOURSELF

Take a small glass bottle (for example, brilliant green is sold in pharmacies in such bottles), a stopper (preferably rubber) and a thin transparent tube (you can take an empty transparent ballpoint pen).
Make a hole in the cork and close the bottle. Fill a tube with a drop of colored water and insert the rod into the cork. Seal the gap between the plug and the rod thoroughly.
The thermometer is ready.
Now you need to calibrate it, i.e. make a measuring scale.
It is clear that when the air in the bubble is heated, it will expand, and a drop of liquid will rise up the tube. Your task is to mark the divisions on the rod or cardboard attached to it that correspond to different temperatures.
For calibration, you can take another ready-made thermometer and lower both thermometers into a glass of warm water. Thermometer readings must match. Therefore, if the finished thermometer shows a temperature of, for example, 40 degrees, you can safely put a mark of 40 on the stem of your thermometer in the place where the drop of liquid is located. The water in the glass will cool down, and you can mark the measuring scale this way.
You can make a thermometer by completely filling it with liquid.

Or you can do it another way:

Do it in the lid plastic bottle hole and insert a thin plastic tube.
Partially fill the bottle with water and attach it to the wall. Mark a temperature scale at the free end of the tube. You can calibrate the scale using a regular room thermometer.
As the temperature in the room changes, the water will expand or contract, and the water level in the tube will also “creep” along the scale.

You can also see how a thermometer works!
Wrap your hands around the bottle and warm it.
What happened to the water level in the tube?

TEMPERATURE SCALES

Celsius scale - introduced by the Swedish physicist A. Celsius in 1742. Designation: C. The scale has both positive and negative temperatures. Reference points: 0C – ice melting temperature, 100C – water boiling temperature.

Fahrenheit scale - introduced by Fahrenheit, a glassblower from Holland, in 1724. Designation: F. The scale has both positive and negative temperatures. Reference points: 32F is the melting temperature of ice, 212F is the boiling temperature of water.

Reaumur scale - introduced by the French physicist Reaumur in 1726. Designation: R. The scale has both positive and negative temperatures. Reference points: 0R – ice melting temperature, 80R – water boiling temperature.

Kelvin scale - introduced by the English physicist Thomson (Lord Kelvin) in 1848. Designation: K. The scale shows only positive temperatures. Reference points: 0K – absolute zero, 273K – ice melting temperature. T = t + 273

THERMOSCOPE

The first device for determining temperature was invented by Galileo in 1592. A small glass balloon was soldered to a thin tube with an open end.

The balloon was heated by hand and the end of the tube was immersed in a vessel with water. The balloon was cooled to ambient temperature and the water level in the tube rose. Those. By changing the volume of gas in the vessel, one could judge the change in temperature. There was no numerical scale yet, so this device was called a thermoscope. The measuring scale appeared only 150 years later!

DO YOU KNOW

The highest temperature on Earth recorded in Libya in 1922 is +57.80C;
the most low temperature, registered on Earth - –89.20С;
above a person's head the temperature is higher than the temperature environment at 1 – 1.50С; average temperature of animals: horses - 380C, sheep - 400C, chicken - 410C,
temperature at the center of the Earth - 200000C;
the temperature on the surface of the Sun is 6000 K, in the center - 20 million degrees.

What is the temperature of the Earth's interior?
Previously, various hypothetical assumptions were made and calculations were made, according to which the temperature at a depth of 15 km was 100...400°C. Now the Kola superdeep well,
which passed the 12 km mark, gave an exact answer to the question posed. At first (up to 3 km), the temperature increased by 1° every 100 m of excavation, then this increase was 2.5° for every new 100 m. At a depth of 10 km, the temperature of the Earth’s interior turned out to be equal to 180°C!
Science and life

By the end of the 18th century, the number of temperature scales invented reached two dozen.

Italian polar scientists, having made an expedition to Antarctica, were faced with an amazing mystery. Near the Bay of Inglei, they discovered an icy gorge, where a super-fast and super-cold wind constantly blows. A flow of air with a temperature of minus 90 degrees rushes at a speed of 200 km per hour. It is not surprising that this gorge was called the “gates of hell” - no one can stay there without risking their lives for more than one minute: the wind carries ice particles with such force that it instantly tears clothes to shreds.

SHOULD WE BREAK YOUR HEAD?

Tricky problems

1. How to measure the body temperature of an ant using a regular thermometer?

2. There are thermometers that use water. Why are such water thermometers inconvenient for measuring temperatures close to the freezing point of water?

I'm waiting for your answer (in class or by mail)!

DO YOU KNOW THIS?

In fact, the Swedish astronomer and physicist Celsius proposed a scale in which the boiling point of water was designated by the number 0, and the melting point of ice by the number 100! “But in winter there will be no negative numbers!” - Celsius liked to say. But then the scale was “turned upside down.”

· A temperature of -40 degrees Celsius is exactly the same as a temperature of -40 degrees Fahrenheit. This is the only temperature at which these two scales converge.

At one time, physics laboratories used a so-called gravimetric thermometer to measure temperature. It consisted of a hollow platinum ball filled with mercury, in which there was a capillary hole. The change in temperature was judged by the amount of mercury flowing out of the hole.

It turns out there is a flat thermometer. This is a “piece of paper” that is placed on the patient’s forehead. At high temperature The "paper" turns red.

Our senses, usually reliable, can fail when determining temperature. For example, there is a well-known experiment when one hand is placed in hot water and the other in cold water. If after some time you put both hands in warm water, then the hand that was previously in hot water, will feel cold, and the hand that was in cold water- heat!

The concept of temperature does not apply to an individual molecule. We can only talk about temperature if there is a sufficiently large population of particles.

Most often, physicists measure temperature on the Kelvin scale: 0 degrees Celsius = 273 degrees Kelvin!

Highest temperature.

It was received at the center of the explosion thermonuclear bomb– about 300...400 million°C. Maximum temperature, achieved during a controlled thermonuclear reaction at the TOKAMAK thermonuclear test facility at the Princeton Plasma Physics Laboratory, USA, in June 1986, is 200 million °C.

Lowest temperature.

Absolute zero on the Kelvin scale (0 K) corresponds to –273.15° Celsius or –459.67° Fahrenheit. The lowest temperature, 2 10–9 K (two-billionth of a degree) above absolute zero, was achieved in a two-stage nuclear demagnetization cryostat at the Low Temperature Laboratory of the Helsinki University of Technology, Finland, by a team of scientists led by Professor Olli Lounasmaa (b. 1930). ), which was announced in October 1989.

The smallest thermometer.

Dr. Frederick Sachs, a biophysicist from State University of New York State, Buffalo, USA, constructed a microthermometer to measure the temperature of individual living cells. The diameter of the thermometer tip is 1 micron, i.e. 1/50th the diameter of a human hair.

To study the topic “Thermal Movement” we need to repeat:

In the world around us, various kinds of physical phenomena occur that are directly related to changes in body temperature.

Since childhood, we remember that the water in the lake is first cold, then barely warm, and only after a while it becomes suitable for swimming

With words such as “cold”, “hot”, “slightly warm”, we define varying degrees“heating” of bodies, or, speaking in the language of physics, different temperatures tel.

If you compare the temperature in the lake in summer and late autumn, the difference is obvious. The temperature of warm water is slightly higher than the temperature of ice water.

As is known, diffusion occurs faster at higher temperatures. It follows from this that the speed of movement of molecules and temperature are deeply interrelated.

Conduct an experiment: Take three glasses and fill them with cold, warm and hot water, and now put a tea bag in each glass and observe how the color of the water changes? Where will this change occur most intensely?

If you increase the temperature, the speed of movement of molecules will increase, if you decrease it, it will decrease. Thus, we conclude: body temperature directly depends on the speed of movement of molecules.

Hot water consists of exactly the same molecules as cold water. The difference between them is only in the speed of movement of the molecules.

Phenomena that relate to heating or cooling of bodies and temperature changes are called thermal. These include heating or cooling not only liquid bodies, but also gaseous and solid air.

More examples of thermal phenomena: metal melting, snow melting.

Molecules or atoms, which are the basis of all bodies, are in endless chaotic motion. The movement of molecules in different bodies occurs differently. Gas molecules move randomly at high speeds along a very complex trajectory.When they collide, they bounce off each other, changing the magnitude and direction of the velocities.

Liquid molecules oscillate around equilibrium positions (since they are located almost close to each other) and relatively rarely jump from one equilibrium position to another. The movement of molecules in liquids is less free than in gases, but more free than in solids.

In solids, molecules and atoms vibrate around certain average positions.

As the temperature increases, the particle speed increases, That's why The chaotic movement of particles is usually called thermal.

Interesting:

What is the exact height of the Eiffel Tower? And this depends on the ambient temperature!

The fact is that the height of the tower varies by as much as 12 centimeters.

and the temperature of the beams can reach up to 40 degrees Celsius.

And as you know, substances can expand under the influence of high temperature.

Chaotic is the most important feature thermal movement. One of the most important evidence of the movement of molecules is diffusion and Brownian motion. (Brownian motion is the movement of tiny solid particles in a liquid under the influence of molecular impacts. As observation shows, Brownian motion cannot stop). Brownian movement was discovered by the English botanist Robert Brown (1773-1858).

Absolutely all molecules of the body participate in the thermal movement of molecules and atoms, which is why with a change in thermal movement, the state of the body itself and its various properties change.

Let's remember how the properties of water change with temperature changes.

Body temperature directly depends on the average kinetic energy of molecules. We draw an obvious conclusion: the higher the temperature of a body, the greater the average kinetic energy of its molecules. And, conversely, as the body temperature decreases, the average kinetic energy of its molecules decreases.

Temperature - a quantity that characterizes the thermal state of the body or, in other words, a measure of the “heating” of the body.

The higher the temperature of a body, the greater the average energy of its atoms and molecules.

Temperature is measured thermometers, i.e. temperature measuring instruments

Temperature is not directly measured! The measured value is temperature dependent!

Currently, there are liquid and electric thermometers.

In modern liquid thermometers, this is the volume of alcohol or mercury. The thermometer measures your own temperature! And, if we want to measure the temperature of some other body using a thermometer, we must wait some time until the temperatures of the body and the thermometer are equal, i.e. thermal equilibrium will occur between the thermometer and the body. A home thermometer “thermometer” needs time to give an accurate reading of the patient’s temperature.

This is the law of thermal equilibrium:

For any group of isolated bodies, after some time the temperatures become the same,

those. a state of thermal equilibrium occurs.

Body temperature is measured using a thermometer and is most often expressed in degrees Celsius(°C). There are also other units of measurement: Fahrenheit, Kelvin and Reaumur.

Most often, physicists measure temperature on the Kelvin scale. 0 degrees Celsius = 273 degrees Kelvin

The atoms and molecules that make up various substances, are in a state of continuous thermal movement.

The first feature of thermal motion is its randomness; no direction of molecular motion stands out among other directions. Let us explain this: if you follow the movement of one molecule, then over time, due to collisions with other molecules, the speed and direction of movement of this molecule change completely randomly; further, if at some point in time we record the speeds of movement of all molecules, then in direction these speeds turn out to be evenly scattered in space, and in magnitude they have a wide variety of values.

The second feature of thermal motion is the existence of energy exchange between molecules, as well as between various types movements; the energy of translational motion of molecules can be converted into the energy of their rotational or vibrational motion and vice versa.

The exchange of energy between molecules, as well as between various types of their thermal motion, occurs due to the interaction of molecules (collisions between them). At large distances, the interaction forces between molecules are very small and can be neglected; at short distances these forces have a noticeable effect. In gases, molecules spend most of the time at relatively large distances from each other; Only during very short periods of time, when they are close enough to each other, do they interact with each other, changing the speed of their movements and exchanging energies. Such short-term interactions of molecules are called collisions. There are two types of collisions between molecules:

1) collisions, or impacts, of the first kind, as a result of which only the speeds and kinetic energies of the colliding particles change; the composition or structure of the molecules themselves do not undergo any changes;

2) collisions, or impacts, of the second kind, as a result of which changes occur inside the molecules, for example, their composition or the relative arrangement of atoms inside these molecules changes. During these collisions, part of the kinetic energy of the molecules is spent on doing work against the forces acting inside the molecules. In some cases, on the contrary, a certain amount of energy may be released due to a decrease in the internal potential energy of the molecules.

In what follows, we will only refer to collisions of the first kind that occur between gas molecules. The exchange of energy during thermal motion in solids and liquids is a more complex process and is considered in special sections of physics. Collisions of the second kind are used to explain the electrical conductivity of gases and liquids, as well as the thermal radiation of bodies.

To describe each type of thermal motion of molecules (translational, rotational or vibrational), it is necessary to specify a number of quantities. For example, for the translational motion of a molecule, it is necessary to know the magnitude and direction of its speed. For this purpose, it is enough to indicate three quantities: the value of the speed and two angles between the direction of the speed and the coordinate planes, or three projections of the speed onto the coordinate axes: (Fig. 11.1, a). Note that these three quantities are independent: for a given angle and can have any values ​​and, conversely, for a given angle, for example, the values ​​and can be any. Likewise, specifying a specific value does not impose any restrictions on the opposite values. Thus, to describe the translational motion of a molecule in space, it is necessary to specify three quantities independent of each other: and or The energy of the translational motion of a molecule will consist of three independent components:

To describe the rotational motion of a molecule around its axis, it is necessary to indicate the magnitude and direction of the angular velocity of rotation, i.e., again, three quantities independent of each other: and c or (Fig. II. 1, b). The energy of rotational motion of a molecule will also consist of three independent components:

where the moments of inertia of the molecule relative to three mutually perpendicular coordinate axes. For a monatomic molecule, all these moments of inertia are very small, so the energy of its rotational motion is neglected. In a diatomic molecule (Fig. II.1, c), the energy of rotational motion relative to the axis passing through the centers of the atoms is neglected, therefore, for example,

To describe the vibrational motion of atoms in a molecule, it is first necessary to divide this motion into simple vibrations occurring along certain directions. It is convenient to decompose a complex oscillation into simple linear oscillations occurring in three mutually perpendicular directions. These oscillations are independent of each other, i.e., the frequency and amplitude of oscillations in one of these directions can correspond to any frequency and amplitude of oscillations in other directions. If each of these rectilinear oscillations is harmonic, then it can be described using the formula

Thus, to describe an individual rectilinear vibration of atoms, it is necessary to specify two quantities: the vibration frequency co and the vibration amplitude. These two quantities are also independent of each other: at a given frequency, the vibration amplitude is not bound by any conditions, and vice versa. Consequently, to describe the complex vibrational motion of a molecule around a point (i.e., its equilibrium position), it is necessary to specify six quantities independent of each other: three frequencies and vibration amplitudes in three mutually perpendicular directions.

Values ​​independent from each other that determine the state of a given physical system, are called degrees of freedom of this system. When studying thermal motion in bodies (to calculate the energy of this motion), the number of degrees of freedom of each molecule of this body is determined. In this case, only those degrees of freedom between which energy exchange occurs are calculated. A monatomic gas molecule has three degrees of freedom of translational motion; a diatomic molecule has three degrees of freedom of translational and two degrees of freedom of rotational motion (the third degree of freedom, corresponding to rotation around an axis passing through the centers of the atoms, is not taken into account). Molecules containing three

an atom or more, have three translational and three rotational degrees of freedom. If oscillatory motion also participates in the energy exchange, then for each independent rectilinear oscillation two degrees of freedom are added.

By considering separately the translational, rotational and vibrational motions of molecules, one can find the average energy that falls on each degree of freedom of these types of motion. Let's first consider the translational motion of molecules: let's say a molecule has kinetic energy (the mass of the molecule). The sum is the energy of translational motion of all molecules. Dividing by degrees of freedom, we obtain the average energy per degree of freedom of translational motion of molecules:

It is also possible to calculate the average energies per degree of freedom of rotational motion and vibrational motion. If each molecule has translational degrees of freedom, rotational degrees of freedom and vibrational degrees of freedom, then the total energy of thermal motion of all molecules will be equal to

This lesson examines the concept of thermal motion and such a physical quantity as temperature.

Thermal phenomena are of great importance in human life. We encounter them both during weather forecasts and when boiling ordinary water. Thermal phenomena are associated with such processes as the creation of new materials, the melting of metals, the combustion of fuel, the creation of new types of fuel for cars and aircraft, etc.

Temperature is one of the most important concepts associated with thermal phenomena, since often it is temperature that is the most important characteristic of the occurrence of thermal processes.

Definition.Thermal phenomena- these are phenomena associated with heating or cooling of bodies, as well as with changes in their state of aggregation (Fig. 1).

Rice. 1. Ice melting, water heating and evaporation

All thermal phenomena are associated with temperature.

All bodies are characterized by the state of their thermal equilibrium. The main characteristic thermal equilibrium is temperature.

Definition.Temperature- this is a measure of the “warmth” of the body.

Since temperature is a physical quantity, it can and should be measured. To measure temperature, a device called thermometer(from Greek thermo- "warm", metreo- “measuring”) (Fig. 2).

Rice. 2. Thermometer

The first thermometer (or rather, its analogue) was invented by Galileo Galilei (Fig. 3).

Rice. 3. Galileo Galilei (1564-1642)

Galileo's invention, which he presented to his students at university lectures at the end of the 16th century (1597), was called thermoscope. The operation of any thermometer is based on the following principle: physical properties substances change depending on temperature.

Galileo's experiment was as follows: he took a flask with a long stem and filled it with water. Then he took a glass of water and turned the flask upside down, placing it in the glass. Some of the water naturally poured out, but as a result a certain level of water remained in the leg. If you now heat the flask (which contains air), the water level will drop, and if you cool it, then, on the contrary, it will rise. This is due to the fact that when heated, substances (in particular, air) tend to expand, and when cooled, they tend to contract (this is why the rails are not continuous, and the wires between the posts sometimes sag a little).

Rice. 4. Galileo's experiment

This idea formed the basis of the first thermoscope (Fig. 5), which made it possible to evaluate temperature changes (it is impossible to accurately measure temperature with such a thermoscope, since its readings will greatly depend on atmospheric pressure).

Rice. 5. Copy of Galileo's thermoscope

At the same time, the so-called degree scale was introduced. The word itself degree translated from Latin means “step”.

To date, three main scales have been preserved.

1. Celsius

The most widely used scale is one that everyone has known since childhood - the Celsius scale.

Anders Celsius (Fig. 6) is a Swedish astronomer who proposed the following temperature scale: - boiling point of water; - freezing temperature of water. Nowadays we are all accustomed to the inverted Celsius scale.

Rice. 6 Andres Celsius (1701-1744)

Note: Celsius himself said that this choice of scale was caused by a simple fact: but in winter there will be no negative temperature.

2. Fahrenheit scale

In England, the USA, France, Latin America and some other countries, the Fahrenheit scale is popular.

Gabriel Fahrenheit (Fig. 7) is a German researcher and engineer who first used his own scale for making glass. The Fahrenheit scale is more subtle: in terms of dimension, a degree on the Fahrenheit scale is smaller than a degree on the Celsius scale.

Rice. 7 Gabriel Fahrenheit (1686-1736)

3. Reaumur scale

The technical scale was invented by the French researcher R.A. Reaumur (Fig. 8). According to this scale, it corresponds to the freezing temperature of water, but Reaumur chose a temperature of 80 degrees as the boiling point of water.

Rice. 8. René Antoine Reaumur (1683-1757)

In physics, the so-called absolute scale - Kelvin scale(Fig. 8). 1 degree Celsius is equal to 1 degree Kelvin, but the temperature corresponds approximately (Fig. 9).

Rice. 9. William Thomson (Lord Kelvin) (1824-1907)

Rice. 10. Temperature scales

Let us recall that when the temperature of a body changes, its linear dimensions change (when heated, the body expands, when cooled, it contracts). This is due to the behavior of molecules. When heated, the speed of movement of particles increases; accordingly, they begin to interact more often and the volume increases (Fig. 11).

Rice. 11. Changing linear dimensions

From this we can conclude that temperature is related to the movement of the particles that make up bodies (this applies to solid, liquid, and gaseous bodies).

The movement of particles in gases (Fig. 12) is random (since molecules and atoms in gases practically do not interact).

Rice. 12. Movement of particles in gases

The movement of particles in liquids (Fig. 13) is “jump-like”, that is, the molecules lead a “sedentary lifestyle”, but are able to “jump” from one place to another. This determines the fluidity of liquids.

Rice. 13. Movement of particles in liquids

The movement of particles in solids (Fig. 14) is called oscillatory.

Rice. 14. Movement of particles in solids

Thus, all particles are in continuous motion. This movement of particles is called thermal movement(disorderly, chaotic movement). This movement never stops (as long as the body has temperature). The presence of thermal movement was confirmed in 1827 by the English botanist Robert Brown (Fig. 15), after whom this movement is called Brownian motion.

Rice. 15. Robert Brown (1773-1858)

Today it is known that the lowest temperature that can be achieved is approximately . It is at this temperature that the movement of particles stops (however, the movement inside the particles themselves does not stop).

Galileo's experiment was described earlier, and in conclusion let's consider another experiment - the experience of the French scientist Guillaume Amonton (Fig. 15), who in 1702 invented the so-called gas thermometer. With minor changes, this thermometer has survived to this day.

Rice. 15. Guillaume Amonton (1663-1705)

Amonton's experience

Rice. 16. Amonton's experience

Take a flask with water and plug it with a stopper with a thin tube. If you now heat the water, then due to the expansion of the water its level in the tube will increase. Based on the level of water rise in the tube, we can conclude that the temperature is changing. Advantage Amonton thermometer is that it does not depend on atmospheric pressure.

In this lesson we looked at such an important physical quantity as temperature. We studied ways to measure it, characteristics and properties. In future lessons we will study the concept internal energy.

Bibliography

1. Gendenshtein L.E., Kaidalov A.B., Kozhevnikov V.B. / Ed. Orlova V.A., Roizena I.I. Physics 8. - M.: Mnemosyne.
2. Peryshkin A.V. Physics 8. - M.: Bustard, 2010.
3. Fadeeva A.A., Zasov A.V., Kiselev D.F. Physics 8. - M.: Enlightenment.

1. Internet portal “class-fizika.narod.ru” ()
2. Internet portal “school.xvatit.com” ()
3. Internet portal "ponimai.su" ()

Homework

1. No. 1-4 (paragraph 1). Peryshkin A.V. Physics 8. - M.: Bustard, 2010.

2. Why can’t Galileo’s thermoscope be calibrated?

3. An iron nail was heated on a stove:

How did the speed of movement of iron molecules change?

How will the speed of the molecules change if a nail is placed in cold water?

How will the speed of movement of water molecules change?

How does the volume of the nail change during these experiments?

4. The balloon was moved from the room to the cold:

How will the volume of the ball change?

How will the speed of air molecules inside the ball change?

How will the speed of the molecules inside the ball change if it is returned to the room and, in addition, placed next to the battery?