Ticket No. 17

1. Atomistic hypothesis of the structure of matter and its experimental evidence. Ideal gas model. Absolute temperature. Temperature as a measure of the average kinetic energy of warm particle motion.

1. Laws of reflection and refraction of light; complete internal reflection; lenses; thin lens formula; optical instruments.

a. 1. All substances consist of molecules with spaces between them. Proof: 1. if you break an object, then the cut is rough; 2. any body can always be compressed - this is due to the spaces between the molecules.

b. All molecules are in continuous, chaotic motion. Proof: 1. diffusion - the phenomenon of mixing substances with each other. If you combine two substances, they will mix after some time without stirring (for example: pickling cucumbers); 2. Brownian motion is the movement of large particles suspended in a liquid or gas. (for example: dust particles “dance” in the air - this happens due to the fact that air molecules move continuously and randomly and knock down molecules).

c. Between molecules there are simultaneously attractive and repulsive forces (for example: a trampoline, a car spring, etc.)

An ideal gas is a model in physics. A gas in a vessel is taken to be an ideal gas when a molecule flying from wall to wall of the vessel does not experience collisions with other molecules.

The basic MKT equation connects macroscopic parameters (pressure, volume, temperature) of a gas system with microscopic ones (mass of molecules, average speed of their movement).

Where is the concentration, 1/mol; - molecular mass, kg; - root mean square speed of molecules, m/s; - kinetic energy molecular movements, J.

Absolute temperature – measured in K (kelvins)

Absolute zero is a temperature equal to -273 degrees Celsius - at which all movement should cease.

To explain the properties of matter in the gaseous state, the ideal gas model is used. A gas is considered ideal if: a) there are no attractive forces between the molecules, that is, the molecules behave like absolutely elastic bodies;

B) the gas is very discharged, i.e. the distance between molecules is much greater than the size of the molecules themselves;

C) thermal equilibrium throughout the entire volume is achieved instantly. The conditions necessary for a real gas to acquire the properties of an ideal gas are met under the appropriate rarefaction of the real gas. Some gases, even at room temperature and atmospheric pressure, differ slightly from ideal ones. The main parameters of an ideal gas are pressure, volume and temperature.

One of the first and important successes of MCT was the qualitative and quantitative explanation of gas pressure on the walls of a vessel. The qualitative explanation is that gas molecules, when colliding with the walls of a vessel, interact with them according to the laws of mechanics as elastic bodies and transfer their impulses to the walls of the vessel.

Based on the use of the basic principles of molecular kinetic theory, the basic MKT equation for an ideal gas was obtained,

Which looks like this: , where p is the pressure of an ideal gas, m0 is the mass of the molecule, the average value

Concentration of molecules, square of the speed of molecules.

Designating the average value of the kinetic energy of the translational motion of ideal gas molecules

We get the main equation

MCT of an ideal gas in the form:

However, by measuring only gas pressure, it is impossible to know either the average kinetic energy of individual molecules or their concentration. Consequently, to find the microscopic parameters of a gas, it is necessary to measure some other physical quantity related to the average kinetic energy of the molecules. This quantity is temperature. Temperature - scalar physical quantity, describing the state of thermodynamic equilibrium (a state in which there is no change in microscopic parameters). As a thermodynamic quantity, temperature characterizes the thermal state of the system and is measured by the degree of its deviation from what is assumed to be zero; as a molecular-kinetic quantity, it characterizes the intensity of the chaotic movement of molecules and is measured by their average kinetic energy. Ek = 3/2 kT, where k = 1.38 10^(-23) J/K and is called Boltzmann’s constant.

The temperature of all parts of an isolated system in equilibrium is the same. Temperature is measured by thermometers in degrees of various temperature scales. There is an absolute thermodynamic scale (the Kelvin scale) and various empirical scales that differ in their starting points. Before the introduction of the absolute temperature scale, the Celsius scale was widely used in practice (the freezing point of water is taken to be 0 °C, and the boiling point of water at normal atmospheric pressure is taken to be 100 °C).

The unit of temperature on the absolute scale is called Kelvin and is chosen to be equal to one degree on the Celsius scale 1 K = 1 °C. In the Kelvin scale, absolute zero temperature is taken as zero, that is, the temperature at which the pressure of an ideal gas at constant volume is zero. Calculations give the result that absolute zero temperature is -273 °C. Thus, there is a relationship between the absolute temperature scale and the Celsius scale T = t °C + 273. Absolute zero temperatures are unattainable, since any cooling is based on the evaporation of molecules from the surface, and when approaching absolute zero, the speed of translational motion of molecules slows down so much that evaporation practically stops. Theoretically, at absolute zero, the speed of translational motion of molecules is zero, i.e., the thermal motion of molecules stops.

The term "temperature" appeared at a time when physicists thought that warm bodies consisted of more specific substance - caloric - than the same bodies, but cold. And temperature was interpreted as a value corresponding to the amount of caloric in the body. Since then, the temperature of any body has been measured in degrees. But in fact it is a measure of the kinetic energy of moving molecules, and, based on this, it should be measured in Joules, in accordance with the System of Units C.

The concept of “absolute zero temperature” comes from the second law of thermodynamics. According to it, the process of heat transfer from a cold body to a hot one is impossible. This concept was introduced by the English physicist W. Thomson. For his achievements in physics, he was given the title of nobility “Lord” and the title “Baron Kelvin”. In 1848, W. Thomson (Kelvin) proposed using a temperature scale in which he took absolute zero temperature, corresponding to extreme cold, as the starting point, and took degrees Celsius as the division value. The Kelvin unit is 1/27316 of the temperature of the triple point of water (about 0 degrees C), i.e. temperature at which pure water is immediately found in three forms: ice, liquid water and steam temperature is the minimum possible low temperature at which the movement of molecules stops and it is no longer possible to extract it from the substance thermal energy. Since then, the absolute temperature scale has been named after him.

Temperature is measured on different scales

The most commonly used temperature scale is called the Celsius scale. It is built on two points: on the temperature of the phase transition of water from liquid to steam and water to ice. A. Celsius in 1742 proposed dividing the distance between reference points into 100 intervals, and taking water as zero, with the freezing point as 100 degrees. But the Swede K. Linnaeus suggested doing the opposite. Since then, water has frozen at zero degrees A. Celsius. Although it should boil exactly at Celsius. Absolute zero Celsius corresponds to minus 273.16 degrees Celsius.

There are several more temperature scales: Fahrenheit, Reaumur, Rankin, Newton, Roemer. They have different division prices. For example, the Reaumur scale is also built on the reference points of boiling and freezing of water, but it has 80 divisions. The Fahrenheit scale, which appeared in 1724, is used in everyday life only in some countries of the world, including the USA; one is the temperature of the mixture of water ice and ammonia and the other is the temperature of the human body. The scale is divided into one hundred divisions. Zero Celsius corresponds to 32 Conversion of degrees to Fahrenheit can be done using the formula: F = 1.8 C + 32. Reverse conversion: C = (F - 32)/1.8, where: F - degrees Fahrenheit, C - degrees Celsius. If you are too lazy to count, go to an online service for converting Celsius to Fahrenheit. In the box, enter the number of degrees Celsius, click "Calculate", select "Fahrenheit" and click "Start". The result will appear immediately.

Named after the English (more precisely Scottish) physicist William J. Rankin, former contemporary Kelvin and one of the creators of technical thermodynamics. On his scale important points three: the beginning is absolute zero, the freezing point of water is 491.67 degrees Rankine and the boiling point of water is 671.67 degrees. The number of divisions between the freezing of water and its boiling for both Rankine and Fahrenheit is 180.

Most of these scales are used exclusively by physicists. And 40% of American high school students surveyed today said that they do not know what absolute zero temperature is.

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The thermal movement of molecules of substances in a liquid state is similar to their movement for substances in crystalline and gaseous states. In crystals, the thermal motion of molecules is expressed mainly in vibrations of molecules relative to equilibrium positions, which practically do not change over time. The thermal motion of molecules in gases is mainly their translational movement and rotation, the directions of which change in collisions.  

The thermal movement of molecules of a substance on the surface of a substrate is called migration. During migration, it becomes possible for molecules to collide - two or less often three - with each other. Colliding molecules come together under the influence of van der Waals forces. So, doublets and triplets are formed. They are more difficult to desorb than single molecules, since their bonds with the surface are noticeably stronger. These formations are active centers during the condensation of subsequent settling molecules.  

Since the thermal movement of the molecules of a body substance disrupts their ordered arrangement, magnetization decreases with increasing temperature.  

Since the thermal movement of the molecules of a body substance disrupts their ordered arrangement, magnetization decreases with increasing temperature. If this body is removed from the external field, then the chaotic movement of the molecules will lead to its complete demagnetization.  

Pressure saturated vapors created by the thermal movement of molecules of a substance in the vapor phase at a certain temperature.  

The gaseous state occurs when the energy of thermal motion of the molecules of a substance exceeds the energy of their interaction. The molecules of the substance in this state acquire a rectilinear forward motion, A individual properties substances are lost, and they obey the laws common to all gases. Gaseous bodies do not have their own shape and easily change their volume when exposed to external forces or when temperature changes.  

Absolute zero (0 K) is characterized by the cessation of thermal movement of the molecules of a substance and corresponds to a temperature below 0 C by 273 16 C.  

Kinetic theory matter allows us to establish a connection between pressure and the kinetic energy of thermal motion of the molecules of a substance.  

If the internal movements in molecules are connected with their external thermal movement, then it is impossible to understand the properties of a substance, its chemical behavior, without studying this connection, without taking into account those factors that affect the thermal movement of the molecules of a substance (temperature, pressure, environment, etc. ) and through this thermal movement also affect the state internal movement in every single molecule.  

Thus, it was found that any substance can be converted from a gaseous state to a liquid state. However, each substance can experience such a transformation only at temperatures below a certain, so-called critical temperature Tc. Above the critical temperature, the substance does not turn into a liquid or solid at any pressure. It is obvious that at a critical temperature the average kinetic energy of thermal motion of the molecules of a substance exceeds the potential energy of their binding in a liquid or solid. Since the attractive forces acting between the molecules of different substances are different, the potential energy of their connection is also different, hence the values ​​of the critical temperature for different substances are also different.  

Relaxation times 1 and T2 are introduced above as constants, which must be determined from experience. The values ​​of 7 measured for various substances lie in a wide range from K) 4 sec for solutions of paramagnetic salts to several. Experienced data indicates close connection values ​​of relaxation times with the structure and nature of thermal motion of the molecules of the substance.  

The absolute temperature T, K, characterizes the degree of heating of the body. In particular, the melting point of ice (0 C) and the boiling point of water (100 C) at normal atmospheric pressure were taken as the initial values ​​used in constructing the International Practical Celsius Temperature Scale to establish the origin of temperature and its unit of measurement - degrees. Temperatures above 0 C are considered positive, and temperatures below 0 C are considered negative. In the SI system of units, temperature calculations are made from absolute zero in degrees of the Kelvin thermodynamic scale. The absolute zero of this scale (0 K) is characterized by the cessation of thermal movement of the molecules of a substance and corresponds on the Celsius scale to a temperature of - 273 15 C. Thus, both scales differ only starting point counting, and the division price (degree) is the same.  

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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

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

If you spray tiny grains of any substance on the surface of a liquid,
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:

Make a hole in the cap of a plastic bottle 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. Anchor 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 lowest temperature recorded on Earth is –89.20C;
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 Kola ultra-deep 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 lower both hands into 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 obtained at the center of a thermonuclear bomb explosion - 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.