Temperature is a measure of the average kinetic energy of molecules. Basic MKT equation. Temperature as a measure of the average kinetic energy of the chaotic motion of molecules

When the absolute temperature of an ideal gas decreases by 1.5 times, the average kinetic energy thermal movement of molecules

1) will increase by 1.5 times

2) will decrease by 1.5 times

3) will decrease by 2.25 times

4) will not change

Solution.

When the absolute temperature decreases by 1.5 times, the average kinetic energy will also decrease by 1.5 times.

Correct answer: 2.

Answer: 2

When the absolute temperature of an ideal gas decreases by 4 times, the mean square speed of thermal motion of its molecules

1) will decrease by 16 times

2) will decrease by 2 times

3) will decrease by 4 times

4) will not change

Solution.

The absolute temperature of an ideal gas is proportional to the square of the mean square speed: Thus, when the absolute temperature decreases by 4 times, the mean square speed of its molecules will decrease by 2 times.

Correct answer: 2.

Vladimir Pokidov (Moscow) 21.05.2013 16:37

We were sent such a wonderful formula as E = 3/2kT. The average kinetic energy of the thermal motion of the molecules of an ideal gas is directly proportional to its temperature, as the temperature changes, so does the average kinetic energy of the thermal motion of the molecules.

Alexei

Good afternoon

That's right, in fact, temperature and average energy of thermal motion are one and the same. But in this problem we are asked about speed, not about energy

When the absolute temperature of an ideal gas increases by 2 times, the average kinetic energy of thermal motion of molecules

1) will not change

2) will increase 4 times

3) will decrease by 2 times

4) will increase by 2 times

Solution.

The average kinetic energy of thermal motion of molecules of an ideal gas is directly proportional to the absolute temperature, for example, for a monatomic gas:

When the absolute temperature increases by 2 times, the average kinetic energy will also increase by 2 times.

Correct answer: 4.

Answer: 4

When the absolute temperature of an ideal gas decreases by 2 times, the average kinetic energy of thermal motion of molecules

1) will not change

2) will decrease by 4 times

3) will decrease by 2 times

4) will increase by 2 times

Solution.

The average kinetic energy of thermal motion of molecules of an ideal gas is directly proportional to the absolute temperature:

When the absolute temperature decreases by 2 times, the average kinetic energy will also decrease by 2 times.

Correct answer: 3.

Answer: 3

When the root mean square speed of thermal motion of molecules increases by 2 times, the average kinetic energy of thermal motion of molecules

1) will not change

2) will increase 4 times

3) will decrease by 4 times

4) will increase by 2 times

Solution.

Consequently, an increase in the mean square speed of thermal motion by 2 times will lead to an increase in the average kinetic energy by 4 times.

Correct answer: 2.

Answer: 2

Alexey (St. Petersburg)

Good afternoon

Both formulas hold. The formula used in the solution (first equality) is simply mathematical notation determination of average kinetic energy: that you need to take all the molecules, calculate their kinetic energies, and then take the arithmetic average. The second (identical) equality in this formula is just a definition of what the root mean square speed is.

Your formula is actually much more serious, it shows that the average energy of thermal motion can be used as a measure of temperature.

When the root mean square speed of thermal motion of molecules decreases by 2 times, the average kinetic energy of thermal motion of molecules

1) will not change

2) will increase 4 times

3) will decrease by 4 times

4) will increase by 2 times

Solution.

The average kinetic energy of thermal motion of molecules is proportional to the square of the root mean square speed of thermal motion of molecules:

Consequently, a decrease in the root mean square speed of thermal motion by 2 times will lead to a decrease in the average kinetic energy by 4 times.

Correct answer: 3.

Answer: 3

When the average kinetic energy of thermal motion of molecules increases by 4 times, their root mean square speed

1) will decrease by 4 times

2) will increase 4 times

3) will decrease by 2 times

4) will increase by 2 times

Solution.

Consequently, with an increase in the average kinetic energy of the thermal motion of molecules by 4 times, their root mean square speed will increase by 2 times.

Correct answer: 4.

Answer: 4

Alexey (St. Petersburg)

Good afternoon

A sign is an identical equality, that is, an equality that is always satisfied; in fact, when such a sign appears, this means that the quantities are equal by definition.

Yana Firsova (Gelendzhik) 25.05.2012 23:33

Yuri Shoitov (Kursk) 10.10.2012 10:00

Hello, Alexey!

There is an error in your solution that does not affect the answer. Why did you need to talk about the square of the average value of the velocity module in your solution? There is no such term in the assignment. Moreover, it is not at all equal to the root mean square value, but only proportional. Therefore your identity is false.

Yuri Shoitov (Kursk) 10.10.2012 22:00

Good evening, Alexey!

If this is so, what is the joke that you denote the same quantity differently in the same formula?! Perhaps to make it more scientific. Believe me, in our method of teaching physics, this “good” is enough without you.

Alexey (St. Petersburg)

I just can’t understand what’s bothering you. I have written that the square of the root mean square speed, by definition, is the average value of the square of the speed. B is simply part of the designation for root mean square speed, and b is the averaging procedure.

When the average kinetic energy of thermal motion of molecules decreases by 4 times, their root mean square speed

1) will decrease by 4 times

2) will increase 4 times

3) will decrease by 2 times

4) will increase by 2 times

Solution.

The average kinetic energy of thermal motion of molecules is proportional to the square of the root mean square velocity:

Consequently, when the average kinetic energy of the thermal motion of molecules decreases by 4 times, their root mean square speed will decrease by 2 times.

Correct answer: 3.

Answer: 3

When the absolute temperature of a monatomic ideal gas increases by 2 times, the mean square speed of thermal motion of molecules

1) will decrease by a factor

2) will increase by times

3) will decrease by 2 times

4) will increase by 2 times

Solution.

The absolute temperature of an ideal monatomic gas is proportional to the square of the root mean square speed of thermal motion of the molecules. Really:

Consequently, when the absolute temperature of an ideal gas increases by 2 times, the mean square speed of thermal motion of molecules will increase by a factor.

Correct answer: 2.

Answer: 2

When the absolute temperature of an ideal gas decreases by 2 times, the mean square speed of thermal motion of molecules

1) will decrease by a factor

2) will increase by times

3) will decrease by 2 times

4) will increase by 2 times

Solution.

The absolute temperature of an ideal gas is proportional to the square of the root mean square speed of thermal motion of molecules. Really:

Consequently, when the absolute temperature of an ideal gas decreases by 2 times, the mean square speed of thermal motion of molecules will decrease by a factor.

Correct answer: 1.

Answer: 1

Alexey (St. Petersburg)

Good afternoon

Don't be confused average value of the square of the speed is not equal to the square of the average speed, but to the square of the root mean square speed. The average speed for a gas molecule is generally zero.

Yuri Shoitov (Kursk) 11.10.2012 10:07

You are the one who is confusing and not the guest.

In all school physics, the letter v without an arrow denotes the modulus of velocity. If there is a line above this letter, then this indicates the average value of the velocity modulus, which is calculated from the Maxwell distribution, and it is equal to 8RT/pi*mu. The square root of the mean square velocity is 3RT/pi*mu. As you can see, there is no equality in your identity.

Alexey (St. Petersburg)

Good afternoon

I don’t even know what to say, it’s probably a question of notation. In Myakishev’s textbook, the mean square speed is denoted this way; Sivukhin uses the notation. How are you used to denoting this value?

Igor (Who needs it, knows) 01.02.2013 16:15

Why did you calculate the temperature of an ideal gas using the kinetic energy formula? After all, the root mean square speed is found by the formula: http://reshuege.ru/formula/d5/d5e3acf50adcde572c26975a0d743de1.png = Root of (3kT/m0)

Alexey (St. Petersburg)

Good afternoon

If you look closely, you will see that your definition of root mean square speed is the same as that used in the solution.

By definition, the square of the mean square velocity is equal to the mean square of the velocity, and it is through the latter that the gas temperature is determined.

When the average kinetic energy of thermal motion of molecules decreases by 2 times, the absolute temperature

1) will not change

2) will increase 4 times

3) will decrease by 2 times

4) will increase by 2 times

Solution.

The average kinetic energy of thermal motion of molecules of an ideal gas is directly proportional to the absolute temperature:

Consequently, when the average kinetic energy of thermal motion decreases by 2 times, the absolute temperature of the gas will also decrease by 2 times.

Correct answer: 3.

Answer: 3

As a result of heating neon, the temperature of this gas increased 4 times. The average kinetic energy of the thermal motion of its molecules in this case

1) increased 4 times

2) increased by 2 times

3) decreased by 4 times

4) has not changed

Thus, when neon is heated 4 times, the average kinetic energy of the thermal motion of its molecules increases 4 times.

Correct answer: 1.

• An important corollary follows from the basic equation of the molecular kinetic theory of gas: temperature is a measure of the average kinetic energy of molecules. Let's prove it.

For simplicity, we will assume the amount of gas to be 1 mol. We denote the molar volume of the gas by V M. The product of the molar volume and the concentration of molecules is Avogadro's constant N A, i.e., the number of molecules per 1 mole.

Let's multiply both sides of equation (4.4.10) by the molar volume V M and take into account that nV M = N A. Then

Formula (4.5.1) establishes a connection between macroscopic parameters - pressure p and volume V M - with the average kinetic energy of the translational motion of molecules.

At the same time, the experimentally obtained equation of state of an ideal gas for 1 mole has the form

The left-hand sides of equations (4.5.1) and (4.5.2) are the same, which means their right-hand sides must also be equal, i.e.

This implies a relationship between the average kinetic energy of translational motion of molecules and temperature:

The average kinetic energy of the chaotic movement of gas molecules is proportional to the absolute temperature. The higher the temperature, the faster the molecules move.

The relationship between temperature and the average kinetic energy of translational motion of molecules (4.5.3) is established for rarefied gases. However, it turns out to be valid for any substances whose movement of atoms or molecules obeys the laws of Newtonian mechanics. It is true for liquids, as well as for solids, in which atoms can only oscillate around equilibrium positions at the nodes of the crystal lattice.

As the temperature approaches absolute zero, the energy of thermal motion of molecules also approaches zero (1).

Boltzmann's constant

Equation (4.5.3) includes the ratio of the universal gas constant R to Avogadro’s constant N A. This ratio is the same for all substances. It is called the Boltzmann constant, in honor of L. Boltzmann, one of the founders of molecular kinetic theory.

Ludwig Boltzmann (1844-1906) - great Austrian physicist, one of the founders of molecular kinetic theory. In the works of Boltzmann, the molecular kinetic theory first appeared as a logically harmonious, consistent physical theory. Boltzmann gave a statistical interpretation of the second law of thermodynamics. He did a lot to develop and popularize Maxwell's theory of the electromagnetic field. A fighter by nature, Boltzmann passionately defended the need for a molecular interpretation of thermal phenomena and bore the brunt of the struggle against scientists who denied the existence of molecules.

Boltzmann's constant is

Equation (4.5.3) taking into account the Boltzmann constant is written as follows:

Physical meaning of the Boltzmann constant

Historically, temperature was first introduced as a thermodynamic quantity, and its unit of measurement was established - degrees (see § 3.2). After establishing the connection between temperature and the average kinetic energy of molecules, it became obvious that temperature can be defined as the average kinetic energy of molecules and expressed in joules or ergs, i.e. instead of the value T, introduce the value T * so that

The temperature thus defined is related to the temperature expressed in degrees as follows:

Therefore, Boltzmann's constant can be considered as a quantity that relates temperature, expressed in energy units, to temperature, expressed in degrees.

Dependence of gas pressure on the concentration of its molecules and temperature

Expressing from relation (4.5.5) and substituting into formula (4.4.10), we obtain an expression showing the dependence of gas pressure on the concentration of molecules and temperature:

From formula (4.5.6) it follows that at the same pressures and temperatures, the concentration of molecules in all gases is the same.

This implies Avogadro's law: equal volumes of gases at the same temperatures and pressures contain same number molecules.

The average kinetic energy of the translational motion of molecules is directly proportional to the absolute temperature. The proportionality coefficient - the Boltzmann constant k ≈ 10 23 J/K - must be remembered.

(1) At very low temperatures (near absolute zero), the movement of atoms and molecules no longer obeys Newton’s laws. According to more precise laws of motion of microparticles - the laws of quantum mechanics - absolute zero corresponds to the minimum value of the energy of movement, and not to the complete cessation of any movement at all.

LESSON

Subject . Temperature is a measure of the average kinetic energy of molecular motion.

Target: develop knowledge about temperature as one of the thermodynamic parametersand to the extentthe average kinetic energy of molecular motion, the Kelvin and Celsius temperature scales and the relationship between them, and the measurement of temperature using thermometers.

Lesson type: lesson in learning new knowledge.

Equipment: liquid thermometer demonstration.

During the classes

1. 1. 1. 1. 1. 1. Organizational stage

                  Update background knowledge

                  1. Do gases have their own volume?

                     Do gases have shape?

                     Do gases form jets? are they leaking?

                     Is it possible to compress gases?

                     How are molecules located in gases? How do they move?

                     What can be said about the interaction of molecules in gases?

Questions for the class

1. Why can gases be considered ideal at high temperatures?

( The higher the temperature of the gas, the greater the kinetic energy of the thermal movement of molecules, which means the gas is closer to ideal .)

2. Why do the properties of real gases at high pressure differ from the properties of ideal gases? (As pressure increases, the distance between gas molecules decreases and their interaction can no longer be neglected .)

1. 1. 1. 1. 1. 1. Communicating the topic, purpose and objectives of the lesson

We inform you about the topic of the lesson.

IV. Motivation educational activities

Why is it important to study gases and be able to describe the processes that occur in them? Justify your answer using the knowledge you have acquired in physics and your own life experience.

V. Learning new material

3. Temperature as a thermodynamic parameter of an ideal gas. The state of a gas is described using certain quantities called state parameters. There are:

1. microscopic, i.e. characteristics of the molecules themselves - size, mass, speed, momentum, energy;

   macroscopic, i.e. parameters of gas as a physical body - temperature, pressure, volume.

Molecular kinetic theory allows us to understand what the physical essence of such complex concept like the temperature.

Are you familiar with the word "temperature"? early childhood. Now let's get acquainted with temperature as a parameter.

We know that different bodies can have different temperatures. Therefore, temperature characterizes internal state bodies. As a result of the interaction of two bodies with different temperatures, as experience shows, their temperatures will become equal after some time. Numerous experiments indicate that the temperatures of bodies in thermal contact are equalized, i.e. thermal equilibrium is established between them.

Thermal or thermodynamic equilibrium called a state in which all macroscopic parameters in the system remain unchanged for an arbitrarily long time . This means that the volume and pressure in the system do not change, the aggregate states of the substance and the concentration of substances do not change. But microscopic processes inside the body do not stop even in thermal equilibrium: the positions of the molecules and their speeds during collisions change. In a system of bodies in a state of thermodynamic equilibrium, volumes and pressures can be different, but the temperatures are necessarily the same.Thus, temperature characterizes the state of thermodynamic equilibrium of an isolated system of bodies .

The faster molecules move in the body, the stronger feeling warmth when touched. Higher molecular speed corresponds to higher kinetic energy. Therefore, based on the temperature, one can get an idea of ​​the kinetic energy of molecules.

Temperature is a measure of the kinetic energy of thermal motion of molecules .

Temperature is a scalar quantity; in SI measured inKehlwines (K).

2 . Temperature scales. Temperature measurement

Temperature is measured using thermometers, the action of which is based on the phenomenon of thermodynamic equilibrium, i.e. A thermometer is a device for measuring temperature by contact with the body being examined. In the manufacture of thermometers different types takes into account the temperature dependence of different physical phenomena: thermal expansion, electrical and magnetic phenomena and so on.

Their action is based on the fact that when temperature changes, other physical parameters of the body, such as pressure and volume, also change.

In 1787, J. Charles experimentally established a direct proportional relationship between gas pressure and temperature. From the experiments it followed that with the same heating, the pressure of any gases changes equally. The use of this experimental fact formed the basis for the creation of a gas thermometer.

There are suchtypes of thermometers : liquid, thermocouples, gas, resistance thermometers.

Main types of scales:

In physics, in most cases, they use the absolute temperature scale introduced by the English scientist W. Kelvin (1848), which has two main points.

First main point - 0 K, or absolute zero.

Physical meaning absolute zero: is the temperature at which thermal motion of molecules stops .

At absolute zero, molecules do not move forward. The thermal motion of molecules is continuous and infinite. Consequently, absolute zero temperature is unattainable in the presence of molecules of a substance. Absolute zero temperature is the lowest temperature limit; there is no upper limit.

Second main point - This is the point at which water exists in all three states (solid, liquid and gas), it is called the triple point.

In everyday life, another temperature scale is used to measure temperature - the Celsius scale, named after the Swedish astronomer A. Celsius and introduced by him in 1742.

There are two main points on the Celsius scale: 0°C (the point at which ice melts) and 100°C (the point at which water boils). Temperature, which is determined on the Celsius scale, is designated t . The Celsius scale has both positive and negative values.

P Using the figure, we will trace the connection between temperatures on the Kelvin and Celsius scales.

The division value on the Kelvin scale is the same as on the Celsius scale:

ΔT = T 2 - T 1 =( t 2 +273) - ( t 1 +273) = t 2 - t 1 = Δt .

So,ΔT= Δt, those. a change in temperature on the Kelvin scale is equal to a change in temperature on the Celsius scale.

TK = t° C+ 273

0 K = -273°C

0°C =273 K

Class assignment .

Describe a liquid thermometer as a physical device according to the characteristics of a physical device.

Characteristics of a liquid thermometer as a physical device

Temperature measurement.

A sealed glass capillary with a liquid reservoir in the lower part filled with mercury or tinted alcohol. The capillary is attached to the scale and is usually placed in a glass case.

As the temperature increases, the liquid inside the capillary expands and rises, and as the temperature decreases, it falls.

Used to measure. temperature of air, water, human body, etc.

The range of temperatures that can be measured using liquid thermometers is wide (mercury from -35 to 75 °C, alcohol from -80 to 70 °C). The disadvantage is that when heated, different liquids expand differently; at the same temperature, the readings may differ slightly.

3. Temperature is a measure of the average kinetic energy of molecular motion

ABOUT It was experimentally established that at constant volume and temperature, the pressure of a gas is directly proportional to its concentration. Combining the experimentally obtained dependences of pressure on temperature and concentration, we obtain the equation:

p = nkT , Where -k=1.38×10 -23 J/C , the proportionality coefficient is Boltzmann's constant.Boltzmann's constant relates temperature to the average kinetic energy of motion of molecules in a substance. This is one of the most important constants in MCT. Temperature is directly proportional to the average kinetic energy of thermal motion of particles of a substance. Consequently, temperature can be called a measure of the average kinetic energy of particles, characterizing the intensity of thermal motion of molecules. This conclusion is in good agreement with experimental data showing an increase in the speed of particles of matter with increasing temperature.

The reasoning that we carried out to clarify the physical essence of temperature applies to an ideal gas. However, the conclusions we obtained are valid not only for ideal gases, but also for real gases. They are also valid for liquids and solids. In any state, the temperature of a substance characterizes the intensity of thermal motion of its particles.

VII. Summing up the lesson

We summarize the lesson and evaluate the students’ activities.

Homework

1. Learn theoretical material according to the notes. §_____ p._____

Teacher of the highest category L.A. Donets

Page 5

« Physics - 10th grade"

Absolute temperature.

Instead of temperature Θ, expressed in energy units, we introduce temperature, expressed in degrees familiar to us.

Θ = kТ, (9.12)

where k is the proportionality coefficient.

>The temperature determined by equality (9.12) is called absolute.

This name, as we will now see, has sufficient grounds. Taking into account definition (9.12), we obtain

This formula introduces a temperature scale (in degrees), independent of the substance used to measure temperature.

The temperature determined by formula (9.13) obviously cannot be negative, since all the quantities on the left side of this formula are obviously positive. Consequently, the lowest possible value of temperature T is the value T = 0 if the pressure p or volume V is equal to zero.

The limiting temperature at which the pressure of an ideal gas vanishes at a fixed volume or at which the volume of an ideal gas tends to zero at a constant pressure is called absolute zero temperature.

This is the most low temperature in nature, that “greatest or last degree of cold”, the existence of which Lomonosov predicted.

The English scientist W. Thomson (Lord Kelvin) (1824-1907) introduced the absolute temperature scale. Zero temperature on an absolute scale (also called Kelvin scale) corresponds to absolute zero, and each temperature unit on this scale is equal to a degree on the Celsius scale.

The SI unit of absolute temperature is called kelvin(denoted by the letter K).

Boltzmann's constant.

Let us determine the coefficient k in formula (9.13) so that a change in temperature by one kelvin (1 K) is equal to a change in temperature by one degree Celsius (1 °C).

We know the values ​​of Θ at 0 °C and 100 °C (see formulas (9.9) and (9.11)). Let us denote the absolute temperature at 0 °C by T 1, and at 100 °C by T 2. Then according to formula (9.12)

Θ 100 - Θ 0 = k(T 2 -T 1),

Θ 100 - Θ 0 = k 100 K = (5.14 - 3.76) 10 -21 J.

Coefficient

k = 1.38 10 -23 J/K (9.14)

called Boltzmann constant in honor of L. Boltzmann, one of the founders of the molecular kinetic theory of gases.

Boltzmann's constant relates the temperature Θ in energy units to the temperature T in kelvins.

This is one of the most important constants in molecular kinetic theory.

Knowing Boltzmann's constant, you can find the value of absolute zero on the Celsius scale. To do this, we first find the absolute temperature value corresponding to 0 °C. Since at 0 °C kT 1 = 3.76 10 -21 J, then

One kelvin and one degree Celsius are the same. Therefore, any value of absolute temperature T will be 273 degrees higher than the corresponding temperature t Celsius:

T (K) = (f + 273) (°C). (9.15)

The change in absolute temperature ΔT is equal to the change in temperature on the Celsius scale Δt: ΔT(K) = Δt (°C).

Figure 9.5 shows the absolute scale and the Celsius scale for comparison. Absolute zero corresponds to temperature t = -273 °C.

In the USA the Fahrenheit scale is used. The freezing point of water on this scale is 32 °F, and the boiling point is 212 °E. Temperature is converted from the Fahrenheit scale to the Celsius scale using the formula t(°C) = 5/9 (t(°F) - 32).

Note the most important fact: Absolute zero temperature is unattainable!

Temperature is a measure of the average kinetic energy of molecules.

The most important corollary follows from the basic equation of molecular kinetic theory (9.8) and the definition of temperature (9.13):
absolute temperature is a measure of the average kinetic energy of molecular motion.

Let's prove it.

From equations (9.7) and (9.13) it follows that This implies a relationship between the average kinetic energy of the translational motion of a molecule and temperature:

The average kinetic energy of the chaotic translational motion of gas molecules is proportional to the absolute temperature.

The higher the temperature, the faster the molecules move. Thus, the previously put forward guess about the connection between temperature and the average speed of molecules received reliable justification. The relationship (9.16) between temperature and the average kinetic energy of translational motion of molecules has been established for ideal gases.

However, it turns out to be true for any substances in which the movement of atoms or molecules obeys the laws of Newtonian mechanics. This is true for liquids and also for solids, where atoms can only oscillate around equilibrium positions at the nodes of the crystal lattice.

As the temperature approaches absolute zero, the energy of thermal motion of molecules approaches zero, i.e., the translational thermal motion of molecules stops.

Dependence of gas pressure on the concentration of its molecules and temperature. Considering that from formula (9.13) we obtain an expression showing the dependence of gas pressure on the concentration of molecules and temperature:

From formula (9.17) it follows that at the same pressures and temperatures, the concentration of molecules in all gases is the same.

This follows Avogadro's law, known to you from your chemistry course.

Avogadro's Law:

Equal volumes of gases at the same temperatures and pressures contain the same number of molecules.

The MCT behavior of molecules in bodies can be characterized by the average values ​​of certain quantities, which relate not to individual molecules, but to all molecules as a whole. T, V, P

MKT MECHANICAL QUANTITIES V T P a quantity characterizing the internal state of a body (it does not exist in mechanics)

MCT MACROSCOPIC PARAMETERS Values ​​that characterize the state of macroscopic bodies without taking into account the molecular structure of bodies (V, P, T) are called macroscopic parameters.

Temperature The degree of heating of bodies. cold T 1 warm

Temperature Why doesn't the thermometer show body temperature immediately after it comes into contact with it?

Thermal equilibrium is a state in which all macroscopic parameters remain unchanged for as long as desired. It is established over time between bodies that have different temperatures.

Temperature An important property of thermal phenomena. Any macroscopic body (or group of macroscopic bodies), under constant external conditions, spontaneously passes into a state of thermal equilibrium.

Temperature Constant conditions means that in the system 1 Volume and pressure do not change 2 There is no heat exchange 3 The temperature of the system remains constant

Temperature Microscopic processes inside the body do not stop even in thermal equilibrium 1 The velocities of molecules change during collisions 2 The position of molecules changes

Temperature The system can be in different states. In any state, temperature has its strictly defined value. Other physical quantities may have different meanings, which do not change over time.

Temperature measurement You can use any physical quantity, which depends on temperature. Most often: V = V(T) Temperature scales Celsius absolute (Kelvin scale) Fahrenheit

Temperature measurement Temperature scales Celsius scale = international practical scale 0°C Melting temperature of ice Reference points P 0 = 101325 Pa 100°C Boiling point of water Reference points – points on which the measurement scale is based

Temperature measurement Temperature scales Absolute scale (Kelvin scale) Zero temperature on the Kelvin scale corresponds to absolute zero, and each temperature unit on this scale is equal to a degree on the Celsius scale. 1 K = 1 °C William Thomson (Lord Kelvin) Temperature unit = 1 Kelvin = K

Temperature measurement Absolute temperature = measure of the average kinetic energy of molecular motion Θ = κT [Θ] = J [T] = K κ – Boltzmann's constant Establishes the relationship between temperature in energy units and temperature in kelvins