Presentation on the topic temperature in physics. Presentation on temperature

Presentation on the topic "Temperature" in physics in powerpoint format. In this presentation for 10th grade schoolchildren, the topic “Temperature” is discussed in detail, the concept of thermal equilibrium, absolute zero is given, and the Celsius and Kelvin scales are discussed in comparison. The presentation contains tasks and a test on this topic. Author of the presentation: Kononov Gennady Grigorievich, physics teacher.

Fragments from the presentation

Repetition

• Name the main provisions of the ICT
• What is diffusion called and what does it depend on?
• What does the speed of molecules depend on?
• What does the state of aggregation of a substance depend on?
• Name macroscopic and microscopic parameters.

Thermal equilibrium

Thermal equilibrium- this is a state of a system of bodies in thermal contact in which there is no heat transfer from one body to another, and all macroscopic parameters of the bodies remain unchanged.

Temperature

At thermal equilibrium in the system, the volume and pressure do not change, the aggregate states of the substance, and the concentrations of the 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.

Temperature measurement

To measure temperature, special devices are used - thermometers. Their action is based on the fact that when temperature changes, other physical parameters of the body, such as pressure and volume, also change.

Celsius:

• 0 °C - ice melting point
• 100 oC - boiling point of water
• - 273 oC - the lowest temperature in nature

Gas thermometer

A special place in physics is occupied by gas thermometers, in which the thermometric substance is a rarefied gas (helium, air) in a vessel of constant volume, and the thermometric quantity is the gas pressure p. Experience shows that gas pressure (at V = const) increases with increasing temperature, measured on the Celsius scale.

Dependence of gas pressure on temperature at V = const.

By extrapolating the graph to the region of low pressures, it is possible to determine a certain “hypothetical” temperature at which the gas pressure would become zero. Experience shows that this temperature is –273.15 °C and does not depend on the properties of the gas. It is impossible to experimentally obtain a gas in a state with zero pressure by cooling, since at very low temperatures all gases turn into liquid or solid states.

Kelvin scale

• The English physicist W. Kelvin in 1848 proposed using the point of zero gas pressure to construct a new temperature scale (Kelvin scale). In this scale, the temperature unit is the same as in the Celsius scale, but the zero point is shifted:
• T = t + 273
• In the SI system, it is customary to call the unit of temperature measured on the Kelvin scale kelvin and denoted by the letter K. For example, room temperature t = 20 °C on the Kelvin scale is T = 293 K.
• The Kelvin temperature scale is called the absolute temperature scale. It turns out to be most convenient when constructing physical theories.

Absolute zero temperature

the limiting temperature at which the pressure of an ideal gas goes to zero for a given volume or the volume of an ideal gas tends to zero at a constant pressure

Temperature is a measure of the kinetic energy of molecules

• The average kinetic energy of molecular motion is proportional to the absolute temperature
• The average kinetic energy of the translational motion of a molecule does not depend on its mass. A Brownian particle suspended in a liquid or gas has the same average kinetic energy as an individual molecule, the mass of which is many orders of magnitude less than the mass of the Brownian particle.

Slide 1

TEMPERATURE

Physics teacher, State Budgetary Educational Institution Secondary School No. 270, St. Petersburg PAPIAN S. V.

Slide 2

Temperature Features

Features of temperature as a macroscopic characteristic of a gas: changes when the state of the gas changes; characterizes the state of thermal equilibrium of the system; indicates the direction of heat exchange; can be measured.

Slide 3

Temperature measurement

The body must be brought into thermal contact with the thermometer. The thermometer must have a mass significantly less than body weight. The thermometer reading should be taken only after thermal equilibrium has occurred.

Slide 4

Thermometers

Liquid thermometer (mercury: -38 to 260 0C; glycerin: -50 to 100 0C). Thermocouple (from -269 to 2300 0C). Thermistors are semiconductor devices whose resistance depends on temperature. Gas thermometers.

Slide 5

Body temperature is a measure of the average kinetic energy of molecular motion.

What physical quantity is the same for all bodies in thermal equilibrium? Let us assume that at thermal equilibrium the average kinetic energies of the molecules are the same. From the basic MKT equation one can obtain:

Slide 6

Conclusion: the value pV/N i.e. Ek=mv2/2 depends only on temperature.

Let's consider an experiment to measure the pV/N value for 1 mole of hydrogen and 1 mole of oxygen.

Slide 7

The difference between the values ​​of pV/N obtained in the experiment is 1.38 * 10-21 J. Let's divide the resulting value by 100, and find that one degree Celsius corresponds to k=1.38*10-23 Kelvin. k=1.38*10-23 J/K – Boltzmann’s constant.

Boltzmann's constant

Slide 8

Absolute temperature and absolute zero

From the resulting equality it follows that at T = 0 either the pressure (i.e., the movement and collision of molecules with the walls stops) or the volume of the gas (i.e., compression to zero) must be equal to zero. Hence the concept of absolute zero temperature (0 K) - the temperature at which the movement of molecules should stop. Let us establish a connection between absolute temperature and temperature in Celsius: since at t = 0 kT = 3.76*10 -21 J, where k = 1.38*10-23 J/K, then T = 3.76* 10 -21/ 1.38*10-23 ≈ 273.15 (K) Thus T ≈ t + 273

The presentation contains material on the topic "Temperature and its measurement" and can be used in grade 8. in the lesson "Thermal motion. Temperature" and in the 10th grade in the lesson "Temperature - a measure of average kinetic energy."

Download:

Preview:

To use presentation previews, create a Google account and log in to it: https://accounts.google.com

Slide captions:

Temperature and its measurement Completed by: G.P. Krivchikova, physics teacher at gymnasium No. 12 in Belgorod.

Temperature and its measurement Before the invention of the thermometer, people could only judge their thermal state by their immediate sensations: warm or cool, hot or cold.

Invention of the thermometer In 1592, Galileo Galilei created the first instrument for observing changes in temperature, calling it the thermoscope. The thermoscope was a small glass ball with a soldered glass tube. The ball was heated and the end of the tube was dipped into water. When the ball cooled, the pressure in it decreased, and the water in the tube, under the influence of atmospheric pressure, rose to a certain height. As the weather warmed, the water level in the tubes dropped. The disadvantage of the device was that it could only be used to judge the relative degree of heating or cooling of the body, but it did not have a scale

In the 17th century, the air thermoscope was converted into an alcohol thermoscope by the Florentine scientist Torricelli. The device was turned upside down, the vessel with water was removed, and alcohol was poured into the tube. The operation of the device was based on the expansion of alcohol when heated - now the readings did not depend on atmospheric pressure. This was one of the first liquid thermometers. The readings of the instruments did not agree with each other, since no specific system was taken into account when calibrating the scales. In 1694, Carlo Renaldini proposed taking the melting point of ice and the boiling point of water as two extreme points. In 1714, D. G. Fahrenheit made a mercury thermometer.

Thermometer (Greek θέρμη - heat and μετρέω - I measure) - a device for measuring the temperature of air, soil, water, and so on. Types of thermometers: Liquid Liquid thermometers are based on the principle of changing the volume of liquid that is poured into the thermometer (usually alcohol or mercury) when the ambient temperature changes.

Mechanical thermometers This type of thermometer operates on the same principle as liquid thermometers, but a metal spiral or bimetal tape is usually used as a sensor.

Electric thermometers The operating principle of electric thermometers is based on the change in conductor resistance when the ambient temperature changes. Gas thermometer At the end of the 18th century. Charles found that the same heating of any gas leads to the same increase in pressure, if the volume remains constant. When the temperature changes, the dependence of the gas pressure at a constant volume is expressed by a linear law. And it follows from this that gas pressure (at V=const) can be taken as a quantitative measure of temperature. By connecting the vessel containing the gas to a pressure gauge and calibrating the device, you can measure the temperature using the readings of the pressure gauge. The most accurate results are obtained if hydrogen or helium is used as the working fluid. Optical thermometers Optical thermometers allow you to record temperature by changing the luminosity level

Temperature scales Celsius scale In technology, medicine, meteorology and in everyday life, the Celsius scale is used, in which the freezing point of water is taken as 0, and the boiling point of water at normal atmospheric pressure is taken as 100°. The scale was proposed by Anders Celsius in 1742. This is a temperature scale a scale in which 1 degree (1 °F) is equal to 1/180 of the difference between the boiling point of water and the melting point of ice at atmospheric pressure, and the melting point of ice is +32 °F. Temperature on the Fahrenheit scale is related to temperature on the Celsius scale (t °C) by the ratio t °C = 5/9 (t °F - 32), 1 °F = 9/5 °C + 32. Proposed by G. Fahrenheit in 1724. Fahrenheit

Reaumur scale Proposed in 1730 by R. A. Reaumur, Unit - degree Reaumur (°R), 1 °R is equal to 1/80 of the temperature interval between the reference points - the temperature of melting ice (0 °R) and boiling water (80 °R ) 1 °R = 1.25 ° C. Currently, the scale has fallen out of use; it was preserved longest in France, the author’s homeland.

Kelvin temperature scale The concept of absolute temperature was introduced by W. Thomson (Kelvin). The absolute temperature scale is called the Kelvin scale. The unit of absolute temperature is kelvin (K). The lower limit of temperature is absolute zero, that is, the lowest possible temperature at which, in principle, it is impossible to extract thermal energy from a substance. Absolute zero is defined as 0 K, which is equal to −273.15 °C. The boiling point of water is 373 K, the melting temperature of ice is 273 K. The number of degrees Celsius and kelvins between the freezing and boiling points of water is the same and equal to 100. Therefore, degrees Celsius are converted to kelvins using the formula T = t °C + 273.15.

The highest temperature of + 58 0 degrees in the shade was recorded on September 13, 1922 in the town of Al-Azizia in Libya. The record low temperature on the Earth's surface -89 0 degrees was recorded on July 21, 1983 at the Soviet Antarctic research station Vostok. The coldest inhabited place is Oymyakon (with a population of 4 thousand people) in Yakutia. There the temperature dropped to almost -68 0 degrees. The warmest year on the planet over the past century and a half was 1990. The sharpest drop in temperature that occurred during the day was recorded on January 23-24, 1916 in the US state of Montana. It amounted to 56 0 C (from +7 to -49 0 C). The greatest temperature difference is observed in Yakutia. At the “pole of cold”, in Verkhoyansk, it reaches 106.7 0 C (from -70 0 in winter to +36.7 0 in summer). The highest ocean water temperature - 404 0 C - was recorded by an American research submarine at a hot spring 480 kilometers off the west coast of North America. Water heated to such a high temperature did not turn into steam due to high pressure, since the source was located at a considerable depth. Temperature records

1 slide

PHYSICS LESSON IN 10TH GRADE Temperature Teacher Kononov Gennady Grigorievich Secondary school No. 29 Slavyansky district of Krasnodar region

2 slide

REPEATMENT 1. Name the main provisions of ICT 2. What is called diffusion and what does it depend on? 3. What does the speed of molecules depend on? 4. What does the state of aggregation of a substance depend on? 5. Name macroscopic and microscopic parameters.

3 slide

THERMAL EQUILIBRIUM Thermal equilibrium is a state of a system of bodies in thermal contact in which there is no heat transfer from one body to another, and all macroscopic parameters of the bodies remain unchanged.

4 slide

At thermal equilibrium in the system, the volume and pressure do not change, the aggregate states of the substance, and the concentrations of the 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. TEMPERATURE

5 slide

TEMPERATURE MEASUREMENT To measure temperature, special devices are used - thermometers. Their action is based on the fact that when temperature changes, other physical parameters of the body, such as pressure and volume, also change.

6 slide

THERMOMETER SCALE Celsius scale: 0 °C - melting point of ice 100 °C - boiling point of water - 273 °C - the lowest temperature in nature

7 slide

Swedish scientist Anders Celsius Swedish naturalist Carl Linnaeus creators of the Celsius scale

8 slide

GAS THERMOMETER A special place in physics is occupied by gas thermometers, in which the thermometric substance is a rarefied gas (helium, air) in a vessel of constant volume, and the thermometric quantity is the gas pressure p. Experience shows that gas pressure (at V = const) increases with increasing temperature, measured on the Celsius scale.

Slide 9

Dependence of gas pressure on temperature at V = const. By extrapolating the graph to the region of low pressures, it is possible to determine a certain “hypothetical” temperature at which the gas pressure would become zero. Experience shows that this temperature is –273.15 °C and does not depend on the properties of the gas. It is impossible to experimentally obtain a gas in a state with zero pressure by cooling, since at very low temperatures all gases turn into liquid or solid states.

10 slide

KELVIN SCALE The English physicist W. Kelvin in 1848 proposed using the point of zero gas pressure to construct a new temperature scale (Kelvin scale). In this scale, the unit of measurement of temperature is the same as in the Celsius scale, but the zero point is shifted: T = t + 273 In the SI system, it is customary to call the unit of measurement of temperature on the Kelvin scale kelvin and denoted by the letter K. For example, room temperature t = 20 ° C on the Kelvin scale is equal to T = 293 K. The Kelvin temperature scale is called the absolute temperature scale. It turns out to be most convenient when constructing physical theories.

11 slide

12 slide

ABSOLUTE ZERO TEMPERATURE - the limiting temperature at which the pressure of an ideal gas goes to zero for a given volume or the volume of an ideal gas goes to zero at a constant pressure

Slide 13

TEMPERATURE IS A MEASURE OF THE KINETIC ENERGY OF MOLECULES The average kinetic energy of the movement of molecules is proportional to the absolute temperature; the average kinetic energy of the translational movement of a molecule does not depend on its mass. A Brownian particle suspended in a liquid or gas has the same average kinetic energy as an individual molecule, the mass of which is many orders of magnitude less than the mass of the Brownian particle.

Slide 14

p = nkT k = 1.38 10 J/K - Boltzmann's constant Consequences: 1. at the same pressures and temperatures, the concentration of molecules in all gases is the same 2. for a mixture of two gases, the pressure is p = p1 + p2 TEMPERATURE AND PRESSURE – 23

In 1714, the Dutch scientist D. Fahrenheit made a mercury thermometer. In 1730, the French physicist R. Reaumur proposed an alcohol thermometer. In 1848, the English physicist William Thomson (Lord Kelvin) proved the possibility of creating an absolute temperature scale. R. Reaumur Lord Kelvin

It is curious that ... 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. Somewhat later, the Celsius scale was given a modern look by his compatriot Stroemer.

This is the temperature at which atoms ionize (which lose their electrons) and matter enters a fourth state called plasma. (above °C) High temperatures –

The highest temperature obtained at the center of a thermonuclear bomb explosion is about million °C. The maximum temperature reached during a controlled thermonuclear reaction at the TOKAMAK fusion test facility at the Princeton Plasma Physics Laboratory, USA, in June 1986, is 200 million °C.

Cryogenic temperatures, typically temperatures below the boiling point of liquid air (about 80 K). Such temperatures are usually counted from absolute zero temperature (-273.15 C, or 0 K) and expressed in kelvins (K). To obtain and maintain low temperatures, liquefied gases are usually used. Low temperatures -

Lowest temperature The lowest temperature created by man was obtained in 1995 by Eric Cornell and Carl Wieman from the USA when cooling rubidium atoms. It was less than 1/170 billionth of a degree above absolute zero (5.9 × 1012).

Application Separation of gases (production of oxygen and nitrogen) producing high vacuum (allows you to simulate conditions characteristic of outer space, and test materials and devices under these conditions.) in medicine. (local freezing of tissues, treatment of brain tumors, urological and other diseases. Long-term storage of living tissues)

How? Liquefaction of gases includes several stages necessary to convert the gas into a liquid state. Many gases can be liquefied simply by cooling at normal atmospheric pressure; others, such as carbon dioxide, also require increased pressure.

Application In medicine and biology (for preservation and long-term storage of blood, bone marrow, blood vessels and muscle tissue) Storage and transportation of food products in automobiles and railways. refrigerators Rocketry Cryogenic vacuum technology Microcryogenic cooling devices Study of the fundamental properties of gas molecules (for example, intermolecular forces of interaction Gas storage