Mass of molecules
Molecules- these are the smallest particles of many substances, the composition and chemical properties of which are the same as those of the given substance. Any substance consists of particles, therefore the amount of substance is considered to be proportional to the number of particles. The unit of quantity of a substance is the mole. A mole is equal to the amount of substance in a system containing the same number of particles as are contained in atoms in carbon weighing 12 g. The ratio of the number of molecules to the amount of substance is called Avogadro's constant.
The molar mass of a substance is equal to the ratio of the mass of the substance to the corresponding amount of the substance:
Brownian motion: Brownian motion is the movement of particles suspended in a gas or liquid. In 1827, the English botanist Brown discovered the random movement of solid particles visible through a microscope in a liquid.
This phenomenon was called Brownian motion. This movement does not stop: as the movement increases, its intensity increases. Brownian motion is the result of fluctuation (a noticeable deviation from the average value). The reason for the Brownian motion of a particle is that the collisions of molecules in a liquid with the particle do not cancel each other out.
Control questions.
1. Define thermal phenomena.
2. What is thermal motion?
3. What is the significance of thermal phenomena?
4. Estimate the size of the molecules.
5. In what units is the mass of molecules measured?
Option I
1. What energy does the mechanical energy of a lead ball transform into when it hits a lead plate?
A) energy becomes equal to 0;
B) mechanical energy turns into internal energy;
C) mechanical energy increases.
2. Which of the following substances have the lowest thermal conductivity?
A) hard; B) liquid; B) gaseous; D) solid and liquid.
3. A cold metal spoon was dipped into a glass of hot water. Has the internal energy of the spoon changed, and if so, in what way?
A) increased by doing work;
B) decreased due to work being done;
B) increased due to heat transfer; D) has not changed.
4. In which of the following substances can convection occur?
A) in solids; B) in liquid; B) in gaseous; D) in gaseous and liquid.
5. In which of the following substances does heat transfer occur mainly by thermal conductivity?
A) air;
B) brick;
6. How can you change the internal energy of the body?
A) only by performing work; B) only by heat transfer;
C) the performance of work and heat transfer.
7. How is energy transferred from the Sun to the Earth?
A) thermal conductivity;
B) radiation;
B) convection;
D) work.
8. What type of heat transfer is not accompanied by the transfer of matter?
A) convection only;
B) thermal conductivity only;
B) only radiation and convection.
9. Which of the following substances has good thermal conductivity?
A) glass;
To the air;
10. In what case will the internal energy of water change?
A) carry water in a bucket;
B) pour water from a bucket into a kettle;
C) heat the water to a boil.
11. What is thermal motion called?
A) ordered movement of a large number of molecules;
B) continuous random movement of a large number of molecules;
B) rectilinear movement of an individual molecule.
12. Which of the following is the definition of internal energy?
A) the energy that a body possesses due to its movement;
B) energy, which is determined by the position of interacting bodies or parts of one body;
C) the energy of movement and interaction of the particles that make up the body.
13. What physical quantities does the internal energy of a body depend on?
A) on the mass and speed of the body;
B) on height above the ground and speed;
C) on temperature and body weight.
14. The copper wire clamped with pliers is bent and unbent several times. Will the internal energy change, and if so, in what way?
A) yes by heat transfer;
B) yes, by doing work;
B) yes, by heat transfer and work;
D) will not change.
15. What physical phenomenon is used for the design and operation of a mercury thermometer?
A) melting of a solid when heated;
B) convection in a liquid when heated;
B) expansion of a liquid when heated;
D) evaporation of liquid.
The text of the work is posted without images and formulas.
The full version of the work is available in the "Work Files" tab in PDF format
Hypothesis: Thanks to scientific knowledge and achievements, lightweight, durable, low-thermal conductivity materials have been created for clothing and home protection, air conditioners, fans and other devices. This allows us to overcome difficulties and many problems associated with heat. But it is still necessary to study thermal phenomena, since they have an extremely large impact on our lives.
Target: study of thermal phenomena and thermal processes.
Tasks: talk about thermal phenomena and thermal processes;
study the theory of thermal phenomena;
in practice, consider the existence of thermal processes;
show the manifestation of these experiences.
Expected Result: conducting experiments and studying the most common thermal processes.
: material on the topic was selected and systematized, experiments and a blitz survey of students were conducted, a presentation was prepared, a poem of one’s own composition was presented.
Thermal phenomena are physical phenomena that are associated with heating and cooling of bodies.
Heating and cooling, evaporation and boiling, melting and solidification, condensation are all examples of thermal phenomena.
Thermal movement - process of chaotic (disorderly) movement
particles that form matter.
The higher the temperature, the greater the speed of particle movement. The thermal motion of atoms and molecules is most often considered. Molecules or atoms of a substance are always in constant random motion.
This movement determines the presence in any substance of internal kinetic energy, which is associated with the temperature of the substance.
Therefore, the random motion in which molecules or atoms are always found is called thermal.
The study of thermal phenomena shows that as much as the mechanical energy of bodies decreases in them, their mechanical and internal energies increase, which remains unchanged during any process.
This is the law of conservation of energy.
Energy does not appear from nothing and does not disappear anywhere.
It can only pass from one type to another, maintaining its full meaning.
The thermal movement of molecules never stops. Therefore, any body always has some kind of internal energy. Internal energy depends on body temperature, the state of aggregation of matter and other factors and does not depend on the mechanical position of the body and its mechanical movement. A change in the internal energy of a body without doing work is called heat transfer .
Heat transfer always occurs in the direction from a body with a higher temperature to a body with a lower temperature.
There are three types of heat transfer:
Thermal processes are a type of thermal phenomena; processes in which the temperature of bodies and substances changes, and it is also possible to change them states of aggregation. Thermal processes include:
Heating
Cooling
Vaporization
Boiling
Evaporation
Crystallization
Melting
Condensation
Combustion
Sublimation
Desublimation
Let us consider, as an example, a substance that can be in three states of aggregation: water (L - liquid, T - solid, G - gaseous)
Heating- the process of increasing the temperature of a body or substance. Heating is accompanied by the absorption of heat from the environment. When heated, the state of aggregation of a substance does not change.
Experiment 1: Heating.
Let's take water from the tap into a glass and measure its temperature (25°C),
then put the glass in a warm place (window on the sunny side), and after a while measure the water temperature (30°C).
After waiting some more time, I measured the temperature again (35°C). Conclusion: The thermometer shows an increase in temperature first by 5°C, and then by 10°C.
Cooling- the process of lowering the temperature of a substance or body; Cooling is accompanied by the release of heat into the environment. When cooled, the state of aggregation of a substance does not change.
Experiment 2: Cooling. Let's see how cooling occurs experimentally.
Let's take hot water from a tap into a glass and measure its temperature (60°C), then place this glass on the windowsill for a while, after which we measure the temperature of the water and it becomes equal (20°C).
Conclusion: the water cools and the thermometer shows a decrease in temperature.
Experiment 3: Boiling.
We encounter boiling water every day at home.
Pour water into the kettle and place it on the stove. First, the water heats up, and then the water boils. This is evidenced by the steam coming out of the kettle's spout.
Conclusion: When the water boils, steam from the neck of the kettle comes out through a small hole and whistles, and we turn off the stove.
Evaporation- This is vaporization occurring from the free surface of a liquid.
Evaporation depends on:
Substance temperatures(the higher the temperature, the more intense the evaporation);
Liquid surface area(the larger the area, the greater the evaporation);
Kind of substance(different substances evaporate at different rates);
Presence of wind(in the presence of wind, evaporation occurs faster).
Experiment 4: Evaporation.
If you have ever observed puddles after rain, then you have undoubtedly noticed that the puddles become smaller and smaller. What happened to the water?
Conclusion: she evaporated!
Crystallization(solidification) is the transition of a substance from a liquid state of aggregation to a solid state. Crystallization is accompanied by the release of energy (heat) into the environment.
Experiment 5: Crystallization. To detect crystallization, let's conduct an experiment.
Let's take water from the tap into a glass and put it in the freezer of the refrigerator. After some time, the substance hardens, i.e. a crust appears on the surface of the water. Then all the water in the glass completely turned into ice, that is, it crystallized.
Conclusion: First the water cools to 0 degrees, then freezes.
Melting- the transition of a substance from a solid to a liquid state. This process is accompanied by the absorption of heat from the environment. To melt a solid crystalline body, a certain amount of heat must be transferred to it.
Experiment 6: Melting. Melting is easily detected experimentally.
We take out a glass of frozen water from the freezer compartment of the refrigerator, which we placed. After some time, water appeared in the glass - the ice began to melt. After some time, all the ice melted, that is, it completely turned from solid to liquid.
Conclusion: Over time, ice receives heat from the environment and will melt over time.
Condensation-transition of a substance from a gaseous state to a liquid state.
Condensation is accompanied by the release of heat into the environment.
Experiment 7: Condensation.
We boiled water and held a cold mirror to the spout of the kettle. After a few minutes, drops of condensed water vapor are clearly visible on the mirror.
Conclusion: steam settling on the mirror turns into water.
The phenomenon of condensation can be observed in summer, in the early cool mornings.
Droplets of water on grass and flowers - dew - indicate that the water vapor contained in the air has condensed.
Combustion is the process of burning fuel, accompanied by the release of energy.
This energy is used in various
spheres of our life.
Experiment 8: Combustion. Every day we can watch natural gas burn in a stove burner. This is the process of fuel combustion.
Also the process of fuel combustion is the process of burning wood. Therefore, to conduct an experiment on fuel combustion, it is enough to just light the gas
burner or match.
Conclusion: When fuel burns, heat is released and a specific smell may appear.
The result of the project: in my project work I studied the most common thermal processes: heating, cooling, vaporization, boiling, evaporation, melting, crystallization, condensation, combustion, sublimation and desublimation.
In addition, the work touched upon such topics as thermal motion, aggregate states of substances, as well as the general theory of thermal phenomena and thermal processes.
Based on simple experiments, one or another thermal phenomenon was considered. The experiments are accompanied by demonstration pictures.
Based on experiments, the following is considered:
The existence of various thermal processes;
The relevance of thermal processes in human life has been proven.
I also conducted a blitz survey of 9 “A” class students consisting of 15 people.
Blitz - survey of 9th grade students.
Questions:
1. What are thermal phenomena?
2. Give examples of thermal phenomena
3. What movement is called thermal?
4. What is thermal conductivity?
5. Aggregate transformations are...
6. The phenomenon of turning liquid into vapor?
7. The phenomenon of turning steam into liquid?
8. What process is called melting?
9. What is evaporation?
10. Name the processes reverse to heating, melting, evaporation?
Answers:
1. Thermal phenomena - physical phenomena associated with heating and cooling of bodies
2. Examples of thermal phenomena: heating and cooling, evaporation and boiling, melting and solidification, condensation
3. Thermal motion - random, chaotic movement of molecules
4. Thermal conduction - transfer of heat from one part to another
5. Aggregate transformations are phenomena of the transition of a substance from one state of aggregation to another
6. Vaporization
7. Condensation
8. Melting is the transition of a substance from a solid to a liquid state. This process is accompanied by the absorption of heat from the environment
9. Evaporation is vaporization occurring from the free surface of a liquid
10. Processes reverse to heating, melting, evaporation - cooling, crystallization, condensation
Blitz survey results:
1. Correct answer - 7 people - 47%
Wrong answer - 8 people - 53%
2. Correct answer -6 people - 40%
Wrong answer -9 people - 60%
3. Correct answer - 10 people - 67%
4. Correct answer -6 people - 40%
Wrong answer - 9 people - 60%
5. Correct answer - 8 people - 53%
6. Correct answer - 12 people - 80%
Wrong answer - 3 people - 20%
7. Correct answer - 8 people - 53%
Wrong answer - 7 people - 47%
8. Correct answer - 10 people - 67%
Wrong answer - 5 people - 33%
9. Correct answer - 13 people - 87%
Wrong answer - 2 people - 13%
10. Correct answer - 8 people -53%
Wrong answer - 7 people - 47%
The flash survey showed that students do not have sufficient knowledge of this topic, and I hope that my project will help them fill the missing gaps on this topic.
The goal and objectives of the project work that I set were completed.
I want to finish my work with a poem that I wrote together with my grandfather.
Thermal phenomena
We study phenomena
We want to know about warmth.
We live in a wonderful world -
Everything is like two and two are four.
We do the work
Having rocked the company of molecules,
We chop a log for firewood -
We feel warm.
A very important task -
This is heat transfer.
Heat can be transferred
Take from heated water.
All bodies are thermally conductive:
The water heats the radiator,
Air flows from bottom to top
Transfers heat into the house.
And the window glass
Keeps the house warm.
There is an air layer in the frame -
It's a mountain for warmth.
It doesn't allow heat to pass through
And he keeps it in the apartment.
Well, during the day, we know ourselves,
The sun will give warmth with its rays...
To know all these properties,
To live in friendship with warmth in the world,
And actually apply -
We need to learn PHYSICS!!!
Bibliography
1. Rakhimbaev M.M. Flash textbook: “Physics. 8th grade". 2. Teaching physics that develops the student. Book 1. Approaches, components, lessons, tasks / Compiled and ed. EM. Braverman: - M.: Association of Physics Teachers, 2003. - 400 p. 3. Dubovitskaya T.D. Diagnosis of the significance of an academic subject for the development of students’ personality. Bulletin of OSU, No. 2, 2004. 4. Kolechenko A.K. Encyclopedia of educational technologies: A manual for teachers. - St. Petersburg: KARO, 2004. 5. Selevko G.K. Pedagogical technologies based on activation, intensification and effective management of educational programs. M.: Research Institute of School Technologies, 2005. 6. Electronic resources: Website http://school-collection.edu.ru Website http://obvad.ucoz.ru/index/0 Website http://zabalkin.narod.ru Website http://somit.ru
a) if it is widely known
a) only in gaseous
b) in gaseous and liquid
c) in all conditions
d) in no condition
1) which of the following refers to physical phenomena? a) molecule b) melting c) kilometer d) gold2) which of the following is a physical quantity?
a) second b) force c) melting d) silver
3) what is the basic unit of mass in the international system of units?
a) kilogram b) newton c) watt d) joule
4) in what case in physics is a statement considered true?
a) if it is widely known
d) if it has been experimentally tested many times by different scientists
5) in which state of the substance at the same temperature the speed of movement of molecules is greater?
a) in solid b) in liquid c) in gas d) in all the same
6) in what state of matter is the speed of random movement of molecules decreases with decreasing temperature?
a) only in gaseous
b) in gaseous and liquid
c) in all conditions
d) in no condition
7) the body retains its volume and shape. What state of aggregation is it in? the substance from which the body is made?
a) in liquid b) in solid c) in gas c) in any state
Help) But we need it urgently 1) Which of the following is a physical body? (1. Hurricane. 2. Water. 3. Knife) A) 1. B) 2. C) 3. D) 1,2. D)1.3. E) 2.3. G) 1,2,3
2) Choose the correct statement:
A) Only solids are made up of molecules. B) Only liquids consist of molecules. C) Only gases consist of molecules. D) All bodies are made of molecules.
3) In what media does diffusion occur?
A) Only in gases.. B) Only in liquids. B) Only in solids. D) In gases and liquids. D) In liquids and solids. E) In gases and solids. G) In gases, liquids and solids.
4) Does the speed of movement of molecules change as the temperature of a substance increases?
A) Does not change. B) Decreases. B) It increases. D) It changes only for gases. D) It changes only for molecules of liquids and gases.
5) Which of the following is a substance? (1. Iron.2. Rope.3. Paper)
A) 1. B) 2. C) 3. D) 1,2. D) 1.3. E) 2.3. G) 1,2,3
6) The car covered a distance of 200 m in 10 seconds. What is its speed?
A) 2000 m/s. B) 20 m/s. B) 2 m/s. D) 2 km/h. D) 20 km/h.
7) How far will a cyclist travel at a speed of 5 m/s in 20 s?
A) 4 m. B) 100 m. C) 100 km.
8) How long will it take a pedestrian to cover a distance of 1200 m, moving at a speed of 2 m/s?
A) 600 s. B) 2400 s. B) 600 min. D) 6 hours.
8. The tram moves at a speed of 36 km/h. What distance in meters will he travel in 720 seconds?9. During the flight, a flock of 30 birds covered 15 km in 30 minutes. Determine the average speed of one bird in km/h.
10. What is the mass of gasoline in a five-liter can? (Density 0.71 g/cm3)
14. How many millimeters are in three meters?
17. Gas takes up half the volume of a three-liter bottle. What volume does gas occupy in SI units?
18. The pictures show a beaker with kerosene and a lead weight weighing 113 g. Determine the volume of liquid in the beaker after lowering the weight into it. Lead density 11.3 g/cm3 (photo below)
19. Convert 100 mm2 to cm2.
20. Which of the following relates to thermal phenomena?
21. Before the lesson, the physics teacher selected a copper wire of the required diameter. To do this, he wound it tightly around the rod. The number of turns obtained from the teacher turned out to be 30 pieces, with a total length of 15 cm. Determine the diameter of the wire in mm.
22. Determine the mass of the part shown in the figure if its density is 7.6 g/cm3. Round your answer to the nearest whole number (photo below)
23. At night the air temperature was -4°C, and during the day it rose to 4°C. Determine the difference between these temperatures.
27. What formula is used to calculate the density of a substance through the mass of the molecule (m0) and concentration n?
28. Which of the following quantities are vector quantities? (Strength, density, speed, mass)
29. Which of the listed forces is always directed towards the center of the earth?
30. What formula is used to calculate the elastic force of a deformed body in physics?
Whatever you can, please.
OPTION 1
1). body falling to Earth 2). heating a pan of water 3) melting ice 4) reflection of light 5) movement of one molecule
A. 1, 2 and 5 B. 2, 3, 5 C. 2, 3 D. 2, 4 E. 1, 5 E. All
They have internal energy
A. All bodies B. Only solids C. Only liquids D. Only gases
How can you change the internal energy of the body?
A. Heat transfer. B. By doing work. B. Heat transfer and work. D. The internal energy of the body cannot be changed.
A. Heat transfer. B. By doing work. B. Heat transfer and work. D. The internal energy of the plate does not change.
What type of heat transfer is accompanied by the transfer of matter?
A. Convection only. B. Thermal conductivity only. B. Radiation only.
D. Convection and thermal conductivity. D. Convection and radiation.
E. Convection, thermal conductivity, radiation. G. Thermal conductivity, radiation.
OPTION-2
Which of the following examples relate to thermal phenomena?
1) evaporation of liquid 2) echo 3) inertia 4) gravity 5) diffusion
A. 1, 3 B. 1, 4 C. 1, 5 D. 2, 4 C. All
The internal energy of a body depends on
A. Mechanical movement of the body B. Position of the body relative to other bodies C. movement and interaction of particles of the body D. Mass and density of the body.
Can the internal energy of a body change during work and heat transfer?
A. The internal energy of the body cannot change. B. Can only when doing work. B. It can only with heat transfer. D. Can during work and heat transfer.
A. Heat transfer. B. By doing work. B. Heat transfer and work. D. The internal energy of the wire does not change.
What type of heat transfer is not accompanied by the transfer of matter?
A. Radiation. B. Convection. B. Thermal conductivity. D. Radiation, convection, thermal conductivity. D. Radiation, convection. E. Radiation, thermal conductivity.
G. Convection, thermal conductivity.
Option 1
The copper wire clamped with pliers is bent and unbent several times. Does this change the internal energy of the wire? If yes, then in what way?
Why do many plants die in snowless winters, while they can withstand significant frosts if the snow cover is large?
The spacesuits worn by astronauts are usually painted white. At the same time, some surfaces of spaceships are black. What explains the choice of color?
When is the fastest time for a kettle of boiling water to cool down: when is it put on ice or when ice is placed on the lid of the kettle?
Why do many animals sleep curled up in a ball in cold weather?
Option 2
The steel plate was placed on a hot electric stove. In what way does the internal energy of the plate change?
Why can you burn your hands when sliding quickly down a rope or pole?
Scissors and a pencil lying on the table have the same temperature. Why do scissors feel colder to the touch?
Why does snow covered with soot or dirt melt faster than clean snow?
In industrial refrigerators, air is cooled using pipes through which cooled liquid flows. Where is the best place to place these pipes?