Creativity of the poet, dialectic philosopher, the art of the researcher -
here are the materials from which the Great Scientist is composed.
Clement Arkadyevich Timiryazev
Clement Arkadyevich Timiryazev (03.06.1843-28.04.1920) - Russian naturalist, physiologist - the founder of the Russian
and British scientific schools of plant physiologists, a historian of science.
Cascade quality challenges in physics
Structure of substance, molecules, diffusion
Didactic materials in physics For students, as well as their parents ;-) And, of course, for creative teachers. For those who love to learn! Your attention 40 qualitative tasks in physics on the topic: "The structure of substances, molecules, diffusion". Accompany the tasks of cognitive notes and comments - for curious to some tasks we will give deployed Answers ;-) and ... according to the tradition of green pages we wake yourself masterpieces of world painting…
Task number 1
Who is the first experimentally discovered the movement of molecules?
Answer: In 1827, British Botany Robert Brown.In exploring pollen from its colors under the microscope, it established that floating in water pollen grains move continuously and chaotic. Brown was a real scientist and, facing incomprehensible, conscientiously investigated an open phenomenon. He found that in hot water, the particles jump faster than in the cold. I was convinced that the path of them is absolutely accidental and does not depend on London Kebov, raising on the pavement ...
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Task number 2.
Why and how does Brownian movement of suspended particles depends on their size?
Answer: More Robert Brown noticed that very small particles suspended in the microscope were in a state of continuous erratic movement and, the smaller the particle, the more intense it moves. The cause of Brownian motion is accurately established: continuously and chaotic moving fluid molecules hit from all sides of the firm bodies and lead them in a messy movement. The less the mass of the grains, the faster it moves, and vice versa. Thus, the Brownian movement of grains is due to the movement of fluid molecules.
Robert Brown. (Robert Brown; 1773-1858) - British Botanic, Morphologist and Plant Systematizer. All his life, Robert Brown was confident that his track would remain in history thanks to Botanic merit. But ... almost the only one botanist firmly entered the history of physics.
Stephen Pierce (Stephen Pearce; 11/16/1819-31.01.1904) - British painter-portraitist.
Task number 3.
If we consider a drop of strongly diluted milk in a microscope, you can see that floating in liquid small drops of oil are continuously moving. Explain this phenomenon. Why, when milk temperature increases, their movement accelerates?
Answer: Because the fluid molecules move continuously and randomly, and with an increase in temperature, the speed of their movement increases.
Task number 4.
In which environment, at the same temperature, Brownian movement occurs intensively in a drop of water or in a drop of oil?
Answer: In water, as a less viscous environment.
Task number 5.
How to explain the spread of gasoline, spirits, varnish and other fragile substances in the air?
Answer: The smell of fragile substances is distributed usually due to convection, in a completely calm atmosphere, the spread of odors is due to the diffusion associated with the random movement of molecules.
Task number 6.
"Old woman isergil", 1895, Maxim Gorky
Maksim Gorky (03/28/1868-18.06.1936) - Russian writer, prose, playwright. One of the most significant and famous Russian writers and thinkers in the world.
"... the air was satisfied acute sea odor And the fat evaporation of the Earth, shortly before the evening abundantly moistened with the rain. Also and now scraps clutch, lush, strange outlines and paints, here - soft, like smoke clubs, SIZY and ash and blue, there - sharp, like wreckage of rocks, matte-black or brown ... "
How many different memories, bright unforgettable emotions, is connected with many of us with the sea! What to compare a special unique smell of the sea? And what explained from the point of view of physics at the same time you can do?
Ivanovsky Ivan Konstantinovich (Hovhannes Avazyan; 07/29/1817-02.05.1900) - the world-famous Russian marinist artist, battalist, collector, patron.
For curious: From the surface of the seas and oceans, water is continuously evaporated. Together with her, the atmosphere comes annually several hundred thousand tons of iodine, some amount of boric acid, phosphates and, obviously, others chemical substances. During the strong winds, a clear boundary between the surface of the sea and the atmosphere is destroyed. Wind together with splashes and foam salt, Gumus, Detritwhich then partially fall out on land and ... together with iodine take part in the creation inimitable sophonia odor odor... and conducting this magic orchestra convection and diffusion.
§ Sea color and the color of the sea wave on the green page "Journey to Green Color", as well as - shades of green in paints and figures ;-)
§ Oarser of marine landscapes in the moonlight of Ivan Konstantinovich Aivazovsky on the green page "Moon in painting" and ... some interesting details about the visible sizes of the moon ;-)
Task number 7.
If at one end of the room shed some amount of smell and volatile fluid, then after a few seconds its smell will be felt in the other end of the room. Does this fact that the average speed of gas molecules at room temperature is greater than the bullet speed and is several hundred meters per second?
Task number 8.
What is the difference between the movement of the same molecule in the air and in vacuo?
Answer: In vacuum, the molecule moves uniformly and straightforwardly. In the air, due to collisions with other molecules, the same molecule moves along a broken zigzag line with a changing rate.
Task number 9.
If you mix equal volumes of mercury and water, and then alcohol and water, then in the first case it turns out the double volume of the mixture, and in the second - less than doubled volume. Why?
Answer: The alcohol and water molecules mutually penetrate the intervals between them and enter chemical interaction. As a result, the volume of the mixture of water and alcohol is less than the sum of the initial volumes.
Task number 10.
Why are gases are easier compressing than solid bodies and liquids?
Task number 11.
Oil placed in a durable steel cylinder and treated in tens of thousands of atmospheres, appears to break through the cylinder walls. What does this experience say?
Answer: Experience testifies to the presence of intermolecular gaps in the substance of the cylinder walls - the distance between the iron atoms in crystal lattice More than the size of oil molecules have become.
Task number 12.
Are the dimensions and composition of hot and cold water molecules, as well as ice molecules?
Task number 13.
Why in gases and liquids diffusion proceeds faster than in solid bodies?
Task number 14.
What physical processes play a leading role when suiting the lead to the wilderness?
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Peter Mörk Mönsted (Peder Mork Monsted; 10.12.1859-20.06.1941) - Danish realist artist, recognized master landscape.
Task number 15.
Explain on what phenomenon is the extraordinary feeding of seedlings and fruit trees by spraying their leaves.
Answer: On the phenomenon diffusion. Diffusion exchange Through the surface of the leaves of plants performs the function of not only breathing, but, partially, and nutrition. You can add the answer to this question with the words of the great Russian physiologist of the Clement Arkadyevich Timiryazev From his monumental work "Life of plants"published in 1898. "Will we talk about feeding the root at the expense of substances in the soil, will we talk about the air diet of the leaves due to the atmosphere or nutrition of one body at the expense of another, neighboring, - everywhere we will resort to the same reasons for explanation: diffusion».
Task number 16.
What phenomenon is based on a saline of vegetables, mushrooms, fish and other products?
Task number 17.
In order for cucumbers for a long time, the brine with cucumbers must be stored in a cold room - cellar or refrigerator. Why?
Task number 18.
Austed oak barrels in which they intend to plant cucumbers, they are pre-lowered for some time in a Chan with hot water, after which the slots in the kegs disappear. Explain the physical essence of this procedure.
Task №19
"Three in the boat, not counting the dogs", 1889, Jerome Kull Jerome
Jerome Kull Jerome (Jerome Klapka Jerome; 02.05.1859-14.06.1927) - English Writer-humorist, playwright.
"... from other things George offered to take eggs for the first breakfast with ham, which is easy to cook, cold meat, tea, bread with butter and jam. For the second breakfast, it recommended cookies, cold meat, bread with butter and jam, but not only cheese. Cheese, like Kerosene, imagines too much. He wants to capture the whole boat for himself. It penetrates through the basket and gives everything cheese. You do not know what you eat, apple pie, sausages or strawberries with cream. Everything seems to you cheese. Cheese too much smell ... "
Due to which physical phenomenon, the cheese can "capture the whole boat for himself"? However, for the Russian and Adygean cheese in the refrigerator, I did not notice such a rapid activity, but for fish dishes and seafood such a comprehensive behavior is very much found ;-) and therefore it is necessary to store them in hermetic dishes, and even better in a separate section of the refrigerator.
Georg Phlegel (Georg Flegel; 1566-1638) - German artist, founder of the German Still Life School.
Task number 20.
What phenomenon is based on salty herring? Explain how the sealing of salmon salt takes place.
Answer: The soaking of salty herring is based on the phenomenon of diffusion. Salt molecules in the solution are disintegrated into ions, and ions as a result of the diffusion process move into water, exchanging places with water ions.
Task # 27.
Why milk cream faster defend in a cold room than in warm?
Answer: At low temperature, the fat particle is less susceptible to the influence of the surrounding molecules, since the speeds of their movement are less, they are easily "sticking out", attracting each other.
Task # 22.
Why should not be wet cloth painted in dark color, leave for a long time in contact with a white cloth?
Answer: Paint molecules diffuse on white cloth and paint it.
Task # 23.
Throw the crystal crystalline to the water. After some time, a purple cloud is formed around it. Explain the phenomenon.
Answer: The substance dissolving diffuses in water, painting it with purple color.
Task # 24.
At a minute of danger, some cephalopions emit a "ink bomb" to the extended mouth - a stream of dark-painted fluid. Ink is blurred in the water with a dense cloud, and under the cover of the "smoke curtain" the mollusk is more or less safely surprised, leaving the enemy to wander in the dotters. Why after a while the space filled with this liquid, even in calm water becomes transparent?
Champion: a flock squid (Ommastrephes Sloaneipacificus); octopus (Octopus vulgaris); russia (Rossia Glaucopis); cuttlefish (Sepia officinalis).
Kondakov Nikolay Nikolaevich (1908-1999) - Russian animal artist, zoologist and traveler.
For curious: "... In the ink cephalopods contain organic paint from the melanin group, close to the composition of the pigment, which are painted our hair. The shade of ink is not all chasing the same: Caracatiet has a blue-black tone (in strong dilution of the color "Sepia"), the octopus is black, the squid - brown. Ink produces a special body - pear-shaped rectal grows. It is called ink bag. Not all the contents of the ink bag splashes at a time. An ordinary octopus can put a "smoke vest" six times in a row, and after half an hour, the entire consumed stock ink is completely restored. The coloring ability of ink liquid is unusually large. Caracatias in five seconds paints all the water in the tank with a capacity of 5.5 thousand liters with an overwhelmed ink. And the giant squid erupt so much ink fluid that marine water purges for hundreds of meters! "
"CHALON CHALLENGE CHOPHALOPODA", 1968,
Igor Ivanovich Akimushkin
Task №25
Why the smoke from the fire, as his lifting ceases to be visible even in windless weather?
Answer: Particles of smoke and air molecules are mixed due to convection and diffusion. At the same time, the concentration of smoke particles is continuously reduced and it becomes invisible.
Task number 26.
Children's balloons usually fill helium. Why are they after a day of the balls lose elasticity, shriven and stop climbing?
Answer: Helium diffuses through the ball shell.
Task # 27.
In the water of rivers, lakes, and other water bodies contain molecules of gases that are part of the air. Due to the phenomenon, these molecules fall into the water? Why do they penetrate the bottom of the reservoir? Describe how air stirring with water happens?
For curious: Diffusion processes in the supply of natural reservoirs are playing a major role. Oxygen falls into a deeper water layers in standing waters due to diffusion through their free surface. Therefore, all sorts of limitations of the free surface of the water are undesirable. For example, leaves or rods covering the surface of the water can completely overlap the access of oxygen to water and lead to the death of its inhabitants. For the same reason, the vessels with a narrow throat are not suitable for use as aquarium.
Volkov Efim Efimovich (03/23/1844-17.02.1920) - Russian painter - a landscape system, a member of the partnership of mobile art exhibitions, a valid member and academician of the Imperial Academy of Arts.
Polenov Vasily Dmitrievich (06/01/1844-18.07.1927) - Russian artist, master of historical, landscape and genre painting, teacher.
Task №28.
In what processes and how does the diffusion occur in the human body and animals? Prepare on this topic expanded message.
Task number 29.
Inhalation is the method of administering medicines based on inhalation of gas, steam or smoke. Inhalation is natural, for example, in salt caves, at sea resorts or in the forest (inhalation of phytoncides) and artificial, with the use of special dispensers - inhalers. What physical phenomenon is based on this method of administration of medicines? And what is phytoncides?
For curious: Fitoncides - Biologically active volatile substances that kill or overwhelming and developing bacteria, microscopic fungi, simplest ... Hectar pine boron highlights about 5 kilograms of volatile phytoncides per day, and the juniper forest - about 30 kilograms! Pine phytoncides are destructive for the chopstick of the Cocratian of tuberculosis; Fitoncides Fir kill a cough stick; Birch phytoncides are striking the microbe of golden staphylococcus ...
Shishkin Ivan Ivanovich (01/25/1832-20.03.1898) - Russian painter-landscape officer, Academician, Professor, head of the landscape workshop of the Imperial Academy of Arts, one of the founders of the partnership of mobile art exhibitions.
§ Picture "Morning in a pine forest" On the green page "Seasons: Spring". Hanging corner of a dense pine forest performed by Ivan Ivanovich Shishkin and a bear family performed by Konstantin Apollonovich Savitsky.
Task number 30.
Explain the phenomenon of the steel cementation process - obtaining a solid tempered "crust" on the surface of a soft steel product.
Answer: When calculating steel products in a mixture of coal and various salts, carbon atoms diffuse into the surface layer of metal. This contributes to improving the strength of the product.
Task number 31.
The technique uses the method of cold "welding" of metals. To do this, overlap one iron part to another, they are very compressed and, they get a very strong connection. What happens in the process of cold "welding" of metals?
Answer: With strong compression, the surfaces of the products are softened, accompanied by mutual diffusion of particles, the clutch forces becomes as significant that they provide a solid connection of products.
Task number 32.
What is the process of staining solid bodies with dyes?
Task number 33.
Why do you write in chalk on the blackboard, not a piece of white marble? What can be said about the interaction between particles of these substances? Why particles of chalk do not disappear from the surface of the board?
Answer: The forces of attraction between the chalk molecules are weaker than between marble molecules, and when we write chalk on the board, chalk particles are peeled and remain on the board, while holding it with the forces of intermolecular clutch.
Bogdanov-Belsky Nikolai Petrovich (08.12.1868-19.02.1945) - Russian Mobile Artist, Academician of Painting.
Task number 34.
To reduce the friction force between the contacting surfaces, they are grin and polished. However, after careful polishing, the friction force begins to increase again. Explain the reason for this phenomenon.
Answer: Increases intermolecular clutch forces.
Task number 35.
To close the glass vial tightly, use prolonged plugs, for example, vials with expensive perfumes. The cork and part of the bottle of the bottle is smoothly polished in the place where they come into contact. What is the use of priest traffic jams?
Task number 36.
What is explained that dust does not fall even from the surface drawn down?
Answer: Dust particles are held on the surface of the force of mutual attraction of molecules.
Task number 37.
Why are paper tapes are put on with the folding of polished brazers?
Answer: So that the glasses did not stick through the action of the forces of mutual attraction of molecules.
Task number 38.
Why can not be connected in one two wooden rules, putting them tightly to each other?
Answer: Due to the irregularities of the surfaces of the lines attached to each other, a small number of points of contact is formed, where the forces of molecular attraction appear.
Task number 39.
The most important factor in the process of forming karst caves is the diffusion of carbon dioxide from air to water. For the formation of the cave, a sufficient amount of water precipitation is necessary and a successful form of relief. There are karst caves only where it lies: limestone, dolomite, chalk, as well as plaster and stone salt. Why?
Answer: Limestone, dolomite, chalk, plaster and stone salt - rocks, easily blurred by water. Limestone is very poorly soluble with pure distilled water. Its solubility increases several times if dissolved carbon dioxide is present in water, and it is always present in natural water due to diffusion. However, while the limestone is slightly dissolved in water compared to plaster or salt. But ..., this positively affects the formation of extended karst caves, since gypsum and salt caves are not only quickly formed, but also quickly destroy.
Karl Khash (Carl Hasch; 08.11.1834-04.01.1897) - Austrian painter-landscape.
For curious: Blurring rocks, water not only takes out their particles outward, forming emptiness, it creates luxurious cave decorations: stalactites, stalagmites, staples... They arise as a result of falling into the precipitate of calcium carbon dioxide when the water of carbon dioxide is removed from the water saturated. Stalactites and stalagmites grow by layers, concentric patterns are noticeable on them, like annual rings in trees. The form and the name of these formations depend on how water flows.
Stalactites (from the Greek Stalaktós - a drop of droplets) - sideways, drip, dried in the form of icicles, tubes, rowing, fringe from the ceiling cave.
Stalagmitians (from the Greek Stálagma - drop) - sideways-drip formations, patchwork, conical shape, rising from the bottom of the cave.
Stalactites and stalagmites in a sense of the twins-brothers :-) Stalagmite is growing almost under each stalactite. They grow towards each other and in the end merge, forming a column - stalablet.
§ Several photos from a large Asian cave on the green page "Photo Album:" Adygea ", summer 2005" - Stalactites: "Angel wings", stalagmites: "Priest with a retinue", staples: "Tree of happiness" and "Palm of desires".
Task number 40.
"On the nature of things", titles of lucretry car
Tit Lucretia Car (Titus Lucretius Carus; about 99 years before our era - 55 years BC) - Roman poet and philosopher. It is considered one of the brightest adherents of atomistic materialism, according to which sensually perceived (material) things consist of chemically indivisible particles - atoms.
"... and, finally, on the sea shore, breaking the waves,
The dress is always raw, and in the sun hanging, it dries;
See, however, it is impossible, as moisture on it settles,
And it is not visible how she disappears from the heat.
It means that water is crushed into such smallest parts,
What they are not available completely for our eyes.
So ring from the inside that long time on the finger
Worn, out of year it becomes thinner and thinner;
A drop over the drop is hammering, falling, a rock; curved
Plow Iron coulter is imperceptibly erased in the soil;
And bridges paved by stones see
Coated legs of the crowd; and right hands in statues
Bronze near the gate of urban gradually lose weight
From the savings to them passing by the people.
It is obvious to us that the thing from the styramine becomes less,
But the separation of bodies, from her every moment of exit,
Our eyes see forbid the nature of jealous…»
How can you comment on this passage from the point of view of modern physics? Although the existence of molecules and atoms has been established for a long time and even identified their size, until recently it was not possible to consider individual molecules. Only in 1945, Alexander Alekseevich Lebedev With the help of an "electron microscope", which allows to investigate the objects of very small sizes, managed to take a picture of some large protein molecules (albumin). What increase is modern models of electron microscopes, which make it possible to significantly expand the possibilities of science and production? Prepare on this topic expanded message.
Lebedev Alexander Alekseevich (11/27/1893-15.03.1969) - Russian, Soviet physicist, specialist in the field of applied and electronic optics, optics of the atmosphere and hydrophtics, laser technology, the theory of glass-like state, the study of the properties and structure of glass, outer radiation.
§ Another seven quality tasks on the topic "Brownian motion. Diffusion" On the green page "Box of high-quality problems in physics" Collection Salonka ":-) The box consists of four thematic blocks: 1) Brownian movement. Diffusion; 2) atmospheric pressure; 3) fluid properties. Archimedova force; 4) thermal phenomena.
I wish you success in an independent decision
qualitative tasks in physics!
Literature:
§ Katz Ts.B. Biophysics in physics lessons
§ Lukashik V.I. Physical Olympiad
Moscow: Publishing House "Enlightenment", 1987
§ Tarasov L.V. Physics in nature
Moscow: Publishing House "Enlightenment", 1988
§ Perelman Ya.I. Do you know physics?
Domodedovo: VAP Publishing House, 1994
§ Zolotov V.A. Questions and challenges in physics 6-7 class
Moscow: Publishing House "Enlightenment", 1971
§ Tulchinsky M.E. Qualitative Tasks in Physics
Moscow: Publisher "Enlightenment", 1972
§ Kirillova I.G. Physics reading book 6-7 class
Moscow: Publisher "Enlightenment", 1978
§ Erdavletov S.R., Rutkovsky Oh. Entertaining geography of Kazakhstan
Alma-Ata: Publisher "Mecpep", 1989.
70. The solid body molecules are in continuous motion. Why do not solid bodies disintegrate into individual molecules?
The solid body molecules interact quite strongly.
71. Why can we split pencil we can connect so that it has become a whole?
To do this, it is necessary to bring the surface of the fault over the distance at which the interaction of the pencil molecules becomes quite strong. Practically make it impossible.
72. Why after rain dust on the road not rises?
Dust particles, moistened with water, stick together, and their mass increases. Therefore, they are harder to lift into the air.
73. Why is it much more effort to separate paper sheets of paper moistened with water, than when turning dry pages of the book?
The interaction between the wet leaf molecules is stronger than the interaction between the dry sheet molecules.
74. Why is it written on the blackboard with chalk, not a piece of white marble? What can be said about the interaction between particles of these substances?
The interaction between marble molecules is so strong that marble friction forces about the board is not enough to crush marble. The attraction force between the chalk molecules is much less than that of marble.
75. In what of substances (lead, wax, zinc) under normal conditions the force of attraction between particles is the largest; The smallest?
Maximum - steel, minimal y - wax.
76. Flat-parallel terminal lengths (Johansson tiles) are polished so that at contact, they stick to each other and restrained (Fig. 17). Explain the reason for this phenomenon.
Due to the smoothness of the plates, with their contact, many surface particles come closer to distances where the forces of intermolecular attraction begin to play an important role.
77. Welding of metal parts can be performed with a cold way if connecting them to survive very much. With what condition such welding can be performed?
Such welding can be performed provided that most of the particles on the surface of the welded parts will be interchanged over the distance of mutual attraction.
78. Glass plate suspended on the rubber cord, lowered to contact with the surface of the water (Fig. 18). Why when lifting the plate the cord stretches?
Water as a result of intermolecular interaction wets and attracts a glass plate.
79. In what condition is a solid or liquid - the force of attraction between lead molecules is greater?
In solid.
80. The oil is relatively easily removed from the clean surface of copper. It is impossible to remove mercury from the same surface. What can be said about mutual attraction between oil and copper molecules, mercury and copper?
Oil molecules interact with copper weaker mercury molecules.
81. Molecules of the substance are attracted to each other. Why are there intervals between them?
Because there are also repulsive strengths between molecules.
82. What is common between paper gluing and the soldering of metal products?
When gluing paper and the soldering of metal products into the surface layers of the glued sheets (soldered bodies) penetrate the adhesive particles (solder). In this case, the interaction between the glue and paper molecules (metal particles and solder) is greater than between the molecules of the glued sheets of paper (soldered metal products).
83. What is the difference between welding metal parts from the soldering of metal products?
When welding, they cost without solder, due to the diffusion of the molecules of the welded tel.
During the lessons, I watched the chalk leaves my traces on the board and I had a question: "Why do we write chalk?".
For many years and even centuries, school chalk remains an indispensable assistant for the teacher. How did people guessed the use of chalk for learning children? Why make chalk writes on the board? What does it consist of? Can I use other minerals for writing on the board? I wanted to answer these questions.
I shared my thoughts with Alla Petrovna, my teacher, and she suggested that I was researching and independently find answers to all questions.
I put forward a hypothesis: suppose that on the board you can write not only chalk. After the experiments, I came to the conclusion that Mel is a soft limestone, therefore, particles are easily separated from it, leaving the trail on the board. Thus, it becomes clear why on the board it is easy to write with chalk.
What else can you write on the board? For this, I chose two more substances: charcoal and gypsum that have a loose structure. Why exactly them?
For a long time, with the help of charcoal, painted on stones and paper. Coal was known for the ancient Greeks, which from the charred bids of willow, grapes and walnuts received a material similar to the one that artists enjoy these days.
Gypsum I also chose not by chance. The name of the gypsum comes from the Greek word Gipsos (gypsum or chalk). It is very similar to the chalk: white and crumbs. Molded school chalk consist of 40% of the chalk and 60% of the gypsum.
However, after the experiment, I came to the conclusion that the gypsum in pure form Leaves on a scratching board, because it is a crystalline substance, more hard and dense than chalk. Coal is also not suitable, because it crumble, leaves poorly noticeable traces and dirty hands.
Thus, I proved that the chalk is the most convenient material for writing on the board.
Working on the project, I learned a lot of interesting things: how the chalk appeared, where in Russia there are "White Mountains". In the future, I plan to continue working on experiments and research related to chalk and its use in our everyday lifeBecause Mel pays a lot of mysteries.
68. Where is it better to preserve a children's rubber ball filled with hydrogen: in cold or warm room?
69. One jug with milk put in the refrigerator, the other was left in the room. Where is the cream stand faster? Why?
G. E \u003d! T.
1 2 Z.
Fig. sixteen
yu
5. Attraction and repulsion of molecules
70. The solid body molecules are in continuous movement. Why do not solid bodies disintegrate into individual molecules?
71. Why, breaking a pencil, we can't connect the thread of it so that it again becomes whole?
72. Why after rain dust on the road not rises?
73. Why is it much more effort to separate paper moistened paper than when turning dry pages of the book?
74. Why is it written on the blackboard with chalk, not a piece of white marble? What can be said about the interaction between particles of these substances?
75. Attraction between particles of which substances (lead, wax, steel) is the largest, the smallest?
76. The terminal measures of length (tiles) are polished so that at the contact they "stick" to each other and mutually retention (Fig. 17). Explain the reason for this phenomenon.
77. Welding of metal parts can be performed with a cold way if they are connected, very much. With what condition details can be welded?
78. Glass plate suspended on the rubber cord, lowered to contact with the surface of the water (Fig. 18). Why when lifting the plate the cord stretches?
79. In what condition is a solid or liquid - the attraction between lead molecules is greater?
80. The oil is relatively easily removed from the clean surface of copper. If the surface of the copper is moistened with mercury, it is impossible to remove mercury from the surface of the copper. What can be said about mutual attraction between oil and copper molecules, mercury and copper?
81. Molecules of the substance are attracted to each other. Why are there intervals between them?
82. Why, when the air molecule is collided, they differ, fly apart from each other, and not connect together?
83. What explains the low compressibility solid tel and liquids?
6. Three states of the substance
84. In what condition are the following substances at room temperature: water, sugar, air, tin, alcohol, ice, oxygen, aluminum, milk, nitrogen? Answers write to the table:
condition
solid liquid gaseous
85. Is it possible to fill the open vessel with a 50% volume with gas?
86. What is the similarity and difference between the properties of gases and liquids? liquids and solids?
87. Can there be oxygen in a liquid state, nitrogen?
88. Can there be mercury in the gaseous state, iron, lead?
89. Fog formed summer evening over the swamp. What is this condition of water?
90. In a winter frosty day over a hide in the river, fog formed. What is this condition of water?
91. What substance gets a different name when switching it from a liquid state into solid?
92. What is the similarity and difference in the movement of gases and liquids molecules? molecules of liquids and solids?
93. Are cold water molecules from warm and hot water molecules? From ice molecules?
94. Water evaporated and turned into steam. Was the water molecules themselves? How has their location and movement changed?
II. Movement and power
7. Mechanical movement
95. In the moving carriage of the passenger train on the table lies the book. At rest or movement is a book regarding: a) the table; b) rails; c) Paul Vagon; d) telegraph poles?
96. What a trajectory when moving a car describes the center of its wheel relative to the straight road?
97. Consider the movement of the end of the minute and clockwise clock clock. What between these movements is common? What do they differ from each other?
98. The cyclist moves uniformly and straight. What is the trajectory of movement of the wheel rim plates relative to the bike frame?
99. What parts of the bike with its movement describe straight and which are curvilinear trajectories relative to the road?
100. After docking the Soyuz-31 Soviet spacecraft with the Salute-6 orbital complex - Soyuz-29, the Salute-6 orbital station and space ships moved together. What is the speed of the station and ships relative to each other with such flight?
101. Figure 19 shows a part of the trajectory of the earth's movement around the sun. The arrows show the directions of the movement of the Earth and its rotation. When Moscow residents move in space faster than the Sun: at noon or at midnight? Why?
102. A group of aircraft (Fig. 20) simultaneously performs the shapes of the highest pilot, while maintaining the specified system. What can be said about the movement of aircraft relative to a friend?
103. The ball in the tube with water (Fig. 21) is evenly lowered and 5 cm passes each second. In which direction and at what speed should be moved
Fig. nineteen
Fig. twenty
13
tube so that the ball relative to the surface of the earth remains at rest?
104. The cyclist drove the path from L to B (Fig. 22). Are the paths of the front and rear wheels of the bicycle at the same time?
105. Are the same paths pass the right and left vehicle wheels when turning (Fig. 23)?