Molecule substance structure Brownian motion presentation. Section of the presentation on Brownian motion

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BROWNIAN MOTION In the summer of 1827, Brown, while studying the behavior of pollen under a microscope, suddenly discovered that individual spores perform absolutely chaotic impulsive movements. He determined for certain that these movements are in no way connected with the eddies and currents of water, or with its evaporation, after which, having described the nature of the movement of particles, he honestly signed his own impotence to explain the origin of this chaotic movement. However, being a meticulous experimenter, Brown found that such a chaotic movement is characteristic of any microscopic particles, be it pollen of plants, suspensions of minerals, or in general any crushed substance.

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BROWNIAN MOTION is the thermal motion of the smallest particles suspended in a liquid or gas. Brownian particles move under the influence of molecular impacts. Due to the chaotic nature of the thermal motion of the molecules, these impacts never counterbalance each other. As a result, the speed of a Brownian particle randomly changes in magnitude and direction, and its trajectory is a complex zigzag line.

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FORCES OF INTERACTION If there were no forces of attraction between the molecules, then all bodies under any conditions would be only in a gaseous state. But the forces of attraction alone cannot ensure the existence of stable formations of atoms and molecules. At very small distances between molecules, repulsive forces necessarily act. Thanks to this, the molecules do not penetrate each other and the pieces of matter never shrink to the size of one molecule.

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Although the molecules in general are electrically neutral, nevertheless significant electrical forces act between them at small distances: there is an interaction of electrons and atomic nuclei of neighboring molecules.

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AGGREGATE STATES OF SUBSTANCE Depending on the conditions, one and the same substance can be in different aggregate states. The molecules of a substance in a solid, liquid or gaseous state do not differ from each other. The aggregate state of a substance is determined by the location, the nature of the movement and interaction of molecules.

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PROPERTIES OF SOLID, LIQUID AND GASEOUS BODIES. The state of the substance. Particle arrangement. The nature of the movement of particles. Energy of interaction. Some properties. Solid. Distances are comparable to particle sizes. Truly solids have a crystalline structure (long-range ordering). Oscillations around the equilibrium position. The potential energy is much higher than the kinetic one. The forces of interaction are great. Retains shape and volume. Elasticity. Strength. Hardness. Have a definite melting point and crystallization point. Liquid Are located almost closely to each other. A short-range ordering is observed. Basically they oscillate around the equilibrium position, occasionally jumping to another. The kinetic energy is only slightly less in terms of the potential energy. They retain their volume, but do not retain their shape. Slightly compressible. Fluid. Gaseous. The distances are much larger than the particle sizes. The location is completely chaotic. Chaotic movement with numerous collisions. The speeds are relatively high. The kinetic energy is much greater than the potential in absolute value. They do not retain their shape or volume. Easily compressible. Fill in the entire volume provided to them.

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The gas expands until it fills the entire volume allocated to it. If we consider the gas at the molecular level, we will see molecules randomly tossing and colliding with each other and with the walls of the vessel, which, however, practically do not interact with each other. If the volume of the vessel is increased or decreased, the molecules will be evenly redistributed in the new volume STRUCTURE OF GASES

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STRUCTURE OF GASES 1. Molecules do not interact with each other 2. Distances between molecules are tens of times larger than the size of molecules 3. Gases are easily compressed 4. High speed of movement of molecules 5. They occupy the entire volume of the vessel 6. Impacts of molecules create gas pressure

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At a given temperature, a liquid occupies a fixed volume, but it also takes the form of a vessel to be filled - but only below its surface level. At the molecular level, a liquid is most easily represented in the form of spherical molecules, which, although they are in close contact with each other, have the freedom to roll relative to each other, like round beads in a jar. Pour liquid into the vessel - and the molecules will quickly spread and fill the lower part of the vessel volume, as a result, the liquid will take its shape, but will not spread to the full volume of the vessel. STRUCTURE OF LIQUIDS

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Brownian motion.
Completed by: Bakovskaya Yulia and Voznyak Albina, students of grade 10 Checked by: Tsipenko L.V., physics teacher 2012

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Brownian motion - in natural science, the chaotic movement of microscopic, visible, suspended in a liquid (or gas) solid particles (dust particles, plant pollen particles, etc.) caused by the thermal motion of liquid (or gas) particles. The concepts of "Brownian motion" and "thermal motion" should not be confused: Brownian motion is a consequence and evidence of the existence of thermal motion.

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The essence of the phenomenon
Brownian motion occurs due to the fact that all liquids and gases consist of atoms or molecules - the smallest particles that are in constant chaotic thermal motion, and therefore continuously push the Brownian particle from different sides. It was found that large particles with a size of more than 5 microns practically do not participate in Brownian motion (they are stationary or sediment), smaller particles (less than 3 microns) move progressively along very complex trajectories or rotate. When a large body is immersed in the medium, the tremors occurring in huge quantities are averaged and form a constant pressure. If a large body is surrounded by the environment on all sides, then the pressure is practically balanced, only the lifting force of Archimedes remains - such a body smoothly floats or sinks. If the body is small, like a Brownian particle, then pressure fluctuations become noticeable, which create a noticeable randomly changing force, leading to oscillations of the particle. Brownian particles usually do not sink or float, but are suspended in a medium.

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Discovery of Brownian motion
This phenomenon was discovered by R. Brown in 1827, when he was conducting research on plant pollen. Scottish botanist Robert Brown (sometimes his surname is transcribed as Brown) during his lifetime, as the best connoisseur of plants, received the title of "Prince of Botanists". He made many wonderful discoveries. In 1805, after a four-year expedition to Australia, he brought to England about 4000 species of Australian plants unknown to scientists and devoted many years to their study. Described plants brought from Indonesia and Central Africa. He studied plant physiology, for the first time described in detail the nucleus of a plant cell. Petersburg Academy of Sciences made him an honorary member. But the name of the scientist is now widely known not at all because of these works. In 1827 Brown conducted research on plant pollen. He, in particular, was interested in how pollen participates in the fertilization process. Once he examined under a microscope the elongated cytoplasmic grains suspended in water, isolated from the cells of the pollen of the North American plant Clarkia pulchella (Clarkia pretty). Suddenly, Brown saw that the smallest solid grains, which could hardly be seen in a drop of water, were constantly trembling and moving from place to place. He found that these movements, in his words, "are not associated either with flows in the liquid, or with its gradual evaporation, but are inherent in the particles themselves." Now, to repeat Brown's observation, it is enough to have a not very strong microscope and use it to examine the smoke in a blackened box, illuminated through a side hole with a beam of intense light. In a gas, the phenomenon appears much brighter than in a liquid: small patches of ash or soot (depending on the source of the smoke) scattering light are visible, which continually jump to and fro. It is possible to observe the Brownian motion in the ink solution: at a magnification of 400x, the motion of the particles is already easily distinguishable. As is often the case in science, many years later, historians discovered that as early as 1670 the Dutch inventor of the microscope, Anthony Leeuwenhoek, apparently observed a similar phenomenon, but the rarity and imperfection of microscopes, the embryonic state of molecular science at that time did not attract attention to the observation of Leeuwenhoek, therefore the discovery is rightly attributed to Brown, who first studied and described it in detail.

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The presentation on the topic "Brownian motion. The structure of matter" can be downloaded absolutely free of charge on our website. Project subject: Physics. Colorful slides and illustrations will help you engage your classmates or audience. To view the content, use the player, or if you want to download the report - click on the corresponding text under the player. The presentation contains 15 slide (s).

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CLASS 10 PHYSICS LESSON

Brownian motion. The structure of matter Teacher Kononov Gennady Grigorievich secondary school number 29 Slavyanskiy district of Krasnodar region

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BROWNIAN MOTION

Back in the summer of 1827, Brown, while studying the behavior of pollen under a microscope, suddenly discovered that individual spores make absolutely chaotic impulse movements. He determined for certain that these movements are in no way connected with the eddies and currents of water, or with its evaporation, after which, having described the nature of the movement of particles, he honestly signed his own impotence to explain the origin of this chaotic movement. However, being a meticulous experimenter, Brown found that such a chaotic movement is characteristic of any microscopic particles, be it pollen of plants, suspensions of minerals, or in general any crushed substance.

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This is the thermal movement of the smallest particles suspended in a liquid or gas. Brownian particles move under the influence of molecular impacts. Due to the chaotic nature of the thermal motion of the molecules, these impacts never counterbalance each other. As a result, the speed of a Brownian particle randomly changes in magnitude and direction, and its trajectory is a complex zigzag line.

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FORCES OF INTERACTION

If there were no forces of attraction between the molecules, then all bodies under any conditions would be only in a gaseous state. But the forces of attraction alone cannot ensure the existence of stable formations of atoms and molecules. At very small distances between molecules, repulsive forces necessarily act. Thanks to this, the molecules do not penetrate each other and the pieces of matter never shrink to the size of one molecule.

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AGGREGATE STATES OF SUBSTANCE

Depending on the conditions, one and the same substance can be in different states of aggregation. The molecules of a substance in a solid, liquid or gaseous state do not differ from each other. The aggregate state of a substance is determined by the location, the nature of the movement and interaction of molecules.

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The gas expands until it fills the entire volume allocated to it. If we consider the gas at the molecular level, we will see molecules randomly rushing and colliding with each other and with the walls of the vessel, which, however, practically do not interact with each other. If the volume of the vessel is increased or decreased, the molecules will be evenly redistributed in the new volume.

STRUCTURE OF GASES

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A liquid at a given temperature occupies a fixed volume, but it also takes the form of a vessel to be filled - but only below its surface level. At the molecular level, a liquid is most easily represented in the form of spherical molecules, which, although they are in close contact with each other, have the freedom to roll relative to each other, like round beads in a jar. Pour liquid into the vessel - and the molecules will quickly spread and fill the lower part of the vessel volume, as a result, the liquid will take its shape, but will not spread to the full volume of the vessel.

STRUCTURE OF LIQUIDS

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The solid body has its own shape, does not spread over the volume of the container and does not take its shape. At the microscopic level, atoms are attached to each other by chemical bonds, and their position relative to each other is fixed. At the same time, they can form both rigid ordered structures - crystal lattices - and a disorderly heap - amorphous bodies (this is exactly the structure of polymers, which look like tangled and stuck together pasta in a bowl).

STRUCTURE OF SOLID BODIES

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The work was completed by: Ekaterina Makarova, a 7th grade student, GOU SOSH № 546, Moscow Supervisor: Kazakova Yu.V., physics teacher

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In 1827, Brown, examining under a microscope the cytoplasmic grains suspended in water, isolated from the cells of the pollen of the North American plant Clarkia pulchella, suddenly discovered that they were constantly trembling and moving from place to place.

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Purpose of the work: to observe and study the Brownian motion of particles suspended in water. Research object: Brownian motion. Subject of research: features of observation and the nature of Brownian motion. Place of work: Educational and Scientific Radiophysical Center of Moscow State Pedagogical University

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Research objectives: To study the history of the discovery of Brownian motion. Study the significance of the discovery of Brownian motion for the development of science. Find out the influence of various factors on the nature of Brownian motion. Conduct an experiment to observe Brownian motion. Research methods: Study of literature and materials of Internet sites on this topic. Study of the nature of Brownian motion using a model. Observation of Brownian motion.

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In 1824, a new type of microscope appeared, providing a magnification of 500-1000 times. It allowed to enlarge particles up to a size of 0.1-1 mm.But in his article, Brown specifically emphasizes that he had ordinary biconvex lenses, which means he could magnify objects no more than 500 times, that is, the particles increased to a size of only 0 , 05-0.5 mm. The size of pollen cells ranges from 2.5 µm to 250 µm. Brownian particles have a size of about 0.1–1 µm. 18th century microscopes

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Back in 1670, Dutchman Anthony Leeuwenhoek, the inventor of the microscope, may have observed a similar phenomenon, since his microscope magnified up to 300 times, but the rudimentary state of molecular science at that time did not attract attention to Leeuwenhoek's observation. Anthony van Leeuwenhoek (1632-1723)

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An excerpt from Lucretius Kara's poem "On the nature of things" Look here: whenever the sunlight enters our homes and the darkness cuts through with its rays, Many small bodies in the void, you will see, flickering, Rushing back and forth in the radiant radiance of light ...

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Low temperature (1 min) High temperature (1 min) Comparison of the nature of particle motion using the Brownian motion model

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Conclusions: Brownian particles move under the influence of random collisions of molecules. Brownian motion is chaotic. The trajectory of the particle can be used to judge the intensity of movement, the less the mass of the particle, the more intense the movement becomes. The intensity of Brownian motion directly depends on temperature. Brownian motion never stops.

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Marian Smoluchowski (1872–1917) For the first time in 1904 he gave a rigorous explanation of Brownian motion

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Albert Einstein (1879-1955) In 1905, he created the first quantitative theory of Brownian motion. Using statistical methods, he derived a formula for the mean value of the square of the displacement of a Brownian particle: where B is the particle mobility, which is inversely proportional to the viscosity of the medium and the particle size, t is the observation time, and T is the temperature of the liquid.< r 2 >= 6kTBt

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Jean Baptiste Perrin (1870 - 1942) In 1906, he began to conduct experiments that confirmed Einstein's theory. Summing up the results in 1912, he declared: “The atomic theory has triumphed. Once numerous, its opponents are defeated and one after another renounce their views, which for such a long time were considered valid and useful. " In 1926, Perrin received the Nobel Prize for his work on the "discrete nature of matter"

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Brownian motion of a gummigut particle in water. The dots mark the successive positions of the particle after 30 s. The observations were carried out under a microscope at a magnification of approx. 3000. Particle size about 1 micron. One cell corresponds to a distance of 3.4 μm.

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MICROSCOPE NIKON Eclipse LV 100 Camcorder Eyepiece Stage Lens Monitor Screws for horizontal movement of the stage Screws for adjusting focus

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Conclusions: 1. Brownian motion could be accidentally observed by scientists before Brown, but due to imperfection of microscopes and lack of understanding of the molecular structure of substances, it has not been studied by anyone. After Brown, it was studied by many scientists, but no one could give it an explanation. 2. Creation of the quantitative theory of Brownian motion by Einstein and its experimental confirmation by Perrin made it possible to convincingly prove the existence of molecules and their continuous disorderly motion. 3. The reasons for the Brownian motion are the thermal motion of the molecules of the medium and the lack of accurate compensation for the impacts experienced by the particle from the molecules surrounding it. 4. The intensity of the Brownian motion is influenced by the size and mass of the Brownian particle, the temperature and viscosity of the liquid. 5. Observation of Brownian motion is a very difficult task, since you need to: be able to use a microscope, exclude the influence of negative external factors (vibration, table tilt), conduct observation quickly, until the liquid has evaporated.

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http://ru.wikipedia.org http://krugosvet.ru/enc/nauka_i_tehnika/fizika/BROUNOVSKOE_DVIZHENIE.html http://www.physics.nad.ru/Physics/Cyrillic/brow_txt.htm http: // bse .sci-lib.com / article001503.html http://scorcher.ru/art/theory/determinism/broun.php http://marklv.narod.ru/mkt/ris2.htm http://elementy.ru/ trefil / 30 http://allphysics.ru/phys/brounovskoe-dvizhenie http://dxdy.ru/topic24041.html http://vita-club.ru/micros1.htm