Class: 10
Lesson type: explanation of new material
Lesson Objectives:
- Tutorials: repeat and systematize knowledge about the properties of crystals, consider the features of amorphous bodies, make comparisons, introduce the concepts of "isotropy", "anisotropy", "polycrystal", "monocrystal".
- Developing: development of interest in physics and mathematics, development of logical thinking, attention, memory, independence in finding solutions.
- Educational: the formation of a scientific outlook, the education of accuracy, mutual assistance.
Means of education:
- Textbook “Physics. Grade 10 "Gendenstein L.E.
- Collection of problems in physics. Gendenstein L.E.
- Projector, computer, video materials (Appendix 1).
- Demonstration equipment - a model of a crystal lattice, samples of crystals of mica, quartz.
- Laboratory equipment- microscopes, samples of substances - salt, sugar, sugar candy.
Teaching methods:
- Verbal (teacher's explanation)
- Visual (video)
- Practical ( pilot study– observation through a microscope, problem solving)
Lesson plan:
- Org. moment
- Actualization and motivation of knowledge (review)
- Explanation of new material
- Anchoring
- Summarizing. Homework
During the classes
1. Org. moment.
2. Let me remind you that we continue to study the molecular-kinetic theory.
- What is the main task of the ICT? (Answer: MKT explains the properties of macroscopic bodies on the basis of knowledge about the structure of matter and the behavior of molecules).
We examined in detail in previous lessons the features of gases and liquids. To complete the MKT, we need to consider the features of solids.
- What features about the structure of solids do we know from the course of physics? (Answers: the molecules are located very close to each other, the interaction forces between the molecules are large, the molecules oscillate around their equilibrium positions).
What are the differences in the structure of liquids and solids? (Answer: in the forces of interaction between molecules, in the arrangement of particles, in the speeds and types of movement of molecules).
So, the main feature is the correct arrangement of atoms, i.e. the presence of a crystal lattice, so most solids are called crystalline. However, there is another group of solids that we have not talked about before - these are amorphous bodies. So, the topic of today's lesson is "Crystalline and amorphous bodies." (Slide 1)(Attachment 1)
3. We know some properties of crystals. Remember what can be said about the shape and volume of solids? (Answer: both shape and volume are preserved)
To systematize knowledge about solids and to compare crystals and amorphous bodies during the lesson, we will fill out the following table (the table was prepared in advance on the blackboard or can be displayed on the screen via a computer):
Draw a table in your notebook.
In the column "Crystal bodies" write what we know about the shape and volume of crystalline bodies.
(Slide 2)
The figure shows the crystal lattices of various substances. Pay attention to the fact that the lines connecting the positions of the atoms form regular geometric shapes: squares, rectangles, triangles, 6-gons, etc.
Those. crystals are solids whose atoms are arranged in a certain order (write in a table).
The correct arrangement of atoms is well demonstrated by the model of the crystal lattice.
Demonstration graphite crystal lattice models.
(Slide 3) You know from chemistry lessons that crystal lattices can consist not only of neutral atoms, but also of ions. In the figure - ionic crystal lattices table salt and cesium chloride. In this case, we again observe the correct arrangement of particles in space.
(Slide 4) It happens that the same atoms form different substances with completely different properties depending on the type of crystal lattice: on the left - a layered lattice of graphite (the model of which we have just seen). Graphite is a soft, opaque, conductive substance. On the right is a diamond with a cascade lattice consisting of the same carbon atoms. Diamond is a transparent crystal, a dielectric, the most durable substance in nature.
(Slide 5) Graphite and diamond.
The consequence of the correct arrangement of atoms is the presence of flat faces and the correct geometric shape of crystals (regardless of size), symmetry. Pay attention to this on the following slides:
(Slide 6) Lead iodide. The sizes of the crystals are different, and the shape is repeated. In addition, if the crystal breaks into pieces, then they will all be the same shape.
(Slide 7) Diamonds
(Slide 9) Snowflakes.
(Slide 10) Quartz.
Study. You have various substances and microscopes on your table. Adjust the light in the microscope, put grains of salt on a glass slide and examine them. Which of the features of crystals already listed is confirmed by observing salt crystals? (The correct form in the form of cubes, flat faces are visible).
Inside the crystal, the distances between atoms in different directions are different, and therefore the interactions between atoms are different. Let's think about what this leads to.
Let's take another look at the graphite lattice model.
– Where are atoms more strongly bound: in separate layers or between layers? (Answer: in separate layers, since the particles are closer to each other).
– How can this affect the strength of the crystal? (Answer: the strength will most likely be different).
- In which direction will heat transfer faster - along the layer or in the perpendicular direction? (Answer: along the layer).
So, the physical properties are different in different directions. It is called anisotropy . Let's write in the table: crystals anisotropic, i.e. their physical properties depend on the direction chosen in the crystal(thermal conductivity, electrical conductivity, strength, optical properties). This is the main property of crystals!!
Demonstration pieces of mica and its ability to easily delaminate, but it is difficult to break the mica plate across the layers.
(Slide 11) Let us consider one more feature of crystals.
How are these two objects different? (Answer: sugar in the form of separate grains on the left, and fused crystals on the right).
Single crystals are called single crystals , and a lot of crystals soldered to each other - polycrystals (write in the table).
(Slide 12) Examples of single crystals are precious stones (sapphires, rubies, diamonds). This is what a ruby crystal looks like in nature.
(Slide 13) For jewelry, they are given an additional cut. All metals are polycrystals.
(Slide 14) And here sugar is in three states: granulated sugar, refined sugar, and sugar candy.
– Are there single crystals among these samples? (Answer: granulated sugar).
– Is there a polycrystal among these samples? (Answer: refined sugar).
– Can we say that the lollipop has the correct shape? Does it have flat edges? (Answers: no).
Study. Examine grains of sugar and pieces of candy under a microscope. What can be said about the shape of the grains, the presence of flat edges, the repeatability of the shape in different grains? (answer: grains of sugar have all the signs of crystals, grains of candy do not have them).
(Slide 15) Here are photographs taken with a microscope: on the left is a grain of granulated sugar, on the right is a piece of candy. Pay attention to the chipped lollipop.
Unlike crystals, sugar candy can both crack and soften, gradually turning into a liquid state, while changing shape. All amorphous bodies are substances whose atoms are arranged in a relative order, there is no strict repeatability of the spatial structure.(Slide 16) The consequence of this is isotropy- the same physical properties in different directions (write in the table).
(Slide 17) Another example of a substance in crystalline and amorphous states (sand and glass). It is important that due to different distances between atoms, even in neighboring cells, the spatial lattice will not collapse at a certain temperature, as happens in crystals. Amorphous bodies have a temperature range at which the substance smoothly passes into the liquid state.
(Slide 18) Examples of amorphous bodies are resin, rosin, amber, plasticine and others. .
4. For anchoring of the material, we answer questions No. 597, No. 598 from the collection of problems of Rymkevich A.P., No. 17.26, 17.30 from the collection of problems of Gendenshtein L.E.
If there is time left, we solve problems from the USE (A10, A11).
5 . Homework: complete the table, §30.
slide 1
Crystalline and amorphous bodies
Surface tension of liquids
slide 2
Basic states of matter
Gaseous Liquid Solid Crystals Amorphous bodies Any substance can be in 3 states of aggregation, depending on the conditions (temperature and pressure) Plasma
slide 3
Crystals are solids whose atoms or molecules occupy certain, ordered positions in space.
In crystalline bodies, the particles are arranged in a strict order, forming spatial periodically repeating structures throughout the volume of the body (long-range order). For a visual representation of such structures, spatial crystal lattices are used, at the nodes of which the centers of atoms or molecules of a given substance are located. Most often, the crystal lattice is built from ions (positively and negatively charged) atoms that are part of the molecule of a given substance.
slide 4
crystals
Melt at a certain temperature (melting point) Crystal properties depend on the type of crystal lattice
A monocrystal is a single crystal. Physical properties: 1) Regular geometric shape 2) Constant melting point.
slide 5
Crystal lattices
Molecular Atomic Metallic Ionic
Molecules are located at the nodes. There are weak forces of attraction between them, so the substances are volatile, they have low melting and boiling points, and low hardness. Ice, iodine. The nodes are individual atoms. The bonds between them are the strongest, so the substances are the hardest, they do not dissolve in water, they have high melting and boiling points. Diamond (carbon) The nodes contain metal atoms that easily turn into ions when electrons are donated for general use. Substances are malleable, plastic, have a metallic luster, high thermal and electrical conductivity. Positive and negative ions are located at the nodes. The bond between them is strong, so the substances have high hardness, refractoriness, non-volatile, but many can dissolve in water. Sodium chloride (salt)
slide 6
crystals
Slide 7
Colombian emerald
Cap of Monomakh
Slide 8
Polycrystals
Bismuth polycrystal
Amethyst (a type of quartz)
Polycrystals are solids made up of many small crystals. Examples: metals, sugar cube.
Slide 9
Crystal anisotropy - dependence physical properties from the direction inside the crystal
Different mechanical strength in different directions (mica, graphite) Different thermal and electrical conductivities Different optical properties of the crystal (different light refraction - quartz) All crystalline bodies are anisotropic
Slide 10
Amorphous bodies
These are solids, where only the short-range order in the arrangement of atoms is preserved. (Silica, resin, glass, rosin, sugar candy). They do not have a constant melting point and are fluid. At low temperatures, they behave like crystalline bodies, and at high temperatures they are like liquids.
slide 11
Amorphous bodies are isotropic, physical properties are the same in all directions
Amorphous, petrified tree sap
slide 12
liquid crystals
Possess simultaneously the properties of a crystal and a liquid (anisotropy and fluidity) Liquid crystals - mainly organic matter, whose molecules have a long filamentous shape or the shape of flat plates
slide 13
Liquids
In liquids, short-range order is observed - an ordered relative arrangement (or mutual orientation in liquid crystals) of neighboring particles of a liquid inside its small volumes
Slide 14
Liquids
The structure is similar to the structure of amorphous bodies Difference: they have a high fluidity
slide 15
Liquid
Surface phenomena are phenomena associated with the existence of a free surface in a liquid. The excess energy possessed by the molecules of the surface layer compared to the molecules in the bulk of the liquid is called surface (excess) energy. Specific surface energy - the ratio of surface energy to surface area σ= E sur/s [σ]=1 J/m2
slide 16
The number of molecules remaining on the surface of a liquid is such that its area remains minimal for a given volume of liquid. Liquid droplets take a shape close to spherical, in which the surface area is minimal. Own shape - spherical Surface tension is a phenomenon caused by the attraction of the molecules of the surface layer to the molecules inside the liquid. Surface tension force is a force directed tangentially to the surface of the liquid, perpendicular to the section of the contour that bounds the surface, in the direction of its contraction.
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Let's do an experiment. We will need a piece of plasticine, a stearin candle and an electric fireplace. Put plasticine and a candle at equal distances from the fireplace. After some time, some of the stearin will melt (become a liquid), and some will remain in the form of a solid piece. Plasticine for the same time will only soften a little. After some time, all the stearin will melt, and the plasticine will gradually “disperse” over the surface of the table, softening more and more. Let's do the experiment. We will need a piece of plasticine, a stearin candle and an electric fireplace. Put plasticine and a candle at equal distances from the fireplace. After some time, some of the stearin will melt (become a liquid), and some will remain in the form of a solid piece. Plasticine for the same time will only soften a little. After some time, all the stearin will melt, and the plasticine will gradually “correct” over the surface of the table, softening more and more
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slide 11
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Let's do the following experiment. Let's throw a piece of resin or wax into a glass funnel and leave it in a warm room. After about a month, it will turn out that the wax has taken the form of a funnel and even began to flow out of it in the form of a "jet" (see figure). Unlike crystals, which retain their shape almost forever, amorphous bodies are fluid even at low temperatures. Therefore, they can be considered as very thick and viscous liquids. Let's do the following experiment. Let's throw a piece of resin or wax into a glass funnel and leave it in a warm room. After about a month, it will turn out that the wax has taken the form of a funnel and even began to flow out of it in the form of a "jet" (see figure). Unlike crystals, which retain their shape almost forever, amorphous bodies are fluid even at low temperatures. Therefore, they can be considered as very thick and viscous liquids.
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All deformations of solids are reduced to tension (compression) and shear. With elastic deformations, the shape of the body is restored, and with plastic deformations it is not restored. All deformations of solids are reduced to tension (compression) and shear. With elastic deformations, the shape of the body is restored, and with plastic deformations it is not restored. Thermal motion causes vibrations of the atoms (or ions) that make up a solid body. The vibration amplitude is usually small compared to the interatomic distances, and the atoms do not leave their places. Since the atoms in a solid are interconnected, their vibrations occur in concert, so that a wave propagates through the body at a certain speed.
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crystalline
and amorphous
Prepared by: teacher of mathematics and physics of the OGBOU SPO "Tulun Agricultural College" Guznyakov Alexander Vasilyevich
Lesson Objectives:
teaching-
- form concepts: crystalline body”, “crystal lattice”, “monocrystal”, “polycrystal”, “amorphous body”;
- reveal the main properties of crystalline and amorphous bodies;
- develop the ability to highlight the main thing;
- develop the ability to systematize the material;
- develop cognitive interest in the subject, using a variety of forms of work;
- develop a scientific outlook.
developing-
educational -
Barely transparent ice, fading over the lake, Crystal covered motionless jets.
A.S. Pushkin.
And the crazy chill of emerald, And the warmth of golden topaz, And simple calcite wisdom - Only they will not deceive even once. In them, in silent fragments of the universe, Sparks of eternal harmonies sparkle. An haughty image of everyday life In these sparks, it turns pale and melts. They give peace and protection, They give the fire of inspiration, Weaving in a single chain, With our frailty - links in eternity.
Viktor Slyotov
emerald crystals
Practical work
|
Indications dry thermometer, °С |
Reading difference dry and wet thermometers, ° С |
Wet thermometer readings, °С |
|||||||
Determine
humidity
entrance test
1. Name three states of matter.
- gaseous, liquid, solid.
2. Complete the sentence.
“The aggregate state of matter is determined by the location, nature of movement and interaction ...”
- molecules.
entrance test
3. Find a correspondence between the state of aggregation of a substance and the distance between molecules.
- 1b; 2a; 3c.
4. Name the properties of solids.
- retain volume and shape.
1) gaseous;
2) solid;
3) liquid.
a) are arranged in an orderly manner, close to each other;
b) the distance is many times greater than the size of the molecules;
c) are located randomly next to each other.
entrance test
5. Fill in the missing words.
"The transition of a substance from a liquid to a solid state is called ... or ... "
- hardening, crystallization.
Most of the solids around us are substances in a crystalline state. These include building and construction materials: various grades of steel, various metal alloys, minerals, etc. A special area of physics - solid state physics - deals with the study of the structure and properties of solids. This area of physics is leading in all physical research. It is the foundation of modern technology.
Solid state physics
Properties of solids
Doesn't change
Doesn't change
What is the reason?
Properties of crystalline bodies
- melting temperature is constant
- Have a crystal lattice
- Each substance has its own melting point.
- Anisotropic (mechanical strength, optical, electrical, thermal properties)
Crystal types
Amorphous substances
(other Greek ἀ “non-” and μορφή “type, form”) do not have a crystalline structure and, unlike crystals, do not split with the formation of crystalline faces, as a rule, they are isotropic, that is, they do not show different properties in different directions, do not have certain melting point.
Properties of amorphous bodies
- Do not have a constant melting point
- They do not have a crystalline structure
- isotropic
- Have fluidity
- Able to go into a crystalline and liquid state.
- They have only "short order" in the arrangement of particles
Minerals
Variety of crystals
Amorphous bodies
Look at the root
Crystal types
Cubic system
tetragonal
Hexagonal
Rhombohedral
Rhombic
Monoclinic
Triclinic
liquid crystals
substances that have both
properties as liquids (fluidity),
and crystals (anisotropy).
Liquid Crystal Applications
Based on liquid crystals, pressure meters and ultrasound detectors have been created. But the most promising field of application of liquid crystal substances is information technology. It took only a few years from the first indicators, familiar to everyone from electronic watches, to color televisions with a liquid crystal screen the size of a postcard. These TVs provide a very High Quality, consuming a negligible amount of energy from a small-sized battery or battery.
Diamond cutting
The diamond is recognized as the most beautiful and frequently used form of brilliant cut, created for the optimal combination of brilliance and "play" of light, revealing the gem properties of the diamond.
Diamond "Shah"
Diamond "Orlov"
Problem solving
1. A ball machined from a single crystal, when heated, can change not only the volume, but also the shape. Why?
Answer :
Due to anisotropy, crystals expand unevenly when heated.
Problem solving
2. What is the origin of patterns on the surface of galvanized iron?
Answer :
Patterns appear due to the crystallization of zinc.
exit test
1. Complete the sentence.
“The dependence of physical properties on the direction inside the crystal is called…”
- anisotropy.
2. Fill in the missing words.
"Solid bodies are subdivided into ... and ..."
- crystalline and amorphous.
3. Find a correspondence between solids and crystals.
- 1a; 2b.
4. Find a correspondence between the substance and its state.
- 1b; 2c; 3b; 4a.
exit test
exit test
5. Find a correspondence between the bodies and the melting point.
- 1b; 2a.
You can find out more: http://ru.wikipedia.org/wiki; http://physics.ru/courses/op25part1/content/chapter3/section/paragraph6/theory.html; http://www.alhimik.ru/stroenie/gl_17.html; http://bse.sci-lib.com/article109296.html; http://fizika2010.ucoz.ru/socnav/prep/phis001/kris.html.
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