Guidelines for laboratory work. Solids, their characteristics and some properties Symmetry and classification of crystals

Often solids are bodies that retain their shape and volume. However, from a physical point of view, it can be difficult to distinguish between the solid and liquid states of a substance using these characteristics.

A special class of substances, which in appearance can also resemble solids, are polymers.

Polymers (from the Greek polymeres - consisting of many parts, from poly - many and meros - share, part) are compounds with high molecular weight, the molecules of which consist of a large number of regularly and irregularly repeating identical or different units.

Natural polymers include natural rubber, cellulose, proteins, and natural resins. Examples of synthetic polymers are polystyrene, polyethylene, and polyesters.

Truly solids - these are crystals, one of the characteristic features of which is correctness of their appearance.

One can only marvel at the perfection of the shape of snowflakes and admire their beauty.

If a saturated solution of hyposulfite, a substance used in photography to fix images, is left in an open bath for several days, then large crystals, also of a fairly regular shape, form at its bottom.

Crystals of table salt and sugar also have the correct shape.

The natural shape of crystals is polyhedra with flat faces and angles between them that are constant for each substance.

The shape of crystals of different substances is not the same. But crystals of the same substance can be of different colors. For example, quartz crystals are colorless, golden, pink, and pale lilac. Depending on the color, they are given different names. Quartz crystals, for example, may be called rock crystal, smoky rock crystal, or amethyst. From a jeweler's point of view, many crystals of the same substance can differ in fundamental ways. From the point of view of a physicist, there may be no difference between them at all, since the overwhelming majority of the properties of multi-colored crystals of the same substance are the same.

The physical properties of a crystal are determined not by its color, but by its internal structure. A very clear illustration of this statement is the difference in many properties of diamond and graphite, which have the same chemical composition.

Single crystals are called single crystals . Some substances, such as rock crystal, can form very large single crystals, sometimes with very regular shapes.

A feature of many single crystals is anisotropy – difference in physical properties in different directions.

The anisotropy of crystals is closely related to their symmetry. The lower the symmetry of the crystal, the more pronounced the anisotropy.

Let's take two plates cut from a quartz crystal in different planes. Let's drop wax onto the plates and let it harden, after which we touch the resulting wax spots with a hot needle. Based on the shape of the melted wax, we can conclude that a plate cut from a crystal in a vertical plane has different thermal conductivity in different directions.

If you cut two identical bars from a large piece of ice in mutually perpendicular directions, place them on two supports and load them, then the bars will behave differently. One block will slowly bend as the load increases. The other will retain its shape up to a certain load value and then break.

In a similar way, we can talk not only about the anisotropy of thermal conductivity and strength, but also other thermal, mechanical, as well as electrical and optical properties of single crystals.

Most solids have polycrystalline structure , that is, it consists of many randomly arranged crystals and does not have anisotropy of physical properties.

From the list of signs (properties), write down those that relate to bodies: Heat-conducting, soft, round, flat, colorless, wooden, insoluble, transparent, gaseous, hard, crystalline, long, heavy, oval, soluble, square, yellow.

Picture 10 from the presentation “Chemicals” for chemistry lessons on the topic “Matter”

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Substance

“Reasons for the diversity of substances” - Allotropic modifications of oxygen. Allotropy. Tin Plague. Reasons. Reasons for diversity. Painting by an unknown artist. Reasons for the diversity of substances. Consider the composition. Homologs. Scandalous story. Substances. Rhombic sulfur. Red phosphorus. Molecular formula. Isomerism. Formulas of substances. Graphene.

“Genetic relationships between classes of substances” - Diagnostic results at the end of the year (grade 8). Determination of the features of mastering the concept of genetic connection. Diagnostic results (grade 8). Compilation of the main genetic series of hydrocarbons. Contradictions. Consistent development. Compilation of basic genetic series. Diagnostic results at the end of the year (grade 10).

“Isomerism” - Isomerism of the position of a multiple bond. Alkene cycloalkane. Optical isomerism of carbohydrates. Numbering. Dynamic isomerism. Geometric isomers of butene. Asymmetric carbon atom. Amino acid nitro compound. Types of isomerism. Plain alcohol. Isomerism. Optical isomerism. Nomenclature rules. Rotation around a double bond.

“Substances in nature” - In what states substances can exist in nature. What are bodies made of? End of the bridge. What do substances consist of? Signs of a chemical reaction. Electrically charged particle. Substances without impurities. Shadow. What are molecules made of? How a rainbow is formed. Signs of living bodies. Drawing. What are the origins of bodies?

“Simple and complex chemical substances” - Simple and complex substances. Possible options for connecting particles. Type of chemical bond. Chemically indivisible particle. Covalent polar. Grounds. Substances. Metal connection. Simple substances. Chemical bond. Schemes. Complex substances. Types of chemical bonds. Ionic bond. Atom. Hydrogen bond.

“Complex compounds” - Basic provisions of coordination theory. Name the complex compounds. Nomenclature of complex compounds. Complex connections. Diamminesilver chloride. Complex ion. Make up formulas. Connections. Inner sphere. Names of anions. Preparation of sodium tetrahydroxoaluminate. Chemical properties.

There are a total of 34 presentations in the topic

Lesson objectives:

1. Summarize and systematize knowledge about natural bodies and form students’ knowledge about the properties of bodies.
2. Develop memory and thinking.

Tasks:

1. Teach to distinguish between natural and artificial bodies, various body shapes.
2. Learn to measure the mass of bodies using electronic scales.

Equipment: ball, Rubik's cube, box, flower, foam cube, flask, electronic scales, aluminum plates, geometric shapes, magnets.

Lesson progress

I. Organizational moment:

a) mutual greeting;

b) marking absentees;

Opening remarks.

Hello guys. In previous lessons we talked to you about nature and today we will continue to talk about it.

Question: Remember what nature is?

Answer: Nature is all the diversity of the world around us, everything that arose naturally.

Man has always had a remarkable quality - curiosity, an irresistible desire to know the world around him, to explore it, to comprehend the essence of the phenomena occurring in it. And he succeeded and succeeds with the help of various scientific methods.

Question: What methods of studying nature do you know?

Answer: Observation and experiment.

You know that observation and experiment are interconnected. During the observation of any phenomenon or event, a person carefully records all the changes occurring in bodies, then expresses a hypothesis about how the phenomenon occurs, about the reasons that cause it. The correctness of the hypothesis is verified experimentally. Then he draws conclusions. At the same time, he uses special words - terms. What is a “term”?

A term is a word or combination of words that precisely designates a specific concept. (The definition of the term is written down on the pieces of paper.)(Appendix 1, slide No. 2).

Question: Look around and tell me what surrounds you?

Answer: There are desks, chairs, books, children, etc. around us.

Question: That's right, we are surrounded by various objects. What term do scientists call all objects?

Answer: Bodies.

Question: When you read or hear the word “body,” what do you imagine?

Answer: The body of a person, an animal.

In Ozhegov’s dictionary there is the following meaning: “Body is the organism of a person or animal in its external and physical forms.” But this word has another meaning.

All objects surrounding us are called bodies.

II. Learning new material.

Nature consists of a huge number of different bodies. Today in class we will continue to study bodies.

The purpose of our lesson– find out what properties bodies have? What are the properties of bodies?

Answer: Body properties are signs by which bodies are distinguished from each other.

You know that among the countless and varied bodies of nature there are bodies natural , which are created by nature, and there are also bodies made by man. They are called artificial .

Question: Look at the pictures and name the bodies that belong to the first group.

Answer: Tree, grass, stone, Sun, butterfly and others.

Question: Name the bodies that belong to the second group.

Answer: Pencil, book, pen, table, bag and others.

Question: Look at the pictures and tell me what two other groups are bodies divided into?

Answer: Bodies are divided into living and nonliving.

Question: Give examples of living and nonliving bodies of nature.

Answer: Living: plants, animals. Non-living: stone, moon.

The first property of bodies is the division into living and nonliving.

The topic of the lesson is written on the board, then using a magnet we attach pieces of paper with the properties of bodies (slide No. 3).

On the board:

Let's try to find out other properties of bodies by solving riddles (slide number 4).

Riddles.

1. Miracle Yudo - giant
   A fountain is carried on its back.
   (whale)
2. Black toddler
   He can't pull the load according to his height.
   (ant)

Question: What property of the body do you think is spoken about in these riddles?

Answer: About size, body length? What is body size?

Size - the size of an object, the scale of some phenomenon (slide number 5).

Body size is found using a ruler or measuring tape. So, the second property of the body is size.

On the board:

Now listen to other riddles (slide number 6).

1. The pancake floats alive -
   He has a tail and a head.
   (flounder)
2. Balloon, gold
   Stopped over the river
   Swung over the water
   And then... he disappeared behind the forest!
   (Sun)

Question: What other property of the body is mentioned in the riddles?

Answer: About body shape (slide number 7).

Form (lat. forma) – external outline, appearance, contours of an object.

Look at the objects on the table. On one side there are geometric shapes, on the other - bodies. What shape are they? (On the table there is a soccer ball (ball), granite (no shape), pencil (cylinder), chalk box (cuboid), book (cuboid), Rubik's cube (cube), triangular Rubik's pyramid (tetrahedron), flask (cone), nut (hexagonal prism), flower (no shape)).

Please note that some bodies have a regular geometric shape, others have an irregular shape.

Guys, remember which bodies of regular geometric shapes you have already seen?

(On slide No. 7 there are photographs or drawings of objects with various shapes).

(Examples of bodies with regular and irregular geometric shapes are written down on the pieces of paper.)

On the board:

Now look again at the objects lying on the table and tell me, what other property of the body have we not named? Describe the ball. What is he like?

Answer: Round, blue or light blue (or other color).

The fourth property of bodies is it's a color.

On the board:

In addition to size, shape, and color, bodies also have other characteristics. Let's talk about one of them. Look closely at the table. There are two cubes on the table. One is made of foam and the other is made of plastic. They are the same in size and shape, but there are differences between them.

Question: How do you think these cubes differ from each other?

Answer: They differ in mass.

That's right, every body has mass. Do you know in what units mass is measured? The unit of mass is the kilogram. The international sample (standard) kilogram is stored in France in the city of Sevres. Copies of this sample were made with great precision for other countries. The unit of mass (kilogram) was taken platinum iridium weight in the shape of a cylinder with a diameter and height of 39 mm. It is stored under two glass domes from which the air is pumped out. This is done to ensure that the alloy does not combine with air. Otherwise, the weight of the weight may increase significantly.

To measure the mass of any body, scales are used (slide No. 8).

Question: What scales do you know?

Answer: Mechanical, electronic.

Look at the screen (photos of various scales).

We also have scales. Some are electronic, others are lever. There are electronic scales on your table. They can only measure the mass of bodies up to 200 grams. The blue stands (boxes) contain foam and aluminum plates. You will need to measure the mass of these plates. To do this, you need to take the scales out of the box, place it on the table, then press the red button and wait until two zeros appear. Then take the plates one by one and measure their mass, recording the results on a piece of paper. Let us formulate the goal of the laboratory work: determine the mass of the foam and aluminum plates and draw a conclusion about which body weighs more. Do the work, and then enter the data obtained into the table and draw a conclusion.

In the next lesson we will learn how to measure the mass of bodies using lever scales.

So, let's summarize. What properties of bodies did you learn about in this lesson?

Answer: We learned that bodies are living and nonliving, natural and artificial, have different shapes, colors, sizes and weights.

On the board:

Question: Guys, do you think we have studied all the properties of bodies?

Today we didn’t remember one more property. What property do you think we haven't mentioned? This property of the body is always of great interest to the doctor. When we sick people come to see a doctor, he is always interested in the body temperature of the sick person. Do you know what human body temperature is considered normal? (36.6 ºC) Temperature is measured in degrees Celsius (after the Swedish astronomer and physicist Anders Celsius).

Celsius, a temperature scale in which 1 degree (1 °C) is equal to 1/100 of the difference between the boiling point of water and the melting point of ice at atmospheric pressure, the melting point of ice is taken to be 0 °C, the boiling point of water is taken to be 100 °C. Proposed in 1742 by A. Celsius.

Just like the human body and other bodies have temperature. For example, what temperature can a piece of ice have? Zero degrees or less. To measure a person’s body temperature, a mercury or electronic thermometer is used (slide No. 9).

On the board:

All properties written on the board are integral features of the body as a scientific concept. Now we can give a complete definition of the body (slide number 10).

Body - an object of nature or the man-made world that has a certain shape, color, mass, size, temperature.

In science, the concept of “physical body” is more often used.

III. Fixing the material

1. Didactic game “Attention” - physical body!

The teacher pronounces various words denoting bodies and phenomena. The guys need to clap when they hear the name of the body.

Words: sunset, rainbow, rain, tree, volcanic eruption, book, bear, ruler, sunrise, clock, wardrobe, thunder, ball, lightning, Sun, earthquake, frog.

2. Working with the literary text “Vasily the Beautiful” .

The children’s task is to identify the signs of Vasily the cat as a physical body (the text is written on pieces of paper).

The cat Vasily (to his relatives and friends simply Vasyanya) was very well-fed and shaped like the pyramid of Cheops, if sitting, and honey barrel, if standing. From the tip of his nose to the tip of his tail there was 92 cm. His striped back smoothly turned into orange-yellow belly.

Vasily was affectionate, patient, loving, clean, and knew how to cheer up and improve the well-being of the owner. He was also famous for the fact that he only caught a mouse once. But when the weight passed him for 7 kg, his hunting instincts fell asleep forever, and there was no better activity for him than to take a nap in the arms of his owner. Such warmth emanates from a cat sleeping in your arms and such tenderness is born. It's because normal cat temperature +38-39.5 °C.

IV. Grading for the lesson.

V. Homework assignment.§ 11 (draw bodies of different shapes and sizes on album sheets or come up with puzzles about bodies, fill out a workbook using pieces of paper.)

Solids are crystalline and amorphous bodies. Crystal is what ice was called in ancient times. And then they began to call quartz a crystal and considered these minerals to be petrified ice. Crystals are natural and are used in the jewelry industry, optics, radio engineering and electronics, as supports for elements in ultra-precision instruments, as an ultra-hard abrasive material.

Crystalline bodies are characterized by hardness and have a strictly regular position in space of molecules, ions or atoms, resulting in the formation of a three-dimensional periodic crystal lattice (structure). Outwardly, this is expressed by a certain symmetry of the shape of a solid body and its certain physical properties. In their external form, crystalline bodies reflect the symmetry inherent in the internal “packing” of particles. This determines the equality of the angles between the faces of all crystals consisting of the same substance.

In them, the distances from center to center between neighboring atoms will also be equal (if they are located on the same straight line, then this distance will be the same along the entire length of the line). But for atoms lying on a straight line with a different direction, the distance between the centers of the atoms will be different. This circumstance explains the anisotropy. Anisotropy is the main difference between crystalline bodies and amorphous ones.

More than 90% of solids can be classified as crystals. In nature they exist in the form of single crystals and polycrystals. Monocrystals are single crystals, the faces of which are represented by regular polygons; They are characterized by the presence of a continuous crystal lattice and anisotropy of physical properties.

Polycrystals are bodies consisting of many small crystals, “grown together” somewhat chaotically. Polycrystals are metals, sugar, stones, sand. In such bodies (for example, a fragment of a metal), anisotropy usually does not appear due to the random arrangement of elements, although anisotropy is characteristic of an individual crystal of this body.

Other properties of crystalline bodies: strictly defined temperature (presence of critical points), strength, elasticity, electrical conductivity, magnetic conductivity, thermal conductivity.

Amorphous - having no shape. This is how this word is literally translated from Greek. Amorphous bodies are created by nature. For example, amber, wax. Humans are involved in the creation of artificial amorphous bodies - glass and resins (artificial), paraffin, plastics (polymers), rosin, naphthalene, var. do not have due to the chaotic arrangement of molecules (atoms, ions) in the structure of the body. Therefore, for any amorphous body they are isotropic - the same in all directions. For amorphous bodies there is no critical melting point; they gradually soften when heated and turn into viscous liquids. Amorphous bodies are assigned an intermediate (transitional) position between liquids and crystalline bodies: at low temperatures they harden and become elastic, in addition, they can split into shapeless pieces upon impact. At high temperatures, these same elements exhibit plasticity, becoming viscous liquids.

Now you know what crystalline bodies are!

Exercise: 1

Phileo (Greek) means “love”, phobos - “fear”. Give an explanation of the terms “chemophilia” and “chemophobia”, which reflect the sharply opposite attitudes of groups of people towards chemistry. Which one is right? Justify your point of view.

"Hemophilia"- interest, aptitude for chemistry. Also, people are passionate about the science of chemistry, interested in it, who believe that the modern world is impossible without the development of new chemicals, and have a positive attitude towards the production of chemicals needed in industry, agriculture, the space industry, the food industry, in everyday life, etc.
"Hemophobia"- rejection of chemistry and everything chemical, opposition of “chemical” and “natural”. (For example, when growing plants for food.) Also, people who have a negative attitude towards chemistry cite environmental pollution of soil, water, and air as an example. This leads to increased morbidity in people and animals living near chemical production facilities.
Both “chemophiles” and “chemophobes” are right - without chemistry the existence of the modern world is impossible, but the creation of waste-free industries that do not poison the environment, the creation of industries for the recycling of various plastic and other wastes is absolutely necessary. Chemistry is only a science, and whether it brings benefit or harm to people depends on the people themselves.

Exercise: 5

Compare the concepts of “simple substance” and “complex substance”. Find similarities and differences.

Common to simple and complex substances, that they consist of molecules and atoms.
Miscellaneous: simple ones consist of atoms of one chemical element, and complex ones - of atoms of different chemical elements.

Exercise: 6

Determine which of the substances whose molecular models are shown in Figure 6 include: a) to simple substances; b) to complex substances.

Simple substances: oxygen, sulfur, helium, ozone.
Complex substances: ethyl alcohol, methane, carbon dioxide, carbon monoxide.

Exercise: 8

Indicate where oxygen is referred to as a chemical element and where it is referred to as a simple substance:
c) the air contains 20% oxygen (by volume);
d) oxygen is part of carbon dioxide.

About the chemical element:
b) water molecules consist of two hydrogen atoms and one oxygen atom;
d) oxygen is part of carbon dioxide.
About a simple substance:
a) oxygen is slightly soluble in water;
c) the air contains 20% oxygen (by volume).

Exercise: 10

Consider the connection between the properties of a substance and its use using the example of: a) glass; b) polyethylene; c) sugar; d) iron.

Glass: a solid, transparent substance that, when melted, can take on different shapes and retain them, and is not toxic. The use of glass in the production of window glass, tableware, and optical instruments is based on these properties.

Polyethylene: a light, plastic substance, non-toxic, capable of being stretched into thin films, and when melted, capable of taking on different shapes and retaining them. The use of polyethylene in the production of disposable tableware, packaging material, and pipe production is based on these properties.

Sugar: a white solid, highly soluble in water, non-toxic, odorless, and has a sweet taste. It is used as food and is also used in the food industry and medicine.

Iron: silvery-white shiny metal, melting point = 15390C, ductile, therefore easily processed, forged, rolled, stamped, thermally and electrically conductive. Iron can be magnetized and demagnetized; it is used as electromagnet cores in various electrical machines and devices. Iron is the basis of modern technology and agricultural engineering, transport, and communications of all modern civilization. From a sewing needle to space technology.