To date, more than 3 million are known to exist. various substances. And this figure is growing every year, as synthetic chemists and other scientists are constantly making experiments to obtain new compounds that have some useful properties.

Some substances are natural inhabitants that form naturally. The other half are artificial and synthetic. However, in both the first and second cases, a significant part is made up of gaseous substances, examples and characteristics of which we will consider in this article.

Aggregate states of substances

Since the 17th century, it has been generally accepted that all known compounds are capable of existing in three states of aggregation: solid, liquid, gaseous substances. However, careful research of recent decades in the field of astronomy, physics, chemistry, space biology and other sciences have proved that there is another form. This is plasma.

What does she represent? This is partially or completely And it turns out that the overwhelming majority of such substances in the Universe. So, it is in the plasma state that there are:

• interstellar matter;
• space matter;
• the upper layers of the atmosphere;
• nebulae;
• composition of many planets;
• stars.

Therefore, today they say that there are solid, liquid, gaseous substances and plasma. By the way, each gas can be artificially transferred to such a state if it is subjected to ionization, that is, forced to turn into ions.

Gaseous substances: examples

There are many examples of substances under consideration. After all, gases have been known since the 17th century, when van Helmont, a naturalist, first obtained carbon dioxide and began to study its properties. By the way, he also gave the name to this group of compounds, since, in his opinion, gases are something disordered, chaotic, associated with spirits and something invisible, but tangible. This name has taken root in Russia.

It is possible to classify all gaseous substances, then it will be easier to give examples. After all, it is difficult to cover all the diversity.

The composition is distinguished:

• simple,
• complex molecules.

The first group includes those that consist of the same atoms in any number. Example: oxygen - O 2, ozone - O 3, hydrogen - H 2, chlorine - CL 2, fluorine - F 2, nitrogen - N 2 and others.

• hydrogen sulfide - H 2 S;
• hydrogen chloride - HCL;
• methane - CH 4;
• sulfur dioxide - SO 2;
• brown gas - NO 2;
• freon - CF 2 CL 2;
• ammonia - NH 3 and others.

Classification by the nature of substances

You can also classify the types of gaseous substances according to belonging to the organic and inorganic world. That is, by the nature of the constituent atoms. Organic gases are:

• the first five representatives (methane, ethane, propane, butane, pentane). General formula C n H 2n+2 ;
• ethylene - C 2 H 4;
• acetylene or ethyne - C 2 H 2;
• methylamine - CH 3 NH 2 and others.

Another classification that can be subjected to the compounds in question is division based on the particles that make up the composition. It is from atoms that not all gaseous substances consist. Examples of structures in which there are ions, molecules, photons, electrons, brownian particles, plasma, also refer to compounds in such a state of aggregation.

Properties of gases

The characteristics of substances in the considered state differ from those for solid or liquid compounds. The thing is that the properties of gaseous substances are special. Their particles are easily and quickly mobile, the substance as a whole is isotropic, that is, the properties are not determined by the direction of movement of the constituent structures.

It is possible to identify the most important physical properties gaseous substances, which will distinguish them from all other forms of existence of matter.

1. These are connections that cannot be seen and controlled, felt in ordinary human ways. To understand the properties and identify a particular gas, they rely on four parameters that describe them all: pressure, temperature, amount of substance (mol), volume.
2. Unlike liquids, gases are able to occupy the entire space without a trace, limited only by the size of the vessel or room.
3. All gases are easily mixed with each other, while these compounds do not have an interface.
4. There are lighter and heavier representatives, so under the influence of gravity and time, it is possible to see their separation.
5. Diffusion is one of the most important properties of these compounds. The ability to penetrate other substances and saturate them from the inside, while making completely disordered movements within its structure.
6. real gases electricity they cannot conduct, however, if we talk about rarefied and ionized substances, then the conductivity increases sharply.
7. The heat capacity and thermal conductivity of gases is low and varies from species to species.
8. Viscosity increases with increasing pressure and temperature.
9. There are two options for the interphase transition: evaporation - the liquid turns into vapor, sublimation - the solid, bypassing the liquid, becomes gaseous.

A distinctive feature of vapors from true gases is that the first certain conditions able to go into a liquid or solid phase, while the latter are not. It should also be noted the ability of the compounds under consideration to resist deformation and be fluid.

Similar properties of gaseous substances allow them to be widely used in the most various fields science and technology, industry and national economy. In addition, specific characteristics are strictly individual for each representative. We have considered only features common to all real structures.

Compressibility

At different temperatures, as well as under the influence of pressure, gases are able to compress, increasing their concentration and reducing the volume occupied. At elevated temperatures they expand, at low temperatures they shrink.

Pressure also changes. The density of gaseous substances increases and, upon reaching a critical point, which is different for each representative, a transition to another state of aggregation may occur.

The main scientists who contributed to the development of the doctrine of gases

There are many such people, because the study of gases is a laborious and historically long process. Let's focus on the most famous personalities who managed to do the most significant discoveries.

1. made a discovery in 1811. It doesn't matter what gases, the main thing is that under the same conditions they are contained in one volume of them in an equal amount by the number of molecules. There is a calculated value named after the name of the scientist. It is equal to 6.03 * 10 23 molecules for 1 mole of any gas.
2. Fermi - created the doctrine of an ideal quantum gas.
3. Gay-Lussac, Boyle-Marriott - the names of scientists who created the basic kinetic equations for calculations.
4. Robert Boyle.
5. John Dalton.
6. Jacques Charles and many other scientists.

The structure of gaseous substances

The most main feature in the construction of the crystal lattice of the substances under consideration, this is that at its nodes there are either atoms or molecules that are connected to each other by weak covalent bonds. Van der Waals forces are also present when we are talking about ions, electrons and other quantum systems.

Therefore, the main types of lattice structures for gases are:

• atomic;
• molecular.

The bonds inside break easily, so these compounds do not have a permanent shape, but fill the entire spatial volume. This also explains the lack of electrical conductivity and poor thermal conductivity. But the thermal insulation of gases is good, because, thanks to diffusion, they are able to penetrate solids and occupy free cluster spaces inside them. At the same time, air is not passed, heat is retained. This is the basis for the use of gases and solids in combination for construction purposes.

Simple substances among gases

Which gases belong to this category in terms of structure and structure, we have already discussed above. These are the ones that are made up of the same atoms. There are many examples, because a significant part of non-metals from all periodic system under normal conditions, it exists in this state of aggregation. For example:

• white phosphorus - one of this element;
• nitrogen;
• oxygen;
• fluorine;
• chlorine;
• helium;
• neon;
• argon;
• krypton;
• xenon.

The molecules of these gases can be both monatomic (noble gases) and polyatomic (ozone - O 3). The type of bond is covalent non-polar, in most cases it is rather weak, but not in all. Crystal cell molecular type, which allows these substances to easily move from one state of aggregation to another. So, for example, iodine under normal conditions - dark purple crystals with a metallic sheen. However, when heated, they sublimate into clubs of bright purple gas - I 2.

By the way, any substance, including metals, under certain conditions can exist in gaseous state.

Complex compounds of a gaseous nature

Such gases, of course, are the majority. Various combinations of atoms in molecules, united by covalent bonds and van der Waals interactions, allow hundreds of different representatives of the aggregate state under consideration to form.

Examples complex substances among gases can be all compounds consisting of two or more different elements. This may include:

• propane;
• butane;
• acetylene;
• ammonia;
• silane;
• phosphine;
• methane;
• carbon disulfide;
• sulphur dioxide;
• brown gas;
• freon;
• ethylene and others.

Crystal lattice of molecular type. Many of the representatives easily dissolve in water, forming the corresponding acids. Most of such compounds are an important part of chemical syntheses carried out in industry.

Methane and its homologues

Sometimes general concept"gas" means a natural mineral, which is a whole mixture gaseous products predominantly organic. It contains substances such as:

• methane;
• ethane;
• propane;
• butane;
• ethylene;
• acetylene;
• pentane and some others.

In industry, they are very important, because it is the propane-butane mixture that is the household gas on which people cook food, which is used as a source of energy and heat.

Many of them are used for the synthesis of alcohols, aldehydes, acids and other organic matter. Annual Consumption natural gas is estimated in trillions of cubic meters, and this is quite justified.

Oxygen and carbon dioxide

What gaseous substances can be called the most widespread and known even to first graders? The answer is obvious - oxygen and carbon dioxide. After all, they are the direct participants in the gas exchange that occurs in all living beings on the planet.

It is known that it is thanks to oxygen that life is possible, since without it only certain species can exist. anaerobic bacteria. And carbon dioxide is required product"nutrition" for all plants that absorb it in order to carry out the process of photosynthesis.

From a chemical point of view, both oxygen and carbon dioxide are important substances for synthesizing compounds. The first is a strong oxidizing agent, the second is more often a reducing agent.

Halogens

This is such a group of compounds in which atoms are particles of a gaseous substance connected in pairs to each other due to a covalent non-polar bond. However, not all halogens are gases. Bromine is a liquid under ordinary conditions, while iodine is a highly sublimable solid. Fluorine and chlorine are poisonous substances hazardous to the health of living beings, which are the strongest oxidizing agents and are widely used in synthesis.

Gas (gaseous state) Gas is a state of aggregation of a substance, characterized by very weak bonds between its constituent particles (molecules, atoms or ions), as well as their high mobility.

Features of gases Easy to compress. They do not have their own shape and volume. Any gases are mixed with each other in any ratio.

Avogadro's number The value NA = 6.022…×1023 is called Avogadro's number. This is a universal constant for the smallest particles of any substance.

A consequence of Avogadro's law 1 mole of any gas at n. y. (760 mm Hg and 00 C) occupies a volume of 22.4 liters. Vm \u003d 22. 4 l / mol - molar volume of gases

The most important natural mixtures of gases Composition of air: φ(N 2) = 78%; φ(O 2) = 21%; φ(CO 2) = 0. 03 Natural gas is a mixture of hydrocarbons.

Obtaining hydrogen. In industry: Cracking and reforming of hydrocarbons during oil refining: C 2 H 6 (t = 10000 C) → 2 C + 3 H 2 From natural gas. CH 4 + O 2 + 2 H 2 O → 2 CO 2 +6 H 2 O

Hydrogen H 2 In the laboratory: The effect of dilute acids on metals. To carry out such a reaction, zinc and dilute sulfuric acid are most often used: Zn + 2 HCl → Zn. Cl 2 + H 2 Interaction of calcium with water: Ca + 2 H 2 O → Ca (OH) 2 + H 2 Hydrolysis of hydrides: Ca. H 2 + 2 H 2 O → Ca (OH) 2 +2 H 2 The action of alkalis on zinc or aluminum: Zn + 2 Na. OH + 2 H 2 O Na 2 + H 2

Properties of hydrogen The lightest gas, it is 14.5 times lighter than air. Hydrogen has the highest thermal conductivity among gaseous substances. Its thermal conductivity is about seven times higher than that of air. The hydrogen molecule is diatomic - H 2. Under normal conditions, it is a colorless, odorless and tasteless gas.

Oxygen In industry: From the air. Main industrial way obtaining oxygen, is cryogenic distillation. In the laboratory: From potassium permanganate (potassium permanganate): 2 KMn. O 4 = K 2 Mn. O4 + Mn. O 2 + O 2; 2 H 2 O 2 \u003d 2 H 2 O + O 2.

Properties of Oxygen Under normal conditions, oxygen is a colorless, tasteless and odorless gas. 1 liter of it has a mass of 1.429 g. It is slightly heavier than air. Slightly soluble in water and alcohol. Very soluble in molten silver. It is paramagnetic.

Carbon monoxide (IV) In the laboratory: From chalk, limestone or marble: Na 2 CO 3 + 2 HCl = 2 Na. Cl + CO 2 + H 2 O Ca. CO 3 + HCl \u003d Ca. Cl 2 + CO 2 + H 2 O In nature: Photosynthesis in plants: C 6 H 12 O 6 + 6 O 2 = 6 CO 2 + 6 H 2 O

Carbon monoxide (IV) Carbon monoxide (IV) (carbon dioxide) is a colorless, odorless gas with a slightly sour taste. Heavier than air, soluble in water, with strong cooling, it crystallizes in the form of a white snow-like mass - “dry ice”. At atmospheric pressure it does not melt, but evaporates, the sublimation temperature is -78 °C.

Ammonia (n.a.) is a colorless gas with a pungent characteristic odor (smell ammonia). Ammonia is almost twice as light as air, the solubility of NH 3 in water is extremely high. Ammonia is produced in the laboratory by: Interaction of alkalis with ammonium salts: NH 4 Cl + Na. OH=Na. Cl + H 2 O + NH 3 In industry: Interaction of hydrogen and nitrogen: 3 H + N = 2 NH

Ethylene In the Lab: Dehydration ethyl alcohol In industry: Cracking of petroleum products: C 4 H 10 → C 2 H 6 + C 2 H 4 ethane ethene

Ethylene is a colorless gas with a slight sweetish odor and is relatively high density. Ethylene burns with a luminous flame; Forms an explosive mixture with air and oxygen. Ethylene is practically insoluble in water.

Receiving, collecting and recognizing gases Gas name (formula) Hydrogen (H 2) Oxygen (O 2) Carbon dioxide(CO 2) Ammonia (NH 3) Ethylene (C 2 H 4)

Challenges Challenge #1. 13.5 grams of zinc (Zn) interact with hydrochloric acid(HCl). The volume fraction of the yield of hydrogen (H 2) is 85%. Calculate the amount of hydrogen released? Task number 2. There is gas mixture, mass fractions gas in which are equal (%): methane - 65, hydrogen - 35. Determine the volume fraction of gases in this mixture.

Problem number 1 1) Let's write the reaction equation for the interaction of zinc (Zn) with hydrochloric acid (HCl): Zn + 2 HCl = Zn. Cl 2 + H 2 2) n (Zn) = 13.5/65 = 0.2 (mol). 3) 1 mole of Zn displaces 1 mole of hydrogen (H 2), and 0.2 mole of Zn displaces x mole of hydrogen (H 2). We get: V theor. (H 2) \u003d 0.2 ∙ 22.4 \u003d 4.48 (l). 4) Calculate the volume of hydrogen practical by the formula: V practical. (H 2) \u003d 85 ⋅ 4.48 / 100 \u003d 3.81 (l).

Task number 2 There is a gas mixture, the mass fractions of gas in which are equal (%): methane - 65, hydrogen - 35. Determine the volume fractions of gases in this mixture.

gaseous substances.

Lecture #12

Topic:"Means acting on the central nervous system".

1. Means for anesthesia.

2. Ethyl alcohol.

3. Sleeping pills

4. Antiepileptic drugs.

5. Antiparkinsonian drugs

6. Analgesics.

Means affecting the central nervous system

Drugs for anesthesia.

Substances that cause surgical anesthesia include. Narcosis is a reversible depression of the central nervous system, which is accompanied by loss of consciousness, loss of sensitivity, a decrease in reflex excitability and muscle tone.

Means for anesthesia inhibit the transmission of nerve impulses in the synapses of the central nervous system. Synapses of the central nervous system have unequal sensitivity to narcotic substances. This explains the presence of stages in the action of drugs for anesthesia.

Stages of anesthesia:

1st stage of analgesia (stunning)

2. stage of excitation

3. stage of surgical anesthesia

1st level – superficial anesthesia

2nd level light anesthesia

3rd level deep anesthesia

4th level ultra-deep anesthesia

4. stage of awakening or agonal.

Depending on the route of administration, there are: inhaled and non-inhaled drugs.

Inhalation drugs.

Enter through Airways.

These include:

1. Volatile liquids - ether for anesthesia, halothane (halothane), chloroethyl, enflurane, isoflurane, sevoflurane.

2. gaseous substances - nitrous oxide, cyclopropane, ethylene.

It is an easily controlled anesthetic.

volatile liquids.

Ether for anesthesia- colorless, transparent, volatile liquid, explosive. Highly active. Irritates the mucous membrane of the upper respiratory tract, depresses respiration.

stages of anesthesia.

Stage 1 - stunning (analgesia). The synapses of the reticular formation are inhibited. main feature - confusion, decreased pain sensitivity, impaired conditioned reflexes, unconditional preserved, respiration, pulse, blood pressure almost unchanged. At this stage, short-term operations can be performed (opening an abscess, phlegmon, etc.).

Stage 2 - excitement. The synapses of the cerebral cortex are inhibited. Inhibitory influences of the cortex on the subcortical centers are switched on, excitation processes predominate (the subcortex is disinhibited). "Rebellion of the subcortex." Consciousness is lost, motor and speech excitement (sing, swear), increases muscle tone(the sick are tied up). unconditioned reflexes- cough, vomiting. Respiration and pulse are quickened, blood pressure is increased.

Complications: reflex respiratory arrest, secondary respiratory arrest: spasm of the glottis, retraction of the tongue, aspiration of vomit. This stage of the ether is very pronounced. It is impossible to operate at this stage.

Stage 3 - surgical anesthesia. Inhibition of synapses of the spinal cord. Unconditioned reflexes are inhibited, muscle tone decreases.

The operation starts at level 2, and is carried out at level 3. The pupils will be slightly dilated, almost do not react to light, the tone of the skeletal muscles is sharply reduced, blood pressure decreases, the pulse is faster, breathing is less, rare and deep.

When not correct dosage drug overdose may occur. And then the 4th level of super-deep anesthesia develops. The synapses of the centers of the medulla oblongata - respiratory and vasomotor - are inhibited. The pupils are wide and do not react to light, the breathing is shallow, the pulse is frequent, the blood pressure is low.

When breathing stops, the heart may still work for a while. Resuscitation begins, tk. there is a sharp depression of respiration and blood circulation. Therefore, anesthesia must be maintained at stage 3, level 3, not brought to level 4. Otherwise, the agonal stage develops. With the correct dosage of narcotic substances and the cessation of their administration develops Stage 4 - awakening. Restoration of functions goes in reverse order.

With ether anesthesia, awakening occurs in 20-40 minutes. Awakening is replaced by a long post-anesthetic sleep.

During anesthesia, the patient's body temperature decreases, metabolism is inhibited. Decreased heat production . After ether anesthesia, complications may occur: pneumonia, bronchitis (ether, irritates the respiratory tract), degeneration of parenchymal organs (liver, kidneys), reflex respiratory arrest, cardiac arrhythmias, damage to the conduction system of the heart.

Fluorothane - (halothane) - colorless, transparent, volatile liquid. Non-combustible. Stronger than ether. Mucous membranes are not irritating. The arousal stage is shorter, awakening is faster, sleep is shorter. Side effect - dilates blood vessels, lowers blood pressure, causes bradycardia (atropine is administered to prevent it).

Chloroethyl- stronger than ether, causes easily controlled anesthesia. It comes on quickly and passes quickly. Flaw- small breadth of narcotic action. It has a toxic effect on the heart and liver. Use for round anesthesia(short anesthesia when opening phlegmon, abscesses). Widely used for local anesthesia, applied to the skin. Boils at body temperature. Cools tissues, reduces pain sensitivity. Apply for superficial anesthesia surgical operations, with myositis, neuralgia, sprains, muscles. It is impossible to overcool tissues, because. may be necrosis.

gaseous substances.

Nitrous oxide- laughing gas.

Available in pressurized bottles. Applied in a mixture with O 2. Weak drug. Combine with others drugs- ether, substances for intravenous anesthesia.

Anesthesia occurs quickly, without a stage of excitation. Awakens quickly. The anesthesia is superficial. side effects no. Apply with injuries, myocardial infarction, transportation of patients, surgical interventions.

Cyclopropane- gas. 6 times stronger than nitrous oxide. Active. The anesthesia is easy to manage.

The stage of excitation is short, weakly expressed. Awakening immediately. There are almost no consequences. Complications- cardiac arrhythmias. Explosive.

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Age: Grade 3

Topic: Bodies, substances, particles.

Lesson type: learning new material.

Lesson duration: 45 minutes.

Lesson Objectives: to form the concept of a body, substance, particle, to teach to distinguish substances according to their characteristics and properties.

Tasks:

• To acquaint children with the concepts of body, substance, particle.
• Learn to distinguish between substances in different states of aggregation.
• Develop memory, thinking.
• Improve self-esteem and self-control skills.
• Increase the psychological comfort of the lesson, relieve muscle tension ( dynamic pauses, change of activity).
• form friendly relations in a collective.
• Cultivate an interest in the environment.

Equipment:

1. Multimedia interactive presentation (Attachment 1). Presentation management Appendix 2

2. Drawings (solid, liquid, gaseous substances).

3. Metal ruler, rubber ball, wooden cube (at the teacher).

4. For the experiment: a glass, a teaspoon, a sugar cube; boiled water(on the children's tables).

During the classes

I. Organizational moment.

The teacher greets the children, checks the readiness for the lesson, addressing the students: “Today you will do all the tasks in groups. Let's repeat the rules of working in a group ”(slide No. 2).

1. Treatment of comrades - "politeness";
2. The opinion of others - “learn to listen, prove your point of view”;
3. Working with sources of information (with a dictionary, a book) - highlight the main thing.

II. Learning new material.

staging learning goal: today we begin to study the topic “This wonderful nature”- let's take a virtual tour (slide number 3). On the slide: a drop of water, a sugar bowl (storage container), a hammer, a wave (water), clay, metal.

The teacher asks the question “Did all the words make it possible to accurately represent the subject?”

Those words that accurately help to represent the subject, namely, have outlines, shape, are called bodies. What these objects are made of is called substances.

Working with the source of information (dictionary of S.I. Ozhegov):

Write the definition in a notebook: “Those objects that surround us are called bodies” (slide number 4).

Slide number 5. The teacher invites students to compare the pictures on the slide: a rubber ball, an envelope, a wooden cube.

Task 1: find common. All bodies have a size, shape, etc.

Task 2: identify the main features of bodies. Answer on slide 6: control button “answer 2”.

Slide number 6. Pictures are triggers. The ball is round, rubber, bright. Envelope - rectangular, paper, white. Cube - wooden, large, beige.

Together with the guys we conclude “Every body has a size, shape, color”. We write in a notebook.

Slide number 7. What is nature? Choose the correct answer from the three options:

Slide number 8 - work with cards. Students have cards with images of bodies (objects) on their tables. We will offer students to divide the cards into two groups: table, sun, tree, pencil, cloud, stone, books, chair. Write down the answers in your notebook. We ask students to read the names of the bodies, this will be 1 group. On what basis did they place the words in this group? We do the same with the second group.

Correct answer:

We draw a conclusion. How did we divide the words (by what principle?): there are bodies that are created by nature, and there are those that are created by human hands.

We draw up a block in a notebook (Figure 1).

Slide number 9. Reception "Interactive tape". The slide shows natural and artificial bodies. Using the scroll button, which is also a trigger, we view natural and artificial bodies (each time pressing the button changes the grouped pictures).

We consolidate the knowledge gained with the help of the game “Traffic Light” (slides 10-12). The game is to find the correct answer.

Slide 10. Task: find natural bodies. Of the proposed bodies on the slide, you must select only natural bodies. The picture is a trigger - when pressed, a traffic light (red or green) appears. The sound files help students to make sure they choose the right answer.

Teacher: Let's remember what we talked about at the beginning. We found it difficult to determine exactly whether metal, water, clay are bodies and came to the conclusion that they do not have exact outlines, shapes, and therefore are not bodies. We call these words substances. All bodies are made up of matter. Write down the definition in your notebook.

Slide 13. On this slide, we will consider two examples.

Example 1: scissors are a body, what they are made of is a substance (iron).

Example 2: water drops - bodies, the substance of which the drops are composed - water.

Slide number 14. Consider bodies that consist of several substances. For example, a pencil and a magnifying glass. On the slide, we separately look at the substances that make up the pencil. To demonstrate, we press the control buttons: “graphite”, “rubber”, “wood”. In order to remove unnecessary information, click the cross.

Consider what substances the magnifying glass consists of. We press the triggers “glass”, “wood”, “metal”.

Slide number 15. To consolidate, consider two more examples. What is a hammer made of? The hammer is made of iron and wood (handle). What are knives made of? Knives are made of iron and wood.

Slide number 16. Consider two objects that consist of several substances. Meat grinder: made of iron and wood. Sledge: made of iron and wood.

Slide 17. We conclude: bodies can consist of one substance, or they can consist of several.

Slides 18, 19, 20. Reception "Interactive tape". Demonstrate to students. One substance can be part of several bodies.

Slide 18. Substances are wholly or partially composed of glass.

Slide 19. Substances are completely or partially composed of their metal.

Slide 20. Substances wholly or partly consist of plastics.

Slide 21. The teacher asks the question “Are all substances the same?”

On the slide, click the control button “Start”. Writing in a notebook: all substances are composed of the smallest invisible particles. We introduce the classification of substances according to their state of aggregation: liquid, solid, gaseous. The slide uses triggers (arrows). When you click on the arrow, you can see a picture with particles in a given state of aggregation. Pressing the arrow again will make the objects disappear.

Slide 22. Experimental part. It is necessary to prove that the particles are the smallest, invisible to the eye, but retaining the properties of matter.

Let's do an experiment. On the students' tables there are trays with a set of the simplest laboratory equipment: a glass, a stirring spoon, a napkin, a sugar cube.

Dip a piece of sugar into a glass, stir until completely dissolved. What are we seeing? The solution has become homogeneous, we no longer see a piece of sugar in a glass of water. Prove that sugar is still present in the glass. How? To taste. Sugar: substance white color, sweet in taste. Conclusion: after dissolution, sugar did not cease to be sugar, because it remained sweet. This means that sugar consists of tiny particles that are not visible to the eye (molecules).

Slide 23. Consider the arrangement of particles in substances with a solid state of aggregation. We demonstrate the location of particles and matter (examples) using the “interactive tape” technique - the scroll button allows you to show the pictures the required number of times. We write down the conclusion in a notebook: in solids, particles are located close to each other.

Slide 24. The location of particles in liquid substances. In liquid substances, the particles are located at some distance from each other.

Slide No. 25. The location of particles in gaseous substances: the particles are located far from each other, the distance between them significantly exceeds the particle size itself.

Slide 31. It's time to take stock. Together with the teacher, they recall what they learned in the lesson. The teacher asks questions:

1. Everything that surrounds us is called .... bodies
2. Bodies are natural and artificial.
3. Write the diagram in your notebook. Teacher: Let's look at the diagram. Bodies are natural and artificial, substances can be solid, liquid, gaseous. Substances are made up of particles. The particle retains the properties of the substance (recall that sugar remained sweet when dissolved). The slide uses triggers. Click on the “Body” shape, arrows appear, then shapes labeled “Artificial” and “Natural”. When you click on the “substance” figure, three arrows appear (liquid, solid, gaseous).

Slide number 30. Fill in the table. Read the instructions carefully.

(Mark with “ + ” in the appropriate column, which of the listed substances are solid, liquid, gaseous).

Substance	Solid	liquid	gaseous
Salt
Natural gas
Sugar
Water
Aluminum
Alcohol
Iron
Carbon dioxide

Checking the progress of work (slide 30). In turn, the children name the substance and explain to which group it was assigned.

Lesson summary

1) Summing up

You worked together.

Find out which group was the most attentive in the lesson. The teacher asks the question: "What are called bodies, what characterizes the body, give an example." Students answer. Everything that surrounds us is called bodies. What are the substances according to the state of aggregation: liquid, solid, gaseous. What are substances made of? Give examples of how particles retain the properties of substances. For example, if we salt the soup, how do we know that the properties of the substance have been preserved? To taste. Fill in the diagram (Figure 2)

Discussion: what do you agree with, what do you disagree with.

What have you learned? Children report. ( Bodies are all the objects that surround us. Bodies are made up of substances. Substances - from particles).

Homework

The teacher tells the children homework(optional):

• solve a small test (Appendix 5).
• interactive test (Appendix 3).
• view a presentation about water (Annex 7). The presentation introduces six known facts about water. Think guys, why do you need to get to know this substance better? Answer: The most common substance on Earth. And what other substance would you like to invite to your place (creating virtual tours).
• study the electronic textbook (Appendix 4).

Note: the teacher can additionally use slides No. 32, 33, 36.

Slide number 32. Task: test yourself. Find products (interactive test).

Slide number 33. Task: test yourself. Find the bodies of animate and inanimate nature (interactive test).

Slide number 36. Task: divide the bodies into bodies of animate and inanimate nature (interactive test).

Literature.

1. Gribov P.D. how a person explores, studies, uses nature. 2-3 classes. Volgograd: Teacher, 2004.-64 p.
2. Maksimova T.N. Lesson developments for the course “ The world”: Grade 2. - M.: VAKO, 2012.-336s. - (To help the school teacher).
3. Reshetnikova G.N., Strelnikov N.I. The world. Grade 3: entertaining materials. - Volgograd: Teacher, 2008. - 264 p.: ill.
4. Tikhomirova E.M. Tests on the subject “The world around us”: Grade 2: to the A.A. Pleshakov “The world around us. Grade 2”. - M.: Publishing house "Exam", 2011. - 22 p.

gaseous state of matter

Polymers are of natural (plant and animal tissues) and artificial (plastics, cellulose, fiberglass, etc.) origin.

Just as in the case of ordinary molecules, a system of macromolecules. forming a polymer tends to the most probable state - a stable equilibrium corresponding to a minimum of free energy. Therefore, in principle, polymers should also have a structure in the form of a crystal lattice. However, in view of the bulkiness and complexity of macromolecules, perfect macromolecular crystals have been obtained only in a few cases. In most cases, polymers are composed of crystalline and amorphous regions.

liquid state It is characteristic that the potential energy of attraction of molecules somewhat exceeds absolute value their kinetic energy. The force of attraction between molecules in a liquid ensures the retention of molecules in the bulk of the liquid. At the same time, the molecules in a liquid are not bound together by stationary stable bonds, as in crystals. They densely fill the space occupied by the liquid, so liquids are practically incompressible and have a fairly high density. Groups of molecules can change their mutual position, which ensures the fluidity of liquids. The property of a fluid to resist flow is called viscosity. Liquids are characterized by diffusion and Brownian motion, however, to a large extent lesser degree than gases.

The volume occupied by the liquid is limited by the surface. Since, for a given volume, a ball has the minimum surface, the liquid in a free state (for example, in weightlessness) takes the form of a ball.

Liquids have a certain structure, which, however, is much less pronounced than that of solids. The most important property of liquids is the isotropy of properties. A simple ideal fluid model has not yet been created.

There is an intermediate state between liquids and crystals, which is called liquid crystal. A feature of liquid crystals from a molecular point of view is the elongated, spindle-shaped shape of their molecules, which leads to the anisotropy of their properties.

There are two types of liquid crystals - nematics and smectics. Smectics are characterized by the presence of parallel layers of molecules that differ from each other in the orderliness of the structure. In nematics, order is provided by the orientation of the molecules. The anisotropy of the properties of liquid crystals determines their important optical properties. Liquid crystals may, for example, be transparent in one direction and opaque in the other. It is important that the orientation of liquid crystal molecules and their layers can be easily controlled using external influences(eg temperature, electric and magnetic fields).

gaseous state of matter occurs when

kinetic energy thermal motion molecules exceeds the potential energy of their binding. The molecules tend to move away from each other. The gas has no structure, it occupies the entire volume provided to it, it is easily compressible; Diffusion occurs easily in gases.

The properties of substances in the gaseous state are explained by the kinetic gas theory. Its main postulates are as follows:

All gases are made up of molecules;

The dimensions of the molecules are negligible compared to the distances between them;

Molecules are constantly in a state of chaotic (Brownian) motion;

Between collisions, the molecules remain constant speed movement; trajectories between collisions - segments of straight lines;

Collisions between molecules and molecules with vessel walls are ideally elastic, i.e. the total kinetic energy of the colliding molecules remains unchanged.

Consider a simplified model of a gas that obeys the above postulates. Such a gas is called an ideal gas. Let an ideal gas in the amount of N identical molecules, each of which has a mass m, is located in a cubic vessel with edge length l(Fig. 5.14). Molecules move randomly; their average speed<v>. To simplify, let's break all the molecules into three equal groups and assume that they move only in directions perpendicular to two opposite walls of the vessel (Fig. 5.15).

Rice. 5.14.

Each of the gas molecules moving at a speed<v> at absolutely elastic collision with the wall of the vessel, it will change the direction of movement to the opposite without changing the speed. momentum of a molecule<R> = m<v> becomes equal to - m<v>. The change in momentum in each collision is obviously . The force acting during this collision is F= -2m<v>/Δ t. The total change in momentum upon collision with the walls of all N/3molecules equals . Let us define the time interval Δ t, during which all N/3 collisions will occur: D t = 2//< v >. Then the average value of the force acting on any wall,

Pressure R gas to the wall is defined as the ratio of the force<F> to wall area l 2:

where V = l 3 - the volume of the vessel.

Thus, the pressure of a gas is inversely proportional to its volume (recall that this law was established empirically by Boyle and Mariotte).

Let us rewrite expression (5.4) as

Here is the average kinetic energy of gas molecules. it is proportional absolute temperature T:

where k is the Boltzmann constant.

Substituting (5.6) into (5.5), we obtain

It is convenient to go from the number of molecules N to the number of moles n gas, we recall that ( N A is Avogadro's number), and then

where R = kN A - - universal gas constant.

Expression (5.8) is the equation of state for a classical ideal gas for n moles. This equation, written for an arbitrary mass m gas

where M - molar mass gas is called the Clapeyron-Mendeleev equation (see (5.3)).

Real gases obey this equation within limited limits. The point is that equations (5.8) and (5.9) do not take into account the intermolecular interaction in real gases - van der Waals forces.

Phase transitions. A substance, depending on the conditions in which it is located, can change its state of aggregation, or, as they say, pass from one phase to another. Such a transition is called a phase transition.

As stated above, the most important factor that determines the state of a substance is its temperature T characterizing the average kinetic energy of the thermal motion of molecules and pressure R. Therefore, the states of matter and phase transitions are analyzed according to the state diagram, where the values ​​are plotted along the axes T and R, and each point on the coordinate plane determines the state of the given substance corresponding to these parameters. Let's analyze a typical diagram (Fig. 5.16). Curves OA, AB, AK separate states of matter. When enough low temperatures Almost all substances are in a solid crystalline state.

The diagram highlights two characteristic points: BUT and To. Dot BUT called the triple point; at the appropriate temperature ( T t) and pressure ( R m) it is in equilibrium at the same time gas, liquid and solid.

Dot To indicates a critical condition. At this point (at T kr and R cr) the difference between liquid and gas disappears, i.e. the latter have the same physical properties.

Curve OA is the sublimation (sublimation) curve; at the appropriate pressure and temperature, the transition gas - solid body (solid body - gas) is carried out, bypassing the liquid state.

Under pressure R t< R < R kr the transition from the gaseous to the solid state (and vice versa) can only occur through the liquid phase.

Curve AK corresponds to evaporation (condensation). At the appropriate pressure and temperature, the transition "liquid - gas" (and vice versa) is carried out.

Curve AB is the transition curve "liquid - solid" (melting and crystallization). This curve has no end, since the liquid state always differs from the crystalline state in structure.

For illustration, we present the shape of the surfaces of states of matter in the variables p, v, t(Fig. 5.17), where V- volume of substance

The letters Г, Ж, Т denote areas of surfaces, the points of which correspond to the gaseous, liquid or solid states, and the areas T-G surfaces, W-T, T-W - two-phase states. Obviously, if we project the dividing lines between the phases on coordinate plane RT, we get the phase diagram (see Fig. 5.16).

Quantum liquid - helium. At ordinary temperatures in macroscopic bodies, due to the pronounced chaotic thermal motion, quantum effects are imperceptible. However, as the temperature decreases, these effects can come to the fore and manifest themselves macroscopically. So, for example, crystals are characterized by the presence of thermal vibrations of ions located at the nodes of the crystal lattice. As the temperature decreases, the oscillation amplitude decreases, but even when approaching absolute zero, the oscillations, contrary to classical concepts, do not stop.

The explanation for this effect follows from the uncertainty relation. A decrease in the oscillation amplitude means a decrease in the particle localization area, i.e., in the uncertainty of its coordinates. In accordance with the uncertainty relation, this leads to an increase in the momentum uncertainty. Thus, "stopping" the particle is forbidden by the laws of quantum mechanics.

This purely quantum effect is manifested in the existence of matter remaining in liquid state even at temperatures close to absolute zero. Helium is such a "quantum" liquid. Zero point energy is enough to destroy crystal lattice. However, at a pressure of about 2.5 MPa, liquid helium still crystallizes.

Plasma. The message to the atoms (molecules) of the gas from the outside of significant energy leads to ionization, i.e., the decay of atoms into ions and free electrons. This state of matter is called plasma.

Ionization occurs, for example, when a gas is strongly heated, which leads to a significant increase in the kinetic energy of atoms, when electrical discharge in gas (impact ionization by charged particles), when the gas is exposed to electromagnetic radiation (autoionization). Plasma obtained at ultrahigh temperatures is called high temperature.

Since ions and electrons in plasma carry uncompensated electric charges, them mutual influence essential. Between the charged particles of the plasma there is not a pair (as in a gas), but a collective interaction. Due to this, the plasma behaves as a kind of elastic medium, in which various oscillations and waves are easily excited and propagate

Plasma actively interacts with electric and magnetic fields. Plasma is the most common state of matter in the universe. Stars are made of high-temperature plasma, cold nebulae are made of low-temperature plasma. Weakly ionized low-temperature plasma exists in the Earth's ionosphere.

Literature for Chapter 5

1. Akhiezer A. I., Rekalo Ya. P. Elementary particles. - M.: Nauka, 1986.

2. Azshlov A. The world of carbon. - M.: Chemistry, 1978.

3. M. P. Bronstein, Atoms and Electrons. - M.: Nauka, 1980.

4. Benilovsky VD These amazing liquid crystals. - M: Enlightenment, 1987.

5. N. A. Vlasov, Antimatter. - M.: Atomizdat, 1966.

6. Christie R., Pitti A. The structure of matter: an introduction to modern physics. - M.: Nauka, 1969.

7. Kreychi V. The world through the eyes modern physics. - M.: Mkr, 1984.

8. Nambu E. Quarks. - M.: Mir, 1984.

9. Okun' LB α, β, γ, …,: elementary introduction to the physics of elementary particles. - M.: Nauka, 1985.

10. Yu. I. Petrov, Physics of Small Particles. - M.: Nauka, 1982.

11. I, Purmal A. P. et al. How substances are transformed. - M.: Nauka, 1984.

12. Rosenthal I. M. Elementary particles and the structure of the universe. - M.: Nauka, 1984.

13. Smorodinsky Ya. A. Elementary particles. - M.: Knowledge, 1968.