| Matter properties | Oxygen | Acetic acid | Aluminum |
| 1. Aggregate state under normal conditions | Gas | Liquid | Solid |
| 2. Color | no color | no color | Silver white |
| 3. Taste | Tasteless | Sour | Tasteless |
| 4. Smell | Doesn't have | sharp specific | Doesn't have |
| 5. Solubility in water | Poorly soluble | Soluble | Practically insoluble |
| 6. Thermal conductivity | Low | small | high |
| 7. Electrical conductivity | Is absent | Malaya | high |
Knowledge of the properties of substances is necessary for their practical application. For example, Figure 6 shows the areas of application of aluminum, due to the properties of this metal.
1. What subjects are natural?
2. Give examples of positive human impact on the environment.
3. Give examples of the negative impact of man on nature.
4. What does chemistry study?
5. From the following list of names, write out the bodies and substances separately: snowflake, dew drop, water, ice, granulated sugar, sugar cube, chalk, school chalk. How many bodies and how many substances are named in this list?
6. Compare the properties of substances (that is, establish the common and different between them):
a) carbon dioxide and oxygen
b) nitrogen and carbon dioxide;
c) sugar and salt;
d) acetic and citric acids.
7. What properties of aluminum underlie its application?
8. Why begin to study chemistry later than biology, geography, physics?
You begin to get acquainted with a new subject - chemistry. What does chemistry study?
As you know from the course of physics, many substances are made up of molecules, and molecules are made up of atoms. Atoms are so small that many billions of them can fit on the point of a needle. Nevertheless, only 114 types of atoms are distinguished.
Substances such as neon, argon, krypton, and helium are composed of individual isolated atoms. They are also called noble or inert gases, because their atoms do not combine with each other and hardly combine with atoms of other chemical elements. Hydrogen atoms are quite another matter. They can exist singly (Fig. 4, a), as in the Sun, which consists of more than half of individual hydrogen atoms. Two atoms can combine into molecules (Fig. 4, b), forming molecules of the lightest gas, which, like a chemical element, is called hydrogen. Hydrogen atoms can also combine with atoms of other chemical elements. For example, two hydrogen atoms, connecting with one oxygen atom (Fig. 4, c), form molecules of a well-known substance - water.
Rice. 4.
Forms of existence of the chemical element hydrogen:
a - hydrogen atoms; b - hydrogen molecules; c - hydrogen atoms in a water molecule
Similarly, the concept of "chemical element oxygen" combines isolated oxygen atoms, oxygen - a simple substance, the molecules of which consist of two oxygen atoms, and oxygen atoms that are part of complex substances. So, the composition of carbon dioxide molecules includes oxygen and carbon atoms, the composition of sugar molecules includes carbon, hydrogen and oxygen atoms.
Therefore, each chemical element exists in three forms: free atoms, simple substances and complex substances (see Fig. 4).
The concept of "chemical element" is broader, and should not be confused with the concept of "simple substance", especially if their names coincide. For example, when they say that water contains hydrogen, they mean a chemical element, and when they say that hydrogen is an environmentally friendly type of fuel, they mean a simple substance.
Different substances differ from each other in their properties. So, hydrogen is a gas, very light, colorless, odorless, tasteless, has a density of 0.00009 g / cm 3, boils at a temperature of -253 ° C, and melts at a temperature of -259 ° C, etc. These properties substances are called physical.
You can describe the physical properties of a substance using the following plan:
- In what state of aggregation (gaseous, liquid, solid) is the substance under these conditions?
- What color is the substance? Does it have shine?
- Does the substance have an odor?
- What is the hardness of a substance according to the relative hardness scale (Mohs scale) (Fig. 5)? (See reference books.)
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Hardness scale
- Does the substance exhibit plasticity, fragility, elasticity?
- Does the substance dissolve in water?
- What is the melting point and boiling point of the substance? (See reference books.)
- What is the density of matter? (See reference books.)
- Does a substance have thermal and electrical conductivity? (See reference books.)
Lab Experience #1
Comparison of the properties of solid crystalline substances and solutions
Compare using the one on p. 10 plan, the properties of the samples of substances given to you in cups:
- option 1 - crystalline sugar and table salt;
- option 2 - glucose and citric acid.
Knowing the properties of substances, a person can use them with greater benefit for himself. For example, consider the properties and applications of aluminum (Figure 6).
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Application of aluminum:
1 - aircraft construction; 2 - rocket science; 3 - production of power lines; 4 - production of tableware, cutlery and packaging foil
Due to its lightness and strength, aluminum and its alloys are used in aircraft and rocket manufacturing; it is not for nothing that aluminum is called the “winged metal”.
The lightness and good electrical conductivity of aluminum is used in the manufacture of electrical wires for power lines (TL).
Thermal conductivity and non-toxicity are important in the manufacture of aluminum cookware.
Non-toxicity and plasticity make it possible to widely use thin sheets of aluminum - foil - as a packaging material for chocolate bars, tea, margarine, milk, juices, and other products, as well as for medicines placed in contour cells.
The introduction of aluminum alloys in construction increases the durability and reliability of structures.
These examples illustrate that different physical bodies can be made from one substance - material (aluminum).
Aluminum is capable of burning with a dazzling flame (Fig. 7), so it is used in colorful fireworks and in the manufacture of sparklers (remember N. Nosov's story "Bengal Lights"). During combustion, aluminum turns into another substance - aluminum oxide.
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Burning aluminum - the basis of sparklers and fireworks
Keywords and phrases
- The subject of chemistry.
- Substances are simple and complex.
- Properties of substances.
- A chemical element and forms of its existence: free atoms, simple substances and complex substances, or compounds.
Work with computer
- Refer to the electronic application. Study the material of the lesson and complete the suggested tasks.
- Search the Internet for email addresses that can serve as additional sources that reveal the content of the keywords and phrases of the paragraph. Offer the teacher your help in preparing a new lesson - make a report on the key words and phrases of the next paragraph.
Questions and tasks
- Phileo (Greek) means "I love", phobos - "I'm afraid." Give an explanation of the terms "chemophilia" and "chemophobia", reflecting the sharply opposite attitude of groups of people towards chemistry. Which of them is right? Justify your point of view.
- A mandatory attribute of an infinite number of espionage and other detective works is potassium cyanide, more precisely, potassium cyanide, which has the property of paralyzing the nervous system, thereby leading the victim to instant death. Give examples of the properties of other substances that are used in literary works.
- Write down separately the names of substances and the names of bodies from the list below: copper, coin, glass, glass, vase, ceramics, wire, aluminum. Use the hint: for the name of the body - a noun - you can pick up a relative adjective formed from the name of the substance, for example: iron and nail - iron nail.
- Write out quality adjectives: light, round, long, heavy, hard, odorous, soluble, weighty, concave, soft, liquid, transparent - which can be attributed to: a) substances; b) to bodies; c) both bodies and substances.
- Compare the concepts of "simple substance" and "complex substance". Find similarities and differences.
- Determine which of the substances whose molecular models are shown in Figure 2 are: a) simple substances; b) to complex substances.
- Which concept is broader - "chemical element" or "simple substance"? Give a demonstrative answer.
- Indicate where oxygen is spoken of as a chemical element, and where - as a simple substance:
a) oxygen is slightly soluble in water;
b) water molecules consist of two hydrogen atoms and one oxygen atom;
c) the air contains 21% oxygen (by volume);
d) oxygen is part of carbon dioxide.
- Indicate where hydrogen is referred to as a simple substance, and where as a chemical element:
a) hydrogen is part of most organic compounds;
b) hydrogen is the lightest gas;
c) balloons are filled with hydrogen;
d) a methane molecule contains four hydrogen atoms.
- Consider the relationship between the properties of a substance and its application on the example of: a) glass; b) polyethylene; c) sugar; d) iron.
Density, heat capacity, properties of oxygen O 2
The table shows the thermophysical properties of oxygen, such as density, enthalpy, entropy, specific heat, dynamic viscosity, thermal conductivity. The properties in the table are given for gaseous oxygen at atmospheric pressure, depending on the temperature in the range from 100 to 1300 K.
The density of oxygen is 1.329 kg / m 3 at room temperature. When oxygen is heated, its density decreases. The thermal conductivity of oxygen is 0.0258 W / (m deg) at room temperature and increases with increasing temperature of this gas.
Specific heat capacity of oxygen at room temperature is 919 J/(kg deg). The heat capacity of oxygen increases with an increase in its temperature. Also, when oxygen is heated, the values of its properties such as enthalpy, entropy, and viscosity increase.
Note: be careful! The thermal conductivity in the table is given to the power of 10 2 . Don't forget to divide by 100.
Thermal conductivity of oxygen in liquid and gaseous states
The table shows the values of the thermal conductivity of oxygen in liquid and gaseous states at various temperatures and pressures. Thermal conductivity is indicated in the temperature range from 80 to 1400 K and pressure from 1 to 600 atm.
The thermal conductivity values in the table above the line refer to liquid oxygen, and below it to gaseous oxygen. According to the table, it can be seen that the thermal conductivity of liquid oxygen is higher than that of gaseous oxygen and increases with increasing pressure.
Unit W/(m deg).
Thermal conductivity of oxygen at high temperatures
The table gives the values of the thermal conductivity of oxygen at high temperatures (from 1600 to 6000 K) and pressures from 0.001 to 100 atm.
At temperatures above 1300°C, oxygen begins to dissociate, and at a certain pressure, its thermal conductivity reaches its maximum values. According to the table, it can be seen that the thermal conductivity of dissociated oxygen at high temperatures can reach values up to 3.73 W/(m deg).
Note: Be careful! The thermal conductivity in the table is given to the power of 10 3 . Don't forget to divide by 1000.
Thermal conductivity of liquid oxygen at the saturation line
The table shows the values of the thermal conductivity of liquid oxygen at the saturation line. The thermal conductivity is given in the temperature range from 90 to 150 K. It should be noted that the thermal conductivity of liquid oxygen decreases with increasing temperature.
Note: Be careful! The thermal conductivity in the table is given to the power of 10 3 . Don't forget to divide by 1000.
Sources:
1.
2. .
The purpose of the lesson. Concretize knowledge about a chemical element and a simple substance. To study the physical properties of oxygen. To form ideas about the methods of obtaining and collecting oxygen in the laboratory.
Tasks:
- Educational:
– Be able to distinguish between the concepts of “chemical element” and “simple substance”
using oxygen as an example.
– Be able to characterize the physical properties of oxygen and methods
collecting oxygen.
– Be able to arrange the coefficients in the reaction equations. - Educational:
the formation of accuracy in the performance of laboratory experiments;
care, respect. - Developing:
– Formation of building logical chains, own chemical
terminology, cognitive activity, inferences and judgments.
Basic concepts. Chemical element, simple substance, physical properties, catalysts.
Planned learning outcomes. To be able to distinguish between the concepts of “chemical element” and “simple substance” using oxygen as an example. To be able to characterize the physical properties of oxygen and the methods of collecting oxygen. Be able to arrange the coefficients in the reaction equations.
Experience: Obtaining oxygen from hydrogen peroxide and confirming its presence.
Demos. Obtaining oxygen from potassium permanganate. Collection of oxygen by the method of displacement of air and confirmation of its presence.
Equipment and reagents: D.I. Mendeleev’s table, handout (test), a device for producing oxygen from potassium permangate (a conical flask with a rubber stopper, a gas outlet tube, PH-12, a tripod, a foot, cotton wool), hydrogen peroxide 20 ml (15 bottles), manganese oxide (IV) (15 bottles), dosing spoon (15 pcs.), alcohol lamp (15 pcs.), matches (15 pcs.), splinter (15 pcs.), potassium permanganate (5 g).
Lesson type: A lesson in learning new knowledge.
Teaching methods:
- Explanatory-illustrative (verbal: conversation, presentation; verbal-visual: independent work of students with visual aids; verbal-visual-practical: work of students with handouts, performing chemical experiments, performing written independent work).
- Partial search (heuristic) method (verbal: conversation-discussion; verbal-visual: discussion with a demonstration of visual aids, independent work of students with a visual aid; verbal-visual-practical: work of students with handouts, performing a chemical experiment, performing a written independent work).
- Research method (verbal-visual-practical: performing a research chemical experiment).
Forms of organization of activity: frontal, group (steam).
I. Organizational stage.
- Greetings.
- Definition of absent.
- Check readiness for the lesson.
The presence of a diary, a class notebook, a textbook on chemistry, a pen.
II. Preparing students for active and conscious assimilation of new material.
Teacher: In order to determine the topic of today's lesson, you and I need to solve a rebus?
slide 1
Solve the puzzle and we will find out the topic of today's lesson.
Rice. one
(BRUSHES) KI + (ELEPHANT) SLO + ROD
OXYGEN
Teacher: The topic of today's lesson: “Oxygen, its general characteristics and presence in nature. Physical properties of oxygen. Receipt".
slide 2
The topic of today's lesson: “Oxygen, its general characteristics and presence in nature. Physical properties of oxygen. Receipt".
slide 3
“Oxygen” is the substance around which Earth's chemistry revolves.
J. Berzelius
Teacher: Using the language of chemistry, it is necessary to write on the board: oxygen as a chemical element and as a simple substance.
Oxygen - as an element - O.
Oxygen - as a simple substance - O 2.
Teacher: Now several phrases (sayings) will appear on the screen, you need to determine in what meaning oxygen is mentioned in them - as a chemical element or as a simple substance.
slide 4
Exercise: Define oxygen as a chemical element or simple substance.
- Oxygen is a part of vital organic substances: proteins, fats, carbohydrates.
- All living things on Earth breathe oxygen.
- Rust contains iron and oxygen.
- Fish breathe oxygen dissolved in water.
- During photosynthesis, green plants release oxygen.
Teacher: You need with the help of PSHE them. D.I. Mendeleev to characterize the chemical element “Oxygen”, according to the following plan:
Slide 5:
- Serial number -
- Relative atomic mass -
- Period -
- Group -
- Subgroup -
- Valency -
Teacher: Let's check the attention to the screen
slide 6
- Ordinal number - 8
- Relative atomic mass - Ar (O) = 16
- Period - second
- Group - VI
- Subgroup - a (main)
- Valence - II
Slide 7
Distribution of oxygen in nature:
First place in terms of prevalence in the earth's crust, i.e. lithosphere, occupies oxygen - 49%, followed by silicon - 26%, aluminum - 7%, iron - 5%, calcium - 4%, sodium - 2%, potassium - 2%, magnesium - 2%, hydrogen - 1%.
AT biosphere About 65% of the mass of living organisms is oxygen.
AT hydrosphere it accounts for 89%.
AT atmosphere: 23% by weight, 21% by volume.
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Teacher: You need with the help of PSHE them. D.I. Mendeleev to characterize the simple substance “Oxygen”.
So, what is the chemical formula of a simple substance - 0 2
Relative molecular weight Mg (0 2) = 32
Slide 8
History of the discovery of oxygen.
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Figure 5 |
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The teacher comments: In 1750 M.V. Lomonosov conducted experiments and proved that the air contains a substance that oxidizes the metal. He called him phlogiston.
Received oxygen in 1771 Karl Scheele. Regardless of him, oxygen was obtained by J. Priestley in 1774.
And the story is simple...
Joseph Priestley once
Mercury oxide heating,
Found a strange gas.
Gas without color, without name,
The candle burns brighter.
Isn't it bad for breathing?
You won't find out from a doctor!
New gas came out of the flask -
Nobody knows him.
Mice breathe this gas
Under a glass cover.
A person breathes it too ...
In 1775, A. Lavoisier established that oxygen is an integral part of air and is contained in many substances.
Nature created the world from atoms:
Two atoms of the lungs took hydrogen,
Added an atom of oxygen -
And it turned out a particle of water,
Sea of water, oceans and ice…
Became oxygen
Almost everywhere stuffing.
With silicon, he turned into a grain of sand.
Oxygen got into the air
Surprisingly,
From the blue depths of the ocean.
And plants appeared on the Earth.
Life appeared:
Breathing, burning...
The first birds and the first beasts
The first people to live in a cave...
Fire was made by friction
Although they did not know the cause of the fire.
The role of oxygen on our Earth
The great Lavoisier understood.
Teacher: Now let's get acquainted with oxygen by experience. Since we will use a heating device (alcohol lamp), it is necessary to remember TB when working with an alcohol lamp:
- When using a spirit lamp, it is impossible to light it from another spirit lamp, as alcohol may spill and a fire will occur.
- To extinguish the flame of the spirit lamp, it should be closed with a cap.
Pour H 2 O 2 (hydrogen peroxide) solution into a beaker.
Light the spirit lamp, bring the torch to the flame and put out the torch. Then add manganese (IV) oxide to a beaker and bring a smoldering torch to the beaker - what is observed?
Student: Luchina - flashes. In this way, we determined that there is oxygen in the beaker.
Teacher: In this experiment, manganese (IV) oxide is a catalyst - a substance that accelerates the process of a chemical reaction, but is not itself consumed.
Demo experiment:"Production of oxygen from potassium permanganate".
We collect the device.
We collect oxygen by displacing air into a conical flask, after a while we check for the presence of oxygen, using a smoldering torch, if it flares up, then a sufficient amount of oxygen has been collected.
We close with a rubber stopper and put it on a lifting table.
And we invite students to characterize the physical properties of oxygen according to the following criteria.
Slide 9
- State of aggregation -...
- Colour - ...
- Smell - ...
- Solubility in water...
- t o kip. –...
- Electrical conductivity is...
- Thermal conductivity is...
- Heavier or lighter than air
Teacher: Let's check the attention to the screen.
Slide 10
- Aggregate state - gas.
- Color - no color
- Smell - odorless
- Solubility in water - poorly soluble
- t° b.p. - 183°С
- Electrical conductivity - non-conductive
- Thermal conductivity - conducts heat poorly (poor)
- Heavier than air
Teacher: We pose a problematic question to the students: Why is oxygen in the picture in the form of a blue liquid?
slide 11
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Students answer (teacher adds): This oxygen is in a liquefied state, and liquid oxygen is blue.
Now let's summarize and write down in a notebook the different ways of obtaining oxygen that we observed today.
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Teacher: At the end of the lesson, we will test our knowledge.
Familiarity with:
The subject is chemistry;
Simple and complex substances;
properties of substances;
Forms of existence of a chemical element
Chemistry- the science of substances, their properties, the transformations of substances and ways to control these transformations
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Slides captions:
The subject of chemistry. Substances.
www.pmedia.ru Motto of the lesson: “Chemistry stretches its hands wide in human affairs” M.V. Lomonosov
The purpose of the lesson: To acquaint with: - the subject of chemistry; - simple and complex substances; -properties of substances; - forms of existence of a chemical element.
1. O.S. Gabrielyan. "Chemistry". 8th grade. Textbook. 2. Notebook for work in the classroom and at home. 3. Notebooks for control and practical work. What is needed for the lesson? Safety precautions!
Natural sciences 1. What sciences study nature? 2. What does biology study; physics; geography; astronomy; geology? 3. Why did you start studying physics in the 7th grade and chemistry in the 8th grade?
What does chemistry study? CHEMISTRY STUDIES SUBSTANCES PROPERTIES OF SUBSTANCES TRANSFORMATIONS OF SUBSTANCES "Father of Chemistry" Robert Boyle (1627 - 1691)
Chemistry is the science of substances, their properties, transformations of substances and ways to control these transformations. Body Substance Molecules Atoms
Substance is what physical bodies consist of Chemical element is a certain type of atoms Substances Natural (carbon dioxide) Synthetic (polyethylene) Substances Simple (hydrogen, oxygen) Complex (water, sugar)
Consider molecular models. What are the similarities and differences between them? Which of the substances is simple and which is complex? Why? Substances Substance Hydrogen Oxygen Water
Substances that are formed by atoms of one chemical element are called simple
Substances that are formed by atoms of different chemical elements are called complex
Exercise number 1 Determine which of the proposed substances is simple and which is complex.
What unites these objects?
Substances and bodies
Substances and bodies
The properties of substances are signs by which substances differ from each other or are similar to each other. The subject of chemistry is the study of substances, their transformations, the creation of substances with desired properties. Chemistry Application Composition Properties
Exercise No. 2 Indicate where oxygen is spoken of as a chemical element, and where - as a simple substance: A) oxygen is slightly soluble in water; B) water molecules consist of two hydrogen atoms and one oxygen atom; C) the air contains 21% oxygen (by volume); D) Oxygen is part of carbon dioxide.
A plan for describing the physical properties of a substance 1. In what state of aggregation - gaseous, liquid or solid - is the substance under these conditions? 2. What color is the substance? Does it have shine? 3. Does the substance have an odor? 4. Does the substance show plasticity, fragility, elasticity? 5. Does the substance dissolve in water? 6. What is the melting point and boiling point of the substance? (See reference books.) 7. What is the density of matter? (See reference books.) 8. Does the substance have thermal and electrical conductivity? (See reference books.)
Exercise number 3 Describe the physical properties of acetic acid, sugar, salt, copper, aluminum according to the proposed plan. (S.5 (21) of the textbook)
Chemistry and environmental protection It is necessary to protect and preserve Nature!
Homework Paragraph 1, ex. 1-4 Reports, presentations on the history of the development of chemistry Table Date Achievements of science