For example, a water molecule is the smallest representative of a substance such as water.
Why don't we notice that substances are made up of molecules? The answer is simple: the molecules are so small that they are simply invisible to the human eye. So what size are they?
An experiment to determine the size of a molecule was carried out by the English physicist Rayleigh. Water was poured into a clean vessel, and a drop of oil was placed on its surface. The oil spread over the surface of the water and formed a round film. Gradually, the area of the film increased, but then the spreading stopped and the area stopped changing. Rayleigh suggested that the thickness of the film became equal to the size of one molecule. Through mathematical calculations it was established that the size of the molecule is approximately 16 * 10 -10 m.
Molecules are so small that small volumes of matter contain huge amounts of them. For example, one drop of water contains the same number of molecules as there are similar drops in the Black Sea.
Molecules cannot be seen with an optical microscope. You can take photographs of molecules and atoms using an electron microscope, invented in the 30s of the 20th century.
Molecules of different substances differ in size and composition, but molecules of the same substance are always the same. For example, the water molecule is always the same: in water, in a snowflake, and in steam.
Although molecules are very small particles, they are also divisible. The particles that make up molecules are called atoms. Atoms of each type are usually designated by special symbols. For example, an oxygen atom is O, a hydrogen atom is H, and a carbon atom is C. In total, there are 93 different atoms in nature, and scientists have created about 20 more in their laboratories. The Russian scientist Dmitry Ivanovich Mendeleev ordered all the elements and placed them in the periodic table, which we will learn more about in chemistry lessons.
An oxygen molecule consists of two identical oxygen atoms, a water molecule consists of three atoms - two hydrogen atoms and one oxygen atom. By themselves, hydrogen and oxygen do not have the properties of water. On the contrary, water only becomes water when such a bond is formed.
The sizes of atoms are very small. For example, if you enlarge an apple to the size globe, then the size of the atom will increase to the size of an apple. In 1951, Erwin Müller invented the ion microscope, which made it possible to see the atomic structure of a metal in detail.
In our time, unlike the times of Democritus, the atom is no longer considered indivisible. At the beginning of the 20th century, scientists managed to study its internal structure.
It turned out that an atom consists of a nucleus and electrons rotating around the nucleus. Later it turned out that core in its turn consists of protons and neutrons.
Thus, experiments are in full swing at the Large Hadron Collider - a huge structure built underground on the border between France and Switzerland. The Large Hadron Collider is a 30-kilometer closed tube through which hadrons (the so-called proton, neutron or electron) are accelerated. Having accelerated almost to the speed of light, the hadrons collide. The force of the impact is so great that the protons are “broken” into pieces. It is assumed that in this way it is possible to study the internal structure of hadrons
It is obvious that the further one goes in studying internal structure substances, the greater the difficulties he faces. It is possible that the indivisible particle that Democritus imagined does not exist at all and particles can be divided ad infinitum. Research in this area is one of the fastest growing topics in modern physics.
A) atom B) molecule
A) liquids B) gases
1.solid 2.liquid 3.gas
1. The smallest particle of a substance that retains its properties is
A) atom B) molecule
B) Brownian particle B) oxygen
2. Brownian motion is….
A) chaotic movement of very small solid particles in a liquid
B) chaotic penetration of particles into each other
B) ordered movement of solid particles in a liquid
D) ordered movement of liquid molecules
3. Diffusion can occur...
A) only in gases B) only in liquids and gases
C) only in liquids D) in liquids, gases and solids
4. They do not have their own shape and constant volume...
A) liquids B) gases
C) solids D) liquids and gases
5. Between the molecules there is….
A) only mutual attraction B) only mutual repulsion
C) mutual repulsion and attraction D) there is no interaction
6. Diffusion is faster
A) in solids B) in liquids
C) in gases D) in all bodies the same
7. What phenomenon confirms that molecules interact with each other?
A) Brownian motion B) wetting phenomenon
C) diffusion D) increase in body volume when heated
8. Correlate the state of aggregation of a substance and the nature of the movement of molecules:
1.solid 2.liquid 3.gas
A) change their position abruptly
B) fluctuate around a certain point
C) move randomly in all directions
9. Correlate the state of aggregation of a substance and the arrangement of molecules:
1.solid 2.liquid 3.gas
A) randomly, close to each other
B) randomly, the distance is tens of times greater than the molecules themselves
B) molecules are arranged in a certain order
10. Correlate the statement about the structure of matter and its experimental substantiation
1. all substances consist of molecules with spaces between them
2. molecules move continuously and randomly
3. molecules interact with each other
A) Brownian motion B) wetting
B) an increase in body volume when heated
Lesson topic: Generalization of the topic “Initial chemical concepts” Lesson goal:
repeat and generalize students’ knowledge of initial chemical concepts;
consolidate understanding of chemical formulas and reaction equations;
improve communication abilities and skills.
Tasks:
1. Educational:
fostering independence, a sense of camaraderie, and cooperation;
formation of logical and abstract thinking;
formation moral qualities– collectivism, ability for mutual assistance, creativity.
2. Educational:
summarize students' knowledge;
highlight the most general and essential initial chemical concepts - substances, phenomena, chemical formulas and equations;
teach basic worldview concepts.
3. Developmental:
development of skills in educational and cognitive activities;
development of intelligence, culture of oral and written speech;
development logical thinking and attention;
development of the ability to use the studied material in practical activities.
Equipment:
table D.I. Mendeleev;
cards with the student's serial number;
task cards;
equipment for experiments,
account screen.
presentation "Initial chemical concepts"
projector;
computer or laptop
Lesson type: combined lesson
Lesson plan:
Organizing time.
Checking homework.
The stage of generalization and systematization of knowledge.
Reflection.
Summing up the lesson.
Homework
During the classes
I Organizational moment.
Hello guys! Who is absent today?
The topic of our lesson: “Repetition. Initial chemical ideas". Guys, today the goal of our lesson is to systematize and generalize knowledge about substances, phenomena, formulas into two teams. You will compete with each other and at the same time repeat the topic you have covered, and I will monitor and evaluate your knowledge and reflect it on the score screen. So how? Ready to get started?
Each participant is given cards with his serial number.
II Updating knowledge.
Frontal work with the class. 1 point is awarded for the correct answer
Warm up. Questions:
What does chemistry study?
What changes occur during chemical reactions?
Give examples of chemical reactions: a) in industry;
b) in nature;
c) in everyday life.
Based on what properties they are used in everyday life:
a) glass; b) rubber; c) concrete; d) copper
Define the following terms:
Molecule, atom, valence, chemical formula, chemical element.
What laws have you already studied?
What is a chemical equation?
Name the types of chemical reactions, give examples
III Stage of generalization and systematization of knowledge.
1 competition
A) Chemical dictation “Physical and chemical phenomena”
Answers must be marked with the letters “X” (chemical phenomena) or “F” (physical phenomena).
Option I
Souring of milk
Perfume aroma
Leaf rotting
Photosynthesis
Formation of green plaque on copper items
Answers Option 1 - ХФХХХ
Option II
Evaporation of alcohol
Wood burning
Sugaring jam
Metal forging
Metal rusting
Option II - FHFFH
B) Chemical dictation “Substances and mixtures”
Answers must be marked with the letters “B” or “C.”
I option II option
Distilled water 1. Copper
Soil 2. Air
Sugar 3. Phosphorus
Granite 4. Table salt
River water 5. Sulfuric acid
Answer: Option I - B C B SS Option II - VSVBB
Competition 2 - “Valence” Team members receive cards with tasks.
Task A
It is necessary to determine the valence of chemical elements. The highest score is 5 points
Option I Knowing that the valence of chlorine is equal to one, determine the valence of another element in these formulas
CaCl2, NCl3, HCl, PCl5, AlCl3
Option II Knowing that the valency of oxygen is two, determine the valency of the other element in these formulas
MnO, P2O5, CO2, Mn2O7, K2O
Task B
Make up formulas for chemical compounds
Option I Ca(II) and O(II), Na (I) and S(II) , Mg (II) and S (II) , AL(III) and O (II) , Pb (IV) and O (II ) .
Option II
Sn (IV) and O(II), C(IV) and O (II), Mg (II) and O(II), S (IV) and O(II), Fe (III) and O (II).
3rd competition - Chemical hockey
Teacher: You were asked homework: prepare 3 questions for the other team. Now, guys, we'll play hockey. To do this, we will give the teams names: “defenders” and “forwards”. Each team will ask their questions one at a time, and the opposing team will answer. For each correct answer 1 point is awarded. Behind interest Ask You can also earn 1 point. The maximum score for this competition is 6 points.
(Teams ask and answer questions one by one)
4th competition – “Chemical experiment”
Equipment: a cup with a mixture of wood and iron filings, a cup with a mixture of starch and granulated sugar, empty glasses, glasses with water, glass rod, filter paper, funnel, tripods, alcohol lamp, magnet,
Teacher: It's time to find out how you can handle chemical glassware and conduct experiments. The first step is to remember the safety rules when performing experiments. Three people from each team are called to the table for experiments. For each team, a mixture consisting of two substances is given. Your task: using your knowledge, divide these mixtures into the substances of which they consist. The maximum score for this competition is 5 points
After completing this task, team members read the task and talk in detail about the experience they did.
Option I: Separate the mixture consisting of starch and granulated sugar Option II: Separate the mixture consisting of iron and wood filings
5th competition - “Equations of chemical reactions and types of reactions”
Teams are given cards with tasks.
Teacher: Competition 5 is called “Equations of chemical reactions and types of reactions.” You have cards with tasks. They contain equations of chemical reactions. You need to put together the missing points with the necessary signs of the chemical elements, arrange the coefficients and indicate the type of chemical reaction. The maximum score is 3 points (the speed of completing the task is taken into account, the team that completes the task faster receives plus 1 point)
Option I
? + O 2 MgO reaction………………
FeO + H2 Fe + H 2O reaction………………
AuO Au + ? reaction………………
Option II
? +HCl FeCl 2+ H 2 reaction………………
H 2+ Br 2 ? reaction………………
HgO Hg + O2 reaction………………
6th competition – From the history of chemistry"
Teacher: The teams were given homework: to prepare a speech about scientists who made a worthy contribution to the development of “Atomic-Molecular Science” or were its founders. The floor is given to the teams. For completing this task, the team can earn 3 points. Students give messages to Robert Boyle and Antoine Lavoisier.
First team performances
Robert Boyle - English chemist, physicist, theologian. Born into a Protestant family on January 25, 1627 at Lismore Castle in Ireland. His father was the aristocrat Richard Boyle, a very rich man, an adventurer by nature, who left England in 1588 at the age of 22. Robert's mother, Catherine Fenton, was already the second wife of Richard Boyle. His first wife died shortly after the birth of their first child. Robert Boyle was the youngest, fourteenth child in the Boyle family, and the seventh, beloved son of Richard Boyle. When Robert was born, his father was already 60 years old and his mother 40. Of course, Robert Boyle was lucky in that his father was one of the most richest people in Great Britain Robert Boyle's parents believed that children should receive upbringing and education outside the family. Therefore, in 1635, at the age of 8, little Robert, along with one of his brothers, was sent to England to receive an education. They entered the fashionable Eton College, where the children of noble nobles studied. The conditions for studying at Eton were quite favorable for the young Boyles. Richard Boyle takes his children from Eton in November 1638. Robert's education continues at home under the supervision of one of his father's priests. In 1638, Robert Boyle, together with his mentor, went on a trip to European countries, continuing his education in Florence and at the Geneva Academy. In Geneva, he intensively studies mathematics, French and Latin, rhetoric and theology. At the beginning of 1642, Boyle visited Florence, the city where the great Galileo Galilei lived and worked. Unfortunately, it was during Boyle's stay in Florence that Galileo Galilei died. Boyle carried his love to Galileo's philosophy throughout my life, keeping it in my scientific creativity belief in the possibility of studying the world through the laws of mathematics and mechanics. In 1644, after the death of his father, Robert Boyle returned to England and settled on his Stelbridge estate, where he lived almost continuously for 10 years, doing research in the field natural sciences, devoting at the same time a lot of time to religious and philosophical issues. It should be noted that Robert Boyle studied theology all his life, and very seriously and enthusiastically. In 1654, Robert Boyle moved to Oxford, where he equipped a laboratory and, with the help of specially invited assistants, conducted experiments in physics and chemistry. One of these assistants was Robert Hooke. And although R. Boyle was a resident of Oxford University for almost 12 years, he never had any university degree or diploma. An M.D. (Oxford, 1665) was his only diploma. In 1680, Robert Boyle was elected as the next president of the Royal Society of London, but he declined the honor because the required oath would violate his religious principles. Perhaps due to religious beliefs, Robert Boyle lived his entire life single and never married. In 1668, Boyle received an honorary doctorate in physics from the University of Oxford and in the same year moved to London, where he settled with his sister and continued his scientific work.
Scientific achievements of Robert Boyle. In 1654, R. Boyle introduced the concept into science chemical analysis composition of tel. In 1660, R. Boyle obtained acetone by distilling potassium acetate. 16764065405 Unfortunately, Boyle was never able to give up his belief in alchemy. He believed in the transformation of elements, and even in 1676 he reported to the Royal Society of London about his desire to turn mercury into gold. He sincerely believed that he was on the road to success in these experiments.
In 1663, Boyle discovered colored rings in thin layers, later called Newtonian rings. In 1663, he discovered the acid-base indicator litmus in the litmus lichen growing in the mountains of Scotland, which he used in his research. Boyle studied a lot chemical processes, occurring during the roasting of metals, dry distillation of wood, transformations of salts, acids and alkalis. In 1680 he developed new way obtaining phosphorus from bones, received phosphoric acid and phosphine. Robert Boyle died in London on December 30, 1691, leaving a rich scientific heritage for future generations. Boyle wrote many books, some of which were published after the scientist’s death, since some of the manuscripts were later found in the archives of the Royal Society of London. He was buried in the Church of Saint-Martin-in-the-Fields next to his sister. The church was later destroyed and unfortunately there are no records or evidence of where his remains were moved.
Performances of the other team
Antoine Laurent Lavoisier - (1743-1794), French chemist, one of the founders of modern chemistry. Antoine Laurent Lavoisier was born into a lawyer's family on August 28, 1743. The child spent the first years of his life in Paris, in Pequet Lane, surrounded by gardens and vacant lots. His mother died giving birth to another girl in 1748, when Antoine Laurent was only five years old. He received his primary education at Mazarin College. This school was established by Cardinal Mazarin for noble children, but external students from other classes were also accepted into it. It was the most popular school in Paris.
Antoine studied well. Like many of the outstanding scientists, he first dreamed of literary fame and, while still in college, began writing a prose drama, “The New Heloise,” but limited himself to only the first scenes. Upon leaving college, Laurent entered the Faculty of Law, probably because his father and grandfather were lawyers and this career was already beginning to become traditional in their family: in old France, positions were usually inherited.
In 1763, Antoine Laurent received a bachelor's degree, and the following year - a licentiate of rights. But legal sciences could not satisfy his boundless and insatiable curiosity. He was interested in everything - from the philosophy of Condillac to street lighting. He absorbed knowledge like a sponge, every new object aroused his curiosity, he felt it from all sides, squeezing everything possible out of it.
Soon, however, from this diversity one group of knowledge begins to stand out, which increasingly absorbs it: the natural sciences.
Lavoisier's first works were made under the influence of his teacher and friend Guétard. After five years of collaboration with Guétard, in 1768, when Lavoisier was 25 years old, he was elected a member of the Academy of Sciences.
Antoine Lavoisier soon married the daughter of the general tax farmer Polza. In 1771, Antoine Lavoisier was 28 years old and his bride was 14. Despite the bride’s youth, the marriage turned out to be happy. Lavoisier found in her an active assistant and collaborator in his studies. She helped him in chemical experiments, kept a laboratory journal, and translated the works of English scientists for her husband. I even made drawings for one of the books. They had no children.
In his life, Antoine Lavoisier adhered to strict order. He made it a rule to study science six hours a day: from six to nine in the morning and from seven to ten in the evening. One day a week was devoted exclusively to science. In the morning, A. Lavoisier locked himself in the laboratory with his colleagues, here they repeated experiments, discussed chemical issues, argued about new system. He spent huge sums on the construction of instruments, representing in this respect the complete opposite of some of his contemporaries.
In 1775, Antoine Lavoisier presented a memoir to the academy, in which the composition of air was accurately clarified for the first time. Air consists of two gases: " clean air”, capable of enhancing combustion and respiration, oxidizing metals, and “mythical air”, which does not have these properties. The names oxygen and nitrogen were given later.
The results of Lavoisier's management of gunpowder factories in 1775-1791 were also fruitful. He took on this task with his usual energy.
During French Revolution, as one of the tax farmers, the scientist Antoine Lavoisier went to prison. On May 8, 1794, the trial took place. On trumped-up charges, 28 tax farmers, including Lavoisier, were sentenced to death. Lavoisier was fourth on the list. His father-in-law, Polz, was executed before him. Then it was his turn.
IV.Reflection
Teacher: Guys, our lesson is coming to an end. I thank you for your active participation in the lesson and for helping your teammates.
Each of you has your own impressions of the lesson. I would like to ask you to comment on the lesson using these phrases:
Students speak in a circle in one sentence, choosing the beginning of a phrase from the reflective screen on the board:
today I found out...
it was interesting…
it was difficult…
I completed tasks...
I realized that...
Now I can…
I felt that...
I purchased...
I learned…
I managed …
I was able...
I will try…
I was surprised...
I wanted…
V. Summing up the lesson
At the end of the lesson, the results are summed up. Each student's scores are calculated and grades are given for participation and answers in the lesson. The winning team is determined and the leaders are identified
Scores for points:
“5” – for 21 or more points
“4” - for 17-20 points
“3” – for 12 -16 points
VI. Homework
To prepare for test work on the topic “Initial chemical concepts”
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Electrical phenomena became known to man first in the formidable form of lightning - discharges of atmospheric electricity, then electricity obtained through friction (for example, skin on glass, etc.) was discovered and studied; finally, after the discovery of chemical current sources (galvanic cells in 1800), electrical engineering arose and quickly developed. In the Soviet state we witnessed the brilliant flourishing of electrical engineering. Russian scientists contributed greatly to such rapid progress.
However, it is difficult to give a simple answer to the question: “What is electricity?" We can say that “electricity is electric charges and related electromagnetic fields" But such an answer requires detailed further explanation: “What are electric charges and electromagnetic fields?” We will gradually show how essentially complex the concept of “electricity” is, although extremely diverse electrical phenomena have been studied in great detail, and in parallel with their deeper understanding, the field has expanded practical application electricity.
Inventors of the first electric machines imagined electricity like the movement of a special electrical fluid in metal wires, but to create vacuum tubes it was necessary to know the electronic nature of electric current.
The modern doctrine of electricity is closely connected with the doctrine of the structure of matter. The smallest particle of a substance that preserves it Chemical properties, is a molecule (from the Latin word "moles" - mass).
This particle is very small, for example, a water molecule has a diameter of about 3/1000,000,000 = 3/10 8 = 3*10 -8 cm and a volume of 29.7*10 -24.
To imagine more clearly how small such molecules are, what a huge number of them fit into small volume, let us mentally carry out the following experiment. Let's somehow mark all the molecules in a glass of water (50 cm 3) and pour this water into the Black Sea. Let us imagine that the molecules contained in these 50 cm 3, evenly distributed throughout the vast oceans, which occupy 71% of the globe's area; Then let’s scoop up another glass of water from this ocean, at least in Vladivostok. Is there a probability of finding at least one of the molecules we labeled in this glass?
The volume of the world's oceans is enormous. Its surface is 361.1 million km 2. Its average depth is 3795 m. Therefore, its volume is 361.1 * 10 6 * 3.795 km 3, i.e. about 1,370 LLC LLC km 3 = 1,37*10 9 km 3 - 1,37*10 24 cm 3.
But at 50 cm 3 water contains 1.69 * 10 24 molecules. Consequently, after mixing, each cubic centimeter of ocean water will contain 1.69/1.37 labeled molecules, and about 66 labeled molecules will end up in our glass in Vladivostok.
No matter how small molecules are, they are made up of even smaller particles - atoms.
An atom is the smallest part of a chemical element, which is the carrier of its chemical properties. A chemical element is usually understood as a substance consisting of identical atoms. Molecules can form identical atoms (for example, a molecule of hydrogen gas H2 consists of two atoms) or different atoms (a molecule of water H20 consists of two hydrogen atoms H2 and an oxygen atom O). In the latter case, when dividing molecules into atoms, chemical and physical properties substances change. For example, when the molecules of a liquid body, water, decompose, two gases are released - hydrogen and oxygen. The number of atoms in molecules varies: from two (in a hydrogen molecule) to hundreds and thousands of atoms (in proteins and high-molecular compounds). A number of substances, in particular metals, do not form molecules, that is, they consist directly of atoms not connected internally by molecular bonds.
For a long time it was believed that the atom the smallest particle matter (the very name atom comes from the Greek word atomos - indivisible). It is now known that the atom is a complex system. Most of the mass of the atom is concentrated in its nucleus. The lightest electrically charged elementary particles - electrons - revolve around the nucleus in certain orbits, just as the planets revolve around the Sun. Gravitational forces hold the planets in their orbits, and electrons are attracted to the nucleus by electrical forces. Electrical charges can be of two different types: positive and negative. From experience we know that only opposite electric charges attract each other. Consequently, the charges of the nucleus and electrons must also have different signs. It is conventionally accepted to consider the charge of electrons to be negative and the charge of the nucleus to be positive.
All electrons, regardless of the method of their production, have the same electrical charges and a mass of 9.108 * 10 -28 G. Consequently, the electrons that make up the atoms of any element can be considered the same.
At the same time, the electron charge (usually denoted e) is elementary, i.e., the smallest possible electric charge. Attempts to prove the existence of smaller charges were unsuccessful.
The belonging of an atom to a particular chemical element is determined by the magnitude of the positive charge of the nucleus. Total negative charge Z electrons of an atom is equal to the positive charge of its nucleus, therefore, the value of the positive charge of the nucleus must be eZ. The Z number determines the place of an element in Mendeleev’s periodic table of elements.
Some electrons in an atom are in inner orbits, and some are in outer orbits. The former are relatively firmly held in their orbits by atomic bonds. The latter can relatively easily separate from an atom and move to another atom, or remain free for some time. These outer orbital electrons determine the electrical and chemical properties of the atom.
As long as the sum of the negative charges of the electrons is equal to the positive charge of the nucleus, the atom or molecule is neutral. But if an atom has lost one or more electrons, then due to the excess positive charge of the nucleus it becomes a positive ion (from the Greek word ion - moving). If an atom has captured excess electrons, then it serves as a negative ion. In the same way, ions can be formed from neutral molecules.
The carriers of positive charges in the nucleus of an atom are protons (from the Greek word “protos” - first). The proton serves as the nucleus of hydrogen, the first element in the table periodic table. Its positive charge e + is numerically equal to the negative charge of the electron. But the mass of a proton is 1836 times greater than the mass of an electron. Protons, together with neutrons, form the nuclei of all chemical elements. The neutron (from the Latin word “neuter” - neither one nor the other) has no charge and its mass is 1838 times greater than the mass of the electron. Thus, the main parts of atoms are electrons, protons and neutrons. Of these, protons and neutrons are firmly held in the nucleus of an atom and only electrons can move inside the substance, and positive charges under normal conditions can only move together with atoms in the form of ions.
The number of free electrons in a substance depends on the structure of its atoms. If there are a lot of these electrons, then this substance allows moving electric charges to pass through it well. It is called a conductor. All metals are considered conductors. Silver, copper and aluminum are especially good conductors. If, under one or another external influence, the conductor has lost some of the free electrons, then the predominance of the positive charges of its atoms will create the effect of a positive charge of the conductor as a whole, that is, the conductor will attract negative charges - free electrons and negative ions. Otherwise, with an excess of free electrons, the conductor will be negatively charged.
A number of substances contain very few free electrons. Such substances are called dielectrics or insulators. They transmit electrical charges poorly or practically not. Dielectrics include porcelain, glass, hard rubber, most plastics, air, etc.
In electrical devices, electrical charges move along conductors, and dielectrics serve to direct this movement.
