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Everything around us - on the street, on a robot, in public transport - is related to chemistry. And we ourselves consist of a number of chemical elements and processes. Therefore, the question of how to learn chemistry is quite relevant.

This article is intended for persons over 18 years of age

Have you already turned 18?

Chemistry teaching methods

Not a single branch of industry or agriculture can do without this miracle science. Modern technologies They use all possible developments to ensure that progress moves forward. Medicine and pharmacology, construction and light industry, cooking and our everyday life - they all depend on chemistry, its theory and research.

But not all young people in school age understand the need and importance of chemistry in our lives, do not attend lessons, do not listen to teachers and do not delve into the essence of the processes. To interest and instill a love for science and the school curriculum among students in grades 8, 9, 10, teachers use different methods and educational technologies, specific methods and use research technologies.

b"> Is it easy to learn chemistry on your own?

It often happens that after finishing a course in a certain subject in high school or college, a student realizes that he did not listen carefully and did not understand anything. This may be reflected in his annual assessment, or it may cost budget place in the University. Therefore, many careless schoolchildren try to study chemistry on their own.

And here questions arise. Is this real? Is it possible to learn a difficult subject on your own? How to organize your time correctly and where to start? Of course, it is possible and quite realistic, the main thing is perseverance and the desire to achieve your goal. Where to start? No matter how trivial it may sound, motivation plays a role decisive role in the whole process. It depends on whether you can sit through textbooks for a long time, learn formulas and tables, break down processes and do experiments.

Once you have identified a goal for yourself, you need to start implementing it. If you are starting to learn chemistry from scratch, you can stock up on textbooks for the 8th grade curriculum, guides for beginners, and laboratory notebooks where you will write down the results of your experiments. But there are often situations when home-based teaching is not effective and does not bring desired results. There can be many reasons: lack of perseverance, lack of willpower, some aspects are unclear, without which further training makes no sense.

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Is it possible to learn chemistry quickly?

Many schoolchildren and students want to learn chemistry from scratch without spending a lot of effort and for a short time, are looking online for ways to learn a subject in 5 minutes, in 1 day, in a week or a month. It is impossible to say how long it will take to learn chemistry. It all depends on the desire, motivation, abilities and capabilities of each individual student. And it is worth remembering that quickly learned information disappears from our memory just as quickly. Therefore, is it worth quickly learning the entire school chemistry course in a day? Or is it better to spend more time, but then pass all exams with flying colors?

Regardless of how long you plan to study chemistry, it is worth choosing convenient methods that will facilitate the already difficult task of learning the basics of organic and Not organic chemistry, features of chemical elements, formulas, acids, alkanes and many more.

The most popular method used in secondary schools is preschool institutions, in courses on studying a particular subject, this is a game method. It allows you to remember a large amount of information in a simple and accessible form without spending a lot of effort. You can buy a young chemist's set (yes, don't let that bother you) and see a variety of important processes and reactions, observe the interaction different substances and at the same time completely safe. In addition, use the method of cards or stickers, which you place on different pieces (this is especially suitable for the kitchen) indicating the name chemical element, its properties, formula. When you come across such pictures throughout the house, you will remember the necessary data on a subconscious level.

Alternatively, you can buy a book for children, which describes the initial and main points in a simple form, or you can watch an educational video where chemical reactions are explained based on home experiments.

Don’t forget to control yourself by doing tests and examples, solving problems - this is how you can consolidate your knowledge. Well, repeat the material you have already learned before, and the new material that you are learning now. It is the return and reminder that makes it possible to keep all the information in your head and not forget it before the exam.

An important point is the help of your smartphone or tablet, on which you can install special educational programs in order to learn chemistry. Such applications can be downloaded for free by selecting the desired level of knowledge - for beginners (if you are learning from scratch), intermediate (course high school) or high (for students of biological and medical faculties). The advantages of such devices are that you can repeat or learn something new from anywhere and at any time.

And finally. Whatever field you will succeed in the future: science, economics, art, Agriculture, military field or industry, remember that knowledge of chemistry will never be superfluous!

Chapter 1.

General chemical and environmental patterns.

Where does chemistry begin?

Is this a difficult question? Everyone will answer it differently.

In secondary school, students study chemistry over a number of years. Many people do quite well on their final exam in chemistry. However…

Conversations with applicants and then first-year students indicate that residual knowledge in chemistry after secondary school is insignificant. Some get confused in various definitions and chemical formulas, while others cannot even reproduce the basic concepts and laws of chemistry, not to mention the concepts and laws of ecology.

Their chemistry never started.

Chemistry, apparently, begins with a deep mastery of its fundamentals, and above all, the basic concepts and laws.

1.1. Basic chemical concepts.

In D.I. Mendeleev’s table there are numbers next to the element symbol. One number indicates the atomic number of the element, and the second atomic mass. The serial number has its own physical meaning. We will talk about it later, here we will focus on atomic mass and highlight in what units it is measured.

It should be noted right away that the atomic mass of an element given in the table is a relative value. The unit of relative atomic mass is taken to be 1/12 of the mass of a carbon atom, an isotope with a mass number of 12, and is called the atomic mass unit /amu/. Therefore, 1 amu equal to 1/12 of the mass of the carbon isotope 12 C. And it is equal to 1.667 * 10 –27 kg. /The absolute mass of a carbon atom is 1.99 * 10 –26 kg./

Atomic mass, given in the table, is the mass of the atom expressed in atomic mass units. The quantity is dimensionless. Specifically for each element, atomic mass shows how many times the mass of a given atom is greater or less than 1/12 of the mass of a carbon atom.

The same can be said about molecular weight.

Molecular mass is the mass of a molecule expressed in atomic mass units. The magnitude is also relative. The molecular mass of a particular substance is equal to the sum of the masses of the atoms of all the elements that make up the molecule.

An important concept in chemistry is the concept of “mole”. Mole– such an amount of substance that contains 6.02 * 10 23 structural units /atoms, molecules, ions, electrons, etc./. Mole of atoms, mole of molecules, mole of ions, etc.

The mass of one mole of a given substance is called its molar / or molar / mass. It is measured in g/mol or kg/mol and is designated by the letter “M”. For example, the molar mass of sulfuric acid M H 2 SO4 = 98 g/mol.

The next concept is “Equivalent”. Equivalent/E/ is the weight amount of a substance that interacts with one mole of hydrogen atoms or replaces such an amount in chemical reactions. Therefore, the equivalent of hydrogen E H is equal to one. /E N =1/. The oxygen equivalent E O is equal to eight /E O =8/.

A distinction is made between the chemical equivalent of an element and the chemical equivalent of a complex substance.

The equivalent of an element is a variable quantity. It depends on the atomic mass /A/ and valence /B/ that the element has in a particular compound. E=A/B. For example, let's determine the equivalent of sulfur in the oxides SO 2 and SO 3. In SO 2 E S =32/4=8, and in SO 3 E S =32/6=5.33.

The molar mass of an equivalent, expressed in grams, is called equivalent mass. Therefore, the equivalent mass of hydrogen ME H = 1 g/mol, the equivalent mass of oxygen ME O = 8 g/mol.

The chemical equivalent of a complex substance /acid, hydroxide, salt, oxide/ is the amount of the corresponding substance that interacts with one mole of hydrogen atoms, i.e. with one equivalent of hydrogen or replaces that amount of hydrogen or any other substance in chemical reactions.

Acid equivalent/E K/ is equal to the quotient of the molecular weight of the acid divided by the number of hydrogen atoms participating in the reaction. For the acid H 2 SO 4, when both hydrogen atoms react H 2 SO 4 +2NaOH=Na 2 SO+2H 2 O the equivalent will be equal to EN 2 SO4 = M H 2 SO 4 /n H =98/2=49

Hydroxide equivalent /E hydr. / is defined as the quotient of the molecular weight of the hydroxide divided by the number of hydroxo groups that react. For example, the equivalent of NaOH will be equal to: E NaOH = M NaOH / n OH = 40/1 = 40.

Salt equivalent/E salt/ can be calculated by dividing its molecular weight by the product of the number of metal atoms that react and their valence. Thus, the equivalent of the salt Al 2 (SO 4) 3 will be equal to E Al 2 (SO 4) 3 = M Al 2 (SO 4) 3 /6 = 342/2.3 = 342/6 = 57.

Oxide equivalent/E ok / can be defined as the sum of the equivalents of the corresponding element and oxygen. For example, the equivalent of CO 2 will be equal to the sum of the equivalents of carbon and oxygen: E CO 2 = E C + E O = 3 + 8 = 7.

For gaseous substances it is convenient to use equivalent volumes /E V /. Since when normal conditions A mole of gas occupies a volume of 22.4 liters, then based on this value, it is easy to determine the equivalent volume of any gas. Let's consider hydrogen. The molar mass of hydrogen 2g occupies a volume of 22.4 liters, then its equivalent mass of 1g occupies a volume of 11.2 liters / or 11200 ml /. Therefore E V N =11.2l. The equivalent volume of chlorine is 11.2 l /E VCl = 11.2 l/. The equivalent volume of CO is 3.56 /E VC O =3.56 l/.

The chemical equivalent of an element or complex substance is used in stoichiometric calculations of exchange reactions, and in the corresponding calculations of redox reactions, oxidative and reduction equivalents are used.

Oxidative equivalent is defined as the quotient of the molecular weight of the oxidizing agent divided by the number of electrons it accepts in a given redox reaction.

The reducing equivalent is equal to the molecular weight of the reducing agent divided by the number of electrons it gives up in a given reaction.

Let's write the redox reaction and determine the equivalent of the oxidizing agent and reducing agent:

5N 2 aS+2KMnO 4 +8H 2 SO 4 =S+2MnSO 4 +K 2 SO 4 +5Na 2 SO 4 +8H 2 O

The oxidizing agent in this reaction is potassium permanganate. The equivalent of the oxidizing agent will be equal to the mass of KMnO 4 divided by the number of electrons accepted by the oxidizing agent in the reaction (ne=5). E KMnO 4 =M KMnO 4 /ne=158/5=31.5. The molar mass of the equivalent of the oxidizing agent KMnO 4 in an acidic medium is 31.5 g/mol.

The equivalent of the reducing agent Na 2 S will be: E Na 4 S = M Na 4 S / ne = 78/2 = 39. The molar mass of Na 2 S equivalent is 39 g/mol.

IN electrochemical processes, in particular during the electrolysis of substances, an electrochemical equivalent is used. The electrochemical equivalent is determined as the quotient of the chemical equivalent of the substance released at the electrode divided by the Faraday number /F/. The electrochemical equivalent will be discussed in more detail in the corresponding paragraph of the course.

Valence. When atoms interact, a chemical bond is formed between them. Each atom can only form a certain number of bonds. The number of connections determines this unique property each element, which is called valency. In the most general view Valency is the ability of an atom to form a chemical bond. One chemical bond that a hydrogen atom can form is taken as a unit of valence. In this regard, hydrogen is a monovalent element, and oxygen is a divalent element, because No more than two hydrogens can form a bond with an oxygen atom.

The ability to determine the valency of each element, including chemical compound, is a necessary condition for successfully mastering the chemistry course.

Valence is also related to such a concept of chemistry as oxidation state. The oxidation substate is the charge that an element has in an ionic compound or would have in a covalent compound if the shared electron pair were completely shifted to a more electronegative element. The oxidation state has not only a numerical expression, but also a corresponding charge sign (+) or (–). Valence does not have these signs. For example, in H 2 SO 4 the oxidation state is: hydrogen +1, oxygen –2, sulfur +6, and the valency, accordingly, will be 1, 2, 6.

Valency and oxidation state in numerical values ​​do not always coincide in value. For example, in a molecule ethyl alcohol CH 3 –CH 2 –OH valence of carbon is 6, hydrogen is 1, oxygen is 2, and the oxidation state, for example, of the first carbon is –3, the second is –1: –3 CH 3 – –1 CH 2 –OH.

1.2. Basic environmental concepts.

Behind Lately The concept of “ecology” enters deeply into our consciousness. This concept, introduced back in 1869 by E. Haeckel, comes from the Greek oikos- house, place, dwelling, logos– the teaching / is disturbing humanity more and more.

In biology textbooks ecology defined as the science of the relationship between living organisms and their environment. An almost consonant definition of ecology is given by B. Nebel in his book “Science of the Environment” - Ecology is the science of various aspects of the interaction of organisms with each other and with the environment. A broader interpretation can be found in other sources. For example, Ecology – 1/. The science that studies the relationship of organisms and their systemic aggregates and environment; 2/. Totality scientific disciplines, exploring the relationship of systemic biological structures /from macromolecules to the biosphere/ among themselves and with the environment; 3/. Discipline that studies general laws functioning of ecosystems at various hierarchical levels; 4/. A comprehensive science that studies the habitat of living organisms; 5/. Study of the position of man as a species in the biosphere of the planet, his connections with ecological systems and the impact on them; 6/. The science of environmental survival. / N.A. Agidzhanyan, V.I. Torshik. Human ecology./. However, the term “ecology” refers not only to ecology as a science, but to the state of the environment itself and its impact on humans, flora and fauna.

If you have entered the university, but by this time have not understood this difficult science, we are ready to reveal a few secrets to you and help you study organic chemistry from scratch (for dummies). All you have to do is read and listen.

Basics of organic chemistry

Organic chemistry is distinguished as a separate subtype due to the fact that the object of its study is everything that contains carbon.

Organic chemistry is a branch of chemistry that deals with the study of carbon compounds, the structure of such compounds, their properties and methods of joining.

As it turned out, carbon most often forms compounds with the following elements- H, N, O, S, P. By the way, these elements are called organogens.

Organic compounds, the number of which today reaches 20 million, are very important for the full existence of all living organisms. However, no one doubted it, otherwise the person would have simply thrown the study of this unknown into the back burner.

The goals, methods and theoretical concepts of organic chemistry are presented as follows:

• Separation of fossil, animal or plant materials into individual substances;
• Purification and synthesis of various compounds;
• Identification of the structure of substances;
• Determination of the mechanics of chemical reactions;
• Finding the relationship between the structure and properties of organic substances.

A little history of organic chemistry

You may not believe it, but back in ancient times, the inhabitants of Rome and Egypt understood something about chemistry.

As we know, they used natural dyes. And often they had to use not a ready-made natural dye, but extract it by isolating it from a whole plant (for example, alizarin and indigo contained in plants).

We can also remember the culture of drinking alcohol. The secrets of producing alcoholic beverages are known in every nation. Moreover, many ancient peoples knew recipes for preparing “ hot water» from starch- and sugar-containing products.

This went on for a long time, long years, and only in the 16th-17th centuries did some changes and small discoveries begin.

In the 18th century, a certain Scheele learned to isolate malic, tartaric, oxalic, lactic, gallic and citric acid.

Then it became clear to everyone that the products that had been isolated from plant or animal raw materials had a lot of common features. At the same time, they were very different from inorganic compounds. Therefore, the servants of science urgently needed to highlight them in separate class This is how the term “organic chemistry” appeared.

Despite the fact that organic chemistry itself as a science appeared only in 1828 (it was then that Mr. Wöhler managed to isolate urea by evaporating ammonium cyanate), in 1807 Berzelius introduced the first term into the nomenclature in organic chemistry for dummies:

The branch of chemistry that studies substances obtained from organisms.

The next important step in the development of organic chemistry was the theory of valency, proposed in 1857 by Kekule and Cooper, and the theory chemical structure Mr. Butlerov from 1861. Even then, scientists began to discover that carbon was tetravalent and capable of forming chains.

In general, since then, science has regularly experienced shocks and excitement thanks to new theories, discoveries of chains and compounds, which allowed the active development of organic chemistry.

Science itself emerged due to the fact that scientific and technological progress was unable to stand still. He went on and on, demanding new solutions. And when there was no longer enough coal tar in industry, people simply had to create a new organic synthesis, which over time grew into the discovery of an incredibly important substance, which to this day is more expensive than gold - oil. By the way, it was thanks to organic chemistry that its “daughter” was born - a subscience that was called “petrochemistry”.

But this is a completely different story that you can study for yourself. Next, we invite you to watch a popular science video about organic chemistry for dummies:

Well, if you have no time and urgently need help professionals, you always know where to find them.