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Properties of simple and complex substances. Simple substances

Under chemical element understand a set of atoms with the same positive charge of the nucleus and with a certain set of properties. Atoms of the same chemical element combine to form simple matter. When atoms of different chemical elements are combined, complex substances (chemical compounds) or mixtures. The difference between chemical compounds and mixtures is that:

They have new properties that the simple substances from which they were derived did not have;

They cannot be mechanically separated into their component parts;

Chemical elements in their composition can only be in strictly defined quantitative ratios.

Some chemical elements (carbon, oxygen, phosphorus, sulfur) can exist in the form of several simple substances. This phenomenon is called allotropy, and varieties of simple substances of the same chemical element are called its allotropic modifications(modifications).

Tasks

1.1. What exists more in nature: chemical elements or simple substances? Why?

1.2. Is it true that sulfur and iron are included in the composition of iron sulfide as substances? If not, what is the correct answer?

1.3. Name the allotropic modifications of oxygen. Do they differ in their properties? If so, how?

1.4. Which of the allotropic modifications of oxygen is chemically more active and why?

1.5. Simple substances or chemical elements are zinc, sulfur and oxygen in the following reactions:

1) СuSO 4 + Zn = ZnSO 4 + Cu;

2) S + O 2 \u003d SO 2;

3) Zn + 2HC1 = ZnCl 2 + H 2 ;

4) Zn + S = ZnS;

5) 2H 2 0 \u003d 2H 2  + O 2 .

1.6. Is it possible to get another simple substance from one simple substance? Give a reasoned answer.

1.7. When a certain substance is burned in oxygen, sulfur oxide (IV), nitrogen and water are obtained. What chemical elements form the original substance?

1.8. Indicate whether simple or complex substances include: H 2 O, C1 2, NaOH, O 2, HNO 3, Fe, S, ZnSO 4, N 2, AgCl, I 2, A1 2 O 3, O 3?

1.9. For which chemical elements allotropic modifications are known? Name these modifications.

1.10. Is it possible for a chemical element to change from one allotropic modification to another? Give examples.

1.11. What chemical elements do they mean when they talk about diamond, ozone?

1.12. Which of the substances are chemical compounds, and which are mixtures:

2) air;

4) sulfuric acid;

1.13. How to prove that sodium chloride is a complex substance?

1.14. Name three allotropic modifications of carbon.

1.15. What are the names of allotropic modifications of phosphorus and how do they differ from each other?

1.16. What are the allotropic modifications of sulfur called and how do they differ from each other?

1.17. Indicate which of the statements is true and why - the composition of barium sulfate includes:

1) simple substances barium, sulfur, oxygen;

2) chemical elements barium, sulfur, oxygen.

1.18. How many liters of ammonia can be obtained from a mixture of 10 liters of nitrogen and 30 liters of hydrogen?

1.19. How many liters of water vapor are formed from a mixture of 10 liters of hydrogen and 4 liters of oxygen? What gas and in what volume will remain in excess?

1.20. How many grams of zinc sulfide (ZnS) can be formed from a mixture of 130 g of zinc and 48 g of sulfur?

1.22. What is a solution of alcohol in water - a mixture or a chemical compound?

1.23. Can a complex substance be made up of atoms of the same kind?

1.24. Which of the following substances are mixtures and which chemical compounds:

1) bronze;

2) nichrome;

3) kerosene;

4) potassium nitrate:

5) rosin;

6) superphosphate.

1.25. Given a mixture of Cl 2 + HCl + CaCl 2 + H 2 O.

1) How many different substances are in the mixture;

2) How many chlorine molecules are in the mixture;

3) How many chlorine atoms are in the mixture;

4) How many molecules of various substances are contained in the mixture.

Simple and complex substances. Chemical element

About atoms and chemical elements

In chemistry, in addition to the terms “atom” and “molecule”, the concept of “element” is often used. What is common and how do these concepts differ?

Chemical element are atoms of the same type. So, for example, all hydrogen atoms are the element hydrogen; all oxygen and mercury atoms are the elements oxygen and mercury, respectively.

Currently, more than 107 types of atoms, that is, more than 107 chemical elements, are known. It is necessary to distinguish between the concepts of "chemical element", "atom" and "simple substance"

Simple and complex substances

By elemental composition, simple substances are distinguished, consisting of atoms of one element (H2, O2, Cl2, P4, Na, Cu, Au), and complex substances, consisting of atoms of different elements (H2O, NH3, OF2, H2SO4, MgCl2, K2SO4) .

Currently, 115 chemical elements are known, which form about 500 simple substances.

Native gold is a simple substance.

The ability of one element to exist in the form of various simple substances that differ in properties is called allotropy. For example, the element oxygen O has two allotropic forms - dioxygen O2 and ozone O3c different number atoms in molecules.

The allotropic forms of the element carbon C - diamond and graphite - differ in the structure of their crystals. There are other reasons for allotropy.

Allotropic forms of carbon:

graphite:

diamond:

Complex substances are often called chemical compounds, for example, mercury (II) oxide HgO (obtained by combining atoms of simple substances - mercury Hg and oxygen O2), sodium bromide (obtained by combining atoms of simple substances - sodium Na and bromine Br2).

So let's summarize the above. Molecules of matter are of two types:

1. Simple Molecules of such substances consist of atoms of the same type. In chemical reactions, they cannot decompose with the formation of several simpler substances.

2.Complex- the molecules of such substances are composed of atoms different kind. In chemical reactions, they can decompose to form simpler substances.

The difference between the concepts of "chemical element" and "simple substance"

The concepts of "chemical element" and "simple substance" can be distinguished by comparing the properties of simple and complex substances. For example, a simple substance - oxygen - a colorless gas necessary for breathing, supporting combustion. The smallest particle of a simple substance oxygen is a molecule that consists of two atoms. Oxygen is also included in carbon monoxide ( carbon monoxide) and water. However, the composition of water and carbon monoxide includes chemically bound oxygen, which does not have the properties of a simple substance, in particular, it cannot be used for breathing. Fish, for example, do not breathe chemically bound oxygen, which is part of the water molecule, but free, dissolved in it. That's why when we are talking about the composition of any chemical compounds, it should be understood that these compounds do not include simple substances, but atoms of a certain type, that is, the corresponding elements.

When complex substances are decomposed, atoms can be released in a free state and combined to form simple substances. Simple substances are made up of atoms of one element. The difference between the concepts of "chemical element" and "simple substance" is also confirmed by the fact that one and the same element can form several simple substances. For example, atoms of the element oxygen can form diatomic oxygen molecules and triatomic ozone molecules. Oxygen and ozone are completely different simple substances. This explains the fact that much more simple substances are known than chemical elements.

Using the concept of "chemical element", we can give the following definition of simple and complex substances:

Simple Substances that are made up of atoms of a single chemical element are called.

complex Substances that are made up of atoms of different chemical elements are called.

The difference between the concepts of "mixture" and "chemical compound"

Complex substances are often called chemical compounds.

Follow the link and view the experience of the interaction of simple substances of iron and sulfur.

Try to answer the questions:

1. What is the difference in the composition of the mixture from chemical compounds?

2. Compare the properties of mixtures and chemical compounds?

3. In what ways can the mixture be divided into constituent components and chemical compound?

4. Is it possible to judge by outward signs about the formation of a mixture and a chemical compound?

Comparative characteristics of mixtures and chemical connections

Tasks for fixing

I. Work with the machines

Trainer #1

Trainer №2

Trainer №3

II. Solve the task

From the proposed list of substances, write out separately simple and complex substances:

NaCl, H2SO4, K, S8, CO2, O3, H3PO4, N2, Fe.

Explain your choice, in each case.

III. Answer the questions

№1

How many simple substances are written in a series of formulas:

H2O, N2, O3, HNO3, P2O5, S, Fe, CO2, KOH.

№2

Both substances are complex:

A) C (coal) and S (sulfur);

B) CO2 (carbon dioxide) and H2O (water);

C) Fe (iron) and CH4 (methane);

D) H2SO4 (sulfuric acid) and H2 (hydrogen).

№3

Choose the correct statement:

Simple substances are made up of atoms of the same kind.

A) right

B) False

№4

Mixtures are characterized by

A) they have a constant composition;

B) Substances in the "mixture" do not retain their individual properties;

C) Substances in "mixtures" can be separated by physical properties;

D) Substances in "mixtures" can be separated by a chemical reaction.

№5

For "chemical compounds" the following is characteristic:

A) Variable composition;

B) Substances in the composition of a "chemical compound" can be separated by physical means;

C) The formation of a chemical compound can be judged by the signs of chemical reactions;

D) permanent composition.

№6

In what case is it about iron as a chemical element?

A) Iron is a metal that is attracted by a magnet;

B) Iron is part of the composition of rust;

C) Iron has a metallic luster;

D) Iron sulfide contains one iron atom.

№7

In which case is it about oxygen as a simple substance?

A) Oxygen is a gas that supports respiration and combustion;

B) Fish breathe oxygen dissolved in water;

C) The oxygen atom is part of the water molecule;

D) Oxygen is present in the air.

Organic and inorganic substances;
> recognize metals and non-metals;
> determine metallic and non-metallic elements by their location in the periodic system of D. I. Mendeleev; understand why all metals are similar in properties.

Atoms under normal conditions cannot exist alone for a long time. They are able to combine with the same or other atoms, which leads to a great variety in the world of substances.

A substance formed by one chemical element is called simple, and a substance formed by several elements is called a complex, or chemical compound.

Simple substances

Simple substances are divided into metals and non-metals. Such a classification of simple substances was proposed by the outstanding French scientist A.L. Lavoisier at the end of the 18th century. The chemical elements from which metals are derived are called metallic, and those that form non-metals are called
non-metallic. In the long version of D. I. Mendeleev’s system (endpaper II), they are delimited by a broken line. metal elements are to the left of it; there are much more of them than non-metallic ones.

This is interesting

Simple substances of 13 elements - Au, Ag, Cu, Hg, Pb, Fe, Sn, Pt, S, C, Zn, Sb and As were known in antiquity.

Each of you can, without hesitation, name several metals (Fig. 36). They differ from other substances in a special "metallic" luster. These substances have many common properties.

Rice. 36. Metals

Under normal conditions, metals are solids (only mercury is a liquid), conduct electricity and heat well, and have mostly high temperature melting (over 500 °C).

Rice. 37. Simplified model internal structure metal

They are plastic; they can be forged, wire drawn from them.

Due to their properties, metals have confidently entered people's lives. Their great significance is evidenced by the names of historical epochs: the Copper Age, the Bronze Age, the Iron Age.

The similarity of metals is due to their internal structure.

The structure of metals. Metals are crystalline substances. Crystals in metals are much smaller than sugar crystals or table salt and cannot be seen with the naked eye.

Molecule - an electrically neutral particle, consisting of two or more connected atoms.

In each molecule, the atoms are interconnected quite firmly, and the molecules in the substance are very weakly connected to each other. Therefore, substances of molecular structure have no high temperatures melting and boiling.

Oxygen and ozone are molecular substances. These are simple oxygen substances. An oxygen molecule contains two oxygen atoms, and an ozone molecule contains three (Fig. 39).

Rice. 39. Models of molecules

Not only Oxygen, but also many other elements form two or more simple substances. Therefore, there are several times more simple substances than chemical elements.

Names of simple substances.

Most simple substances are named after the corresponding elements. If the names are different, then they are given in the periodic system, and the name of a simple substance is located below the name
element (Fig. 40).

Name the simple substances of the elements Hydrogen, Lithium, Magnesium, Nitrogen.

1 The term "molecule" comes from the Latin word moles (mass), diminutive suffix cula and means "small mass".

The names of simple substances are written inside the sentence with a small letter.

Rice. 40. Cell of the periodic system

Complex substances (chemical compounds)

The combination of atoms of different chemical elements generates a set complex substances(there are tens of thousands of times more than simple ones).

There are complex substances with a molecular, atomic and ionic structure. Therefore, their properties are very different.

Molecular compounds are mostly volatile and often have an odor. Their melting and boiling points are much lower than those of compounds with an atomic or ionic structure.

The molecular substance is water. The water molecule consists of two Hydrogen atoms and one Oxygen atom (Fig. 41).

Rice. 41. Water molecule model

The molecular structure of carbon monoxide and carbon dioxide gases, sugar, starch, alcohol, acetic acid, etc. The number of atoms in the molecules of complex substances can be different - from two atoms to hundreds or even thousands.

Some compounds have an atomic structure.

One of them is the mineral quartz, the main constituent of sand. It contains silicon and oxygen atoms (Fig. 42).

Rice. 42. Model of the connection of the atomic structure (quartz)

There are also ionic compounds. These are table salt, chalk, soda, lime, gypsum and many others. Salt crystals consist of positively charged Sodium ions and negatively charged Chlorine ions (Fig. 43). Each such ion is formed from the corresponding atom (§ 6).

Rice. 43. Model of an ionic compound (common salt)

This is interesting

in molecules organic compounds, in addition to carbon atoms, as a rule, hydrogen atoms are contained, often oxygen atoms, and sometimes some other elements.

The mutual attraction of many oppositely charged ions determines the existence of ionic compounds.

An ion formed from one atom is called simple, and an ion formed from several atoms is called complex.

Positively charged simple ions exist for metal elements, and negatively charged - for non-metallic elements.

Names of complex substances.

The textbook has so far provided technical or household names complex substances. In addition, substances have chemical names. For example, chemical name table salt - sodium chloride, and chalk - calcium carbonate. Each such name consists of two words. The first word is the name of one of the elements that form the substance (it is written with a small letter), and the second comes from the name of another element.

organic and inorganic substances.

Previously, organic substances were called those substances that are contained in living organisms. These are proteins, fats, sugar, starch, vitamins, compounds that give color, smell, taste to vegetables and fruits, etc. Over time, scientists began to obtain in laboratories substances similar in composition and properties that do not exist in nature. Now carbon compounds are called organic substances (with the exception of carbon monoxide and carbon dioxide, chalk, soda, and some others).

Most organic compounds are capable of burning, and when heated in the absence of air, they char (coal almost entirely consists of carbon atoms).

To not organic matter other complex substances belong, as well as all simple ones. They form the basis of the mineral world, that is, they are contained in soil, minerals, rocks, air, natural water. In addition, inorganic substances are also found in living organisms.

The material of the paragraph is summarized in Scheme 6.

Laboratory experiment No. 2

Familiarization with substances of various types

You have been given the following substances (the teacher will indicate the option):

option I - sugar, calcium carbonate (chalk), graphite, copper;
option II - paraffin, aluminum, sulfur, sodium chloride (table salt).

Substances are in jars with labels.

Carefully consider the substances, pay attention to their names. Identify among them simple (metals, non-metals) and complex substances, as well as organic and inorganic.

Enter the name of each substance in the table and indicate its type by writing a “+” sign in the appropriate columns.

conclusions

Substances are simple and complex, organic and inorganic.

Simple substances are divided into metals and non-metals, and chemical elements - into metallic and non-metallic.

Metals have many common properties due to the similarity of their internal structure.

Non-metals are composed of atoms or molecules and differ in their properties from metals.

Complex substances (chemical compounds) have an atomic, molecular or ionic structure.

Almost all compounds of Carbon belong to organic substances, and the remaining compounds and simple substances belong to inorganic substances.

?
56. What substance is called simple, and what is complex? What types of simple substances exist and what are the names of the corresponding elements?

57. For what physical properties Can a metal be distinguished from a non-metal?

58. Define a molecule. What is the difference between a molecule of a simple substance and a molecule of a complex substance?
59. Fill in the gaps by inserting the words "Nitrogen" or "nitrogen" in the appropriate cases and explain your choice:
a) ... - gas, which contains the largest amount in the air;
b) a molecule ... consists of two atoms ...;
c) compounds ... enter plants from the soil;
d) ... poorly soluble in water.

60. Fill in the gaps by inserting the words "element", "atom" or "molecule" in the appropriate case and number:
A)... white phosphorus contains four... Phosphorus;
b) there is ... carbon dioxide in the air;
c) gold is a simple substance... Aurum.

About atoms and chemical elements

There is nothing else in nature

neither here nor there, in the depths of space:

everything - from small grains of sand to planets -

of the elements consists of a single.

S. P. Shchipachev, "Reading Mendeleev."

In chemistry, apart from terms "atom" And "molecule" concept is often used "element". What is common and how do these concepts differ?

Chemical element – they are atoms of the same type . So, for example, all hydrogen atoms are the element hydrogen; all oxygen and mercury atoms are the elements oxygen and mercury, respectively.

Currently, more than 107 types of atoms, that is, more than 107 chemical elements, are known. It is necessary to distinguish between the concepts of “chemical element”, “atom” and “simple substance”

Simple and complex substances

According to the elemental composition, they are distinguished simple substances, consisting of atoms of one element (H 2, O 2, Cl 2, P 4, Na, Cu, Au), and complex substances, consisting of atoms of different elements (H 2 O, NH 3, OF 2, H 2 SO 4, MgCl 2, K 2 SO 4).

Currently, 115 chemical elements are known, which form about 500 simple substances.

Native gold is a simple substance.

The ability of one element to exist in the form of various simple substances that differ in properties is called allotropy.For example, the element oxygen O has two allotropic forms - dioxygen O 2 and ozone O 3 with a different number of atoms in molecules.

The allotropic forms of the element carbon C - diamond and graphite - differ in the structure of their crystals. There are other reasons for allotropy.

chemical compounds, for example, mercury (II) oxide HgO (obtained by combining atoms of simple substances - mercury Hg and oxygen O 2), sodium bromide (obtained by combining atoms of simple substances - sodium Na and bromine Br 2).

So let's summarize the above. Molecules of matter are of two types:

1. Simple Molecules of such substances consist of atoms of the same type. In chemical reactions, they cannot decompose with the formation of several simpler substances.

2. Complex- Molecules of such substances consist of atoms of different types. In chemical reactions, they can decompose to form simpler substances.

The difference between the concepts of "chemical element" and "simple substance"

Distinguish concepts "chemical element" And "simple substance" when comparing the properties of simple and complex substances. For example, a simple substance oxygen- a colorless gas necessary for breathing, supporting combustion. The smallest particle of a simple substance oxygen is a molecule that consists of two atoms. Oxygen is also included in the composition of carbon monoxide (carbon monoxide) and water. However, the composition of water and carbon monoxide includes chemically bound oxygen, which does not have the properties of a simple substance, in particular, it cannot be used for breathing. Fish, for example, do not breathe chemically bound oxygen, which is part of the water molecule, but free, dissolved in it. Therefore, when it comes to the composition of any chemical compounds, it should be understood that these compounds do not include simple substances, but atoms of a certain type, that is, the corresponding elements.

When complex substances are decomposed, atoms can be released in a free state and combined to form simple substances. Simple substances are made up of atoms of one element. The difference between the concepts of "chemical element" and "simple substance" is also confirmed by the fact that one and the same element can form several simple substances. For example, atoms of the element oxygen can form diatomic oxygen molecules and triatomic ozone molecules. Oxygen and ozone are completely different simple substances. This explains the fact that much more simple substances are known than chemical elements.

Using the concept of "chemical element", we can give the following definition of simple and complex substances:

Simple substances are substances that consist of atoms of one chemical element.

Substances that are composed of atoms of different chemical elements are called complex.

The difference between the concepts of "mixture" and "chemical compound"

Compounds are often called chemical compounds.

Try to answer the questions:

1. What is the difference in the composition of the mixture from chemical compounds?

2. Compare the properties of mixtures and chemical compounds?

3. In what ways can a mixture and a chemical compound be divided into constituent components?

4. Is it possible to judge by external signs the formation of a mixture and a chemical compound?

Comparative characteristics of mixtures and chemical

Tasks for fixing

I. Work with the machines

II. Solve the task

№1

How many simple substances are written in a series of formulas:
H 2 O, N 2, O 3, HNO 3, P 2 O 5, S, Fe, CO 2, KOH.

№2

Both substances are complex:

A) C (coal) and S (sulfur);
B) CO 2 (carbon dioxide) and H 2 O (water);
B) Fe (iron) and CH 4 (methane);
D) H 2 SO 4 (sulfuric acid) and H 2 (hydrogen).

№3

Choose the correct statement:
Simple substances are made up of atoms of the same kind.

A) right

B) False

№4

Mixtures are characterized by
A) they have a constant composition;
B) Substances in the "mixture" do not retain their individual properties;
C) Substances in "mixtures" can be separated by physical properties;
D) Substances in "mixtures" can be separated by a chemical reaction.

№5

For "chemical compounds" the following is characteristic:
A) Variable composition;
B) Substances in the composition of a "chemical compound" can be separated by physical means;
C) The formation of a chemical compound can be judged by the signs of chemical reactions;
D) permanent composition.

№6

In what case is it about gland how about chemical element?
A) Iron is a metal that is attracted by a magnet;
B) Iron is part of the composition of rust;
C) Iron has a metallic luster;
D) Iron sulfide contains one iron atom.

№7

In which case is it about oxygen as a simple substance?
A) Oxygen is a gas that supports respiration and combustion;
B) Fish breathe oxygen dissolved in water;
C) The oxygen atom is part of the water molecule;
D) Oxygen is present in the air.

All substances that we talk about in the school chemistry course are usually divided into simple and complex. Simple substances are those substances whose molecules contain atoms of the same element. Atomic oxygen (O), molecular oxygen (O2) or simply oxygen, ozone (O3), graphite, diamond are examples of simple substances that form the chemical elements oxygen and carbon. Compounds are divided into organic and inorganic. Among inorganic substances, first of all, the following four classes are distinguished: oxides (or oxides), acids (oxygenous and oxygen-free), bases (water-soluble bases are called alkalis) and salts. Compounds of non-metals (excluding oxygen and hydrogen) are not included in these four classes, we will call them conditionally "and other complex substances."

Simple substances are usually divided into metals, non-metals and inert gases. Metals include all chemical elements whose d- and f-sublevels are being filled, these are elements in the 4th period: Sc - Zn, in the 5th period: Y - Cd, in the 6th period: La - Hg, Ce - Lu, in the 7th period Ac - Th - Lr. If we now draw a line from Be to At among the remaining elements, then metals will be located to the left and below it, and non-metals to the right and top. In group 8 Periodic system inert gases are located. Elements located on the diagonal: Al, Ge, Sb, Po (and some others. For example, Zn) in the free state have the properties of metals, and hydroxides have the properties of both bases and acids, i.e. are amphoteric hydroxides. Therefore, these elements can be considered metal-non-metals, occupying an intermediate position between metals and non-metals. Thus, the classification of chemical elements depends on what properties their hydroxides will have: basic - it means metal, acidic - non-metal, and both (depending on conditions) - metal-non-metal. The same chemical element in compounds with the lowest positive oxidation state (Mn + 2, Cr + 2) exhibits pronounced "metallic" properties, and in compounds with the maximum positive oxidation state (Mn + 7, Cr + 6) it exhibits the properties of a typical non-metal. To see the relationship of simple substances, oxides, hydroxides and salts, we present a summary table.