Is there a difference in the chemical composition of the planets. What is a substance? What are the classes of substances

In life, we are surrounded by various bodies and objects. For example, indoors it is a window, a door, a table, a light bulb, a cup, on the street - a car, a traffic light, asphalt. Any body or object is made up of matter. This article will discuss what a substance is.

What is chemistry?

Water is an essential solvent and stabilizer. It has strong heat capacity and thermal conductivity. The aquatic environment is favorable for the occurrence of basic chemical reactions. It is transparent and practically resistant to compression.

What is the difference between inorganic and organic substances?

There are no particularly strong external differences between these two groups of substances. The main difference lies in the structure, where inorganic substances have a non-molecular structure, and organic substances have a molecular structure.

Inorganic substances have a non-molecular structure, therefore, they are characterized by high melting and boiling points. They do not contain carbon. These include noble gases (neon, argon), metals (calcium, calcium, sodium), amphoteric substances (iron, aluminum) and non-metals (silicon), hydroxides, binary compounds, salts.

Organic substances of molecular structure. They have fairly low melting points and decompose rapidly when heated. Mostly composed of carbon. Exceptions: carbides, carbonates, oxides of carbon and cyanides. Carbon allows the formation of a huge number of complex compounds (more than 10 million are known in nature).

Most of their classes belong to biological origin (carbohydrates, proteins, lipids, nucleic acids). These compounds include nitrogen, hydrogen, oxygen, phosphorus and sulfur.

To understand what a substance is, it is necessary to imagine what role it plays in our life. Interacting with other substances, it forms new ones. Without them, the vital activity of the surrounding world is inseparable and unthinkable. All objects are made up of certain substances, so they play an important role in our lives.

During chemical reactions, other substances are obtained from one substance (not to be confused with nuclear reactions, in which one chemical element is converted into another).

Any chemical reaction is described by a chemical equation:

Reagents → Reaction products

The arrow indicates the direction of the reaction.

For example:

In this reaction, methane (CH 4) reacts with oxygen (O 2), resulting in the formation of carbon dioxide (CO 2) and water (H 2 O), or rather, water vapor. This is exactly the reaction that happens in your kitchen when you light a gas burner. The equation should be read like this: one molecule of methane gas reacts with two molecules of oxygen gas, resulting in one molecule of carbon dioxide and two molecules of water (steam).

The numbers in front of the components of a chemical reaction are called reaction coefficients.

Chemical reactions are endothermic(with energy absorption) and exothermic(with energy release). The combustion of methane is a typical example of an exothermic reaction.

There are several types of chemical reactions. The most common:

• compound reactions;
• decomposition reactions;
• single substitution reactions;
• double substitution reactions;
• oxidation reactions;
• redox reactions.

Connection reactions

In a compound reaction, at least two elements form one product:

2Na (t) + Cl 2 (g) → 2NaCl (t)- the formation of salt.

Attention should be paid to an essential nuance of compound reactions: depending on the conditions of the reaction or the proportions of the reactants that enter into the reaction, different products can be its result. For example, under normal conditions of combustion of coal, carbon dioxide is obtained:
C (t) + O 2 (g) → CO 2 (g)

If there is not enough oxygen, then deadly carbon monoxide is formed:
2C (t) + O 2 (g) → 2CO (g)

Decomposition reactions

These reactions are, as it were, opposite in essence to the reactions of the compound. As a result of the decomposition reaction, the substance decomposes into two (3, 4...) simpler elements (compounds):

• 2H 2 O (g) → 2H 2 (g) + O 2 (g)- water decomposition
• 2H 2 O 2 (g) → 2H 2 (g) O + O 2 (g)- decomposition of hydrogen peroxide

Single substitution reactions

As a result of single substitution reactions, the more active element replaces the less active element in the compound:

Zn (t) + CuSO 4 (solution) → ZnSO 4 (solution) + Cu (t)

The zinc in the copper sulfate solution displaces the less active copper, resulting in a zinc sulfate solution.

The degree of activity of metals in ascending order of activity:

• The most active are alkali and alkaline earth metals.

The ionic equation for the above reaction will be:

Zn (t) + Cu 2+ + SO 4 2- → Zn 2+ + SO 4 2- + Cu (t)

The ionic bond CuSO 4, when dissolved in water, decomposes into a copper cation (charge 2+) and an anion sulfate (charge 2-). As a result of the substitution reaction, a zinc cation is formed (which has the same charge as the copper cation: 2-). Note that the sulfate anion is present on both sides of the equation, i.e., by all the rules of mathematics, it can be reduced. The result is an ion-molecular equation:

Zn (t) + Cu 2+ → Zn 2+ + Cu (t)

Double substitution reactions

In double substitution reactions, two electrons are already replaced. Such reactions are also called exchange reactions. These reactions take place in solution to form:

• insoluble solid (precipitation reaction);
• water (neutralization reactions).

Precipitation reactions

When mixing a solution of silver nitrate (salt) with a solution of sodium chloride, silver chloride is formed:

Molecular equation: KCl (solution) + AgNO 3 (p-p) → AgCl (t) + KNO 3 (p-p)

Ionic equation: K + + Cl - + Ag + + NO 3 - → AgCl (t) + K + + NO 3 -

Molecular-ionic equation: Cl - + Ag + → AgCl (t)

If the compound is soluble, it will be in solution in ionic form. If the compound is insoluble, it will precipitate, forming a solid.

Neutralization reactions

These are reactions between acids and bases, as a result of which water molecules are formed.

For example, the reaction of mixing a solution of sulfuric acid and a solution of sodium hydroxide (lye):

Molecular equation: H 2 SO 4 (p-p) + 2NaOH (p-p) → Na 2 SO 4 (p-p) + 2H 2 O (l)

Ionic equation: 2H + + SO 4 2- + 2Na + + 2OH - → 2Na + + SO 4 2- + 2H 2 O (l)

Molecular-ionic equation: 2H + + 2OH - → 2H 2 O (g) or H + + OH - → H 2 O (g)

Oxidation reactions

These are reactions of interaction of substances with gaseous oxygen in the air, in which, as a rule, a large amount of energy is released in the form of heat and light. A typical oxidation reaction is combustion. At the very beginning of this page, the reaction of the interaction of methane with oxygen is given:

CH 4 (g) + 2O 2 (g) → CO 2 (g) + 2H 2 O (g)

Methane refers to hydrocarbons (compounds of carbon and hydrogen). When a hydrocarbon reacts with oxygen, a lot of heat energy is released.

Redox reactions

These are reactions in which electrons are exchanged between the atoms of the reactants. The reactions discussed above are also redox reactions:

• 2Na + Cl 2 → 2NaCl - compound reaction
• CH 4 + 2O 2 → CO 2 + 2H 2 O - oxidation reaction
• Zn + CuSO 4 → ZnSO 4 + Cu - single substitution reaction

The most detailed redox reactions with a large number of examples of solving equations by the electron balance method and the half-reaction method are described in the section

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

Questions for comparing mixtures with chemical compounds	Mapping
	Mixes	Chemical compounds
How do mixtures differ from chemical compounds in composition?	Substances can be mixed in any ratio, i.e. the composition of mixtures is variable	The composition of chemical compounds is constant.
Compare the properties of mixtures and chemical compounds?	Substances in mixtures retain their properties	Substances that form compounds do not retain their properties, since chemical compounds with different properties are formed.
How can a mixture and a chemical compound be separated into its constituent components?	Substances can be separated by physical means	Chemical compounds can only be decomposed by chemical reactions
Is it possible to judge by external signs the formation of a mixture and a chemical compound?	Mechanical mixing is not accompanied by heat release or other signs of chemical reactions	The formation of a chemical compound can be judged by signs of chemical reactions

Tasks for fixing

I. Work with the machines

II. Solve the task

From the proposed list of substances, write out separately simple and complex substances:
NaCl, H 2 SO 4 , K, S 8 , CO 2 , O 3 , H 3 PO 4 , N 2 , Fe.
Explain your choice, in each case.

III. Answer the questions

№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.

Nature develops in dynamics, living and inert matter continuously undergoes transformation processes. The most important transformations are those that affect the composition of a substance. The formation of rocks, chemical erosion, the birth of a planet or the respiration of mammals are all observable processes that entail changes in other substances. Despite their differences, they all share something in common: changes at the molecular level.

1. In the course of chemical reactions, elements do not lose their identity. Only the electrons of the outer shell of atoms participate in these reactions, while the nuclei of atoms remain unchanged.
2. The reactivity of an element to a chemical reaction depends on the degree of oxidation of the element. In ordinary chemical reactions, Ra and Ra 2+ behave completely differently.
3. Different isotopes of an element have almost the same chemical reactivity.
4. The rate of a chemical reaction is highly dependent on temperature and pressure.
5. The chemical reaction can be reversed.
6. Chemical reactions are accompanied by relatively small changes in energy.

Nuclear reactions

1. During nuclear reactions, the nuclei of atoms undergo changes and, therefore, new elements are formed as a result.
2. The reactivity of an element to a nuclear reaction is practically independent of the degree of oxidation of the element. For example, Ra or Ra 2+ ions in Ka C 2 behave similarly in nuclear reactions.
3. In nuclear reactions, isotopes behave quite differently. For example, U-235 undergoes division quietly and easily, but U-238 does not.
4. The rate of a nuclear reaction does not depend on temperature and pressure.
5. A nuclear reaction cannot be undone.
6. Nuclear reactions are accompanied by large changes in energy.

Difference between chemical and nuclear energy

• Potential energy that can be converted to other forms primarily of heat and light when bonds are formed.
• The stronger the bond, the greater the converted chemical energy.

• Nuclear energy is not associated with the formation of chemical bonds (which are due to the interaction of electrons)
• Can be converted to other forms when there is a change in the nucleus of an atom.

Nuclear change occurs in all three major processes:

1. Nuclear fission
2. Joining two nuclei to form a new nucleus.
3. The release of high energy electromagnetic radiation (gamma rays), creating a more stable version of the same nucleus.

Energy Conversion Comparison

The amount of chemical energy released (or converted) in a chemical explosion is:

• 5kJ for each gram of TNT
• Amount of nuclear energy in a released atomic bomb: 100 million kJ for every gram of uranium or plutonium

One of the main differences between nuclear and chemical reactions related to how the reaction occurs in the atom. While a nuclear reaction takes place in the nucleus of an atom, the electrons in the atom are responsible for the chemical reaction that takes place.

Chemical reactions include:

• Transfers
• Losses
• Gain
• Separation of electrons

According to the atom theory, matter is explained as a result of rearrangement to give new molecules. Substances involved in a chemical reaction and the proportions in which they are formed are expressed in the corresponding chemical equations that form the basis for performing various types of chemical calculations.

Nuclear reactions are responsible for the decay of the nucleus and have nothing to do with electrons. When the nucleus decays, it can go to another atom, due to the loss of neutrons or protons. In a nuclear reaction, protons and neutrons interact inside the nucleus. In chemical reactions, electrons react outside the nucleus.

Any fission or fusion can be called the result of a nuclear reaction. A new element is formed due to the action of a proton or neutron. As a result of a chemical reaction, a substance changes into one or more substances due to the action of electrons. A new element is formed due to the action of a proton or neutron.

When comparing energy, a chemical reaction only involves a low energy change, whereas a nuclear reaction has a very high energy change. In a nuclear reaction, the energy changes in magnitude are 10^8 kJ. It is 10 - 10^3 kJ/mol in chemical reactions.

While some elements are converted into others in the nuclear, the number of atoms remains the same in the chemical. In a nuclear reaction, isotopes react differently. But as a result of a chemical reaction, isotopes also react.

Although a nuclear reaction does not depend on chemical compounds, a chemical reaction is highly dependent on chemical compounds.

Summary

A nuclear reaction takes place in the nucleus of an atom, the electrons in the atom are responsible for chemical compounds.
1. Chemical reactions cover the transfer, loss, amplification and separation of electrons without involving the nucleus in the process. Nuclear reactions involve the decay of the nucleus and have nothing to do with electrons.
2. In a nuclear reaction, protons and neutrons react inside the nucleus; in chemical reactions, electrons interact outside the nucleus.
3. When comparing energies, a chemical reaction uses only a low energy change, whereas a nuclear reaction has a very high energy change.

Offset number 2.

Explore Chapter 2 "The Origin of Life on Earth""pp. 30-80 of the textbook" General biology. Grade 10 "author, etc.

I. Answer the following questions in writing:

1. What are the foundations and essence of life according to ancient Greek philosophers?

2. What is the meaning of F. Redi's experiments?

3. Describe the experiments of L. Pasteur, proving the impossibility of spontaneous generation of life in modern conditions.

4. What are theories of the eternity of life?

5. What materialistic theories of the origin of life do you know?

What are nuclear fusion reactions? Give examples.

6. How, in accordance with the Kant-Laplace hypothesis, are star systems formed from gas-dust matter?

7. Are there differences in the chemical composition of the planets of the same star system?

8. List the cosmic and planetary prerequisites for the emergence of life in an abiogenic way on our planet.

9. What is the significance of the reducing nature of the primary atmosphere for the emergence of organic molecules from inorganic substances on Earth?

10. Describe the apparatus and methodology for conducting the experiments of S. Miller and P. Urey.

11. What is coacervation, coacervate?

12. What model systems can be used to demonstrate the formation of coacervate drops in solution?

13. What opportunities existed in the waters of the primary ocean to overcome low concentrations of organic matter?

14. What are the advantages for the interaction of organic molecules in areas of high concentrations of substances?

15. How could organic molecules with hydrophilic and hydrophobic properties be distributed in the waters of the primary ocean?

16. Name the principle of separating a solution into phases with a high and low concentration of molecules. ?

17. What are coacervate drops?

18. How is the selection of coacervates in the "primary broth"?

19. What is the essence of the hypothesis of the emergence of eukaryotes through symbiogenesis?

20. In what ways did the first eukaryotic cells receive the energy necessary for life processes?

21. In which organisms did the sexual process appear for the first time in the process of evolution?

22. Describe the essence of the hypothesis about the emergence of multicellular organisms?

23. Define the following terms: protobionts, biological catalysts, genetic code, self-reproduction, prokaryotes, photosynthesis, sexual process, eukaryotes.

Test your knowledge on the topic:

The origin of life and the development of the organic world

1. Proponents of biogenesis argue that

All living things - from living

All living things are created by God

All living things - from non-living

Living organisms brought to Earth from the universe

2. Proponents of abiogenesis argue that all living things

Comes from inanimate

Arises from living

・Created by God

Brought in from outer space

3. Experiments by L. Pasteur using flasks with an elongated neck

Proved the inconsistency of the position of abiogenesis

Affirmed the position of abiogenesis

Affirmed the position of biogenesis

Proved the inconsistency of the position of biogenesis

4. Proof that life does not arise spontaneously

L. Pasteur

A. Van Leeuwenhoek

Aristotle

5. Aristotle believed that

Alive only from living

Life comes from the four elements

The living comes from the non-living

The living can come from the inanimate if it has an "active principle"

6. Hypothesis

Strengthens the position of supporters of biogenesis

Strengthens the position of supporters of abiogenesis

Emphasizes the failure of the position of biogenesis

Emphasizes the failure of the position of abiogenesis

7. According to the hypothesis, coacervates are the first

· Organisms

"Organization" of molecules

Protein complexes

Accumulations of inorganic substances

8. At the stage of chemical evolution,

Bacteria

Protobionts

Biopolymers

Low molecular weight organic compounds

9. At the stage of biological evolution,

Biopolymers

· Organisms

low molecular weight organic substances

Inorganic substances

1. According to modern ideas, life on Earth developed as a result of

· Chemical evolution

Biological evolution

Chemical and then biological evolution

· Chemical and biological evolution

Biological and then chemical evolution

10. The first organisms that appeared on Earth ate

Autotrophs

Heterotrophs

Saprophytes

11. As a result of the appearance of autotrophs in the Earth's atmosphere

Increased amount of oxygen

Decreased amount of oxygen

Increased amount of carbon dioxide

The ozone screen appeared

12. The amount of organic compounds in the primordial ocean was decreasing due to

Increase in the number of autotrophs

An increase in the number of heterotrophs

Reducing the number of autotrophs

Reducing the number of heterotrophs

13. The accumulation of oxygen in the atmosphere is due to

The appearance of the ozone layer

Photosynthesis

fermentation

Circulation of substances in nature

14. The process of photosynthesis led to

Formation of a large amount of oxygen

The appearance of the ozone layer

The emergence of multicellularity

The emergence of sexual reproduction

15. Check the correct statements:

Heterotrophs - organisms capable of independently synthesizing organic substances from inorganic

The first organisms on Earth were heterotrophic

Cyanobacteria - the first photosynthetic organisms

The mechanism of photosynthesis was formed gradually

16. Cleavage of organic compounds in anoxic conditions:

fermentation

Photosynthesis

· Oxidation

Biosynthesis

17. With the advent of autotrophs on Earth:

Irreversible changes in the conditions of existence of life began

A large amount of oxygen was formed in the atmosphere

There was an accumulation of solar energy in the chemical bonds of organic substances

All heterotrophs have disappeared

18. Man appeared on earth in

Proterozoic era

Mesozoic era

Cenozoic era

Proterozoic

Mesozoic

Paleozoic

Cenozoic

20. The largest events of the Proterozoic are considered

The emergence of eukaryotes

Emergence of flowering plants

The emergence of the first chordates

21. The process of soil formation on Earth was due to

The water cycle in nature

Settlement by organisms of the upper layer of the lithosphere

The death of organisms

Destruction of hard rocks with the formation of sand and clay

22. were widespread in Archaea.

Reptiles and ferns

Bacteria and cyanobacteria

23. Plants, animals and fungi came to land in

Proterozoic

Paleozoic

Mesozoic

24. Proterozoic era

Mammals and insects

Algae and coelenterates

The first land plants

Dominance of reptiles