In the previous paragraph we called three main provisions of the ICT and noted that they were confirmed by experiments. Most of them are very complex (both in carrying out and in understanding the results), so we will consider only the simplest illustrative experiments.

The existence of gaps between particles. Pour 100 ml of water into one beaker, and 100 ml of colored alcohol into the other. Let's pour the liquid from these beakers into the third one (see picture). Surprisingly, the volume of the mixture will not be 200 ml, but less: 190 ml. However, the mass of the mixture is exactly equal to the sum of the masses of water and alcohol. Why is this happening?

It has been established that water and alcohol are made up of particles called molecules. They are so small that they are not visible either through a magnifying glass or a microscope. However, it is known that alcohol molecules are 2–3 times larger than water molecules, therefore the intermolecular gaps in alcohol are larger than in water. When mixed, water molecules are placed in the spaces between alcohol molecules. Filling out these intermolecular gaps and helps reduce the volume of the mixture without affecting the sum of particle masses.

Small particle sizes of substances. Let's take a few test tubes. Pour water into the first one and throw in a few grains of paint. Having mixed the water, we will see that the grains have dissolved and the water has acquired uniform rich color. Pour part of the solution into a second test tube and add water. The color of the solution will become lighter, but after stirring it will again be uniform. The experiment can be repeated many times, but With any dilution, the color of the solution remains uniform. Why is this happening?

Like water and alcohol, paint is made up of tiny particles that cannot be seen “individually.” If they were larger, then instead of uniform coloring we would see clear water with paint particles floating in it.

Types of particles of substances. Science has established that water, sugar, alcohol and almost all gases consist of different particles, which are classified as molecules. Salt, soda, vinegar also consist of different particles, but they are classified as ions. Diamond, phosphorus, sulfur, helium and neon gases consist of particles that are classified as atoms. For example, salt water contains the following particles: water molecules, sodium and chlorine ions. And in a steel object, such as a knife or spoon, there are iron ions, carbon atoms and other impurity particles that are added to iron in the manufacture of steels and alloys of various grades.

You will be able to understand the types and names of these particles only when you study 8th grade physics and chemistry courses. For now, we will simply say “particles of matter,” meaning molecules, ions and atoms. Please be patient and gradually get used to these new terms.

The constancy of particles of substances. As you know, substances, depending on temperature and pressure, can be solid, liquid, or gaseous. The question arises: are particles of the same substance identical, but in different states?

Physical and chemical experiments found that particles of a substance remain the same when its state changes (that is, their appearance, size and mass are preserved). For example, melted wax or stearin hardens and becomes opaque; In cold weather, water vapor turns into frost crystals and so on. At the same time, the particles of stearin, water, and in general the particles of all substances remain the same, however, the arrangement of particles and the distances between them change.

The figure shows the arrangement of water molecules in solid (a), liquid (b) and gaseous (c) states. Please note: the molecules themselves are the same, but their arrangement and the distances between them are different.

Types of particles of matter. Science has established that water, sugar, alcohol and almost all gases consist of different particles, which are classified as molecules. Salt, soda, vinegar and many acids and alkalis also consist of different particles, but they are classified as ions. Diamond, phosphorus, sulfur, helium and neon gases, as well as other substances consist of particles that are classified as atoms.

For example, salt water contains the following particles: water molecules, sodium and chlorine ions. And in a steel object, for example, a knife or spoon, there are iron ions, carbon atoms and other impurity particles that are added to iron in the manufacture of steels and alloys of various grades.

You will be able to understand the types and names of these particles only when you study physics and chemistry courses for the 8th grade. For now, as a rule, we will simply speak of particles of matter, meaning molecules, ions and atoms. Please be patient and gradually get used to these new terms.

The immutability of particles of matter. As you know, substances, depending on temperature and pressure, can be solid, liquid, or gaseous. The question arises: are particles of the same substance identical, but in different states?

Physical and chemical experiments have established that particles of a substance remain the same when its state changes (that is, their appearance, mass and size are preserved). For example, wax or stearin melted on a candle hardens and becomes opaque; water vapor on a frosty day turns into prickly crystals of frost, etc. However, the particles of stearin, water and, in general, particles of all substances remain the same, however the arrangement of particles and the distances between them changes.

The figure shows the arrangement of water molecules in the solid (a), liquid (b) and gaseous (c) states. Please note that the molecules themselves are the same, but their arrangement and the distances between them are different.

Test your knowledge:

1. The main provisions of the ICT should be called facts, since...
2. The experiment “Mixing water and alcohol” confirms...
3. The left beaker contains...
4. The right beaker contains...
5. The volume of the mixture in the third beaker was equal to...
6. The particles that make up water and alcohol are called...
7. Water molecules fit in between alcohol molecules because...
8. The total volume decreases during mixing because the water molecules are arranged...
9. Reducing the total volume of the mixture of water and alcohol has no effect...
10. The experiment “Successive dissolution of paint in water” confirms...
11. After the paint has dissolved, the water in the first test tube...
12. When diluting part of the saturated solution from the first test tube clean water in the second test tube...
13. How can we summarize the observations from this experiment?
14. Why are we sure that the paint that we successively dissolved in test tubes consists of very small particles?
15. Examples of substances with a molecular structure are...
16. Examples of substances with ionic structure are...
17. Examples of substances consisting only of atoms are...
18. What we unite under common name"particles of matter"?
19. What factors determine the state of a substance?
20. What can be said about particles of the same substance in different states?
21. What can be said about particles of the same substance when its state changes?

§ 07-b. Particles of substances

In the previous paragraph we called three main provisions of the ICT and noted that they were confirmed by experiments. Most of them are very complex (both in carrying out and in understanding the results), so we will consider only the simplest illustrative experiments.

The existence of gaps between particles. Pour 100 ml of water into one beaker, and 100 ml of colored alcohol into the other. Let's pour the liquid from these beakers into the third one (see picture). Surprisingly, the volume of the mixture will not be 200 ml, but less: 190 ml. However, the mass of the mixture is exactly equal to the sum of the masses of water and alcohol. Why is this happening?

It has been established that water and alcohol are made up of particles called molecules. They are so small that they are not visible either through a magnifying glass or a microscope. However, it is known that alcohol molecules are 2–3 times larger than water molecules, therefore the intermolecular gaps in alcohol are larger than in water. When mixed, water molecules are placed in the spaces between alcohol molecules. Filling out these intermolecular gaps and helps reduce the volume of the mixture without affecting the sum of particle masses.

Small particle sizes of substances. Let's take a few test tubes. Pour water into the first one and throw in a few grains of paint. Having mixed the water, we will see that the grains have dissolved and the water has acquired uniform rich color. Pour part of the solution into a second test tube and add water. The color of the solution will become lighter, but after stirring it will again be uniform. The experiment can be repeated many times, but With any dilution, the color of the solution remains uniform. Why is this happening?

Like water and alcohol, paint is made up of tiny particles that cannot be seen “individually.” If they were larger, then instead of a uniform color we would see transparent water with particles of paint floating in it.

Types of particles of substances. Science has established that water, sugar, alcohol and almost all gases consist of different particles, which are classified as molecules. Salt, soda, vinegar also consist of different particles, but they are classified as ions. Diamond, phosphorus, sulfur, helium and neon gases consist of particles that are classified as atoms. For example, salt water contains the following particles: water molecules, sodium and chlorine ions. And in a steel object, such as a knife or spoon, there are iron ions, carbon atoms and other impurity particles that are added to iron in the manufacture of steels and alloys of various grades.

You will be able to understand the types and names of these particles only when you study 8th grade physics and chemistry courses. For now, we will simply say “particles of matter,” meaning molecules, ions and atoms. Please be patient and gradually get used to these new terms.

The constancy of particles of substances. As you know, substances, depending on temperature and pressure, can be solid, liquid, or gaseous. The question arises: are particles of the same substance identical, but in different states?

Physical and chemical experiments have established that particles of a substance remain the same when its state changes (that is, their appearance, size and mass are preserved). For example, melted wax or stearin hardens and becomes opaque; In cold weather, water vapor turns into frost crystals and so on. At the same time, the particles of stearin, water, and in general the particles of all substances remain the same, however, the arrangement of particles and the distances between them change.

The figure shows the arrangement of water molecules in solid (a), liquid (b) and gaseous (c) states. Please note: the molecules themselves are the same, but their arrangement and the distances between them are different.

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In this section we will learn:

• distinguish bodies, substances, particles; describe the substances studied;
• carry out observations and conduct experiments using laboratory equipment;
• explore with
• experiments on the properties of air,
• water, soil composition;
• simulate the water cycle in nature;
• classify plants and animals;

• discover relationships between living and inanimate nature, relationships in living nature, model them and use them to explain the need careful attitude to nature;
• use an atlas-identifier to recognize natural objects;
• use textbook texts and illustrations, and other sources of information to find answers to questions, provide explanations, and prepare your own messages.

Bodies, substances, particles

Let's find out what bodies, substances, particles are. We will learn to classify bodies and substances, make assumptions (hypotheses) and prove them, and depict particles using models.

Remember into what groups all the objects that surround us can be divided.

Bodies

Any item, any living creature can be called a body. A stone, a lump of sugar, a tree, a bird, a wire - these are bodies. It is impossible to list all the bodies; there are countless of them. The sun, planets, and the moon are also bodies. They are called celestial bodies.

• Consider the diagram. What two groups can bodies be divided into? Give examples of bodies from each group.

Substances

Bodies are made up of substances. A piece of sugar is a body, and sugar itself is a substance. Aluminum wire is the body, aluminum is the substance.

There are bodies that are formed not by one, but by several or many substances. Living bodies have a very complex composition. For example, plants contain water, sugar, starch and other substances. The bodies of animals and humans are formed by many different substances.

So, substances are what bodies are made of.

There are solid, liquid and gaseous substances. Sugar, aluminum are examples of solids. Water is a liquid substance. Air consists of several gaseous substances(gases).

Particles

Let's do an experiment. Let's take a body formed by one substance - a piece of sugar. Place it in a glass of water and stir. At first, the sugar is clearly visible, but gradually becomes invisible. Let's taste the liquid. She's sweet. This means that the sugar did not disappear, it remained in the glass. Why don't we see him? Make a guess. Test yourself using the textbook text.

A piece of sugar disintegrated into the smallest particles, invisible to the eye, of which it consisted (dissolved), and these particles mixed with particles of water.

This experiment proves that substances, and therefore bodies, consist of particles.

Each substance consists of special particles that differ in size and shape from the particles of other substances.

Scientists have found that there are gaps between particles. In solids these gaps are very small, in liquids they are larger, in gases they are even larger. In any substance, all particles are constantly moving.

Particles can be represented using models, such as plasticine balls.

1. Check with your textbook to see if the following statements are true.
   • Any object, any living creature can be called a body.
   • Substances are what bodies are made of.
2. Select bodies from the list first, then substances. Test yourself on the “Self-Test Pages” (3).

   Horseshoe, glass, iron, brick, sugar, watermelon, salt, starch, stone.

3. Using a model, show the process of dissolving a piece of sugar in water.
4. Using models, depict the arrangement of particles in solid, liquid, and gaseous substances.

Test yourself

1. What are bodies called? Give examples.
2. What are substances? Give examples.
3. What do substances consist of? How to prove this?
4. What can you tell us about particles?

Tasks for homework

Write in the dictionary: body, substance, particle.

Pages for the curious

Molecules and atoms

Even in ancient times, scientists expressed the idea that bodies consist of visible to the eye particles. This is what they explained to many natural phenomena. Why, for example, do wet clothes dry out? Because particles of water fly away from it, which we do not see.

The great Russian scientist Mikhail Vasilyevich Lomonosov (1711-1765) believed that invisible particles can be complex and simple.

Complex particles are made up of simple ones. The same ones simple particles, combining in different ways, can form different complex particles. This is how M.V. Lomonosov explained the diversity of substances in nature. Later, scientists called complex particles molecules, and simple ones atoms.

Next lesson

Let's find out what substances are, what properties they have and how they are used by humans. We will learn to describe substances according to plan and study them through experiments.

Remember what substances you know.

The world around us is a variety of objects and forms. But all the diversity of our world can be divided into three groups: bodies, substances and particles. How to distinguish them and what characterizes each of these concepts will be discussed in the lesson on the surrounding world in 3rd grade.

Bodies

From the point of view of science, any object is a body. Everything that surrounds you, at home, in the classroom, on the street, is bodies. For example, a mug, table, telephone, stone, chair, ball.

According to the origin of the body there can be:

• natural– created by nature;
• artificial– created by man;
• alive;
• non-living.

Rice. 1. Diversity of bodies

The body is characterized by:

• size;
• shape;
• color
• mass;
• temperature.

When any body divides, it turns into new item. For example, a handle is a body, but if you take it apart, you get several parts.

Substances

Substance is what the body is made of. An object may consist of several substances. For example, a jug is made of clay, a scarf is knitted of wool, a spoon is made of metal.

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Rice. 2. Substances

Substances come in three states:

• hard- those that can be touched;
• liquid– for example, water;
• gaseous- air.

One of amazing properties Some bodies are the ability to move from one state to another under the influence of certain factors. For example, water at temperatures below zero takes the solid form of ice, and at 100 degrees Celsius it begins to boil and turns into a gaseous form - steam.

Unlike the body, substances do not change during division. If a piece of sugar is divided into several more parts, then each of them will still be sugar. Or pour water into cups, it will remain water and will not become a new substance.

Particles

Substances are made up of even smaller units. They are so small that they cannot be seen without a microscope. They are called particles.

Particles retain the properties of matter. As an experiment, you can stir a piece of sugar in water. This will make the liquid sweet, but we will not see the substance, since the sugar particles are mixed with water particles.

There is free space between the particles. The state of a substance will depend on how densely the elements are contained in it. In solid substances there are almost no spaces between particles, in liquid substances there is some distance between the elements, and in gaseous substances the particles move freely because there is a large distance between them.

Rice. 3. Particles in different bodies

What have we learned?

The topic “Bodies, substances, particles” on the surrounding world is a very interesting subject for discussion. Many experiments can be done to study their properties. Bodies are complex objects consisting of one or more substances. In turn, in any material there is a collection of the smallest indivisible elements - particles.