A collection of misconceptions: A spacecraft re-entering the atmosphere heats up from friction against the air. What is air made of? Composition and properties Depict air particles in heated and cooled

Atmosphere(from the Greek atmos - steam and spharia - ball) - the air shell of the Earth, rotating with it. The development of the atmosphere was closely connected with the geological and geochemical processes taking place on our planet, as well as with the activities of living organisms.

The lower boundary of the atmosphere coincides with the surface of the Earth, since air penetrates into the smallest pores in the soil and is dissolved even in water.

The upper limit at an altitude of 2000-3000 km gradually passes into outer space.

Oxygen-rich atmosphere makes life possible on Earth. Atmospheric oxygen is used in the process of breathing by humans, animals, and plants.

If there were no atmosphere, the Earth would be as quiet as the moon. After all, sound is the vibration of air particles. The blue color of the sky is explained by the fact that the sun's rays, passing through the atmosphere, as if through a lens, are decomposed into their component colors. In this case, the rays of blue and blue colors are scattered most of all.

The atmosphere retains most of the ultraviolet radiation from the Sun, which has a detrimental effect on living organisms. It also keeps heat at the surface of the Earth, preventing our planet from cooling.

The structure of the atmosphere

Several layers can be distinguished in the atmosphere, differing in density and density (Fig. 1).

Troposphere

Troposphere- the lowest layer of the atmosphere, whose thickness above the poles is 8-10 km, in temperate latitudes - 10-12 km, and above the equator - 16-18 km.

Rice. 1. The structure of the Earth's atmosphere

The air in the troposphere is heated from the earth's surface, i.e. from land and water. Therefore, the air temperature in this layer decreases with height by an average of 0.6 °C for every 100 m. At the upper boundary of the troposphere, it reaches -55 °C. At the same time, in the region of the equator at the upper boundary of the troposphere, the air temperature is -70 °С, and in the region of the North Pole -65 °С.

About 80% of the mass of the atmosphere is concentrated in the troposphere, almost all water vapor is located, thunderstorms, storms, clouds and precipitation occur, and vertical (convection) and horizontal (wind) air movement occurs.

We can say that the weather is mainly formed in the troposphere.

Stratosphere

Stratosphere- the layer of the atmosphere located above the troposphere at an altitude of 8 to 50 km. The color of the sky in this layer appears purple, which is explained by the rarefaction of the air, due to which the sun's rays almost do not scatter.

The stratosphere contains 20% of the mass of the atmosphere. The air in this layer is rarefied, there is practically no water vapor, and therefore clouds and precipitation are almost not formed. However, stable air currents are observed in the stratosphere, the speed of which reaches 300 km / h.

This layer is concentrated ozone(ozone screen, ozonosphere), a layer that absorbs ultraviolet rays, preventing them from passing to the Earth and thereby protecting living organisms on our planet. Due to ozone, the air temperature at the upper boundary of the stratosphere is in the range from -50 to 4-55 °C.

Between the mesosphere and the stratosphere there is a transitional zone - the stratopause.

Mesosphere

Mesosphere- a layer of the atmosphere located at an altitude of 50-80 km. The air density here is 200 times less than at the surface of the Earth. The color of the sky in the mesosphere appears black, stars are visible during the day. The air temperature drops to -75 (-90)°С.

At an altitude of 80 km begins thermosphere. The air temperature in this layer rises sharply to a height of 250 m, and then becomes constant: at a height of 150 km it reaches 220-240 °C; at an altitude of 500-600 km it exceeds 1500 °C.

In the mesosphere and thermosphere, under the action of cosmic rays, gas molecules break up into charged (ionized) particles of atoms, so this part of the atmosphere is called ionosphere- a layer of very rarefied air, located at an altitude of 50 to 1000 km, consisting mainly of ionized oxygen atoms, nitric oxide molecules and free electrons. This layer is characterized by high electrification, and long and medium radio waves are reflected from it, as from a mirror.

In the ionosphere, auroras arise - the glow of rarefied gases under the influence of electrically charged particles flying from the Sun - and sharp fluctuations in the magnetic field are observed.

Exosphere

Exosphere- the outer layer of the atmosphere, located above 1000 km. This layer is also called the scattering sphere, since gas particles move here at high speed and can be scattered into outer space.

Composition of the atmosphere

The atmosphere is a mixture of gases consisting of nitrogen (78.08%), oxygen (20.95%), carbon dioxide (0.03%), argon (0.93%), a small amount of helium, neon, xenon, krypton (0.01%), ozone and other gases, but their content is negligible (Table 1). The modern composition of the Earth's air was established more than a hundred million years ago, but the sharply increased human production activity nevertheless led to its change. Currently, there is an increase in the content of CO 2 by about 10-12%.

The gases that make up the atmosphere perform various functional roles. However, the main significance of these gases is determined primarily by the fact that they very strongly absorb radiant energy and thus have a significant effect on the temperature regime of the Earth's surface and atmosphere.

Table 1. Chemical composition of dry atmospheric air near the earth's surface

Nitrogen, the most common gas in the atmosphere, chemically little active.

Oxygen, unlike nitrogen, is a chemically very active element. The specific function of oxygen is the oxidation of organic matter of heterotrophic organisms, rocks, and incompletely oxidized gases emitted into the atmosphere by volcanoes. Without oxygen, there would be no decomposition of dead organic matter.

The role of carbon dioxide in the atmosphere is exceptionally great. It enters the atmosphere as a result of the processes of combustion, respiration of living organisms, decay and is, first of all, the main building material for the creation of organic matter during photosynthesis. In addition, the property of carbon dioxide to transmit short-wave solar radiation and absorb part of thermal long-wave radiation is of great importance, which will create the so-called greenhouse effect, which will be discussed below.

The influence on atmospheric processes, especially on the thermal regime of the stratosphere, is also exerted by ozone. This gas serves as a natural absorber of solar ultraviolet radiation, and the absorption of solar radiation leads to air heating. The average monthly values ​​of the total ozone content in the atmosphere vary depending on the latitude of the area and the season within 0.23-0.52 cm (this is the thickness of the ozone layer at ground pressure and temperature). There is an increase in the ozone content from the equator to the poles and an annual variation with a minimum in autumn and a maximum in spring.

A characteristic property of the atmosphere can be called the fact that the content of the main gases (nitrogen, oxygen, argon) changes slightly with height: at an altitude of 65 km in the atmosphere, the content of nitrogen is 86%, oxygen - 19, argon - 0.91, at an altitude of 95 km - nitrogen 77, oxygen - 21.3, argon - 0.82%. The constancy of the composition of atmospheric air vertically and horizontally is maintained by its mixing.

In addition to gases, air contains water vapor And solid particles. The latter can have both natural and artificial (anthropogenic) origin. These are flower pollen, tiny salt crystals, road dust, aerosol impurities. When the sun's rays penetrate the window, they can be seen with the naked eye.

There are especially many particulate matter in the air of cities and large industrial centers, where emissions of harmful gases and their impurities formed during fuel combustion are added to aerosols.

The concentration of aerosols in the atmosphere determines the transparency of the air, which affects the solar radiation reaching the Earth's surface. The largest aerosols are condensation nuclei (from lat. condensatio- compaction, thickening) - contribute to the transformation of water vapor into water droplets.

The value of water vapor is determined primarily by the fact that it delays the long-wave thermal radiation of the earth's surface; represents the main link of large and small moisture cycles; raises the temperature of the air when the water beds condense.

The amount of water vapor in the atmosphere varies over time and space. Thus, the concentration of water vapor near the earth's surface ranges from 3% in the tropics to 2-10 (15)% in Antarctica.

The average content of water vapor in the vertical column of the atmosphere in temperate latitudes is about 1.6-1.7 cm (the layer of condensed water vapor will have such a thickness). Information about water vapor in different layers of the atmosphere is contradictory. It was assumed, for example, that in the altitude range from 20 to 30 km, the specific humidity strongly increases with height. However, subsequent measurements indicate a greater dryness of the stratosphere. Apparently, the specific humidity in the stratosphere depends little on height and amounts to 2–4 mg/kg.

The variability of water vapor content in the troposphere is determined by the interaction of evaporation, condensation, and horizontal transport. As a result of the condensation of water vapor, clouds form and precipitation occurs in the form of rain, hail and snow.

The processes of phase transitions of water proceed mainly in the troposphere, which is why clouds in the stratosphere (at altitudes of 20-30 km) and mesosphere (near the mesopause), called mother-of-pearl and silver, are observed relatively rarely, while tropospheric clouds often cover about 50% of the entire earth surfaces.

The amount of water vapor that can be contained in the air depends on the temperature of the air.

1 m 3 of air at a temperature of -20 ° C can contain no more than 1 g of water; at 0 °C - no more than 5 g; at +10 °С - no more than 9 g; at +30 °С - no more than 30 g of water.

Output: The higher the air temperature, the more water vapor it can contain.

Air can be rich And not saturated steam. So, if at a temperature of +30 ° C 1 m 3 of air contains 15 g of water vapor, the air is not saturated with water vapor; if 30 g - saturated.

Absolute humidity- this is the amount of water vapor contained in 1 m 3 of air. It is expressed in grams. For example, if they say "absolute humidity is 15", then this means that 1 mL contains 15 g of water vapor.

Relative humidity- this is the ratio (in percent) of the actual content of water vapor in 1 m 3 of air to the amount of water vapor that can be contained in 1 m L at a given temperature. For example, if the radio during the transmission of the weather report reported that the relative humidity is 70%, this means that the air contains 70% of the water vapor that it can hold at a given temperature.

The greater the relative humidity of the air, t. the closer the air is to saturation, the more likely it is to fall.

Always high (up to 90%) relative humidity is observed in the equatorial zone, since there is a high air temperature throughout the year and there is a large evaporation from the surface of the oceans. The same high relative humidity is in the polar regions, but only because at low temperatures even a small amount of water vapor makes the air saturated or close to saturation. In temperate latitudes, relative humidity varies seasonally - it is higher in winter and lower in summer.

The relative humidity of the air is especially low in deserts: 1 m 1 of air there contains two to three times less than the amount of water vapor possible at a given temperature.

To measure relative humidity, a hygrometer is used (from the Greek hygros - wet and metreco - I measure).

When cooled, saturated air cannot retain the same amount of water vapor in itself, it thickens (condenses), turning into droplets of fog. Fog can be observed in the summer on a clear cool night.

Clouds- this is the same fog, only it is formed not at the earth's surface, but at a certain height. As the air rises, it cools and the water vapor in it condenses. The resulting tiny droplets of water make up the clouds.

involved in the formation of clouds particulate matter suspended in the troposphere.

Clouds can have a different shape, which depends on the conditions of their formation (Table 14).

The lowest and heaviest clouds are stratus. They are located at an altitude of 2 km from the earth's surface. At an altitude of 2 to 8 km, more picturesque cumulus clouds can be observed. The highest and lightest are cirrus clouds. They are located at an altitude of 8 to 18 km above the earth's surface.

Atmospheric protection

The main sources are industrial enterprises and automobiles. In large cities, the problem of gas contamination of the main transport routes is very acute. That is why in many large cities of the world, including our country, environmental control of the toxicity of car exhaust gases has been introduced. According to experts, smoke and dust in the air can halve the flow of solar energy to the earth's surface, which will lead to a change in natural conditions.

1. On your own or with the help of a textbook, sign on the diagram which gaseous substances are part of the air.

Mark with pencils of different colors (of your choice) which gas living creatures absorb and emit when breathing.
Decipher the conventions you used:

2. According to the results of the research, fill in the table.

3. Use a schematic drawing to depict how air particles are arranged during heating and cooling. (Indicate air particles with circles.)

Wise Turtle and complete her tasks.

Air is the protector of the living

Herbaceous plants wintering under the snow do not freeze because there is a lot of air in it. Thanks to the air, cold snow serves as a warm “blanket” for plants.
By winter, the fur of animals becomes thicker, and that of birds - feathers. Between thick hairs, feathers linger more air, and the animal is warmer in winter.

1) These facts are explained by another property of the air, which we have not talked about yet. Think about what this property is. air is a poor conductor of heat.
2) Give an example proving that this property of air is important not only for plants and animals, but also for humans - there is air between the body and clothing of a person and in the clothing itself, so clothing retains the heat of our body

test yourself.

5. Think up and draw on a separate sheet the poster "Take care of the air!".
Look what your friends have drawn. If you have ideas how you can help protect the air, discuss them and do it.

6. On the instructions of the textbook, find out and write down what is being done in your city to protect the air.

In our city, to protect the air at enterprises, filters are installed on pipes, trees are planted in parks and forests. Also, new traffic interchanges are being built in the city to eliminate traffic jams.

Air has another interesting property - it does not conduct heat well. Many plants wintering under snow do not freeze, because there is a lot of air between the cold particles of snow and the snowdrift resembles a warm blanket covering the stems and roots of plants. In autumn, the squirrel, hare, wolf, fox and other animals molt. Winter fur is thicker and more luxuriant than summer fur. More air is trapped between thick hairs, and animals in a snowy forest are not afraid of frost.

(The teacher writes on the blackboard.)

Air does not conduct heat well.

So what are the properties of air?

V. Physical education

VI. Consolidation of the studied material Completion of tasks in the workbook

No. 1 (p. 18).

- Read the assignment. Look at the picture and sign on the diagram which gaseous substances are part of the air. (Self-test with the diagram in the textbook on p. 46.)

No. 2 (p. 19).

Read the assignment. Write down the properties of air. (After completing the task, a self-test is carried out with notes on the board.)

No. 3 (p. 19).

- Read the assignment. What properties of air must be taken into account in order to correctly complete the task? (Air expands when heated and contracts when cooled.)

How do you explain that air expands when heated? What happens to the particles that make it up? (The particles start to move faster and the gaps between them increase.)

Draw in the first rectangle how the air particles are arranged when heated.

How can you explain why air compresses when it cools? What happens to the particles that make it up? (Particles begin to move more slowly, and the gaps between them decrease.)

- Draw in the second rectangle how the air particles are arranged when cooled.

No. 4 (p. 19).

- Read the assignment. What property of air explains this phenomenon? (Air is a poor conductor of heat.)

VII. Reflection

Group work

Read the first task in the textbook on p. 48. Try to explain the properties of air.

Read the second task on p. 48. Do it.

What pollutes the air? (Industrial enterprises, transport.)

Conversation

There is a factory near my house. From my windows I can see a tall brick chimney. Thick black clouds of smoke pour out of it day and night, which is why the horizon is forever hidden behind a dense serous veil. Sometimes it seems that this is a heavy smoker fumigating the city with his inextinguishable Gulliver pipe. We all cough, sneeze, some even have to be put in the hospital. And for the “smoker”, at least something: know yourself puff and puff, puff and puff.

Children cry: nasty factory! Adults are angry: close immediately!

And in response everyone hears: how so "nasty" ?! How so to "close"?! Our factory produces goods for people. Unfortunately, there is no smoke without fire. We put out the flames of the furnaces - the factory will stop, there will be no goods.

One morning I woke up, looked out the window - no smoke! The giant stopped smoking, the factory is in place, the pipe is still sticking out, but there is no smoke. I wonder for how long? However, I see: it doesn’t smoke tomorrow, and the day after tomorrow, and the day after tomorrow ... Has the factory been closed at all?

Where did the smoke go? They themselves said that there is no smoke without fire.

It soon became clear: finally, our endless complaints were heard - they attached smoke eliminators to the factory chimney, a smoke trap that does not allow soot particles to fly out of the chimney.

And here's what's interesting. It would seem that no one needed and even harmful smoke was forced to do a good deed. It (or rather, soot) is now carefully collected here and sent to the plastics factory. Who knows, maybe this felt-tip pen of mine is just from the same soot caught by smoke detectors. In a word, the benefits of smoke detectors are for everyone: for us, the townspeople (we no longer get sick), and for the factory itself (it sells soot, and does not let it go to the wind, as before), and buyers of plastic products (including felt-tip pens).

List ways to keep the air clean. (Air purification units, electric vehicles.)

- To purify the air, people plant trees. Why? (Plants take in carbon dioxide and give off oxygen.)

Let's take a closer look at the leaf of the tree. The lower surface of the sheet is covered with a transparent film and dotted with very small holes. They are called "stomata", you can only see them well with a magnifying glass. They open and close to collect carbon dioxide. In the light of the sun, from the water that rises from the roots along the stems of plants, and carbon dioxide in green leaves, sugar, starch, and oxygen are formed.

Plants are called the "lungs of the planet" for a reason.

What wonderful air in the forest! It contains a lot of oxygen and nutrients. After all, trees emit special volatile substances - phytoncides that kill bacteria. The resinous smells of spruce and pine, the aroma of birch, oak, larch are very useful for humans. But in the cities the air is completely different. It smells of gasoline, exhaust fumes, because there are a lot of cars in cities, factories, plants that also pollute the air. It is harmful for a person to breathe such air. To purify the air, we plant trees, bushes: lindens, poplars, lilacs.

Goals:

• introduce the composition and properties of air, introduce the concept of "atmosphere";
• consolidate ideas about gaseous substances;
• to form the ability to formulate problematic questions;
• to cultivate a culture of communication, the ability to work in groups;

Lesson type: learning new material.

TSO: projector, screen, computer.

Equipment:

• equipment for experiments;
• presentation (Annex 1);
• textbook A.A. Pleshakova "The World Around Us", 3rd grade, part 1;
• workbook A.A. Pleshakov on the world around 1 part;
• plastic bags, syringes

During the classes

I. Organizational moment. Repetition of the material covered

– Good afternoon my nature lovers. Today we will continue with you to learn the mysteries of our surrounding world. The topic of the lesson, we will determine by guessing the crossword puzzle. (slide 1)

• Substance Science (Chemistry)
• It can be used to detect starch (iodine)
• Citric, formic, oxalic, lactic ... (acid)
• Acid used to make canned food (vinegar)
• A vegetable from which sugar is obtained (beets)
• A type of sugar (glucose)

II. Lesson topic message

(slide 2) Theme of the lesson "Air and its protection"

(slide 3) What do you know about air?

- What do you want to know?

III. Work on the topic of the lesson

1. What is air.

Air is "invisible". We do not see it, but we know that it is all around us. We can see the movement of air when we blow soap bubbles, or fan ourselves with a fan. We can easily verify the reality of the existence of air by doing simple experiments:

1. Fill a plastic bag with air, tie it up, and try to squeeze it gently.
   - Does it compress easily?

1. Fill a small syringe without a needle with air. Pinch the inlet with your finger. Try moving the piston.
   Can you compress air?
   What happens when you release your finger?

(slide 4) The entire planet Earth is shrouded in an invisible transparent veil - air. Air is everywhere - on the street, in the room, in the ground, in the water. Any free space on Earth is filled with air. Air is invisible, but it can be detected with our senses, as we have just done.

Wind is the movement of air. The layer of air that surrounds us and our planet is called atmosphere. (slide 5). The atmosphere is a giant shell of air that stretches upwards for hundreds of kilometers. The thickness of the atmosphere in different parts of the planet is not the same.

The air envelope of the Earth is often called the Fifth Ocean. Does the Earth really need a Fifth Ocean?

- People, plants and animals live at the bottom of the air ocean. Without air, emptiness and silence would reign eternally on the globe. If the Earth were to lose air, it would, like the Moon, be only a lifeless celestial body.

(student reading the poem "Air")

Air
He is a transparent invisible
Light and colorless gas.
Weightless scarf
He envelops us.
He is in the forest - thick, fragrant,
Like a healing potion
It smells of resinous freshness,
Smells like oak and pine.
In summer it is warm
Blows cold in winter
When frost paints glass
And lies on them with a border.
We don't notice it
We don't talk about him.
We just breathe it in
After all, we need it.

This poem talks about the composition of air and some of its properties.

2. Composition and properties of air

– So what is air? It is a gas, or rather, a mixture of gases (slide 6). Just 2 centuries ago, scientists learned that air is a mixture of many gases, mainly nitrogen - 78%, oxygen - 21% and carbon dioxide - 1%.

– Open workbook p.18 and restore the diagram (slide 7), writing down what gaseous substances are part of the air? Underline the name of the gas that living beings absorb when they breathe.

What are the properties of air? (slide 8)

We know that air is everywhere - on the street, in the room, in the ground, in the water.
- Raise the notebook, do you see other objects through it?
- Not.
Can we see the next class through the wall?
- Not.
- Do you see the objects that are in the classroom?
- Yes.
What property of air is this talking about?
The air is transparent. This is evidenced by the fact that we see through it all the surrounding objects.

- Look at indoor plants. What color are they?
- Green.
What color is the school desk?
- Brown.
- What color is the air?
- He colorless.
– That's right, this is another physical property of air.

Have you noticed that different rooms smell differently?
- In the canteen, hairdresser, pharmacy, particles of odorous substances mix with air particles, and we feel different smells. Does clean air smell?
- Clean air does not smell.
The air is odorless.

1. Now we will do an experiment to find out one more property of air. To verify this, you can do experiments:

   Experience 1
   – Take a flask with a tube. Let's put the pipe in the water. Note that water does not enter the tube - it is "not allowed" by air. Let's heat the flask.
   What's happening?
   - Air bubbles began to come out of the tube.
   Why did this become possible?
   This experiment shows that air expands when heated.

   Experience 2
   -Put a cold damp cloth on the flask. Why am I doing this? What do we see?
   We see water rising up the tube. Air, as it were, gives way to water part of its place. This is because the air contracts as it cools.

   Air expands when heated and contracts when cooled.

2. Air is a poor conductor of heat.

   Air has another interesting property - it is a poor conductor of heat. Many plants wintering under snow do not freeze because there is a lot of air between the cold particles of snow, and the snowdrift resembles a warm blanket covering the stems and roots of plants.

   - In autumn, the squirrel, hare, wolf, fox and other animals molt. Winter fur is thicker and more luxuriant than summer fur. More air is trapped between thick hairs, and animals in a snowy forest are not afraid of frost.

   - The gray wolf has a large, fluffy tail. When the animal goes to bed right on the snow, he covers his nose and paws with his magnificent tail.

   - And the fox in the most severe frosts is not cold in a snowy bed, because it takes cover, like a warm blanket, with its tail, between the long hairs of which there is a lot of air that does not let the cold through.

   - And in winter, thick, dense hair grows on the paws of a red-haired beauty, it seems as if the fox put on warm mittens. She is not afraid to walk on snow and ice.

   – Vole mice hide in burrows under high snowdrifts, where it is warm and cozy.

   - And some birds - black grouse, capercaillie - in the most severe frosts burrow into deep snow. So warmer. There is even a poem about it:

   January is blowing cold
   Hazel grouse, black grouse, capercaillie
   Buried deep in the snow.
   He warms them like fur.

   What property of air explains these facts? (air is a poor conductor of heat)

Physical education minute

We'll get some rest
Let's get up and take a deep breath.
Hands to the sides, forward.
At the edge of the bunny is waiting.
Bunny jumped under a bush,
Inviting us into your home.
Hands down, on the belt, up,
We run away from everyone.
Let's run to class.
Let's listen to the story.

Questions Why?(slide 9)

1. Why do birds sit ruffled in extreme cold?
2. Why are double-glazed windows installed in houses for the winter?
3. How do you understand the expression: “The air must be clean!”

The air should contain more oxygen and less carbon dioxide. When we breathe, we take in oxygen and release carbon dioxide. 600 liters of oxygen is necessary for a person to breathe for only one day! Plants, on the other hand, take in carbon dioxide and release oxygen into the atmosphere. No wonder plants are called the lungs of our planet. What wonderful air in the forest! It contains a lot of oxygen and nutrients. After all, trees emit special volatile substances - phytoncides, which kill bacteria. The resinous smells of spruce and pine, the aroma of oak, birch and larch are very useful for humans.

But in cities, the air is completely different, polluted. Can you explain to me with what or with whom this is connected?

Sources of pollution: (slide 10)

• factories and factories emit poisonous gases, soot, dust,
• cars emit exhaust gases, which contain a lot of harmful substances,
• fires, volcanic eruptions,
• pollution of the earth with unprocessed garbage.

Air pollution threatens human health, all life on Earth!

What should people do to keep the air clean? Using the text of the textbook on p.47, find ways to solve this problem. (slide 11)

IV. Consolidation of the studied material

Air test. His guard"(slide 13,14)

1. What substances are in the air?

   A. hydrogen, copper, zinc
   B. oxygen, nitrogen, carbon dioxide
   B. chlorine, fluorine, iodine

2. What air gas is needed for breathing?

   A. nitrogen
   B. oxygen
   B. carbon dioxide

3. What properties does air have?

   A. Clear, colorless, odorless, when heated expands and contracts when cooled conducts heat
   B. Blue, like the sky, conducts sounds, passes the sun's rays, has no smell

4. Windows are double-glazed to keep warm. What property is being used?

   A. Air expands when heated
   B. Air compresses when cooled
   B. Air does not conduct heat well

5. How should the air be protected from pollution?

   A. Stop all factories and factories, stop logging. Prohibit the use of vehicles. Turn the Earth into one huge nature reserve.
   B. Factories and factories should have traps for dust and harmful substances. Transport must be made environmentally friendly. In cities and around them to create belts of gardens, parks and forests.

Answer:(slide 15,16)1. C, 2. C, 3. A, 4. C, 5. B

He is a transparent invisible
Light and colorless gas.
Weightless scarf
He envelops us.
We don't notice it
We don't talk about him.
We just breathe it in
After all, we need it.

(slide 18) For the health of people, all life on Earth, we need clean air. After all, only clean air gives LIFE!

(slide 19)Homework: pp. 44-47, read, answer questions, workbook p. 20 No. 5.

Young children often ask their parents what air is and what it usually consists of. But not every adult can answer correctly. Of course, everyone studied the structure of air at school in nature studies, but over the years this knowledge could be forgotten. Let's try to fill them up.

What is Air?

Air is a unique "substance". You can't see it, touch it, it's tasteless. That is why it is so difficult to give a clear definition of what it is. Usually they just say - air is what we breathe. It is all around us, although we do not notice it at all. You can feel it only when a strong wind blows or an unpleasant smell appears.

What happens if the air disappears? Without it, not a single living organism can live and work, which means that all people and animals will die. It is not bypassed for the process of respiration. What matters is how clean and wholesome the air everyone breathes is.

Where can you find fresh air?

The most useful air is located:

• In forests, especially pine.
• In the mountains.
• Near the sea.

The air in these places has a pleasant aroma and has beneficial properties for the body. This explains why children's health camps and various sanatoriums are located near forests, in the mountains or on the sea coast.

You can enjoy fresh air only away from the city. For this reason, many people buy summer cottages outside the village. Some move to a temporary or permanent place of residence in the village, build houses there. This is especially true for families with small children. People are leaving because the air in the city is heavily polluted.

Fresh air pollution problem

In the modern world, the problem of environmental pollution is especially relevant. The work of modern factories, enterprises, nuclear power plants, cars has a negative impact on nature. They emit harmful substances into the atmosphere that pollute the atmosphere. Therefore, very often people in urban areas experience a lack of fresh air, which is very dangerous.

A serious problem is heavy air inside a poorly ventilated room, especially if there are computers and other equipment in it. Being present in such a place, a person can begin to suffocate from a lack of air, he has pain in his head, weakness occurs.

According to statistics compiled by the World Health Organization, about 7 million human deaths per year are associated with the absorption of polluted air in the street and indoors.

Harmful air is considered one of the main causes of such a terrible disease as cancer. So say organizations involved in the study of cancer.

Therefore, it is necessary to take preventive measures.

How to get fresh air?

A person will be healthy if he can breathe fresh air every day. If it is not possible to move out of town due to important work, lack of money or for other reasons, then it is necessary to look for a way out of the situation on the spot. In order for the body to receive the necessary norm of fresh air, the following rules should be followed:

1. To be on the street more often, for example, to walk in the evenings in parks, gardens.
2. Go for a walk in the woods on weekends.
3. Constantly ventilate living and working areas.
4. Plant more green plants, especially in offices where there are computers.
5. It is advisable to visit resorts located on the sea or in the mountains once a year.

What gases does air consist of?

Every day, every second, people breathe in and out, completely without thinking about the air. People do not react to him in any way, despite the fact that he surrounds them everywhere. Despite its weightlessness and invisibility to the human eye, the air has a rather complex structure. It includes the interrelationship of several gases:

• Nitrogen.
• Oxygen.
• Argon.
• Carbon dioxide.
• Neon.
• Methane.
• Helium.
• Krypton.
• Hydrogen.
• Xenon.

The main part of the air is nitrogen , the mass fraction of which is 78 percent. 21 percent of the total is oxygen, the most essential gas for human life. The remaining percentages are occupied by other gases and water vapor, from which clouds are formed.

The question may arise, why is there so little oxygen, just a little more than 20%? This gas is reactive. Therefore, with an increase in its share in the atmosphere, the likelihood of fires in the world will increase significantly.

What is the air we breathe made of?

The two main gases that make up the basis of the air we breathe every day are:

• Oxygen.
• Carbon dioxide.

We inhale oxygen, we exhale carbon dioxide. Every student knows this information. But where does oxygen come from? The main source of oxygen production is green plants. They are also consumers of carbon dioxide.

The world is interesting. In all ongoing life processes, the rule of maintaining balance is observed. If something has gone from somewhere, then something has come somewhere. So it is with air. Green spaces produce the oxygen that humanity needs to breathe. Humans take in oxygen and give off carbon dioxide, which in turn is used by plants. Thanks to this system of interaction, life exists on planet Earth.

Knowing what the air we breathe consists of, and how much it is polluted in modern times, it is necessary to protect the flora of the planet and do everything possible to increase the representatives of green plants.

Video about the composition of air