1. Indicate what refers to the concept of “physical body” and what to the concept...
Air and its protection
Air is a mixture of gases. The composition of air includes: oxygen, nitrogen, carbon dioxide. Most of the air contains nitrogen.
Properties of air
1. The air is transparent
2. Air is colorless
3. Clean air has no odor
What happens to air when it is heated and cooled?
When heated, air expands.
As air cools, it compresses.
Why does air expand when heated and contract when cooled?
Air is made up of particles with spaces between them. Particles are constantly moving and often collide. When the air heats up, they begin to move faster and collide harder. Because of this, they bounce greater distances from each other. The gaps between them increase and the air expands. When the air cools, the opposite happens.
Guess a riddle.
Passes through the nose into the chest
And the return is on its way.
He's invisible and yet
We cannot live without him.
Answer: Air
Write down the answer. What do we breathe?
Answer: We breathe air
Look at the pictures. Where will the air be the cleanest? Fill in the circle under this picture.
Write down the properties of clean air.
The air is transparent, it has no color and no smell.
The air can keep you warm.
Clothing doesn't keep you warm on its own, but because it prevents your body from losing heat. Clothing is a good air trap. Your body heat cannot penetrate through the trapped one, as it is an insulator. Thick winter clothing also traps a lot of air. Woolen clothing is very warm because a lot of air is trapped between the wool. Birds in winter try to ruffle their feathers in order to absorb as much air as possible between their feathers. The air between the double panes also serves as thermal insulation. Snow is a good insulator because it traps air. Travelers caught in a snowstorm dig shelters in the snow to keep warm.
Answer the questions.
What is between the glass windows? Answer: Air
Under which snow are plants warmer: fluffy or trampled? Answer: Plants are warmer under fluffy snow.
Humans and other living beings need clean air to breathe. But in many places, especially in big cities, it is polluted. Some factories and factories emit toxic gases, soot, and dust from their chimneys. Cars emit exhaust gases, which contain a lot of harmful substances.
Air pollution threatens human health and all life on Earth!
Nowadays, many industries have established control over the level of toxic substances. Thanks to these measures, the air remains sufficiently clean and safe for life. Today, factories are built as far from the city as possible. Scientists are helping industry find solutions to air pollution. For example, they developed an exhaust pipe for cars that effectively filters exhaust gases. They created new cars - electric cars that will not pollute the air.
Special stations have been created in different places, they monitor the cleanliness of the air in large cities, measuring the cleanliness of the air daily, they provide information and monitor the situation.
Goals:
- introduce the composition and properties of air, introduce the concept of “atmosphere”;
- consolidate ideas about gaseous substances;
- develop the ability to pose problematic questions;
- cultivate a culture of communication, the ability to work in groups;
Lesson type: learning new material.
TCO: projector, screen, computer.
Equipment:
- equipment for conducting experiments;
- presentation (Appendix 1);
- textbook A.A. Pleshakova “The World Around Us”, grade 3, part 1;
- workbook A.A. Pleshakov on the world around us, part 1;
- plastic bags, syringes
During the classes
I. Organizational moment. Repetition of covered material
– Good afternoon my nature lovers. Today we will continue to learn the mysteries of our surrounding world. We will determine the topic of the lesson by solving a crossword puzzle. (slide 1)
- Science of substances (chemistry)
- It can be used to detect starch (iodine)
- Citric, formic, oxalic, lactic... (acid)
- Acid used to make canned food (vinegar)
- Vegetable from which sugar is obtained (beets)
- Type of sugar (glucose)
II. Lesson topic message
(slide 2) Lesson topic “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 don't see it, but we know that it is all around us. We can see air movement when we blow bubbles or fan ourselves. We can easily verify the reality of the existence of air by performing simple experiments:
- Fill a plastic bag with air, tie it, and try to squeeze it gently.
– Does it shrink easily?
- Fill a small syringe without a needle with air. Pinch the inlet hole with your finger. Try moving the piston.
– Is it possible to compress air?
– What happens if you let go of your finger?
(slide 4) The entire planet Earth is shrouded in an invisible transparent blanket - 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 using our senses, which is what we did now.
Wind is the movement of air. The layer of air surrounding us and our planet is called atmosphere. (slide 5). The atmosphere is a gigantic shell of air that extends upward for hundreds of kilometers. The thickness of the atmosphere varies in different parts of the planet.
The Earth's air envelope is often called the Fifth Ocean. Is the Fifth Ocean really necessary for the Earth?
– People, plants and animals live at the bottom of the air ocean. Without air, emptiness and silence would reign forever on the globe. If the Earth lost its air, it, like the Moon, would be only a lifeless celestial body.
(student reading the poem “Air”)
Air
He is transparent and invisible
Light and colorless gas.
With a weightless scarf
It envelops us.
He is in the forest - thick, fragrant,
Like a healing infusion,
Smells of resinous freshness,
Smells of oak and pine.
In summer it is warm,
It blows cold in winter,
When frost paints the glass
And lies on them like a border.
We don't notice him
We don't talk about him
We just breathe it in -
After all, we need him.
– This poem talks about the composition of air and some of its properties.
2. Composition and properties of air
– So what is air? This 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 the workbook page 18 and restore the diagram (slide 7), writing down what gaseous substances are included in the air? Underline the name of the gas that living beings absorb when breathing.
– What properties does air have? (slide 8)
- Now we will do an experiment to find out another property of air. To verify this, you can do the following experiments:
Experience 1
– Let's take a flask with a tube. Let's put the tube in the water. Note that water does not enter the tube - air “does not let it in.” We will heat the flask.
What's happening?
– Air bubbles began to come out of the tube.
Why was this possible?
– This experiment shows that air expands when heated.Experience 2
–Place a cold, damp cloth on the flask. Why am I doing this? What do we see?
– We see the water rising through the tube. The air seems to give up some of its space to the water. This happens because air compresses as it cools.When heated, air expands and when cooled, it contracts.
- Air is a poor conductor of heat.
Air has another interesting property - it conducts heat poorly. Many plants that overwinter under snow do not freeze because there is a lot of air between the cold snow particles, 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 retained between the thick hairs, and animals in the snowy forest are not afraid of frost.
– The gray wolf has a large, fluffy tail. When the animal goes to sleep right in the snow, it covers its nose and paws with its bushy tail.
“And even in the most severe frosts, a fox is not cold in a snowy bed, because she covers herself, like a warm blanket, with her tail, between the long hairs of which there is a lot of air that does not allow the cold to pass through.
“And in winter, thick, thick fur grows on the red beauty’s paws, it seems as if the fox was wearing warm mittens.” She is not afraid to walk on snow and ice.
– Vole mice hide in holes under high snowdrifts, it’s warm and cozy there.
- And some birds - black grouse, capercaillie - burrow into deep snow in the bitterest frosts. It's warmer this way. There is even a poem about this:
January is blowing cold,
Hazel grouse, black grouse, capercaillie
Buried deep in the snow.
It warms them like fur.What property of air explains these facts? (air is a poor conductor of heat)
We know that air is everywhere - on the street, in the room, in the ground, in the water.
– Raise the notebook, can you see other objects through it?
- No.
– Can we see the next class through the wall?
- No.
– Do you see the objects that are in the classroom?
- Yes.
– What property of air does this indicate?
The air is clear. This is evidenced by the fact that we see all surrounding objects through it.
– Look at the 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 smell different odors. Does the air smell clean?
– Clean air does not smell.
The air has no smell.
Physical education minute
We'll rest a little
Let's stand up and take a deep breath.
Hands to the sides, forward.
The bunny is waiting at the edge of the forest.
The bunny was jumping under the bush,
Inviting us into your home.
Hands down, on the waist, up,
We are running away from everyone.
Let's quickly run to class.
We'll listen to the story there.
Questions Why?(slide 9)
- Why do birds sit ruffled in extreme cold?
- Why do houses have double glazing for the winter?
- How do you understand the expression: “The air must be clean!”
– There should be more oxygen and less carbon dioxide in the air. When we breathe, we absorb oxygen and release carbon dioxide. A person needs 600 liters of oxygen to breathe for just one day! But plants, on the contrary, absorb carbon dioxide in the light and release oxygen into the atmosphere. It’s not for nothing that 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 beneficial for humans.
But in cities the air is completely different, polluted. Can you explain to me what or who this is connected with?
Sources of pollution: (slide 10)
- factories and factories emit poisonous gases, soot, dust from their chimneys,
- cars emit exhaust gases, which contain a lot of harmful substances,
- fires, volcanic eruptions,
- land pollution with unprocessed waste.
Air pollution threatens human health and all life on Earth!
What should people do to keep the air clean? Using the textbook text on page 47, find ways to solve this problem. (slide 11)
IV. Reinforcing the material learned
Test “Air. His security"(slide 13,14)
- What substances make up air?
A. hydrogen, copper, zinc
B. oxygen, nitrogen, carbon dioxide
B. chlorine, fluorine, iodine - What air gas is needed for breathing?
A. nitrogen
B. oxygen
B. carbon dioxide - What properties does air have?
A. Transparent, colorless, odorless, when heated expands and contracts when cooled, bad conducts heat
V. Blue, like the sky, conducts sounds, allows sunlight to pass through and is odorless - Double frames are installed in the windows to retain heat. What property is being used?
A. When heated, air expands
B. When air cools, it compresses.
B. Air is a poor conductor of heat. - How should we protect air from pollution?
A. Stop all factories and factories, stop logging. Prohibit the use of motor vehicles. Turn the Earth into one huge reserve.
B. Factories and factories must have dust and harmful substance traps. Transport must be made environmentally friendly. Create belts of gardens, parks and forests in and around cities.
Answer:(slide 15,16)1. B, 2. B, 3. A, 4. B, 5. B
He is transparent and invisible
Light and colorless gas.
With a weightless scarf
It envelops us.
We don't notice him
We don't talk about him
We just breathe it in -
After all, we need him.
(slide 18) For the health of people and 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.
1. On your own or with the help of a textbook, label on the diagram what gaseous substances are included in the air.
Mark with pencils of different colors (of your choice) which gas living beings absorb and which they emit when breathing.
Decipher the symbols you used:
2. Based on the research results, fill out the table.
3. Use a schematic diagram to show how air particles arrange themselves when heated and cooled. (Denote air particles with circles.) 
Wise Turtle and complete her tasks.
Air is the protector of living things
Herbaceous plants overwintering under 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, animals' fur becomes thicker, and birds' feathers become thicker. More air is retained between thick hairs and feathers, and the animal is warmer in winter.
1) These facts are explained by another property of air, which we have not yet talked about. Think about what this property is - air does not conduct heat well.
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 a person’s clothes and in the clothes themselves, so clothes retain the heat of our body
check yourself.
5. Come up with and draw a poster “Take care of the air!” on a separate sheet of paper.
Look what your friends have drawn. If you have ideas on how you can help protect the air, discuss them and do it.
6. According to the instructions in 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, enterprises install filters on pipes, and trees are planted in parks and forests. New transport interchanges are also being built in the city to eliminate traffic jams.
LESSON SUMMARY ON THE ENVIRONMENT
FOR 3rd CLASS.
Educational and educational complex "School of Russia"
Subject: Air and its protection.
The purpose of the lesson:
To introduce students to the composition and properties of air.
Tasks:
- educational:
to develop knowledge about the importance of air for all living things
Earth;
in the process of experiments and practical work to form knowledge
about the basic properties of air;
develop practical skills to work with laboratory materials
equipment, conduct experiments, conduct observations;
analyze, summarize and draw conclusions based on the results of observation
Denium;
learn to work with a hypothesis (assumption throughactive method
and practical approach).
Educational:
create conditions for the student’s personal development; revitalization
independent activity and group work; development method-
ability to constructive creativity, observation, ability to compare
draw conclusions;
- educational:
create conditions for instilling respect for the environment
environment;
create conditions for developing a communicative culture, skills
work in groups, listen to and respect the opinions of others;
feelings of mutual assistance and support.
Equipment: for students: textbook “The world around us, grade 3” by A.A. Ple-
Shakova; workbook; magnifying glass, wood leaf
from the teacher: textbook, workbook, presentation, electronic supplement
textbook; plastic bag, laboratory equipment: flask, alcohol lamp,
cloth for experiment, magnifying glass, leaf of wood, computer, presentation, multimedia
new projector, screen.
DURING THE CLASSES.
I. Organizational moment (2 min)
Checking seating and readiness for class.
Today in class you will work in groups. What rules of working in a group must be remembered and followed?
(Work to the best of your ability; listen to everyone
each group member attentively, without interrupting;
speak clearly and to the point; support your comrades;
if you don't agree with someone, say it politely,
choose as captain the one who can choose
the best solution together with everyone; remember: perform
It’s an honor to die on behalf of the group)
II. Updating knowledge. Checking homework. (4 min)
Target: consolidation of knowledge acquired in previous lessons
( Presentation ):
Summary of the stage.
III. Self-determination for activity. (1 min)
Guess the riddle:
Passes through the nose into the chest
And the return is on its way.
He's invisible, but still
We cannot live without him.
(Air)
How did you guess?
(We breathe air, we cannot live without it,
but we don’t see it)
What do you think will be discussed in class today?
(About air, its composition and properties)
IV. Work on the topic of the lesson (20 min)
Conversation
There are 5 oceans on our planet. What are their names?
(Arctic, Pacific, Atlantic, Indian and Southern)- There is another very important ocean in the world - the largest, and every day, every hour, every minute, without noticing it, we “swim” in it. What is the name of this ocean? (Air)
The ocean of air has its own scientific name. Our students will tell you more about this...
Student performance . Pre-prepared students make a presentation.
Target: working with educational, popular science texts accessible to primary schoolchildren, correct and conscious reading aloud. Construction of a monologue statement on a proposed topic, on a given question .
The layer of air surrounding our planet is called the atmosphere.
The atmosphere is a gigantic shell of air that extends upward for hundreds of kilometers. The thickness of the atmosphere varies in different parts of the planet.
The atmosphere protects the earth from excess heat and cold, and from excessive solar radiation. If it suddenly disappeared, then water and other liquids on Earth would instantly boil, and the rays of the sun would burn all living things.
The ocean of air - the atmosphere - is very important for life.
Can living things survive without air? (No)
Why? (You could suffocate and die)
Indeed, if you take a deep breath, cover your mouth and nose with your palm and count to yourself: one, two, three... Before you can count to 60, you will really want to take a breath of fresh air.
When a person goes underwater, climbs high into the mountains or flies into space, he should always have a supply of air with him.
If the ocean of air suddenly disappeared, our planet would become a lifeless planet in a few minutes.
Why is the air ocean so important? (Children's answers)
The air shell of the Earth is its amazing “shirt”. Thanks to it, the planet does not overheat from the sun's rays and does not freeze from the cosmic cold. This “shirt” protects the Earth from meteorite impacts. They simply burn in the air. So the Earth simply needs an air “jacket,” and only thanks to it does intelligent life exist on Earth, the only planet in the Solar System.
Is it possible to verify that air exists? What do you think?
(Children's answers)
It is very easy to verify that air really exists. Try waving your hand. What do you feel?
(Air movement)
I have an empty plastic bag in my hands. I'll wave it and pinch the ends. Why did the bag inflate and become elastic?
(There's air there)
What is the significance of air for humans, plants and animals?
(Air is necessary for breathing, protects the Earth from
overheating and cooling, from meteorites, from
harmful rays of the sun).
Well done!
Physical education minute (1 min)
We'll rest a little
Let's stand up and take a deep breath.
Hands to the sides, forward.
The bunny is waiting at the edge of the forest.
The bunny was jumping under the bush,
Inviting us into your home.
Hands down, on the waist, up,
We are running away from everyone.
(Running in place.)
Let's quickly run to class,
We'll listen to the story there.
Checking the fit.
Practical work “composition and properties of air”. Work in a notebook (pp. 27-29)
Target: teach children to observe, hypothesize, analyze and draw conclusions based on practical actions.
Read the poem. What can you learn about air from it?
(Air is a mixture of gases)
Open the textbook on page 46. Consider the “Composition of Air” diagram.
What gases are included in air?
(Oxygen, nitrogen and carbon dioxide)
What gas is in the air the most? (Nitrogen)
What gas is the least in the air? (Carbon dioxide).
People learned what composition air has only 200 years ago. Joseph Priestley and Antoine Lavoisier were the first to study the composition of air and its properties.
When living things breathe, they absorb oxygen from the air and release carbon dioxide.
Working in pairs
Cover your textbooks.
Open your notebooks on page 27 and complete task No. 1 yourself.
(On your own or with the help of a textbook, sign up for
diagram, which gaseous substances are included in the air
spirit. Mark with pencils of different colors (according to your preference)
boron), what gas living beings absorb when breathing,
and which one is highlighted. Decipher the devices you used
catchy designations).
Exchange notebooks and check each other's work. Draw a conclusion, evaluate the work.
Return the notebooks to each other. Test yourself using the textbook. Correct the mistakes. Evaluate your work. Select the desired icon:
Bottom line . – Who completed the task without errors?
Well done.
Who experienced difficulties during the task?
Correct your mistakes and pay more attention in class.
Guys, what properties does air have?
(The air is elastic, ... (children’s assumptions)
Let's do some experiments and see if you're right.
During practical work we will complete task No. 2 in the notebook.
Look at the table and tell me what questions we should answer as a result of our observations?
(Fill out the table based on the research results.
Properties of air
What we study
Conclusion
Is the air transparent or opaque?
Does air have color?
Does the air have a smell?
What happens to air when heated?
What happens to air when it cools?
- How do you think the first question should be answered? (children's answers)
What will help us prove this? (children's hypotheses).
- Guys, take the textbook, tell me, is it transparent?
Look at the door, is it transparent? Are others visible through these objects?
Why do we see a door, a textbook, a blackboard, a desk? Discuss and give your guesses.
( The air is transparent)
- Record the output in a table. (The air is clear)
What's the next question? (Does air have color?)
How can you answer this question? How to prove this?
(Children's statements)
(If the children find it difficult, the teacher prompts them)
- What color is the board? (Green)
What color is the cabinet? (Brown)
What color is chalk? (White)
What color is the air? (Has no color )
Record your findings in a table. (Air has no color).
Read the third question.
(Does the air have a smell?)
What can you guess? What evidence can we use?
(Children's statements)
(If the children find it difficult, the teacher prompts them)
Guys, raise your hand, which one of you wasin a hair salon, in a cafeteria, in a clinic? Imagine being asked to find out where you are with your eyes closed? Is it possible? How? Discuss and give your guesses.
( We can determine where we might be by smell. We know that odorous particles mix with air particles. Thanks to this, we smell. But clean air has no smell.)
Record the output in a table. (The air has no smell)
- WhatWhat happens to air when it is heated and cooled? We will find out this through experiments.
Experience No. 1.
Target: find out what happens to air when heated.
Let's take a flask with a tube. Let's put the tube in the water. What are we seeing?
(Water does not enter the tube; air does not let it in).
We will heat the flask. What happens now?
(Air bubbles began to come out of the tube.)
( Air expands when heated ) - entry in a notebook).
Experience No. 2.
Target: find out what happens to air when it cools.
Place a cold, damp cloth on the flask. What are we seeing?
(The water rises in the tube. The air seems to give way
water part of its place)
What conclusion can be drawn based on the observations?
( When air cools, it compresses) notebook entry)
Air has another interesting property. In order to find out, let’s complete task No. 4 on page 28 in the workbook.
Read the story of the Wise Turtle and complete her tasks.
(One of the students reads the story aloud)
Think about what property of air is described in the story?
(Children's guesses)
Let's check ourselves. Read the text in the “Test yourself” section.
Well done!
So, what properties does air have?
(The air is transparent, colorless, odorless, when
When heated it expands and when cooled it contracts.
elastic, conducts heat poorly)
Well done!
V. Physical education minute (1 min)
To become strong and agile
Let's start training.
Inhale through your nose and exhale through your mouth.
Let's breathe deeply, and then
Step in place, slowly,
How nice the weather is!
We checked your posture
And they pulled their shoulder blades together.
We walk on our toes
And now - on the heels.
Checking the fit.
VI. Consolidation of the studied material. Work in a notebook (5 min)
Target: consolidate acquired knowledge
Read task No. 3 on page 28 in your notebook.
(Use a schematic diagram to show how the
relies on air particles for heating and cooling)
What properties of air must be taken into account in order to complete the task correctly?
(When heated, air expands, and when cooled,
Denia is shrinking)
How to explain that air expands when heated? What happens to the particles that make it up?
(The particles begin to move faster, and between
ki between them increases)
In the first rectangle, draw how air particles are arranged when heated.
How to explain that air compresses when cooled? What happens to the particles that make it up?
(The particles begin to move more slowly, between
the horrors between them are decreasing)
Draw in the second rectangle how air particles are arranged as they cool.
(After completing the task, a self-test is carried out on the slide:
VII. Reflection (4 min)
Group work
Read the second task on p.48. Complete it.
(Read the text “The air must be clean.” Find information in it: About the sources of air pollution; about ways to protect air purity.)
What pollutes the air?
(Plants and factories, cars)
What methods of air protection do you know?
(Installation for collecting soot, dust,
toxic gases, electric vehicles)
Conversation (5 min)
There is a factory in the city. Clouds of smoke poured out of its chimney day and night. Residents of the city coughed, sneezed, and some were even admitted to the hospital. They even wanted to close the factory, but how could they manage without goods?
One day, smoke stopped pouring out of the factory chimney. It soon became clear that smoke eliminators had been attached to the pipe, which prevented soot particles from flying out of the pipe.
And here's what's interesting. The soot is now carefully collected and sent to a plastics factory, where various plastic things are made.
In a word, everyone benefits from the smoke trap - both city residents, the factory (it sells soot), and plastic manufacturers.
Name ways to protect air purity.
(Air purification units, electric vehicles)
Can you somehow influence the cleanliness of the air?
(You can plant plants, they purify the air)
Why do plants absorb carbon dioxide and release oxygen?
(Children's guesses)
Let's take a close look at the leaf of the tree. The lower surface of the sheet is covered with a transparent film and dotted with small holes. They are called "stomata". They open and close, collecting carbon dioxide. In the light of the sun, sugar, starch and oxygen are formed from water that rises from the roots along the stems of plants and carbon dioxide in green leaves. That’s why plants are called “the lungs of the planet.”
VIII. Summing up the lesson. (2 minutes)
What is air? (Mixture of gases - nitrogen, oxygen and carbon dioxide)
Name the properties of air.
(The air is transparent, colorless, odorless, elastic,
expands when heated, contracts when cooled,
conducts heat poorly)
What new did you learn in the lesson?
IX. Homework (1 min)
Workbook: No. 5 (p. 29)
Air is in us and around us; it is an indispensable condition for life on Earth. Knowledge of the properties of air helps a person to successfully use them in everyday life, farming, construction and much more. In this lesson we will continue to study the properties of air, conduct many exciting experiments, and learn about the amazing inventions of mankind.
Topic: Inanimate nature
Lesson: Properties of Air
Let us repeat the properties of air that we learned about in previous lessons: air is transparent, colorless, odorless, and does not conduct heat well.
On a hot day, window glass is cool to the touch, and the window sill and objects standing on it are warm. This happens because glass is a transparent body that allows heat to pass through, but does not heat up itself. The air is also transparent, so it allows the sun's rays to pass through well.
Rice. 1. Window glass conducts the sun's rays ()
Let's carry out a simple experiment: lower a glass turned upside down into a wide vessel filled with water. We will feel a slight resistance and see that the water cannot fill the glass, because the air in the glass does not “give” its place to the water. If you tilt the glass slightly without removing it from the water, an air bubble will come out of the glass and some of the water will enter the glass, but even in this position of the glass, the water will not be able to fill it completely.
Rice. 2. Air bubbles come out of the tilted glass, giving way to water ()
This happens because air, like any other body, occupies space in the surrounding world.
Using this property of air, man learned to work underwater without a special suit. For this purpose, a diving bell was created: people and the necessary equipment stand under the bell-cap, made of transparent material, and the bell is lowered under the water using a crane.
The air under the dome allows people to breathe for a while, long enough to inspect the damage to a ship, bridge supports or the bottom of a reservoir.
To prove the following property of air, you need to tightly cover the hole of the bicycle pump with your left hand and press the piston with your right hand.
Then, without removing your finger from the hole, release the piston. The finger with which the hole is closed feels that the air is pressing very hard on it. But the piston will move with difficulty. This means that air can be compressed. Air has elasticity because when we release the piston, it returns to its original position.
Elastic bodies are those that, after compression stops, return to their original shape. For example, if you compress a spring and then release it, it will return to its original shape.
Compressed air is also elastic; it tends to expand and take its original place.
In order to prove that air has mass, you need to make a homemade scale. Attach the deflated balloons to the ends of the stick using tape. Place the long stick in the middle of the short one, so that the ends balance each other. Let's connect them with thread. Attach a short stick to two cans with tape. Let's inflate one balloon and attach it to the stick again with the same piece of tape. Let's install it in its original place.
We will see how the stick tilts towards the inflated balloon, because the air filling the balloon makes it heavier. From this experiment we can conclude that air has mass and can be weighed.
If air has mass, then it must exert pressure on the Earth and everything on it. That’s right, scientists have calculated that the air in the Earth’s atmosphere exerts a pressure of 15 tons on a person (like three trucks), but a person does not feel this, because the human body contains a sufficient amount of air, which exerts a pressure of the same force. The pressure inside and outside is balanced, so the person does not feel anything.
Let's find out what happens to air when heated and cooled. To do this, let’s conduct an experiment: heat a flask with a glass tube inserted into it with the heat of our hands and see that air bubbles come out of the tube into the water. This happens because the air in the flask expands when heated. If we cover the flask with a napkin soaked in cold water, we will see that the water from the glass rises up the tube, because when cooled, the air is compressed.
Rice. 7. Properties of air during heating and cooling ()
To learn more about the properties of air, let's conduct another experiment: we attach two flasks to a tripod tube. They are balanced.
Rice. 8. Experience in determining air movement
But if one flask is heated, it will rise higher than the other, because hot air is lighter than cold air and rises. If you attach strips of thin, lightweight paper over a flask of hot air, you will see how they flutter and rise upward, showing the movement of heated air.
Rice. 9. Warm air rises
Man used knowledge of this property of air to create an aircraft - a hot air balloon. A large sphere filled with heated air rises high into the sky and can support the weight of several people.
We rarely think about it, but we use the properties of air every day: a coat, hat or mittens do not warm themselves - the air in the fibers of the fabric does not conduct heat well, therefore, the fluffier the fibers, the more air they contain, and therefore the warmer the thing, made from this fabric.
The compressibility and elasticity of air is used in inflatable products (inflatable mattresses, balls) and tires of various mechanisms (cars, bicycles).
Rice. 14. Bicycle wheel ()
Compressed air can stop even a train at full speed. Air brakes are installed in buses, trolleybuses, and subway trains. The air provides the sound of wind, percussion, keyboard and wind instruments. When the drummer hits the taut drum skin with his sticks, it vibrates and the air inside the drum produces sound. Hospitals have ventilators installed: if a person cannot breathe on his own, he is connected to a device that delivers oxygen-enriched compressed air into the lungs through a special tube. Compressed air is used everywhere: in book printing, construction, repairs, etc.
.jpg)
