Air particles during heating and cooling. Collection of misconceptions: a spacecraft entering the atmosphere heats up due to air friction
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.
When 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 spaces 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 your 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 plants 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 every day, they provide information and monitor the situation.
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 the 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 teacher writes on the board.)
Air does not conduct heat well.
So, what properties does air have?
V. Physical education minute
VI. Consolidating the learned material Completing assignments in the workbook
No. 1 (p. 18).
- Read the assignment. Examine the drawing and label 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 complete the task correctly? (When air is heated, it expands; when cooled, it contracts.)
How to explain that air expands when heated? What happens to the particles that make it up? (The particles begin to move faster, and the gaps between them increase.)
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, and the spaces between them become smaller.)
- Draw in the second rectangle how air particles are arranged as they cool.
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. Follow through.
What pollutes the air? (Industrial enterprises, transport.)
Conversation
There is a factory not far from my house. From my windows I can see a high brick chimney. Thick black clouds of smoke pour out of it day and night, causing the horizon to forever hide behind a thick, serous curtain. Sometimes it seems as if this is a heavy smoker fuming the city with his unquenchable Gulliver pipe. We all cough, sneeze, some even have to be admitted to the hospital. And at least for the “smoker”: just puff and puff, puff and puff.
Children are crying: disgusting factory! Adults are angry: close it immediately!
And everyone hears in response: how so “nasty”?! How to “close” like that?! Our factory produces goods for people. And, unfortunately, there is no smoke without fire. If we extinguish the flames of the furnaces, the factory will stop and there will be no goods.
One morning I woke up, looked out the window - there was no smoke! The giant stopped smoking, the factory is in place, the chimney still sticks out, but there is no smoke. I wonder how long? However, I see: there is no smoke tomorrow, and the day after tomorrow, and the day after tomorrow... Has the factory really been closed down completely?
Where did the smoke go? They themselves said that there is no smoke without fire.
It soon became clear: they finally heard our endless complaints - they attached smoke eliminators to the factory chimney, a smoke trap that prevents soot particles from flying 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 a plastics factory. Who knows, maybe this felt-tip pen of mine is made from the same soot caught by smoke traps. In a word, smoke traps benefit everyone: us, the city residents (we no longer get sick), and the factory itself (it sells soot, and does not waste it as before), and buyers of plastic products (including felt-tip pens).
Name ways to protect air purity. (Air purification units, electric vehicles.)
- To clean the air, people plant trees. Why? (Plants absorb carbon dioxide and release oxygen.)
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 very small holes. They are called “stomata”; you can only see them well with a magnifying glass. 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.
It’s not for nothing that plants are called “the lungs of the 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 birch, oak, and larch are very beneficial for humans. But in cities the air is completely different. It smells of gasoline and exhaust fumes, because in cities there are a lot of cars, factories and factories are operating, which also pollute the air. Breathing such air is harmful to a person. To clean the air, we plant trees and shrubs: linden, poplar, lilac.
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, then 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 belt, 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, what 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)
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 related to the geological and geochemical processes occurring on our planet, as well as to 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 boundary at an altitude of 2000-3000 km gradually passes into outer space.
Thanks to the atmosphere, which contains oxygen, life on Earth is possible. Atmospheric oxygen is used in the breathing process of 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, like through a lens, are decomposed into their component colors. In this case, the rays of blue and blue colors are scattered the most.
The atmosphere traps most of the sun's ultraviolet radiation, which has a detrimental effect on living organisms. It also retains heat near the Earth's surface, preventing our planet from cooling.
The structure of the atmosphere
In the atmosphere, several layers can be distinguished, differing in density (Fig. 1).
Troposphere
Troposphere- the lowest layer of the atmosphere, the thickness of which 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 by the earth's surface, that is, by 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 °C, and in the region of the North Pole -65 °C.
About 80% of the mass of the atmosphere is concentrated in the troposphere, almost all the water vapor is located, thunderstorms, storms, clouds and precipitation occur, and vertical (convection) and horizontal (wind) movement of air occurs.
We can say that weather is mainly formed in the troposphere.
Stratosphere
Stratosphere- a 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 thinness of the air, due to which the sun's rays are almost not scattered.
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 almost no clouds and precipitation form. 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 reaching the Earth and thereby protecting living organisms on our planet. Thanks to ozone, the air temperature at the upper boundary of the stratosphere ranges from -50 to 4-55 °C.
Between the mesosphere and stratosphere there is a transition 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 Earth's surface. The color of the sky in the mesosphere appears black, and stars are visible during the day. The air temperature drops to -75 (-90)°C.
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 an altitude of 150 km it reaches 220-240 ° C; at an altitude of 500-600 km exceeds 1500 °C.
In the mesosphere and thermosphere, under the influence of cosmic rays, gas molecules disintegrate 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, nitrogen oxide molecules and free electrons. This layer is characterized by high electrification, and long and medium radio waves are reflected from it, like from a mirror.
In the ionosphere, aurorae appear - 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.
Atmospheric composition
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 CO 2 content by approximately 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 thereby have a significant impact on the temperature regime of the Earth's surface and atmosphere.
Table 1. Chemical composition of dry atmospheric air near the earth's surface
|
Volume concentration. % |
Molecular weight, units |
|
|
Oxygen |
||
|
Carbon dioxide |
||
|
Nitrous oxide |
||
|
from 0 to 0.00001 |
||
|
Sulfur dioxide |
from 0 to 0.000007 in summer; from 0 to 0.000002 in winter |
|
|
From 0 to 0.000002 |
46,0055/17,03061 |
|
|
Azog dioxide |
||
|
Carbon monoxide |
Nitrogen, The most common gas in the atmosphere, it is 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 under-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 extremely large. It enters the atmosphere as a result of the processes of combustion, respiration of living organisms, and decay and is, first of all, the main building material for the creation of organic matter during photosynthesis. In addition, the ability of carbon dioxide to transmit short-wave solar radiation and absorb part of the thermal long-wave radiation is of great importance, which will create the so-called greenhouse effect, which will be discussed below.
Atmospheric processes, especially the thermal regime of the stratosphere, are also influenced by ozone. This gas serves as a natural absorber of ultraviolet radiation from the sun, and the absorption of solar radiation leads to heating of the air. Average monthly values of the total ozone content in the atmosphere vary depending on the latitude and time of year within the range of 0.23-0.52 cm (this is the thickness of the ozone layer at ground pressure and temperature). There is an increase in ozone content from the equator to the poles and an annual cycle with a minimum in autumn and a maximum in spring.
A characteristic property of the atmosphere is that the content of the main gases (nitrogen, oxygen, argon) changes slightly with altitude: 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, the air contains water vapor And solid particles. The latter can have both natural and artificial (anthropogenic) origin. These are pollen, tiny salt crystals, road dust, and aerosol impurities. When the sun's rays penetrate the window, they can be seen with the naked eye.
There are especially many particulate particles 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 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 importance of water vapor is determined primarily by the fact that it delays long-wave thermal radiation from the earth's surface; represents the main link of large and small moisture cycles; increases the air temperature during condensation of water beds.
The amount of water vapor in the atmosphere varies in time and space. Thus, the concentration of water vapor at 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 (this is the thickness of the layer of condensed water vapor). Information regarding 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, specific humidity increases strongly with altitude. However, subsequent measurements indicate greater dryness of the stratosphere. Apparently, the specific humidity in the stratosphere depends little on altitude and is 2-4 mg/kg.
The variability of water vapor content in the troposphere is determined by the interaction of the processes of evaporation, condensation and horizontal transport. As a result of condensation of water vapor, clouds form and precipitation falls in the form of rain, hail and snow.
The processes of phase transitions of water occur predominantly in the troposphere, which is why clouds in the stratosphere (at altitudes of 20-30 km) and mesosphere (near the mesopause), called pearlescent and silvery, are observed relatively rarely, while tropospheric clouds often cover about 50% of the entire earth's surface. surfaces.
The amount of water vapor that can be contained in the air depends on the air temperature.
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 °C - no more than 9 g; at +30 °C - no more than 30 g of water.
Conclusion: The higher the air temperature, the more water vapor it can contain.
The air may be rich And not saturated water vapor. 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,” this means that 1 m L contains 15 g of water vapor.
Relative humidity- this is the ratio (in percentage) 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 broadcast a weather report that the relative humidity is 70%, this means that the air contains 70% of the water vapor it can hold at that temperature.
The higher the relative humidity, i.e. The closer the air is to a state of saturation, the more likely precipitation is.
Always high (up to 90%) relative air humidity is observed in the equatorial zone, since the air temperature remains high there throughout the year and large evaporation occurs from the surface of the oceans. The relative humidity is also high in the polar regions, but because at low temperatures even a small amount of water vapor makes the air saturated or close to saturated. In temperate latitudes, relative humidity varies with the seasons - it is higher in winter, lower in summer.
The relative air humidity in deserts is especially low: 1 m 1 of air there contains two to three times less water vapor than is 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; it thickens (condenses), turning into droplets of fog. Fog can be observed in 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 clouds.
Cloud formation also involves particulate matter suspended in the troposphere.
Clouds can have different shapes, which depend 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 clouds are cirrus clouds. They are located at an altitude of 8 to 18 km above the earth's surface.
|
Families |
Kinds of clouds |
Appearance |
|
A. Upper clouds - above 6 km |
I. Cirrus |
Thread-like, fibrous, white |
|
II. Cirrocumulus |
Layers and ridges of small flakes and curls, white |
|
|
III. Cirrostratus |
Transparent whitish veil |
|
|
B. Mid-level clouds - above 2 km |
IV. Altocumulus |
Layers and ridges of white and gray color |
|
V. Altostratified |
Smooth veil of milky gray color |
|
|
B. Low clouds - up to 2 km |
VI. Nimbostratus |
Solid shapeless gray layer |
|
VII. Stratocumulus |
Non-transparent layers and ridges of gray color |
|
|
VIII. Layered |
Non-translucent gray veil |
|
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D. Clouds of vertical development - from the lower to the upper tier |
IX. Cumulus |
Clubs and domes are bright white, with torn edges in the wind |
|
X. Cumulonimbus |
Powerful cumulus-shaped masses of dark lead color |
Atmospheric protection
The main sources are industrial enterprises and cars. In large cities, the problem of gas pollution on main transport routes is very acute. That is why many large cities around the world, including our country, have introduced environmental control of the toxicity of vehicle exhaust gases. According to experts, smoke and dust in the air can reduce the supply of solar energy to the earth's surface by half, which will lead to a change in natural conditions.
Friction with the air, of course, occurs, and at the same time a certain amount of heat is released, but another physical process called aerodynamic heating heats up the skin of the descent vehicle and causes fireballs flying towards the ground to burn and explode.
As is known, a shock wave is formed in front of a body moving in a gas at supersonic speed - a thin transition region in which a sharp, abrupt increase in the density, pressure and speed of the substance occurs. Naturally, as the gas pressure increases, it heats up - a sharp increase in pressure leads to a rapid increase in temperature. The second factor - this is actually aerodynamic heating - is the braking of gas molecules in a thin layer adjacent directly to the surface of a moving object - the energy of the chaotic movement of molecules increases, and the temperature rises again. And the hot gas heats up the supersonic body itself, and the heat is transferred both by thermal conductivity and by radiation. True, the radiation of gas molecules begins to play a noticeable role at very high speeds, for example, at the 2nd cosmic speed.
Not only spacecraft designers have to deal with the problem of aerodynamic heating, but also developers of supersonic aircraft - those that never leave the atmosphere.
It is known that the designers of the world's first supersonic passenger aircraft - Concorde and Tu-144 - were forced to abandon the idea of making their aircraft fly at a speed of Mach 3 (they had to be content with “modest” 2.3). The reason is aerodynamic heating. At such a speed, it would heat up the skins of the airliners to such temperatures that could already affect the strength of aluminum structures. Replacing aluminum with titanium or special steel (as in military projects) was impossible for economic reasons. By the way, you can read about how the designers of the famous Soviet high-altitude interceptor MiG-25 solved the problem of aerodynamic heating in
