Air particles during cooling drawing. The composition and structure of the atmosphere. Air is a poor conductor of heat
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, and 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:
- To be on the street more often, for example, to walk in the evenings in parks, gardens.
- Go for a walk in the woods on weekends.
- Constantly ventilate living and working areas.
- Plant more green plants, especially in offices where there are computers.
- 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 plant world of the planet and do everything possible to increase the representatives of green plants.
Video about the composition of air
Friction against the air, of course, occurs, and in this case some amount of heat is released, however, another physical process, called aerodynamic heating, heats up the skin of the descent vehicle and makes fireballs flying towards the earth 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 transitional region in which there is a sharp, abrupt increase in the density, pressure and velocity of matter. Naturally, when 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 deceleration 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 already hot gas heats up the body itself rushing at supersonic speed, and heat is transferred both with the help of heat conduction and with the help of radiation. True, the radiation of gas molecules begins to play a significant role at very high velocities, for example, at the 2nd cosmic one.
The problem of aerodynamic heating is faced not only by spacecraft designers, but also by 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 (had to be content with "modest" 2.3). The reason is aerodynamic heating. At such a speed, he would heat up the skins of the liners to 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, how the designers of the famous Soviet MiG-25 high-altitude interceptor solved the problem of aerodynamic heating can be found in
The air 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 apply them in everyday life, household, construction and much more. In this lesson, we will continue to study the properties of air, conduct many exciting experiments, learn about the amazing inventions of mankind.
Theme: Inanimate nature
Lesson: Properties of air
Let's 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, the window pane is cool to the touch, while 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 transmits the sun's rays well.
Rice. 1. Window glass conducts sunlight ()
Let's carry out a simple experiment: let's put 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 way” to the water. If you slightly tilt the glass 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, a person has learned to work underwater without a special suit. For this, a diving bell was created: under the bell-cap made of transparent material, people and the necessary equipment become and the bell is lowered under the water with a crane.
The air under the dome allows people to breathe for a while, long enough to inspect the damage to the ship, bridge piers or the bottom of the reservoir.
To prove the following property of air, it is necessary to tightly cover the opening of the bicycle pump with the finger of the left hand, and press the piston with the 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 with difficulty, but will move. This means that air can be compressed. Air has elasticity, because when we release the piston, it itself returns to its original position.
Elastic bodies are called bodies that, after cessation of compression, take 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 homemade scales. Attach the deflated balloons to the ends of the sticks with tape. We put a long stick in the middle of a short one, so that the ends balance each other. We will connect them with a thread. Attach a short stick to two cans with tape. Inflate one balloon and attach it to the stick again with the same piece of tape. Let's put it back in place.
We will see how the stick leans towards the inflated balloon, because the air that filled the balloon makes it heavier. From this experience, 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. Indeed, scientists have calculated that the air of 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 that exerts the same pressure. The pressure inside and outside is balanced, so the person does not feel anything.
Find out what happens to air when it is heated and cooled. To do this, let's conduct an experiment: let's 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 is because the air in the bulb expands when heated. If we cover the flask with a cloth soaked in cold water, we will see that the water from the glass rises up the tube, because the air is compressed during cooling.
Rice. 7. Properties of air during heating and cooling ()
To learn more about the properties of air, we will conduct another experiment: we will fix two flasks on a tripod tube. They are balanced.
Rice. 8. Experience in determining the movement of air
But if one flask is heated, it will rise above the other, because hot air is lighter than cold air and rises. If you fasten strips of thin, light paper over a flask with hot air, you will see how they flutter and rise up, showing the movement of heated air.
Rice. 9. Warm air rises
Man used the knowledge of this property of air to create an aircraft - a balloon. A large sphere filled with heated air rises high into the sky and is able to 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 by themselves - the air in the fibers of the fabric does not conduct heat well, therefore, the fluffier the fibers, the more air they contain, which means the warmer the thing, made from this fabric.
Air compressibility and elasticity are 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, subway trains. Air provides the sound of wind, percussion, keyboard and wind instruments. When the drummer strikes the tightly stretched skin of the drum with his sticks, it vibrates and the air inside the drum produces sound. Hospitals have installed lung ventilation devices: if a person cannot breathe on his own, he is connected to such a device, which delivers oxygen-enriched compressed air through a special tube into the lungs. Compressed air is used everywhere: in printing, construction, repair, etc.
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)°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 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
|
Volume concentration. % |
Molecular weight, units |
|
|
Oxygen |
||
|
Carbon dioxide |
||
|
Nitrous oxide |
||
|
0 to 0.00001 |
||
|
Sulfur dioxide |
from 0 to 0.000007 in summer; 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, 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 nitrogen content 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.
Conclusion: 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 a weather report is broadcast over the radio 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.
|
families |
Kinds of clouds |
Appearance |
|
A. Upper clouds - above 6 km |
I. Pinnate |
Threadlike, fibrous, white |
|
II. cirrocumulus |
Layers and ridges of small flakes and curls, white |
|
|
III. Cirrostratus |
Transparent whitish veil |
|
|
B. Clouds of the middle layer - above 2 km |
IV. Altocumulus |
Layers and ridges of white and gray |
|
V. Altostratified |
Smooth veil of milky gray color |
|
|
B. Lower clouds - up to 2 km |
VI. Nimbostratus |
Solid shapeless gray layer |
|
VII. Stratocumulus |
Opaque layers and ridges of gray |
|
|
VIII. layered |
Illuminated gray veil |
|
|
D. Clouds of vertical development - from the lower to the upper tier |
IX. Cumulus |
Clubs and domes 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 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.
