Physical and chemical properties of air. "Water and Air". We form in children a cognitive interest in objects of nature (water, air) How to treat air and water correctly
On the blog pages, we talk a lot about a variety of chemicals and mixtures, but we have not yet had a story about one of the most important complex substances - air. Let's fix this and talk about the air. In the first article: a little history of the study of air, its chemical composition and basic facts about him.
A little history of the study of air
Currently, air is understood as a mixture of gases that form the atmosphere of our planet. But this was not always the case: for a long time, scientists thought that air is a simple substance, an integral substance. And although many scientists expressed hypotheses about the complex composition of the air, things did not go beyond conjectures until the 18th century. In addition, the air was given philosophical meaning. In ancient Greece, air was considered one of the fundamental cosmic elements, along with earth, fire, earth and water, which form everything that exists. Aristotle attributed air to the sublunar light elements, personifying moisture and heat. Nietzsche in his writings wrote about air as a symbol of freedom, as the highest and most subtle form of matter, for which there are no barriers.
In the 17th century, it was proved that air is a material entity, a substance whose properties, such as density and weight, can be measured.
In the 18th century, scientists carried out reactions of air with various substances in sealed chemical vessels. So it was found that about a fifth of the volume of air is absorbed, and the remaining part of combustion and breathing is not supported. As a result, it was concluded that air is a complex substance, consisting of two components, one of which, oxygen, supports combustion, and the second, nitrogen, “spoiled air”, does not support combustion and respiration. This is how oxygen was discovered. A little later, pure nitrogen was obtained. And only at the very end of the 19th century, argon, helium, krypton, xenon, radon and neon, which are also present in the air, were discovered.
Chemical composition
Air is made up of a mixture of about twenty-seven different gases. Approximately 99% is a mixture of oxygen and nitrogen. As part of the remaining percentage: water vapor, carbon dioxide, methane, hydrogen, ozone, inert gases (argon, xenon, neon, helium, krypton) and others. For example, hydrogen sulfide can often be found in the air, carbon monoxide, iodine, nitrogen oxides, ammonia.
It is believed that in clean air under normal conditions, it contains 78.1% nitrogen and 20.93% oxygen. However, depending on geographical location and heights above sea level, the composition of the air can vary.
There is also such a thing as polluted air, that is, air whose composition differs from the natural atmospheric one due to the presence of pollutants. These substances are:
natural origin(volcanic gases and dust, sea salt, fumes and gases from natural fires, plant pollen, dust from soil erosion, etc.).
anthropogenic origin - resulting from industrial and domestic human activities (emissions of carbon, sulfur, nitrogen compounds; coal and other dust from mining and industrial enterprises; agricultural waste, industrial and domestic dumps, accidental oil spills and other hazardous environment substances; vehicle exhaust gases, etc.).
Properties
Pure atmospheric air has no color and smell, it is invisible, although it can be felt. The physical parameters of air are determined by the following characteristics:
Mass; 
temperature;
density;
atmospheric pressure;
humidity;
heat capacity;
thermal conductivity;
viscosity.
Most of the air parameters depend on its temperature, so there are many tables of air parameters for various temperatures. Air temperature is measured using a meteorological thermometer, and humidity is measured using a hygrometer.
Air exhibits oxidizing properties (due to the high oxygen content), supports combustion and respiration; poorly conducts heat, dissolves well in water. Its density decreases as the temperature increases and its viscosity increases.
In the following article, you will learn about a few interesting facts about air and its uses.
The atmosphere of our planet is a unique gas mixture containing nitrogen, oxygen, carbon dioxide and some other components. It's called air. This mixture has many properties. All the most important physicochemical and biological processes occurring around us in living and inanimate nature, are completely determined by the composition of the air, and are dependent on it. These include respiration and combustion, photosynthesis and the reactions of the cycle of chemical elements in nature. This article will be devoted to the study of the physical and chemical properties of the gaseous composition of the atmosphere.
We will also consider in which industries, medicine and Agriculture it can be used physical characteristics. For example, those of them that are the most significant: specific gravity, density, elasticity and thermal conductivity. The article will also provide information on how air is used in modern technical devices and devices created taking into account its physical characteristics.
How to find out the composition of air
The gaseous mixture that we breathe has long been interpreted by various philosophical schools as a unique substance that gives life. Among the Hindus, it was called prana, among the Chinese - qi.
In the middle of the 18th century, the brilliant French naturalist A. Lavoisier, with his chemical experiments, debunked an erroneous scientific hypothesis about the existence of a special substance - phlogiston. It allegedly contained particles of an unknown energy that gives life to everything that exists on Earth. Lavoisier proved that the composition and properties of air are determined by the presence of two main gases: oxygen and nitrogen. They account for more than 98%. The remainder includes carbon dioxide, hydrogen, inert elements and industrial waste impurities such as gaseous oxides of nitrogen or sulfur. The study of the properties of the components of the atmosphere served as an incentive for humans to use this gaseous mixture in various branches of technology and in everyday life.
Air and its role in the life of living organisms
One of the first answers to the question of how a person uses the properties of air will be the following: we need it for breathing. Once inhaled into the upper respiratory tract, its portion reaches the lungs. In the capillaries of the alveoli, oxygen diffuses into the blood. It delivers O 2 molecules to the intercellular fluid. Blood is in direct contact with cell membranes, which allow oxygen to pass directly into the cytoplasm. Having received O 2 particles, the cell consumes them in metabolic reactions. Unlike animals and humans, plants use the elements of the atmosphere not only for respiration, but also for photosynthetic processes, extracting carbon dioxide from it.
Composition and properties of air
An example illustrating the fact of the ability of the elements of the atmosphere to absorb thermal energy, to put it more simply, to heat up, will be as follows: if the gas outlet tube of a preheated flask with a ground stopper is lowered into a container with cold water, then air bubbles will come out of the tube. The heated mixture of nitrogen and oxygen expands, no longer fitting into the container. Part of the air is released and enters the water. When the flask is cooled, the volume of gas in it decreases and contracts, and water flows up the flask through the gas outlet tube.
Consider another experiment conducted in the lessons of natural history for students in grade 2. Air properties, such as elasticity and pressure, are clearly visible when inflated Balloon squeeze with your palms, and then carefully pierce with a needle. A sharp pop and scattered flaps demonstrate the pressure of the gas to children. It can also be explained to students that man has applied these properties in the manufacture of pneumatic devices, such as jackhammers, pumps for inflating bicycle tubes, pneumatic weapons.
Physical characteristics of air
Transparency, lack of color and smell of the gaseous atmosphere that surrounds us, from their own life experience, are well known to students in grade 2. The properties of air, for example, its lightness and mobility, can be explained to the children using the example of wind farms. They are built on hills and hills. After all, the speed of air movement depends on the height. Such power plants are safe in operation and do not harm the environment.
Like other substances, the components of the atmosphere have mass. To solve problems in the course of inorganic chemistry, it is generally accepted that the relative molecular weight of air is 29. Given this value, you can find out which gases are lighter than the atmosphere.
These include, for example, helium, hydrogen. To create aircraft, man conducted experiments and studied the properties of air. The experiments were crowned with success, and the first flight in the world was carried out by the French inventors, the Montgolfier brothers, already in the 18th century. The shell of their balloon was filled with a hot mixture of hydrogen, nitrogen and oxygen.
Airships - more maneuverable and better controlled devices, rise up because their shells are filled with light gases, namely helium or hydrogen. Man uses the ability of a gas mixture to compress in devices such as air brakes. They are equipped with buses, subway trains, trolleybuses. The examples given are a clear illustration of how a person uses the properties of air.
How do sound sensations occur?
One of the most important analyzers of our body is auditory. He perceives vibrations, called sound waves, as external stimuli. They press on the eardrum, causing vibrations in it, which are transmitted to the auditory ossicles of the middle ear. A portion of air is constantly in the cavity of the Eustachian tube and equalizes the pressure on the eardrum. This prevents its deformation and rupture, ensuring the transmission of sound vibrations to the inner ear, where excitation occurs. Through the auditory nerves, it enters the temporal lobe of the cerebral cortex, which causes the appearance of auditory sensations. Such examples show us how a person uses the properties of air to carry out the normal functioning of his own organism.
Air in the service of man
Various characteristics of the atmospheric mixture of gases: density, specific gravity, thermal conductivity, ability to compress and move, are widely used in our industry, medicine and in everyday life. The artificial respiration apparatus delivers an oxygen-enriched mixture directly into the lungs of seriously ill people and saves their lives. Vacuum cleaner and air conditioner have long become familiar in our everyday life.
Both of these devices use the compressed components of the atmosphere: the vacuum cleaner draws dust particles and mechanical impurities from various surfaces with a jet. The flow of cold gases from the air conditioner cools the room in the heat. These examples once again demonstrate the possibilities of how a person uses the properties of air in his life.
Element Air
People of the element of Air are cold and prudent. However, they have a fairly even character, are not prone to mood swings and converge well with representatives of other Elements. People of the Air element are necessary to other people, as Air is necessary, since they are distinguished by rare sociability and pleasantness of character.
Element Water
Water signs live an emotional life. They are unstable and very sensitive. Perceive people and events through feelings and emotional response. They need romance, sublimity. Water always needs support, to confirm its views, as it doubts all the time. Water signs are vulnerable and receptive, they can hold grudges.
Sometimes these elements are drawn to each other, but something sensible rarely comes out of this: either a complete calm or a formidable storm is always either too little or too much for a harmonious union. In some cases, Air can inflate the sails of a family ship so that it slides on Water confidently and in the right direction. To do this, partners need to overcome disagreements caused by the contradictions of the elements - water signs are characterized by a heavy disposition, a sense of ownership, jealousy, and Air needs freedom of action and ease of communication.
Elemental Partner Compatibility
The combination of these elements is not very good - water signs (Cancer, Scorpio and Pisces) live by feelings, but air signs (Gemini, Libra and Aquarius) do not. But not infrequently these elements are attracted to each other - this is like a fatality. The Air Sign thrives on the sensitivity and receptivity, the mystique and mystique, and the intuition of the Water Sign, and the Water Sign loves the sociability, communication skills, good intelligence, and versatility of the Air Sign's interests.
Because of the possessive nature of water, the air man cannot feel free. Just like fire, water oppresses the air with its own seething emotional outbursts. And this, in turn, quite often leads to a break in relations. Very often the air man leaves first.
At the very beginning of the development of these relations, partners, as often happens between antagonistic elements, are completely absorbed in each other: the air seeks to understand the incomprehensible change in the disposition of the spirit of the water man, fascinated by the brilliance of the mind and the ability to communicate with the man of the air. In sex, they both need romance and sublimity. But pretty soon they will begin to understand how different they are from each other and how hard it becomes for them to be together. Water signs need understanding and stability, which air signs cannot give them. The longer the air person communicates with the water person, the more he will understand that it is difficult for him to understand the water person and worry about this - and his experiences will be transferred to the water person, who is very sensitive, the water person will begin to feel uncomfortable with the air person.
Weaknesses in partner relationships
In the relationship between water and air, often the admiration of air for the sensitivity and mystery of water turns into a misunderstanding of the changeable emotional state of a water person. The water partner, captivated, at the beginning of a relationship, by the intellect and sociability of a person of air, will not be able to endure his impartiality and reasoning for a long time. But if people of these elements can learn to understand each other correctly, their marriage can be productive and good: air will teach water to impartially, think judiciously and communicate freely with other people, and an air person can learn from a water person to capture the feelings of other people.
Compatibility of the elements of the Zodiac (Air + Water)
Before proceeding to consider such a topic as the properties of air, let's first talk about what air is.
So, under the concept of air, it is customary to understand a mixture of various gases that dissolve in air. If we talk about air and its composition, it is worth recalling that nitrogen is part of the air, and its percentage is 78% of the total volume, oxygen, in turn, has only 21% of the volume, other inert gases, which are also called noble gases, occupy about 1% from the total volume. The rest of the volume is separated by carbon monoxide IV valency, impurities and water vapor.
From the school chemistry course, we know that depending on the location and climate, the percentage of various impurities, water and the aforementioned carbon monoxide may vary.
How is carbon dioxide formed?
In nature, such a combination occurs during the burning of various objects and materials, decay and decomposition, as well as during the respiration of all living organisms. However, it should be clarified that the largest amount of CO2 appears in the atmospheric space precisely due to human activity.
However, after all the studies that were carried out on the study of air, it was proved that even despite the active life of a person, carbon dioxide is still within the normal range and in most cases does not exceed the limit of 0.03% of the total volume.
If we talk about the content of water vapor in the air, then the amount can be completely different. Scientists have found that the percentage of water vapor can be from hundredths of a percent and up to several full percent. This content is directly dependent on weather conditions and temperature.
In order to accurately determine in your room, you can contact the private research laboratory "EcoTestExpress", where in the shortest possible time a specialist will take air samples for examination, and experienced chemists examine the material taken for various tests.
Chemical properties of air
Understand Chemical properties air is quite simple, for this it is enough just to understand the properties of oxygen.
As mentioned earlier, air contains approximately 21% of oxygen from the total volume. By itself, oxygen has the so-called oxidizing properties, which allow many different materials and substances to flare up, burn or oxidize. Since it is practically impossible to recreate the chemical properties of air on paper, all combustion equations are written down precisely at the expense of oxygen, since. it is the main oxidizing agent in air.
Physical properties of air
The key physical properties are the same for everyone, namely in physical properties we describe temperature, density, specific heat capacity, dynamic viscosity, kinetic viscosity and more. But what properties of air are we interested in?
In order to describe air and its properties from a physical point of view, we are interested in temperature values. In other words, we are only interested in air temperature, because the main characteristic of the physical properties of air is based on temperature.
Scientists have found that when the temperature changes, the physical properties of air change with a certain dependence. After this was checked, the physical properties of the air were described in a table that displays all the necessary values of certain parameters. All these parameters create the most complete characterization of physical properties. It is also worth noting that these tables contain values for each degree of air.
Of course, we are also interested in relative humidity, but what is it? So, when describing such a concept as the main properties of air from the physical side, relative air humidity is usually understood as the ratio of water vapor to their maximum amount of possible content at a certain temperature and pressure. All this is calculated per unit of air. After hundreds of experiments were made, it was found that the higher the pressure and the lower the temperature, the relative humidity of the air increases. If you want to conduct an air test, you can contact our laboratory.
It is also worth paying attention to such a concept as air viscosity. As well as the relative humidity of the air, the viscosity of the air also depends on the temperature, only in this case, as the temperature increases, the viscosity also increases. This applies to both kinetic and dynamic viscosity.
What is the relationship between kinetic and dynamic viscosity? From school courses, we can recall that between these two concepts is carried out through density, or rather the value of air density.
In order to conduct several air studies, including the study of the chemical composition of air, microbiological analysis of air, and so on, you do not need to look for several laboratories, spend a huge amount of time and effort in order to analyze. Our independent research laboratory "EcoTestExpress" carries out several types of air analysis, as well as many other studies, including, thereby giving you the opportunity to choose what you need and order the services you need. Experts travel throughout Moscow and the Moscow region in order to take quality air samples and conduct research.
The history of the discovery of such concepts as air and its properties
We are talking about air, but we have not thought about how we explored and discovered air. But let's start from the very beginning.
In ancient peoples, including Greece and Rome, air was considered something personal and personal substance. Philosopher ancient greece Anaximenes in his teachings wrote that air is the founder of all that exists. In the future, he did not stop at the knowledge of air and was one of the first to begin to speak (and later to consider) air as one of the main elements of nature.
Of course, Anaximenes did not suspect that air has mass, and only Aristotle was able to say that air has mass.
After, of course, many scientists sought to understand the properties of air, but most attempts were in vain. The only one who was able to formulate the first scientific theories was the Alexandrian scientist Heron, who lived in the 140s BC. In his teachings, he expressed the following opinion: “Vessels that seem empty to most people, in fact they are not empty, but filled with air ... The air is formed by small and light particles, mostly invisible ... From here it should be accepted, that air is material. Set in motion, it becomes the wind (since the wind is nothing but air in motion).”
Many tried to find out the composition of the air, but it was the ancient Chinese scientists who were the first to really show how complex the composition of the air was. Chinese chemists indicated many facts in their writings, but they did not have solidity. Of the European thinkers, Leonardo do Vinci, who lived at the end of the fifteenth century, said his thoughts about the composition of the air. However, by experience and experimentation, the chemical composition of air also became known to many around the eighteenth century.
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Air weight
As we all know, air has, though insignificant, but weight. For example, it has been scientifically proven that even in a completely empty bottle there will be air weighing more than one gram. As scientists say: with its weight, air presses on us, as well as on all the objects around us.
Various experiments were carried out, which showed that air is necessary even in an empty container. A vivid example: what will happen if you pump out air from an ordinary tin can. As we know, without air, the iron container will simply flatten.
In everyday life, we do not need to know the weight of air, it is enough just to understand exactly how it helps us in life. In order to take measurements of air, it is enough to contact our company "EcoTestExpress", because our laboratory, with the latest equipment, will help you in the study of air.
If you are interested in such requests as air properties class 3, air properties class 2, as well as more informative questions like air properties report or basic air properties class 5, you should contact our laboratory, where experienced specialists and experts in their field will tell you about all the properties, which may interest you.
Air mobility
Another rather important property of air is its mobility. The mobility of air is determined precisely by the speed of air movement. What is the speed of air movement?
So, the speed of movement is the number of meters that air travels in one second of time. Just the mobility of the air affects how quickly the air will be cooled. In scientific terms, it all goes down due to the influence of air on heat loss through convection and sweat evaporation.
For a person, it is noticeable a little, on the other hand. The slight mobility of air at elevated temperature contributes to its rapid cooling, and the lower temperature, combined with high air mobility, contributes to hypothermia of the body.
From personal experience we know that any frost in calm weather is easier to bear than in strong winds. Moderate wind, no matter how much we want it, has an invigorating effect (5-7 m / s).
But why do we need this air mobility? Air mobility is necessary, because it contributes to the ventilation of buildings, premises, and leads to self-purification of air from pollution. The most favorable speed atmospheric air- 1-5 m/s, indoors - 0.1-0.3 m/s. In order to conduct various studies, including, you can contact "EcoTestExpress".
DEFINITION
Air is a mixture of gases dissolved in each other. The composition of the air includes nitrogen (78% by volume), oxygen (21% by volume), noble (inert) gases (about 1% by volume), carbon monoxide (IV), water vapor and various impurities.
Carbon dioxide is formed in nature as a result of the combustion of plant materials, the respiration of living organisms and decay. A large number of CO 2 enters the atmosphere as a result of human activities. Despite the constant supply of CO 2 to the atmosphere, its average content in the air is almost always at the level of 0.03% by volume.
Chemical properties of air
Due to the presence of oxygen (21% by volume) in the air, which exhibits oxidizing properties, many substances are able to burn in the air, and the equations of chemical reactions of combustion (oxidation) of substances in (in) air are written as the equations of combustion of these substances in oxygen, since it is impossible to display the chemical composition of air on paper.
Physical properties of air
The main physical properties of air include temperature, relative humidity, density, specific heat, thermal conductivity, dynamic and kinematic viscosity, etc. Almost all of these parameters are highly dependent on temperature, so there are special tables that indicate the values of parameters characterizing the physical properties of air, at specific temperatures.
Relative humidity is the ratio of water vapor contained in a unit of air to their maximum possible content at a given temperature and pressure. As the pressure rises and the temperature decreases, the relative humidity of the air increases.
The density of air at 20C is 1.2 kg/m 3 , and when it is heated, it decreases significantly. So, when air is heated to a temperature of 1200C, the air density decreases by 5 times compared to the air density at 20C.
The viscosity of air strongly depends on temperature and increases with its growth, and both kinematic and dynamic viscosity increase. The values of kinematic and dynamic viscosity of air are interconnected through the value of its density.
The heat capacity of air also increases with increasing temperature, however, this physical parameter depends on temperature to a lesser extent than, for example, density. So, when air is heated from 20 to 1200C, the heat capacity of air increases only 1.2 times.
Other parameters characterizing the physical properties of air (thermal diffusivity, Prandtl number, etc.) do not depend on temperature changes.
Examples of problem solving
EXAMPLE 1
| Exercise | Determine the volume of air required for the complete oxidation of hydrogen sulfide with a volume of 448 liters. |
| Solution | The oxidizing power of air is due to the presence of oxygen in the air. The volume fraction of oxygen in the air is 21%, i.e. 1/5 of the total volume of air. Let us write the reaction equation for the complete oxidation of hydrogen sulfide by air oxygen: 2H 2 S + 3O 2 \u003d 2SO 2 + 2H 2 O Find the amount of hydrogen sulfide substance: v(H 2 S) = V(H 2 S)/V m v (H 2 S) \u003d 448 / 22.4 \u003d 20 mol According to the equation, the number of moles of oxygen: v (O 2) \u003d 1.5 × v (H 2 S) v(O 2) \u003d 1.5 × 20 \u003d 30 mol Find the volume of oxygen: V(O 2) \u003d v(O 2) × V m V (O 2) \u003d 30 × 22.4 \u003d 672 l Then the volume of air: V \u003d 672 × 5 \u003d 3360 l |
| Answer | Air volume - 3360 l |
EXAMPLE 2
| Exercise | Determine the volume of air required to burn 36 g of magnesium. |
| Solution | The oxidizing power of air is due to the presence of oxygen in the air. The volume fraction of oxygen in the air is 21%, i.e. 1/5 of the total volume of air. Let us write the reaction equation for the combustion of magnesium with atmospheric oxygen:
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