How to find the mass of air formula. Normal atmospheric pressure for humans

The planet is surrounded by an air mass, which, under the influence of gravity, presses on any object, including the human body. The force is called atmospheric pressure. Each square meter is pressed by a column of air weighing approximately 100,000 kg. Atmospheric pressure is measured using a special device - a barometer. It is measured in pascals, millimeters of mercury, millibars, hectopascals, atmospheres.

The normal atmospheric pressure is 760 mm Hg. Art., or 101 325 Pa. The discovery of the phenomenon belongs to the famous physicist Blaise Pascal. The scientist formulated a law: at the same distance from the center of the earth (it doesn’t matter, in the air, at the bottom of a reservoir), the absolute pressure will be the same. He was the first to propose measuring heights using the barometric alignment method.

This is the air pressure of the atmosphere on the surface of the planet and on all surrounding objects. Due to the sun, air masses are constantly moving, this movement is felt in the form of wind. It transports moisture from bodies of water to land, forming precipitation (rain, snow or hail). This was of great importance in ancient times, when people predicted weather changes and precipitation based on their feelings.

The Earth is habitable due to a number of factors. The first of these is the availability of breathing air. Our planet, like a dome, is covered with an atmosphere consisting of many layers, each of which performs a specific important function. The air mass exerts constant pressure on everything that is on Earth, including humans, which is why it is so important to know what its norm is.

Any deviation of a person’s atmospheric pressure from the norm by 5-10 units or higher will be painfully accepted by our body.

Many people have so-called weather sensitivity. This is a peculiar reaction of the body to a change in the normal atmospheric pressure for a person. It can be expressed, depending on the presence of various health problems, in the appearance of irritability, pain in various parts of the body, a general decrease in performance, and insomnia. A change in normal atmospheric pressure for a person can manifest itself in mental disorders, for example, a state of anxiety, depression, unreasonable fear.

The human body is a kind of chemical laboratory that works normally at the appropriate standard of atmospheric pressure for a person. As soon as these conditions change in any direction, the body reacts with painful manifestations. He lacks something, for example, oxygen. Or vice versa, there is something in excess.

The causes of weather sensitivity are not only health problems, but also poor lifestyle choices. Sedentary activity, poor nutrition with subsequent acquisition of excess weight, and stress play a big role.

There are different types of people: some are able to painlessly withstand climbing mountains or long flights on board an airplane, while for others, changing weather causes severe headaches and a deterioration in general well-being. To define this pathological condition, a special term “meteodependence” (otherwise known as meteopathy) was developed, which indicates the connection between the symptoms that appear and atmospheric pressure, humidity and other weather conditions.

People suffering from vegetative-vascular dystonia, hypertension, atherosclerosis, and endocrine diseases are more prone to weather dependence. The baroreceptors of our organs react to the approach of a cyclone or anticyclone, reducing or increasing blood pressure, making them dependent on weather conditions.

Before talking about what normal atmospheric pressure is in Moscow, you need to understand what it is. So, first things first.

Atmospheric pressure is caused by the weight of air. Its value is determined based on 1 cm2 of the area of ​​a body located on the surface of the Earth. Pressure is measured in several units: from millibars (mb) to millimeters of mercury (mmHg) and Pascals (Pa). In different situations, they use what is more convenient. Millimeters of mercury have become common in meteorology.

The normal value is considered to be at sea level, that is, at an altitude of 0 m, at a temperature of 0 ºС. It turned out to be equal to 760 mm Hg. Art.

However, this number is not always normal. Atmospheric pressure in Moscow, for example, is significantly lower than this value. And even within city limits it can differ significantly.

If we translate it into simple language, it turns out that air weighing 15 tons presses on the human body. Agree, this is a lot.

Atmospheric pressure is not felt because it is balanced by the presence of gases dissolved in the blood. They allow people not to notice the huge column of air above them.

The human body has adapted, and normal atmospheric pressure in Moscow does not have a negative impact on its well-being. If you train for a long time, you can normally exist at a low or high value of mmHg.

You can and should be able to survive “bad days.” To do this you need:

• Get enough sleep.
• Walk in the fresh air.
• Include physical activity, but without fanaticism.
• Don't drive.
• Do not turn on the computer.
• Give up TV.
• Don't listen to loud music.
• No smoking.
• Alcohol is taboo.
• In the morning – shower, in the evening – relaxation bath (temperature no more than 40 C* with essential oils).
• For high blood pressure - hawthorn tincture. When low - lemongrass.
• Eliminate stress.
• Avoid travel.
• Do not wear synthetics (they accumulate static electricity).
• On the eve of the “storm” - a cardioaspirin tablet and rosehip tea.

• Aquatic (fish, crayfish, scorpions) – water procedures.
• Air people (Aquarius, Libra, Gemini) – take more walks.
• Fiery (Aries, Leo, Sagittarius) - bask in the sun.
• Earthly (Virgo, Capricorn, Taurus) - tinker with the earth.

What should blood pressure be in children of different ages?

Changes in blood pressure (BP) in adults do not surprise anyone; similar problems in children worry everyone. Moreover, deviations from the norm occur not only in adolescents, but also in infants. A young body has elastic vascular walls, which is why blood pressure in babies is lower. A newborn's systolic pressure is about 75 mm Hg. As the baby grows, it gradually increases.

The age of the child determines the degree of elasticity of the vascular wall, the width of the lumen of the arteries and veins, and the total area of ​​the capillary network, on which the normal blood pressure in children depends.

From one to 6 years of age, blood pressure increases slightly. Around the age of five, its indicators level out for both sexes; subsequently, boys have slightly higher blood pressure than girls. From 6 years of age until adolescence, systolic blood pressure increases again: in boys - by 2 mm. Hg Art., in girls - by 1 mm Hg. Art. If a child complains of weakness or increased fatigue, do not rush to give him a headache pill. First measure your blood pressure.

Physiotherapy

Healing baths and mud have a good effect. In addition, any water procedures (circular shower, wiping with cold water, swimming pool) cause a positive effect and increase the body's reserve capabilities. Essential oils have positive tonic and calming properties. You can perform inhalation with essential oils of citrus and coniferous plants, mint, rosemary and other substances, or conduct an aromatherapy session.

Sensitivity to changes in pressure is an unpleasant condition that disrupts normal well-being and interferes with a full life. To avoid this, you need to increase the body’s natural resistance and monitor your health.

At-risk groups

This group mainly includes people with chronic diseases and the elderly with age-related health changes. The risk of weather dependence increases in the presence of the following pathologies:

• Respiratory diseases (pulmonary hypertension, chronic obstructive pulmonary disease, bronchial asthma). Severe exacerbations occur.
• Damage to the central nervous system (stroke). There is a high risk of recurrent brain damage.
• Arterial hypertension or hypotension. A hypertensive crisis with the development of myocardial infarction and stroke is possible.
• Vascular diseases (atherosclerosis of the arteries). Atherosclerotic plaques can break away from the walls, causing thrombosis and thromboembolism.

Nutrition and regimen

One of the factors that influences the development of pressure sensitivity is excess weight. Obese patients are more likely to suffer from heart and vascular diseases and, accordingly, are more likely to react to weather disasters. If the patient decides to cope with this disease, then first of all you need to reconsider your lifestyle and diet:

1. A complete and balanced diet with a normal content of vitamins and microelements.
2. Refusal or limitation of alcohol and nicotine consumption.
3. During an attack, you need to switch to a light dairy-vegetable diet to help the body cope with the disease.

Separately, it is worth mentioning the use of adaptogens - drugs that increase the natural adaptive ability of the body. They are of plant and synthetic origin. Some of the most well-known adaptogens are ginseng, eleutherococcus, bee products and reindeer antler preparations. Before taking them, you need to consult a doctor, since there are a number of contraindications and side effects.

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While studying the topic “Mendeleev-Clapeyron Equation” in physics lessons, I often came across problems in which it was necessary to determine the molar mass of air. For example: a ball with a shell mass filled with helium lifts a load of mass m. Atmospheric pressure and temperature are considered known quantities.

I was interested in the question of how to experimentally measure the molar mass of air.

One way to determine the molar mass of air is the air pumping method. But this method requires special equipment, which we do not have at school. I decided to find an accessible way to determine the molar mass of air.

1. History of the discovery of the composition of air and its molar mass

Air is necessary for the normal existence of living organisms on Earth. In industry and in everyday life, atmospheric oxygen is used to burn fuel to produce heat and mechanical energy in internal combustion engines.

Molar mass is a characteristic of a substance, which is equal to the ratio of the mass of the substance to the number of moles of this substance, i.e. the mass of one mole of a substance. For individual chemical elements, the molar mass is the mass of one mole of individual atoms of this element, that is, the mass of atoms of a substance taken in an amount equal to Avogadro’s Number. In this case, the molar mass of the element, expressed in g/mol, numerically coincides with the molecular mass - the mass of an atom of the element, expressed in a. u.m. (atomic mass unit). However, one must clearly understand the difference between molar mass and molecular weight, understanding that they are only equal numerically and differ in dimension.

In the 17th century in works G. Galilee(1638) and R. Boyle(1662) it was shown that air is a material substance and has well-defined physical properties (mass and pressure).

Swedish scientist K. Scheele(1742-1786) conducted a series of experiments. Studying the composition of air, he came to the conclusion that atmospheric air consists of 2 types of air: “fiery”, which supports breathing and combustion (O 2) and “spoiled”, which does not support combustion (N 2). He conducted experiments to study the interaction of air in a confined space in contact with various substances. In all cases, about 1/5 of the original volume of air was absorbed. At the same time, the remaining gas turned out to be lighter than ordinary air and did not support combustion. Scheele first discovered O2.

In 1774, a French scientist A. Lavoisier proved that air is a mixture of mainly two gases - N 2 and O 2 .He wrote the work “Analysis of Atmospheric Air”. He heated the metallic mercury in a retort (see link) on the roaster for 12 days. The end of the retort was brought under a bell placed in a vessel with Hg. As a result, the mercury level in the bell rose by about 1/5. An orange-red substance, mercury oxide, formed on the surface of the mercury in the retort. The air remaining under the bell was unsuitable for breathing. Lavoisier's experiment made it possible to judge the composition of the air; it turned out that the air contains 4/5 N 2 and 1/5 O 2 by volume.

Almost simultaneously with oxygen, another important component of air was isolated and studied - N 2 (Daniel Rutherford in 1772). Somewhat earlier than Rutherford, No. 2 was obtained by an English researcher - G. Cavendish and is called "spoiled air".

________________________________________________________________________

Retort(lat. retorta, literally - turned back) - a device used in chemical laboratory and factory practice for distillation or for reproducing reactions that require heating and are accompanied by the release of gaseous or liquid volatile products, which are immediately subjected to distillation.

Chemist W. Ramsay and physicist D. Rayleigh in 1894 they discovered a heavy gas that is part of the air - argon. A year later Ramsay opened helium. Together with Traverse he opened krypton,xenon and neon . In 1900, the English physicist E. Rutherford discovered radon.

So, air is a mixture of gases that forms the earth's atmosphere.

It includes:

The composition of the earth's atmosphere remains constant over land, over sea, in cities and in rural areas. It also does not change with height. It should be remembered that we are talking about the percentage of air components at different altitudes. However, the same cannot be said about the weight concentration of gases. As you rise upward, the density of the air decreases and the number of molecules contained in a unit of space also decreases. As a result, the weight concentration of the gas and its partial pressure decrease.

1.1 Chemical method for determining the molar mass of air

Molar mass is the mass of one mole of a substance.

There are various ways to determine the molecular weight of air. Let's determine it using the formula from the chemistry course.

Given: SI: Solution:

) 23%)* Mr()+ 𝜔()* Mr()+

() 76% + (Ar)* Mr(Ar) ;

Mr()=32 g/mol 32*kg/mol

Mr() =28 g/mol 28* kg/mol

Mr(Ar) =40 g/mol 40* kg/mol

Answer: The molar mass of air is

1.2 Air pumping method

Installation diagram for pumping air from the flask:

C - glass flask;

A- rubber tube;

B - vacuum gauge.

Using the ideal gas equation of state, the molar mass of the gas can be determined. At not too high pressures, but rather high temperatures, the gas can be considered ideal.

The state of such a gas is described by the Mendeleev-Clapeyron equation:

where P is gas pressure; V - volume of gas; m mass of gas; M is the molar mass of the gas;

R = 8.3145 J/(mol∙K) - universal gas constant; T is the absolute temperature of the gas.

From formula (1) we obtain the expression for the molar mass of the gas:

Therefore, to calculate M, it is necessary to know the mass of the gas m, the temperature T, the gas pressure p and the volume V it occupies.

Let a vessel of volume V contain a gas of mass m 1 under pressure p 1 and at temperature T. The equation of state (1) for this gas will take the form

Let us pump out part of the gas from the vessel without changing its temperature (isothermally). After pumping, the mass of gas in the vessel and its pressure will decrease. Let us denote them m2 and P2, respectively, and again write the equation of state

From equations (3) and (4) we obtain

Using this equation, knowing the change in gas mass and change in pressure, as well as the temperature and volume of the gas, you can determine the molar mass of air.

In this work, the gas under study is air, which, as is known, is a mixture of nitrogen, oxygen, carbon dioxide, argon, water vapor and other gases. Formula (5) is also suitable for determining M of a gas mixture. In this case, the found value of M represents some average or effective molar mass of the gas mixture.

3. Practical part

3.1 Determination of the molar mass of air

Our experiment is based on the following problem: a ball with a shell mass filled with helium lifts a load of mass m. Consider pressure and temperature to be known quantities.

Let's give an idea of ​​the experiment: A helium-filled balloon lifts a plasticine weight. We will add a weight to a children's balloon filled with helium of such mass that it will hover in the air. The shell of the ball is considered inextensible. (Appendix 1)

Let us demonstrate a diagram of the experiment indicating all the forces. The shell of the ball, the helium, and the weight are acted upon by the force of gravity mg, and this force of gravity is balanced by the Archimedes force. According to Newton's second law, the Archimedes force is equal to the sum of the forces of gravity.

Then we get the formula:

Let's use the Mendeleev-Clapeyron formula:

Let's express the molar mass:

Let's substitute the resulting air density from the third formula into the fifth and get a formula for calculating the molar mass of air:

It follows that in order to find the molar mass of air, you need to measure the mass of the load (Appendix 2), the mass of helium, the mass of the shell (Appendix 3), temperature (Appendix 4), air pressure (Appendix 5), and the volume of the ball.

Let's find the volume of the ball. To do this, pour water into the aquarium, put a mark, release helium from the ball and through the hole in the ball, using a tube and funnel, fill the ball with water, the water level has risen exactly by the volume of the ball. Using a beaker, pouring water from the aquarium to the initial mark, determine the volume of the ball (Appendix 6).

We find the mass of helium in the ball using the Mendeleev-Clapeyron equation, taking into account that the helium temperature and pressure are equal to atmospheric indicators:

Let's express the mass of helium:

Let's substitute the known values:

Let's substitute the found values ​​into the general formula for molar mass:

M==0.027 kg/mol

3.2 Measurement errors

When evaluating the results, we can estimate the measurement error. Errors arise in any measurement, but it seems to us that I made the greatest error when measuring the volume of the ball.

Let's find the relative measurement error using the formulas:

Absolute instrumental and absolute reading errors:

Relative measurement error:

27*kg/mol*0.044=

kg/mol27*kg/molkg/mol

*I repeated the experiment several times and got a result close to the first one. This suggests that the experiment I proposed is quite accurate.

4.Conclusion: The method I propose is convenient at home or at school, so I believe that it can be used in one of the 10th grade physics workshops. For a more simplified version of the work, consider the volume of the ball and the mass of the shell to be known quantities. It is also advisable to use a reusable valve.

Therefore, I developed a manual for conducting a workshop in physics (Appendix 6).

5. List of sources used:

Air//Symbols, signs, emblems: Encyclopedia/ed.-compiled by V.E. Bagdasaryan, I.B. Orlov, V.L. Telitsyn; edited by ed. V.L.Teplitsyn.-2nd ed.-

M.: LOKID-PRESS, 2005.-495 p.

G. I. Deryabina, G. V. Kantaria. 2.2.Mole, molar mass. Organic chemistry: web textbook.

http://kf.info.urfu.ru/glavnaja/

https://ru.wikipedia.org/wiki/Molar_mass

https://ru.wikipedia.org/wiki/Air

http://pandia.ru/text/77/373/27738.php

http://ladyretryka.ru/?p=9387

6. Applications:

Appendix 1

Appendix 2

Appendix 3

Appendix 4

Appendix 5

Appendix 6

Air is an intangible quantity, it cannot be touched or smelled, it is everywhere, but for humans it is invisible; finding out how much air weighs is not easy, but possible. If the surface of the Earth, as in a children's game, is drawn into small squares measuring 1x1 cm, then the weight of each of them will be equal to 1 kg, that is, 1 cm 2 of atmosphere contains 1 kg of air.

Can this be proven? Quite. If you build a scale from an ordinary pencil and two balloons, securing the structure to a thread, the pencil will be in balance, since the weight of the two inflated balloons is the same. Once one of the balloons is pierced, the advantage will be in the direction of the inflated balloon, because the air from the damaged balloon has escaped. Accordingly, simple physical experience proves that air has a certain weight. But, if you weigh the air on a flat surface and in the mountains, then its mass will turn out to be different - mountain air is much lighter than the one we breathe near the sea. There are several reasons for the different weights:

The weight of 1 m 3 of air is 1.29 kg.

• the higher the air rises, the more rarefied it becomes, that is, high in the mountains, the air pressure will not be 1 kg per cm 2, but half as much, but the content of oxygen necessary for breathing also decreases by exactly half, which can cause dizziness, nausea and ear pain;
• water content in the air.

The air mixture includes:

1.Nitrogen – 75.5%;

2. Oxygen – 23.15%;

3. Argon – 1.292%;

4. Carbon dioxide – 0.046%;

5. Neon – 0.0014%;

6. Methane – 0.000084%;

7. Helium – 0.000073%;

8. Krypton – 0.003%;

9. Hydrogen – 0.00008%;

10. Xenon – 0.00004%.

The amount of ingredients in the air may change and, accordingly, the mass of air also undergoes changes in the direction of increase or decrease.

• air always contains water vapor. The physical law is that the higher the air temperature, the more water it contains. This indicator is called air humidity and affects its weight.

What is the weight of air measured in? There are several indicators that determine its mass.

How much does a cube of air weigh?

At a temperature of 0° Celsius, the weight of 1 m 3 of air is 1.29 kg. That is, if you mentally allocate a space in a room with a height, width and length equal to 1 m, then this air cube will contain exactly this amount of air.

If air has weight and weight that is quite noticeable, why does a person not feel heaviness? Such a physical phenomenon as atmospheric pressure means that every inhabitant of the planet is pressed by an air column weighing 250 kg. The average palm area of ​​an adult is 77 cm2. That is, in accordance with physical laws, each of us holds 77 kg of air in the palm of our hand! This is equivalent to the fact that we constantly carry 5 pound weights in each hand. In real life, even a weightlifter cannot do this, however, each of us can cope with such a load easily, because atmospheric pressure presses from both sides, both outside the human body and from the inside, that is, the difference is ultimately zero.

The properties of air are such that it affects the human body differently. High in the mountains, due to a lack of oxygen, people experience visual hallucinations, and at great depths, the combination of oxygen and nitrogen in a special mixture - “laughing gas” - can create a feeling of euphoria and a feeling of weightlessness.

Knowing these physical quantities, we can calculate the mass of the Earth’s atmosphere - the amount of air that is held in the near-Earth space by gravitational forces. The upper boundary of the atmosphere ends at an altitude of 118 km, that is, knowing the weight of m 3 of air, you can divide the entire surface area into air columns, with a base of 1x1 m, and add up the resulting mass of such columns. Ultimately, it will be equal to 5.3 * 10 to the fifteenth power of tons. The weight of the planet's air armor is quite large, but it is only one millionth of the total mass of the globe. The Earth's atmosphere serves as a kind of buffer that protects the Earth from unpleasant cosmic surprises. From solar storms alone that reach the surface of the planet, the atmosphere loses up to 100 thousand tons of its mass per year! Such an invisible and reliable shield is air.

How much does a liter of air weigh?

A person does not notice that he is constantly surrounded by transparent and almost invisible air. Is it possible to see this intangible element of the atmosphere? Visually, the movement of air masses is broadcast daily on the television screen - a warm or cold front brings long-awaited warming or heavy snowfall.

What else do we know about air? Probably, it is vitally necessary for all living beings living on the planet. Every day a person inhales and exhales about 20 kg of air, a quarter of which is consumed by the brain.

The weight of air can be measured in different physical units, including liters. The weight of one liter of air will be equal to 1.2930 grams, at a pressure of 760 mm Hg. column and a temperature of 0°C. In addition to the usual gaseous state, air can also be found in liquid form. For the transition of a substance to this state of aggregation, exposure to enormous pressure and very low temperatures will be required. Astronomers suggest that there are planets whose surfaces are completely covered with liquid air.

The sources of oxygen necessary for human existence are the Amazon forests, which produce up to 20% of this important element on the entire planet.

Forests are truly the “green” lungs of the planet, without which human existence is simply impossible. Therefore, living indoor plants in an apartment are not just a piece of furniture, they purify the indoor air, the pollution of which is tens of times higher than outside.

Clean air has long become a shortage in megacities; air pollution is so great that people are ready to buy clean air. “Air sellers” first appeared in Japan. They produced and sold clean air in cans, and any resident of Tokyo could open a can of clean air for dinner and enjoy its freshest aroma.

Air purity has a significant impact not only on human health, but also on animal health. In polluted areas of equatorial waters, near human-populated areas, dozens of dolphins are dying. The cause of death of mammals is a polluted atmosphere; on autopsies of animals, the lungs of dolphins resemble the lungs of miners, clogged with coal dust. The inhabitants of Antarctica, penguins, are also very sensitive to air pollution; if the air contains a large amount of harmful impurities, they begin to breathe heavily and intermittently.

For a person, clean air is also very important, so after working in the office, doctors recommend taking daily hour-long walks in the park, forest, or outside the city. After such “air” therapy, the body’s vitality is restored and well-being significantly improves. The recipe for this free and effective medicine has been known since ancient times; many scientists and rulers considered daily walks in the fresh air a mandatory ritual.

For a modern city dweller, air treatment is very relevant: a small portion of life-giving air, weighing 1-2 kg, is a panacea for many modern ailments!