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Research work "does air have weight". How much does the air in the room weigh? Air and not a lot of weight

Melnikova Valeria

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City Scientific and Practical Conference

"Planet of the Erudites"

Does air have weight?

The world

Melnikova Valeria Igorevna,

4 "A" class, MBOU secondary school No. 14

Supervisor:

Mikhailova I.R.,

primary school teacher, MBOU secondary school No. 14

Dzerzhinsk

2013

Air cleaning.
Air has weight.
Conducting experiments.

Introduction

Our entire planet is shrouded in a transparent veil - air. We don't see it, we don't feel it. But if it suddenly disappears, water and all other liquids will instantly boil on Earth, and the rays of the Sun will burn all living things.

A person can go without food for five weeks, without water for five days, and without air for a maximum of five minutes. Air is needed by humans, animals, and plants to breathe, and therefore to live. And the wind? It's air movement! Without wind, clouds would always be above the sea or river. This means that rain without wind could only fall over water. Under the action of air and water, geological processes take place on the surface of the Earth, weather and climate are formed. By burning fuel (and oxygen, a component of air, must necessarily participate in this), people have long received heat, which is necessary both in everyday life and in production.

Air is the most important source of chemical raw materials. Just two centuries ago, scientists learned that air is a mixture of many gases, mainly oxygen and nitrogen, argon and carbon dioxide. Due to the urgency of this problem, we have identified the followingpurpose of the study:determine if air has weight?

Research objectives:

Review best practices on air science;
Determine the properties of air;
Conduct an experiment to determine the weight of air;
Draw conclusions.

Importance of air for humans.

For humans, temperature, humidity, air movement are of great importance. For example, if you are lightly dressed and engaged in simple work, the best air temperature is 18-20 C. The harder the work, the lower the air temperature can be, but not so much that it becomes difficult to breathe, as in severe frost. People feel best when the air humidity is 40-60 percent. Dry air is usually well tolerated, and high air humidity has an unfavorable effect: at high temperatures, the body overheats, and at low temperatures, it becomes supercooled.

Air cleaning.

The amount of carbon dioxide, chemical compounds that are emitted by industrial enterprises and cars is growing in the air.

There is a widespread movement in the world in defense of nature. We have passed laws and are developing new ones, according to which the heads of enterprises are responsible for cleaning and neutralizing gases before they are released into the atmosphere.

Plants, the lungs of the planet, play a huge role in air purification. They trap dust, soot, absorb carbon dioxide and release oxygen. Among other natural filters, poplar and sunflower are the best at purifying air from pollution. Studies have shown that on busy highways, along which pyramidal poplars were planted and sunflower fields stretched, the air remained clean.

Air has weight.

Air has weight. In a liter bottle, for example, there is more than one gram of air. With its weight, the air presses on us and on all objects around us. If, for example, you pump out air from a tin can, it will flatten.

At a temperature of 0 °C and normal atmospheric pressure, the mass of air with a volume of 1 m3 is 1.29 kg.

Conducting experiments.

Experience can prove that air has weight. In the middle of a stick sixty centimeters long, we will strengthen the rope, and we will tie two identical balloons to both ends of it. Let's hang the stick by the string and see that it hangs horizontally. If you now pierce one of the inflated balloons with a needle, air will come out of it, and the end of the stick to which it was tied will rise up. If you pierce the second ball, then the stick will again take a horizontal position.

This happens because the air in the inflated balloon is denser, and therefore heavier, than the one that is around it.

Another experience:

Get an empty clear plastic bottle. This experience will show whether it is as empty as it seems. Dip the bottle into the basin of water so that it begins to fill. See what happens to the water. You can see bubbles coming out of the neck. It is the water that displaces the air from the bottle. Most things that look empty are actually filled with air.

Feel the air

Is there air around? It's very easy to find out. Wave a piece of cardboard in front of your face. The cardboard will make the air move and you will feel it blow on your face.

Paper racing.

Air can move objects. We propose to arrange such a game: each player will need a piece of cardboard and a sheet of paper. One side of the sheet needs to be bent. Instead of finishing tape, stretch the thread. Now, on command, wave the cartons behind the sheets of paper, and the air will move them forward.

Heavy newspaper.

Take half a piece of newspaper and spread it out on the table. Place a ruler under the newspaper so that its end protrudes beyond the edge of the table. Click on the ruler and try to tear it off the table.

It turns out that this is not so easy to do, because air pressure presses the newspaper against the table.

Flattened package.

For the experiment, take a small juice bag with a hole for the tube. Suck out the juice from the bag through a straw. Keep pulling air through it. See what happens. When part of the air leaves the bag, the outside air will squeeze its walls. Take out the straw and look at the bag.

The walls parted again, because the air entered the bag and straightened it. See what happens to the bag if you blow even more air into it.

Thus, we have proved that air has weight.

Conclusion.

How much air weighs depends on when and where it is weighed. The weight of air above a horizontal plane is atmospheric pressure. Like all objects around us, air is also subject to gravity. This is what gives the air a weight that is equal to 1 kg per square centimeter. The density of air is about 1.2 kg / m3, that is, a cube with a side of 1 m, filled with air, weighs 1.2 kg.

An air column rising vertically above the Earth stretches for several hundred kilometers. This means that a column of air weighing about 250 kg presses on a person standing straight, on his head and shoulders, the area of \u200b\u200bwhich is approximately 250 cm2!

By the way...

In everyday life, when we weigh something, we do it in air, and therefore we neglect its weight, since the weight of air in air is zero. For example, if we weigh an empty glass flask, we will consider the result obtained as the weight of the flask, neglecting the fact that it is filled with air. But if the flask is closed hermetically and all the air is pumped out of it, we will get a completely different result ...

Bibliography

Yu.V. Novikov "Ecology, environment and man"
Encyclopedia "The World Around Us"
Website http://www.5.km.ru/

When we lift a bucket filled with water, we immediately feel its great weight. Lifting a bucket without water, we feel only the weight of the vessel itself. But this bucket is not empty, it is filled with air; so the air itself has no weight? Maybe the air in the bucket weighs nothing because it escapes from the open bucket. Let's take a wineskin or a bull's bladder, fill it with air, tie it up and try to weigh it, and then squeeze the air out of it and weigh it again. It turns out that the readings of the scales will be the same both times, maybe, really, the air weighs nothing and can this be considered proven? At the same time, if we agree with the absence of the weight of air, then many phenomena will seem incomprehensible.

Why, for example, medical cups retract human skin. Why, if we fill a glass with well-polished edges exactly to these edges with water and cover it with a piece of paper, and then quickly turn the glass over, will the water not pour out of the glass? Why does a pump that pumps water from the bottom up work?

All these phenomena seemed inexplicable for a long time, but the pump also made it possible to discover the truth.

In search of an explanation, they turned to the famous scientist Galileo, then an 80-year-old elder. Two variants of further events have come down to us. According to the first of them, Galileo seemed to be embarrassed and did not know what to answer. According to the second version, Galileo weighed the "empty" bottle, then warmed it up strongly, closed it with a cork and, having cooled, weighed it again. It turned out that this time the bottle weighed less. Information has been preserved that in the 17th century a pump was built in the garden of the Duke of Tuscany in Florence to pump water for a fountain to a height of more than 10 meters, but this did not succeed. The pump was made as well as all the others, which worked perfectly, and therefore the failure with it seemed completely incomprehensible.

Galileo correctly explained the decrease in the weight of the bottle by pointing out that when heated, the air expanded and was forced out of the bottle into the atmosphere. Consequently, there was less of it in the bottle, and therefore the weight of the bottle became smaller for the second time. Thus, Galileo established that air has weight, but it weighs less than water, and the new pump, larger than the previous ones, did not work only because the weight of the outside air did not balance the too high column of water.

Undoubtedly, the second version of the story that has come down to us is more correct, since it is known that Galileo had already made similar calculations before. He explained the force that balances the pressure of the air with the "power of emptiness". In those days, there was an opinion that nature was "afraid of emptiness", and as soon as a void forms somewhere, nature immediately fills it. But at the same time, it remained inexplicable that this “fear of emptiness” stopped above 10 meters. Consequently, the mystery has never been fully resolved.

A student of Galileo, Torricelli continued to study the issue and made a series of experiments that allowed him to reliably prove that air has weight, and led him in 1643 to the invention of an instrument now known to us under the name barometer . Torricelli filled a glass tube 100 centimeters long closed at one end with mercury and immersed its open end in a vessel with mercury. At the same time, the mercury did not completely pour out of the tube, but, having lowered a little, stopped at a level of about 76 centimeters; Torricelli correctly concluded that mercury is supported in the tube by the weight of the outside air.

The air pressure on the surface of the mercury in the cup is balanced by the pressure of the mercury column.

For several years, Torricelli's conclusions were not confirmed. Finally, in 1647, the French scientist Pascal decided to finally clarify this issue. He turned to his relative Perrier, who lived in the city of Clermont, at the foot of the Pew de Dome mountain, with a request to make the necessary observations. Pascal's request was fulfilled on September 19, 1648, and from that date the fact that air has weight ceased to be in doubt.

Perrier did just that. He prepared two identical Torricelli tubes and, having measured the height of the mercury column in the tubes at the foot of the mountain, left one of them in place, and climbed to the top with the other. At an altitude of 975 meters, he again measured the height of the mercury in the tube. It turned out that at the top it was 8 millimeters lower than at the foot of the mountain.

Amazed by the result, Perrier checked his measurements many times and, only finally convinced of their correctness, went downstairs. In the tube below, the mercury remained at the same level. At the same level, she stopped in the tube brought from above.

Thus, it was finally proved that air has weight and therefore it presses with more force in the lower layers than at the top, where a smaller amount of it remains above the observer's head. Air presses on the surface of the Earth with the same force that would press a layer of water 10.3 meters thick. That is why the pump of the Duke of Tuscany, raised above the water level above 10 meters, did not work. Mercury is 13.6 times heavier than water. Therefore, it was installed in the Torricelli tube at a height of about 76 centimeters (76x13.6 = 1033.6 centimeters). Air pressure also explains the action of a medical jar, as well as the fact that water does not pour out of an inverted glass, but closed with a piece of paper.

We do not notice this large air weight, since the human body has adapted to it and feels fine in these conditions. All the internal organs of a person are filled with air, which has the same pressure as the pressure of the atmosphere at the surface of the Earth outside our body; this internal pressure balances the external one. Climbing high in the mountains or on an airplane, a person strongly feels a decrease in air pressure with height (Fig. 2) and endures the decrease that occurs at the same time only to a certain limit, after which a feeling of suffocation or even death occurs.

Fish living in the ocean at great depths have adapted to even greater pressure, which is made up of the weight of the atmosphere and the weight of a huge mass of water. Caught at great depths and raised to the surface of the sea, fish die: they are torn apart by internal pressure that is not balanced by external pressure.

Why don't we feel the weight of air when we lift a bucket full of air? Yes, because we weigh it in the very same air. Similarly, when we lower a bucket into a well and fill it with water, we do not feel the weight of the water in the bucket. But it is enough to lift the bucket from the water into the air, as soon as its heaviness is felt.

One cubic meter of air weighs 1.3 kilograms, and the entire atmosphere surrounding the globe weighs 5,300,000,000,000,000 tons. As you can see, air weighs a lot, a lot. The weight of 1 cubic meter of air, equal to 1.3 kilograms, we get when we weigh the air at sea level and at a temperature of 0 °. The higher from the Earth's surface, the less air density becomes and the weight of 1 cubic meter decreases. So, at an altitude of 12 kilometers, 1 cubic meter of air weighs 319 grams, that is, four times less than below; at an altitude of 25 kilometers - 43 grams, and at an altitude of 40 kilometers - only 4 grams (Fig. 3). The increase in air density downwards and its rarefaction at the top are determined by gravity. But no matter how rarefied the air, like a gas, it fills all the space provided to it and, consequently, spreads far upwards from the surface of the Earth.

To what heights does the earth's atmosphere extend? And is it possible to establish its boundary at all, or is the air density gradually fading away?

The second assumption is correct, but nevertheless, theoretically, we can establish the boundaries of the air ocean. This is not difficult to do, since we know the weight of all the atmosphere above our head, and we can calculate the weight of a cubic meter of air at any height.

If the air at all altitudes had the same density as at the surface of the Earth, then the average height of the air envelope surrounding the globe would be close to 8 kilometers. But the density of air decreases rapidly with height, and therefore the height of the atmosphere must be many hundreds of times greater.

Even M. V. Lomonosov analyzed the question of the height of the earth's atmosphere. He reasoned like this. Air is made up of countless tiny particles called molecules. Gas molecules are in continuous motion, rushing up, down, to the sides. Below, where the air is dense and the number of molecules is enormous, they constantly collide with each other and, as it were, "push" in place. The higher, the fewer molecules in the same volume of air, and the path they fly from one collision with a neighboring molecule to another is longer. At the same time, air molecules located at high altitudes often fly down to the Earth; they fall under the influence of gravity, like all other bodies. The fall continues until it collides with molecules located below, in denser layers. Repulsed from them, the falling molecule flies upward again. Such a movement - up and down - all the molecules do countless times. But the molecule moves upward only up to a certain level. This level is determined by the force of gravity, due to which all bodies fall to the Earth, move along its surface and are not carried away from it into the world space. Only those molecules jump out of this level and leave the atmosphere which, at a high altitude, received a push of such a force from a collision with a neighboring molecule that exceeds the force of gravity at this altitude.

Later studies confirmed the correctness of M. V. Lomonosov's reasoning and showed that such a theoretical boundary of the earth's atmosphere lies above the pole at an altitude of 28 thousand kilometers, above the equator at an altitude of 42 thousand kilometers, that is, more than four and seven times the earth's radius.

We, the inhabitants of the earth, are primarily interested in the height of those layers of the atmosphere that still have a measurable density and where those meteorological and physical phenomena take place that we have the opportunity to observe and with which we must reckon.

From this point of view, the height of the earth's atmosphere will be determined by a layer 800-1000 kilometers thick.

Perrier measured the pressure of the atmosphere by the height of a column of mercury in a Torricelli tube, determining its length in millimeters. This method of measurement has been preserved to this day. Modern mercury barometers, in principle, are no different from the Torricelli tube. They are only more technically perfect, which allows you to make readings very accurately, capturing the smallest (up to 1/10 of a millimeter) changes in the height of the mercury column.

As we already know, at sea level, atmospheric pressure on average corresponds to the pressure of a mercury column 760 millimeters high. But this value does not remain constant. In different places at different times of the year and with different weather, it varies widely. The extreme pressure values \u200b\u200bnoted so far are 680 and 802 millimeters.

Changes in air pressure play a significant role in weather phenomena. But this role is still not decisive. Therefore, it is impossible to predict the “weather using the measurement of only one pressure. Therefore, one should not attach much importance to the inscriptions on some metal aneroid barometers: “storm”, “rain” or “dry”. We can easily agree with this if we recall Perrier's experiment described above: the barometer changes its readings not only from the state of the weather, but also from the height at which it is currently located. This property is widely used in aviation, where, according to the readings of the same aneroid barometer ( altimeter ) determine the height of the aircraft.

To facilitate readings, the altimeter scale shows not the pressure value, but the corresponding height.

For a number of theoretical calculations, it is much more convenient to express the value of air pressure not by the length of the mercury column, therefore, not in millimeters, but in units of pressure. The bar is taken as such a unit, equal to the pressure of a million din 2 per 1 square centimeter, which corresponds to the pressure of a mercury column 750.1 millimeters long. In practice, one thousandth of a bar is used - a millibar. The pressure of a mercury column 1 millimeter long is 1.333 millibars. Accordingly, 1 millibar is approximately equal to 0.75 millimeters of mercury. At present, millibars are almost universally used in meteorology, but since the scales of most barometers are made in millimeters, the reading of the pressure value using special tables is then converted to millibars.

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Although we do not feel the air around us, the air is not nothing. Air is a mixture of gases: nitrogen, oxygen and others. And gases, like other substances, are composed of molecules, and therefore have weight, albeit small.

This is because the air in the inflated balloon denser, which means that heavier than the one around it.

How much air weighs depends on when and where it is weighed. The weight of air above a horizontal plane is atmospheric pressure. Like all objects around us, air is also subject to gravity. This is what gives the air a weight that is equal to 1 kg per square centimeter. The density of air is about 1.2 kg / m 3, that is, a cube with a side of 1 m, filled with air, weighs 1.2 kg.

We would not be able to withstand such a weight if it were not opposed by the same pressure inside our body. The following experience will help us understand this. If you stretch a paper sheet with both hands and someone presses a finger on it from one side, then the result will be the same - a hole in the paper. But if you press two index fingers on the same place, but from different sides, nothing will happen. The pressure on both sides will be the same. The same thing happens with the pressure of the air column and the counter pressure inside our body: they are equal.

Air has weight and presses on our body from all sides.
But he cannot crush us, because the counter pressure of the body is equal to the external one.
The simple experience depicted above makes this clear:
if you press your finger on a sheet of paper on one side, it will tear;
but if you press on it from both sides, this will not happen.

By the way...

How much does air weigh and does it weigh at all? We live inside the air, surrounded by it, and do not feel its weight. It may seem that he is weightless. In fact, air has volume and mass. And we feel it when the wind blows - the wind bends the trees to the ground, tears off the hats from the heads.

Does air have weight?

Air does have weight! There is an easy way to be sure.

Take 2 balloons and a straight stick. Tie the balls from different ends of the stick (the length of the threads should be the same). Now tie a rope exactly in the middle of the stick. If everything is done correctly, then holding the rope, the stick will be in a horizontal position - a kind of scales have turned out. Now take one of the balloons and inflate it even more. What will happen? The side of the stick with the balloon you just inflated will be lower because the balloon now has more air and weighs more.

But a fair question may arise - why does a balloon that is filled with air and surrounded by air on the outside weigh more? The answer lies in density.

In a liquid, everything that has a greater density than the environment will sink. When you added air to the balloon, you increased its overall density, since the air inside the balloon is under b about more pressure than outside. More pressure means more density, so the heavy air inside the balloon outweighs the balloon with less air.

How much does air weigh?

At the Earth's surface, one cubic meter of air weighs about 1.25 kg(data for dry air).

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Does air have weight? Do not rush to say "yes" or "no", think.

Let's do this experiment.

Let's take a scale, such as shown in Figure 42. Put a children's balloon on the left scale pan, and pour sand in small portions on the right until balance is reached. Let's fill the balloon with air. We tie it up so that the air does not come out, and put it on the scales. The balance was disturbed - a cup with an inflated ball outweighed. So air has weight.

Rice. 42. This experience proves that air has weight

Air weight

By weighing the air, scientists found that it is very light. Its 1 cubic meter (abbreviated as 1 m 3: 1 m wide, 1 m long and 1 m high) weighs 1290 g. It should be remembered that air has such a weight only at the surface of the Earth. If air is weighed at different distances from the earth, then the weight of 1 m3 of air will decrease with height. The farther from the surface of the Earth, the more rarefied the air, less dense, and therefore weighs less.

Air pressure

Since the thickness of the atmosphere is more than 1000 km, the air exerts significant pressure on the earth's surface: it presses on 1 cm 2 of the Earth's surface with a force of 1 kg. Let us calculate what air pressure a person experiences (the surface of his body is on average 1.5 m 2, or 15 thousand cm 2).

It turns out that 15 tons of air presses on a person! Such a huge pressure, it would seem, he will not withstand. However, the person does not feel it. This is explained by the fact that blood, other liquids and gases in the body are compressed to the same pressure and, acting from the inside, balance the external pressure.

Air exerts pressure on all objects on the surface of the Earth.

To verify this, let's do an experiment.

We put a thin rail on the surface of the table so that half of it protrudes beyond the edge of the table. We cover the rail with a sheet of paper the size of a newspaper (you can use the newspaper itself). The paper should lie flat on the table surface. With a sharp blow of the hand on the rail, we will try to throw the paper off the table. However, the rail broke - the paper remained lying on the table. This is due to the fact that air presses on the paper from almost one side, since it fits snugly against the surface of the table.

Rice. 43. Experience proving that air exerts pressure on all objects on Earth. Even a strong blow to the ruler could not lift the newspaper

Air presses on all surrounding objects from all sides.

Back in 1654, the mayor of Magdeburg, Otto von Guericke, decided to show the townspeople the power of air pressure. For the experiment, two metal hemispheres were made (they were later called "Magdeburg"). Tightly adjacent to each other, they formed a hollow ball. In one of the hemispheres there was a hole for pumping out air, which was then tightly closed so that air could not enter the ball. In the experiment, two eights of horses harnessed to teams were used. Each harness was connected to the hemisphere through a strong hook. After the pump pumped out the air from the ball, collected from the hemispheres, the horses, on command, pulled the hemispheres in different directions to tear them apart. But the ball only swayed and remained unharmed. When air was let inside the ball, the hemispheres disintegrated themselves (Fig. 44).

Rice. 44. Experience with the Magdeburg hemispheres