In this lesson we will talk about the concept of atmospheric pressure. We will see that air masses exert a certain pressure on us, called atmospheric pressure. Let's repeat Pascal's law, after which we will conclude what pressure we experience while in the most compressed lower layer of the atmosphere.
Topic: Pressure solids, liquids and gases
Lesson: Atmosphere pressure
So we live at the bottom of the ocean. Air ocean. Air masses envelop our Earth like a big blanket, like a ball of air. In Greek, air is “atmos”, ball is “sphere”. Therefore, the air shell of the Earth is called the atmosphere (Fig. 1).
Rice. 1. Atmosphere - the air shell of the Earth
Now we will see that air masses can exert pressure on us on the surface of the Earth. This pressure is called atmospheric pressure.
All the molecules that make up the atmosphere are attracted to the Earth due to gravity. The upper layers of the atmosphere press on the lower layers of the atmosphere, and so on. Consequently, the lower layers of the atmosphere experience the greatest pressure; they are most compressed. The pressure that is exerted on all layers of the atmosphere, according to Pascal’s law, is transmitted unchanged to any point atmospheric air. You and I, who are on the surface of the Earth, are affected by the pressure of all the air masses located above us (Fig. 2).
Rice. 2. The upper layers of the atmosphere press on the lower ones
To verify the existence of atmospheric pressure, you can use an ordinary syringe. Let's release the air from the cylinder and lower the fitting (end of the syringe) into the colored water. We will move the piston up. We will see that the liquid will begin to rise behind the piston. Why is this happening?
Why does the liquid rise after the piston, despite the fact that the force of gravity directed downward acts on it? This is explained by the fact that atmospheric pressure acts on the surface of the liquid in the vessel from which we fill the syringe. According to Pascal's law, it is transmitted to any point of this liquid, including to the liquid in the syringe fitting, forcing it to enter the syringe (Fig. 3).
Rice. 3. The water in the syringe rises following the piston
Let's conduct another experiment confirming the existence of atmospheric pressure. Let's take a tube open at both ends. Let's lower it to some depth into the liquid and close it top part tube with your finger and remove the tube from the liquid. We will see that the liquid does not flow out of the tube, although the lower end of the tube is open. But if you remove the finger covering top hole tube, the liquid will immediately flow out of it.
The observed phenomenon is explained as follows. When we lower a tube into a liquid, some of the air leaves the tube through the open top end, as the liquid entering from below displaces this air. We then close the hole with our finger and lift the handset. The atmospheric pressure from below becomes greater than the air pressure inside the tube. Therefore, atmospheric pressure prevents liquid from flowing out of the tube.
And finally, one more experience. Take a cylindrical vessel, pour water into it, cover it with a sheet of paper and turn it over. Water will not spill out of the vessel (Fig. 4). Try to explain on your own why this happens, despite the fact that gravity acts on the water in the vessel.
Rice. 4. Water does not pour out of an upside down glass.
So, each of us experiences pressure from a huge thickness of air masses located above. This pressure is called atmospheric pressure. It is created due to the weight of the air, which is acted upon by the gravitational force of the Earth.
Bibliography
- Peryshkin A.V. Physics. 7th grade - 14th ed., stereotype. - M.: Bustard, 2010.
- Peryshkin A.V. Collection of problems in physics, grades 7-9: 5th ed., stereotype. - M: Publishing House “Exam”, 2010.
- Lukashik V. I., Ivanova E. V. Collection of problems in physics for grades 7-9 educational institutions. - 17th ed. - M.: Education, 2004.
- Unified collection of digital educational resources ().
Homework
- Lukashik V.I., Ivanova E.V. Collection of problems in physics for grades 7-9 No. 548-554.
- form an idea of atmospheric pressure and patterns of its change
- learn to calculate atmospheric pressure with changes in altitude
Slide 2
Repetition of previously learned
- What is air humidity?
- What does it depend on?
- How are fog and clouds formed?
- What types of clouds do you know?
- How are they different from each other?
- How is precipitation formed?
- What types of precipitation do you know?
- How is precipitation distributed over the earth's surface?
Slide 3
- Where is the wettest place on Earth?
- Driest?
- What are the lines called that connect points on maps?
- the same amount of precipitation? Isohyets
- same temperatures? Isotherms
- the same absolute height? Isohypses or horizontal lines
Slide 4
Does air have weight?
How much does air weigh?
Slide 5
- The force with which the atmospheric air column presses on the earth's surface and everything on it is called atmospheric pressure.
- For 1 sq. cm presses a column of atmospheric air with a force of 1 kg 33 g.
- The first to invent a device with which to measure atmospheric pressure was the Italian scientist Evangelista Torricelli in 1643.
Slide 7
The average pressure at sea level at t 0°C is 760 mm Hg. – normal atmospheric pressure.
Slide 8
In the 17th century, Robert Hooke proposed improving the barometer
A mercury barometer is inconvenient and unsafe to use, so an aneroid barometer was invented.
Slide 9
Why does the level of mercury in the tube change with altitude?
Slide 10
Slide 11
Slide 12
For 100 m of ascent, the pressure drops by 10 mm Hg.
- From a height of 2000 m to 150 m of ascent - 10 mm Hg;
- 6000 m for 200 m of ascent - 10 mmHg.
- At an altitude of 10,000 m, the atmospheric pressure is 217 mm Hg.
- At an altitude of 20,000 m 51 mm Hg.
Slide 14
Points on the map with the same atmospheric pressure are connected by lines - isobars
Slide 15
Cyclones and anticyclones
- The earth's surface heats up unequally, and therefore the atmospheric pressure in different parts of it varies
- Cyclone - a moving area with low atmospheric pressure in the center
- Anticyclone - a moving area with high atmospheric pressure in the center
- Cyclones and anticyclones on maps are indicated by closed isobars
Slide 16
This is what these vortices look like from space
Slide 17
Atmospheric pressure (records)
- The highest atmospheric pressure was recorded in the Krasnoyarsk Territory in 1968, 812.8 mm Hg.
- The lowest was in the Philippines in 1979 – 6525 mmHg.
- Moscow is located at an altitude of 145 m above sea level. The most high pressure reached 777.8 mm Hg. Lowest 708 mm Hg.
- Why can't a person feel atmospheric pressure?
- Palm 100 sq.cm. A column of atmospheric air of 100 kg presses on it.
Slide 18
Indians of Peru live at an altitude of 4000 m
Slide 19
Let's solve problems
- Height settlement 2000 m at sea level. Calculate the atmospheric pressure at this altitude.
- At sea level the atmospheric pressure is 760 mmHg
- For every 100 m of rise, the pressure drops by 10 mmHg.
- 2000:100=20
- 20x10 mmHg=200
- 760mmHg-200mmHg=560mmHg.
Slide 20
- The pilot rose to a height of 2 km. What is the atmospheric air pressure at this altitude, if at the surface of the earth it was 750 mm Hg.
- 2000:100=20
- 20x10=200
- 750-200=550
- What is the height of the mountain if the atmospheric pressure at the base is 765 mm Hg and at the top 720 mm Hg?
- 765-720=45 mm Hg.
- At 100 m – 10 mm Hg.
- At x m -45 mm Hg.
- x= 100x45:10=450m
Slide 21
- What is the relative height? mountain peak, if the barometer shows 740 mm at the bottom of the mountain, and 440 mm at the top
- The difference in pressure is 300mm, which means the elevation height = 3000m
Slide 22
- At the foot of the mountain, the atmospheric pressure is 765 mm Hg. At what altitude will the atmospheric pressure be 705 mm Hg?
- At the foot of the hill the pressure is 760 mm Hg.
- What is the height of the hill if the atmospheric pressure at the top is 748 mm Hg. Is it a hill or a mountain?
- 765-705=60
- The difference in pressure is 60mm, therefore at an altitude of 600m
- The difference in pressure is 12mm, which means the height of the rise is 120 m. This is a hill, since the height of the rise does not exceed 200 m
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§ 42. Weight of air. Atmospheric pressure - Physics 7th grade (Peryshkin)
Short description:
We don't notice the air because we all live in it. It's hard to imagine, but air has weight just like all bodies on Earth. This is so because the force of gravity acts on it. The air can even be weighed on a scale by placing it in a glass ball. Paragraph forty-two describes how to do this. We don't notice the weight of the air; nature designed it that way.
The air is held near the Earth by gravity. He doesn't fly into space thanks to her. The multi-kilometer air shell around the Earth is called the atmosphere. Of course, the atmosphere puts pressure on us and on all other bodies. The pressure of the atmosphere is called atmospheric pressure.
We don’t notice it because the pressure inside us is the same as the air pressure outside. In the textbook you will find a description of several experiments proving that there is atmospheric pressure. And, of course, you will try to repeat some of them. Or perhaps you can come up with your own or look it up on the Internet to show it in class and surprise your classmates. There are very interesting experiments about atmospheric pressure.
Physics, 7th grade. Lesson summary
Lesson topic Atmosphere pressure.Lesson type Learning new material
Class 7
Academic subject Physics
UMK“Physics” Expand the definition of atmospheric pressure, study the causes of atmospheric pressure; phenomena caused by atmospheric actions
Planned results
Personal: formation of skills to manage one’s educational activities, formation of interest in physics when analyzing physical phenomena, formation of motivation by revealing the connection between theory and experience, development of logical thinking.
Subject: the formation of ideas about atmospheric pressure, the formation of skills to explain the influence of atmospheric pressure on living organisms, and to use knowledge about atmospheric pressure in everyday life.
Metasubject: develop the ability to determine the goals and objectives of activities, develop the ability to analyze facts when observing and explaining phenomena, conduct observations, experiments, generalize and draw conclusions.
Interdisciplinary connections Geography, biology, literature.
Forms of organization cognitive activity Frontal, group, individual
Teaching methods Reproductive, problematic, heuristic.
Didactic aids Physics. 7th grade: textbook by A.V. Peryshkin, presentation for the lesson, cards with tasks for individual, pair and group work, central educational center “Bustard, 7th grade”.
Equipment Textbook, computer, projector, for the group - a glass of water, pipettes, sheets of paper.
During the classes
I. Organizational moment.Teacher: Hello! Sit down! I am glad to welcome everyone present! I believe that the lesson will go great and everyone will be in a great mood.
II. Updating knowledge
Teacher: Remember what we studied in the last lesson?
Students: Communicating vessels.
Teacher: What vessels are called communicating?
Students: Two vessels connected to each other by a rubber tube are called communicating.
Teacher: Some of you have made models of fountains and communicating vessels. (students show their work).
Teacher: You have task cards on your tables different levels Difficulty: low, medium, high. (Appendix 1) Select the difficulty level of the task and complete it. After completion, exchange notebooks and check the correctness of the task on the screen. Give your ratings. (Collect selectively several works)
III. Goal setting
Teacher: Guys, listen carefully, now I’ll tell you riddles, and you try to guess them.
Is there a blanket for the children?
So that the whole Earth is covered?
So that there is enough for everyone,
And besides, it wasn’t visible?
Neither fold nor unfold,
Neither touch nor look?
It would let in rain and light,
Yes, but it seems not?
What is this?
Students: Atmosphere
Teacher:
Two guys with equal strength
The boards were knocked down and this is the result:
The tip of the nail sank into the hat,
The hat left a small dent,
Together the friends swung a sledgehammer,
This caused the boards to crack in two.
Oh what physical quantity are we talking?
Students: Pressure.
Teacher. Right. What will the topic of today's lesson be?
Students: Atmospheric pressure.
Teacher: What is the purpose of the lesson?
Students: Find out what atmospheric pressure is.
Teacher: Try to identify a number of questions that you and I will have to answer during the lesson.
Students: What is atmospheric pressure, why does it exist, where does atmospheric pressure work, etc.
Teacher: Much of what you said is relevant to our lesson today, we will try to find answers to these questions.
Open your notebooks and write down the topic of the lesson. (inscription on the board)
IV. Discovery of new knowledge
Teacher: From the geography course, remember what atmosphere is? What does it consist of?
Students: The atmosphere is the shell of air surrounding the Earth. Consists of oxygen, nitrogen and other gases.
Teacher: The atmosphere has great importance for a person. For a normal life, a person needs air. Without it, he can live no more than five minutes. Atmospheric air is one of the main vital important elements environment. It must be protected and kept clean. The atmosphere extends to a height of several thousand kilometers and has no clear upper limit. The density of the atmosphere decreases with height. What do you think would happen to the Earth's atmosphere if there were no gravity?
Students: She would have flown away.
Teacher: Why doesn’t the atmosphere “settle” on the surface of the Earth?
Students: The molecules of the gases that make up the atmosphere move continuously and randomly.
Teacher: We are at the depths of the ocean of air. Do you think the atmosphere is putting pressure on us?
Students: Yes.
Teacher: Due to the force of gravity, the upper layers of air compress the lower layers. The air layer adjacent directly to the Earth is compressed the most and, according to Pascal's law, transmits the pressure exerted on it in all directions. As a result of this, the earth's surface and the bodies located in it experience the pressure of the entire thickness of air or, in other words, atmospheric pressure.
Let's try to define atmospheric pressure.
Students: Atmospheric pressure is the pressure exerted by the Earth's atmosphere on the earth's surface and on all bodies located on it.
Teacher: Write the definition in your notebook.
We do not feel air pressure on ourselves. So does it exist?
Teacher: Let's try to verify the existence of atmospheric pressure by performing experiments. Form groups of 4 people. On the tables you have the necessary equipment and task cards. (Appendix 2) Complete them. Discuss the answer in the group.
Why do we squeeze the rubber tip before putting the pipette into the water? (students' answers)
Why won't the water pour out of the glass? (students' answers)
Teacher: What were the experiments you did related to?
Students: With atmospheric pressure.
V. Physical education minute
Teacher: Now get up from your desks and do the exercises with me.
Raise your head up, inhale. Lower your head to your chest, exhale.
Raise your head up, inhale. Lower your head and blow away the lint. Raise your head up, inhale. Lower your head and blow out the candles.
Repeat the exercise again.
VI. Primary consolidation
Teacher: Correct breathing contributes to improvement thought processes. Guys, do you know that it is atmospheric pressure that helps us breathe! The lungs are located in the chest. Inhalation volume chest increases, the pressure decreases, becomes less than atmospheric. And the air rushes into the lungs. When you exhale, the volume of the chest decreases, which causes a decrease in lung capacity. The air pressure increases and becomes higher than atmospheric pressure, and the air rushes into environment. And it’s not just atmospheric pressure that works here. (TsOR – Bustard: fragment)
Here are the texts. (Appendix 3) Work in pairs. And then we’ll listen to those who want to talk about the effect of atmospheric pressure. (students' answers)
Teacher: Now I will read you an excerpt from the poem “Aibolit”.
And the mountains stand in front of him on the way,
And he begins to crawl through the mountains,
And the mountains are getting higher, and the mountains are getting steeper,
And the mountains go under the very clouds!
"Oh, if I don't get there,
If I get lost on the way,
What will happen to them, to the sick,
With my forest animals?
Think about how atmospheric pressure changes with altitude?
Students: The pressure is decreasing.
Teacher: Look at the board, determine where the highest pressure will be at the foot of the mountain or at its top?
Students: At the foot of the mountain.
Teacher: That's right.
There is a card in front of you. (Appendix 4) You need to insert the missing words in the text. (frontal check)
VII. Reflection educational activities
Teacher: Let's summarize the lesson. What are we talking about today?
did you say? Have we achieved the goal of the lesson? Have you covered the topic?
I found out)...
I managed...
It was difficult for me...
I would like to know more...
I am satisfied with my work in class (not really, not satisfied) because...
I'm in a... mood.
Teacher: For work in class... (grading)
VIII. Information about homework
Teacher: Open your diaries, write down homework:
P.42. exercise 19. Additionally - task 1. p.126
Bibliography
1. Gendenshtein L.E. Solutions to key problems in physics for primary school. Grades 7-9.-2nd ed., rev.-M.: ILEKSA, 2016.-208 p.
2. Gromtseva O.I. Control and independent work in physics. 7th grade: to the textbook by A.V. Peryshkin “Physics. 7th grade". Federal State Educational Standard / 7th ed., revised and supplemented. - M.: Publishing House “Examination”, 2016.-112 p.
3. Maron A.E. Physics. 7th grade: educational and methodological manual. - 3rd ed. - M.: Bustard, 2015. - 123 p.
4. Peryshkin A.V. Physics, 7th grade - Moscow: Bustard, 2015.-319.
Annex 1
Card “Communicating vessels”
Tasks low level difficulties
1. Give examples of communicating vessels.
2. Two glass tubes are connected by a rubber tube. Will the liquid level remain the same if the right tube is tilted? If you lift the left handset up?
Medium level tasks
1. Water is poured into communicating vessels. What will happen and why if left side U-shaped tube add some water; add water to the middle vessel of the three-legged tube?
2. Which coffee pot has more capacity?
Tasks high level difficulties
1. Which coffee pot has more capacity?
2. There is mercury in communicating vessels. Water is added to one of the vessels, and kerosene is added to the other. The height of the water column hв = 20 cm. What should be the height hк of the kerosene column so that the mercury levels in both vessels coincide.
Card
F.I.
Check the box next to the difficulty level of the task you have chosen.
Low Medium High
Appendix 2
Card for group work
Experience 1:
Equipment and materials: Water, glass, sheet of paper.
Pour water into a glass, cover it with a sheet of paper and, supporting the sheet with your hand, turn the glass upside down. Remove your hand from the paper. Water will not spill out of the glass. Explain why? (Look at Fig. 133, p. 132)
Experience 2:
Equipment and materials: Water, pipette.
Fill the pipette with water. Think about why, before putting the pipette into the water, we squeeze the rubber tip?
Appendix 3
Card "How we drink"Drawing in liquid through the mouth causes expansion of the chest and thinning of air both in the lungs and in the mouth. The external atmospheric pressure becomes higher than the internal one. And under its influence, the liquid rushes into the mouth.
Card "Why do flies walk on the ceiling"
The flies climb vertically along the smooth window glass and walk freely along the ceiling. How do they do this? All this is available to them thanks to the tiny suction cups with which the fly's legs are equipped. How do these suction cups work? A rarefied air space is created in them, and atmospheric pressure holds the suction cup against the surface to which it is attached.
Card “Who finds it easier to walk in mud”
It is very difficult for a horse with a solid hoof to pull his foot out of deep mud. Under the leg, when she lifts it, a discharged space is formed and atmospheric pressure prevents the leg from being pulled out. In this case, the leg works like a piston in a cylinder. External atmospheric pressure, enormous in comparison with the pressure that has arisen, does not allow one to raise the leg. In this case, the force of pressure on the leg can reach 1000 N. It is much easier to move through such mud for ruminants, whose hooves consist of several parts and, when pulled out of the mud, their legs compress, allowing air into the resulting depression.
Appendix 4
Card for individual work
There is a _________________ around the Earth, which is held together by ________________. The air layer adjacent to the Earth is compressed and, according to the law, ___________ transfers what is produced to it ___________ in all directions. As altitude increases, atmospheric pressure _____________________.
Card for individual work for children with disabilities
Complete the sentences by filling in the gaps.
There is a _________________ around the Earth, which is held together by ________________ _____________. The air layer adjacent to the Earth is compressed and, according to the law, ___________ transfers what is produced to it ___________ in all directions. As altitude increases, atmospheric pressure _____________________.
(gravity, pressure, atmosphere, decreases, Pascal)
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