The purpose of the lesson:
- to form in students an idea of the phenomenon of diffusion;
- show the significance of the phenomenon of diffusion in nature, technology and everyday life.
- help to understand the extent of the harm of smoking to human health and the environment with the help of physical phenomena and patterns;
- convince students of the need for a healthy lifestyle;
Tasks:
Educational: Form:
- the idea of diffusion as a phenomenon of mixing substances due to the movement of molecules.
- the idea that diffusion is observed in solid, liquid and gaseous states of matter;
- an idea of the importance of diffusion in nature and in everyday life.
Educational:
- learn to logically correctly express your thoughts using physical and mathematical language;
- develop observation skills;
- develop the ability to analyze the course of an experiment, make comparisons based on it, highlight the main thing, and formulate logical conclusions;
- develop the ability to work at a high pace.
Educational:
- to develop the ability to use theoretical knowledge to understand the essence of phenomena occurring in nature and in everyday life.
- increase the level of environmental and aesthetic education of students.
Equipment for the lesson: Petri dishes, potassium permanganate, tweezers, plastic glasses, coffee, cold and warm water.
Computer.
During the classes
1. Organizational moment.
Readiness of the class for the lesson.
2. Formulating the purpose of the lesson.
Today we will learn about a very interesting and important phenomenon in our lives related to the molecular structure of matter. The phenomenon with which we will become acquainted plays a very important role in living and inanimate nature, in everyday life, we will find out whether our health is connected with the concept of diffusion and how? We encounter this phenomenon at every step, every day, without thinking about it. This phenomenon is called “Diffusion”.
Open your notebooks and write down the topic and date of the lesson.
3. Updating of basic knowledge.
Let's remember what you have already learned about the structure of substances in previous lessons.
A frontal survey is carried out:
When did the first assumptions about the structure of matter arise?
What experiments confirm that substances consist of individual particles?
How does the volume of a body change when the distance between particles changes?
What is a molecule?
What do you know about molecular sizes?
What particles are molecules made of?
Are molecules of the same substance the same? Different substances?
4. New material
1) The concept of diffusion.
Teacher: (reads an excerpt from the work of Vladimir Soloukhin) “The Third Hunt.”
About garlic.
Many times I have seen in books a mention of the garlic mushroom, or, more simply, the garlic mushroom. It was said that this mushroom has the smell of garlic and that various seasonings and sauces for meat dishes can be prepared from it.
...I mechanically plucked one mushroom, mechanically rubbed it between my fingers, and suddenly the distinct strong smell of fresh garlic spread like a cloud between the wet spruce trees, fragrant with resin and pine needles. It was so unexpected... The smell from the basket was as if it were not mushrooms, but crushed garlic...
...That day I came home with extraordinary booty. It was scary to put mushrooms in a frying pan. But contrary to expectations, it turned out to be a very spicy and fragrant dish.
After reading the passage, the question is asked: Why do you think all food will smell like garlic?
Based on the students’ assumptions and answers, the teacher makes a clarification: Molecules of substances move and penetrate between each other.
The definition of diffusion is given:
The phenomenon in which mutual penetration of molecules of one substance between the molecules of another occurs is called diffusion.
2) causes and patterns of diffusion.
Let's look at diffusion in gases. Let's conduct an experiment. We spray deodorant in the classroom.
Guys, did you smell the deodorant?
Why is it possible for odors to spread in space?
The spread of odors is possible due to the movement of molecules of substances. This movement is continuous and disorderly. Colliding with the molecules of gases that make up the air, the deodorant molecules change the direction of their movement many times and, moving randomly, scatter throughout the room.
Please draw a conclusion about the cause of diffusion.
Reason for diffusion: the molecules of a substance are in continuous and random motion.
Let's write this statement in our notebook.
We observed the process of diffusion in gases. Is diffusion possible in liquids?
There are Petri dishes with water on your tables. Drop a few crystals of potassium permanganate into the water. Don't forget about safety precautions: Avoid contact of skin and mucous membranes with potassium permanganate crystals.
What are you observing?
Do potassium permanganate crystals dissolve quickly? Why?
What causes potassium permanganate crystals to dissolve in water?
Is the process of diffusion possible in solids?
I'll give you an example. If polished plates of lead and gold are placed one on top of the other and compressed with a weight, then at ordinary room temperature (about 20 ° C) in 5 years the gold and lead will mutually penetrate each other to a distance of only about 1 mm.
What conclusion can be drawn from the example given?
Diffusion in solids occurs extremely slowly.
Why do you think?
Let's see how diffusion occurs in solids in nature.
What conclusion can be drawn from the results of considering diffusion in gases, liquids and solids?
Molecules of substances in any state of aggregation continuously move, i.e. Diffusion occurs in gases, liquids, and solids.
What can be said about the rate of diffusion in various states of matter?
Gas molecules are free, since the distance between the molecules is much greater than the size of the molecules, and they move at high speeds. The molecules of liquids are arranged just as randomly as in gases, but they are much closer to each other and therefore interact with each other more strongly than in gases. Each molecule, surrounded by neighboring molecules, seems to be marking time in one place and slowly moving inside the liquid. The molecules of solids are arranged in a strict order, forming a spatial lattice, which ensures the preservation of the shape and volume of the solid. Particles of a solid body oscillate around an equilibrium position, which remains unchanged for a very long time. Diffusion occurs most quickly in gases, slowest in liquids and slowest in solids.
Thus, we became acquainted with one of the laws of diffusion:
1. Diffusion occurs in substances in different states of aggregation, but at different rates. Diffusion occurs most quickly in gases, slowest in liquids and slowest in solids.
Write this statement in your notebook.
Let's do another experiment:
Pour the same amount of water into two identical glasses, but at different temperatures. . Remember about safety precautions.
Drop a few grains of instant coffee into glasses. Watch what happens.
Is there a diffusion phenomenon here? Why?
What can you say about the rate of diffusion in a glass of cold water and a glass of warm water?
The rate of diffusion increases with increasing temperature, as the molecules of interacting bodies begin to move faster.
The diffusion process proceeds faster with an increase in body temperature.
Write this statement in your notebook.
3. Application of diffusion.
Student messages:
1. The role of diffusion in human digestion and respiration .(Krivonosova A)
Presentations:
1. " The role of diffusion in human digestion and respiration"
The process of absorption of nutrients in the intestine is possible due to diffusion.
How does a person breathe? In humans, the entire surface of the body takes part in breathing - from the thickest epidermis of the heels to the hairy scalp. The skin on the chest, back and stomach breathes especially intensely. Interestingly, these areas of the skin are significantly more intense than the lungs in terms of breathing intensity. With the same size respiratory surface, oxygen can be absorbed here by 28% and carbon dioxide can be released even 54% more than in the lungs. However, in the entire respiratory process, the participation of the skin is negligible compared to the lungs, since the total surface area of the lungs, if you expand all 700 million alveoli, microscopic bubbles through the walls of which gas exchange occurs between air and blood, is about 90-100 square meters and the total The surface area of human skin is about 2 square meters, that is, 45-50 times less.
Thanks to diffusion, oxygen from the lungs penetrates into the human blood, and from the blood into the tissues.
2. Application of diffusion in medicine. Artificial kidney device
More than 30 years ago, the German doctor William Kolf used an “artificial kidney” device. Since then it has been used: for emergency chronic care for acute intoxication; to prepare patients with chronic renal failure for kidney transplantation; for long-term (10-15 years) life support for patients with chronic kidney disease.
The use of an artificial kidney device is becoming more of a therapeutic procedure; the device is used both in the clinic and at home. With the help of the device, the recipient was prepared for the world's first successful kidney transplantation, performed in 1965 by academician B.V. Petrovsky.
The device is a hemodialyzer in which the blood comes into contact with a saline solution through a semi-permeable membrane. Due to the difference in osmotic pressure, ions and molecules of metabolic products (urea, uric acid), as well as various toxic substances that must be removed from the body, pass through the membrane from the blood into the saline solution. The device is a system of flat channels separated by thin cellophane membranes, through which blood and dialysate - a saline solution enriched with a gas mixture of CO2 + O2 - slowly move in counter flows. The device is connected to the patient’s circulatory system. This achieves blood purification from nitrogenous wastes in case of insufficient kidney function, i.e. the chemical composition of the blood is regulated.
3. Harmful manifestation of diffusion (Redkozubov A)
Presentation “Harmful manifestations of diffusion”
Chimneys of enterprises emit carbon dioxide, nitrogen oxides and sulfur into the atmosphere. Excess carbon dioxide in the atmosphere is dangerous for the living world of the Earth, disrupts the carbon cycle in nature, and leads to the formation of acid rain. The process of diffusion plays a large role in the pollution of rivers, seas and oceans. The annual discharge of industrial and domestic wastewater in the world is approximately 10 trillion tons.
Pollution of water bodies leads to the disappearance of life in them, and water used for drinking has to be purified, which is very expensive. In addition, chemical reactions occur in contaminated water, releasing heat. The water temperature rises, and the oxygen content in the water decreases, which is bad for aquatic organisms. Due to rising water temperatures, many rivers no longer freeze in winter.
To reduce the emission of harmful gases from industrial pipes and pipes of thermal power plants, special filters are installed. To prevent pollution of water bodies, it is necessary to ensure that garbage, food waste, manure, and various types of chemicals are not thrown near the shores.
Smokers annually “smoke,” i.e., emit into the atmosphere 720 tons of hydrocyanic acid, 384,000 tons of ammonia, 108,000 tons of nicotine, 600,000 tons of tar and more than 550,000 tons of carbon monoxide. The total mass of cigarette butts on Earth per year is 2,520,000 tons. Tobacco smoke, enveloping the Earth, it traps ultraviolet rays. On average, 25% of all types of substances contained in tobacco are burned and destroyed during smoking; 50% goes into the environment; 20% enters the smoker’s body and only 5% remains in the cigarette filter.
The temperature of tobacco smoke is 35-40 degrees higher than the temperature of the air entering the mouth when smoking, which causes a rather sharp temperature difference in the mouth. When smoking one cigarette, 15-20 such changes occur, which has a bad effect on the condition of tooth enamel: it cracks. This is why the teeth of smokers decay earlier than the teeth of non-smokers. The gaseous fraction of tobacco smoke contains gaseous tar, which when cooled turns into a liquid state, i.e. condenses. At the same time, it settles on the fingers, teeth, walls of the airways, lungs, and enters the stomach. When smoking one pack of cigarettes, a smoker produces about 1 gram of liquid tar
Teacher: (conclusion)
We see how great the importance of diffusion is in inanimate nature, and the existence of living organisms would be impossible if it were not for this phenomenon. Unfortunately, we have to deal with the negative manifestation of this phenomenon, but there are many more positive factors and therefore we are talking about the enormous importance of diffusion in nature.
5. Consolidation
Test Printed on sheets for each (5 minutes)
1. Which of the following statements is true?
A) only gases consist of molecules
B) only liquids consist of molecules
B) all bodies are made of molecules
2. In which bodies does diffusion occur faster at the same temperatures?
A) in gases
B) in liquids
B) in solids
3. What does the diffusion process prove?
A) that molecules interact with each other
B) that molecules are made up of atoms
B) that molecules are constantly moving randomly
4. How does the rate of diffusion depend on temperature?
A) does not depend
B) the lower the temperature of the substance, the lower the speed
C) the higher the temperature of the substance, the lower the speed
5. What phenomenon proves the movement of molecules of substances
A) Brownian motion
B) mechanical movement
C) none of the answers is correct
6. Homework: paragraph 9, task No. 2.
For the curious – paragraph 1 on page 172.
Diffusion is quite common in human life. but we don't even think about it.
Examples of diffusion in human life
Diffusion is the penetration of molecules of one substance into the spaces of molecules of another substance.
The phenomenon of diffusion plays a big role in human life. Oxygen from the air penetrates the blood capillaries of the lungs by diffusion through the walls of the alveoli, and then, dissolving in them, spreads throughout the body, enriching it with oxygen.
The phenomenon of diffusion can be observed at home quite often:
- when we use an aroma lamp with essential oils or body or foot sprays, perfumes,
- when we spray means to kill mosquitoes and flies indoors,
- when we glue something together
- when we drink tea or coffee. In a mug there is tea with sugar and a slice of lemon. We stir hot water with a spoon - this speeds up the process of penetration of sugar and lemon molecules between water molecules.
Examples of diffusion in nature
Thanks to diffusion, insects smell the aroma of flowers from many kilometers away and fly to collect nectar, while simultaneously pollinating plants. Animals find their prey or related individuals by smell.
A few words about human digestion. The greatest absorption of nutrients occurs in the small intestines, the walls of which are specially adapted for this. The internal surface area of the human intestine is 0.65 square meters. It is covered with villi - microscopic formations of the mucous membrane 0.2-1 mm high, due to which the actual surface area of the intestine reaches 4-5 square meters, i.e. reaches 2-3 times the surface area of the entire body. The process of absorption of nutrients in the intestine is possible due to diffusion.
Respiration - the transfer of oxygen from the environment into the body through its integuments - occurs the faster, the larger the surface area of the body and the environment, and the slower, the thicker and denser the body's integuments. From this it is clear that small organisms, in which the surface area is large compared to the volume of the body, can do without special respiratory organs at all, being satisfied with the flow of oxygen exclusively through the outer shell (if it is sufficiently thin and moisturized). In larger organisms, respiration through the skin may be more or less sufficient only if the integument is extremely thin (amphibians); with rough coverings, special respiratory organs are required. The main physical requirements for these organs are maximum surface and minimum thickness, high moisture content of the integument. The first is achieved by numerous branches or folds (pulmonary alveoli, fringed shape of the gills).
How does a person breathe? In humans, the entire surface of the body takes part in breathing - from the thickest epidermis of the heels to the hair-covered scalp. The skin on the chest, back and stomach breathes especially intensely. It is interesting that these areas of the skin significantly exceed the lungs in terms of breathing intensity. With the same size respiratory surface, oxygen can be absorbed here by 28% and carbon dioxide can be released even 54% more than in the lungs. However, in the entire respiratory process, the participation of the skin is negligible compared to the lungs, since the total surface area of the lungs, if you expand all 700 million alveoli, microscopic bubbles through the walls of which gas exchange occurs between air and blood, is about 90-100 square meters and the total The surface area of human skin is about 2 square meters, that is, 45-50 times less.
The role of diffusion in plant nutrition.
The main role in diffusion processes in living organisms is played by cell membranes, which have selective permeability. The passage of substances through the membrane depends on:
- * molecular sizes;
- * electric charge;
- * on the presence and number of water molecules;
- * on the solubility of these particles in fats;
- * on the structure of the membrane.
There are two forms of diffusion: a) dialysis is the diffusion of molecules of a dissolved substance; b) osmosis is the diffusion of a solvent through a semi-permeable membrane. Soil solutions contain mineral salts and organic compounds. Water from the soil enters the plant by osmosis through the semi-permeable membranes of the root hairs. The concentration of water in the soil is higher than inside the root hairs, so diffusion occurs from an area of higher concentration to an area of lower concentration. Then the water concentration in these cells becomes higher than in the overlying cells - root pressure arises, causing an upward flow of sap through the roots and stem, and the loss of water by the leaves ensures further water absorption.
Minerals enter the plant: a) by diffusion; b) sometimes by active transport against a concentration gradient, accompanied by energy consumption. There is also turgor pressure - this is the pressure exerted by the contents of the cell on the cell wall. It is almost always lower than the osmotic pressure of the sap cell, because outside there is not pure water, but a saline solution. Turgor pressure value:
- - preservation of the shape of the plant organism;
- - ensuring growth in young plant cells;
- - maintaining the elasticity of plants (demonstration of cactus and aloe plants);
- - shaping in the absence of reinforcing fabric (demonstration of a tomato);
Speaking about the importance of osmosis for living organisms, we cannot help but dwell on plasmolysis.
Plasmolysis.
If the concentration of salts in the fluid bathing the cell is higher than in the cell sap, as, for example, when a lettuce leaf is immersed in a concentrated saline solution, then the water in the cell sap diffuses out of the cell, moving from an area with a higher water concentration to an area with a lower concentration. Finally, the cell contents lose the ability to exert pressure on the cell wall, in other words, the turgor pressure drops to zero and the lettuce wilts (demonstration). When the volume of cell sap decreases as a result of water loss, the cell cytoplasm is no longer pressed against the cellulose cell wall. Instead, the cytoplasm lags behind the cell wall, undergoing a process of plasmolysis. Plant cells that are exposed to a high concentration of salt solution for too long die. If, after a short-term stay in such a solution, the cells are transferred to clean water, then they can restore their turgenicity.
Turgor pressure makes the plant cell solid and capable of recovering from deformation under the influence of any external force.
Plasmolysis is a reversible process. The reverse process is called deplasmolysis, this is a property of the plasma membrane.
Thus, diffusion is of great importance in the life processes of humans, animals and plants. Thanks to diffusion, oxygen from the lungs penetrates into the human blood, and from the blood into the tissues.
In addition to the widespread manifestation of diffusion in the life of living organisms, it is used in everyday life and industry.
If two substances are separated by a semi-permeable partition (membrane), diffusion proceeds in one direction. This phenomenon is called osmosis.
Osmosis from Greek means push, pressure. During osmosis, the concentrations of the solution are equalized on both sides of the membrane, allowing small solvent molecules to pass through, but not larger solute molecules to pass through. Osmosis flows from a pure solvent to a solution or from a dilute solution to a concentrated one. Osmosis was first observed by the French chemist Nollet in 1748.
The transfer of solvent molecules is due to osmotic pressure or diffusion. This is a thermodynamic parameter that characterizes the tendency of a solution to decrease its concentration upon contact with a pure solvent.
Osmotic pressure is caused by a decrease in the chemical potential of a solvent in the presence of a solute. Osmotic pressure in extremely dilute solutions does not depend on the nature of the solvent and solutes; at constant temperature it is determined only by the number of particles. The first measurements of osmotic pressure were made by the German botanist Pfeffer in 1877, while studying aqueous solutions of sugar.
Solutions with the same osmotic pressure are called isosmotic. Thus, various blood substitutes and physiological solutions are isosmotic relative to the internal fluids of the body. If one solution has a higher osmotic pressure compared to another, it is called hypertonic, and one with a lower osmotic pressure is called hypotonic.
Page 1
Municipal educational institution
Remontnensky secondary school No. 2
Diffusion in nature and human life
(experimental research work)
With. Repair
|
Introduction |
3 |
|
|
§1 |
The phenomenon of “diffusion”, its essence |
4 |
|
§2 |
Osmosis and dialysis - forms of manifestation of diffusion |
5 |
|
§3 |
The role of diffusion in nature |
6 |
|
§4 |
The influence of diffusion on human life |
8 |
|
§5 |
Harmful manifestation of diffusion |
9 |
|
Conclusion |
10 |
|
|
Bibliography |
11 |
Introduction
Diffusion plays a huge role in nature, in human life and in technology. Diffusion processes can have both positive and negative effects on the life of humans and animals. However, not all people have a sufficient understanding of the course of this phenomenon.
Relevance The work is that studying the influence of diffusion on the life activity of plants, animals and humans will expand the range of our knowledge about living nature and demonstrate the close connection between physics, biology, ecology, and medicine.
An object research- diffusion phenomenon .
Subject of study - the influence of the phenomenon of diffusion on processes occurring in nature and associated with human life.
Target: consider the role of diffusion in nature and human life, prove the general significance of this phenomenon.
Tasks:
1. Study material about the role of diffusion in nature and human life.
2. Conduct some experiments characterizing the patterns of diffusion.
3. Analyze the information received about the phenomenon of diffusion, and also determine the degree of significance of this phenomenon for plants, animals, and humans.
Methods:
1. Study of literary and other information sources.
2.Analysis and processing of material on the significance of the diffusion phenomenon.
3. Conducting experiments.
§1 The phenomenon of “diffusion”, its essence
Diffusion (from Latin Diffusio - spreading, spreading, scattering) is a phenomenon in which mutual penetration of molecules of one substance between the molecules of another occurs.
We observe the phenomenon of diffusion every day: whether we pour tea leaves into boiling water, or prepare a coloring solution. And even when something burns on the stove, and the smell is felt throughout the house, we are again faced with the phenomenon of diffusion.
The question arises why the smell in the room does not spread instantly, but after some time. The fact is that the movement of an odorous substance in a certain direction is hindered by the movement of air molecules. Molecules (perfume or naphthalene) on their way collide with molecules of gases that are part of the air. They constantly change direction and, moving randomly, scatter around the room.
Since particles move in gases, liquids, and solids, diffusion is possible in all these substances. However, the rate at which this phenomenon occurs is different for them. To confirm this fact, an experiment was conducted. At the same time, they performed three actions: they cut an orange, dropped a tea bag into a glass, and poured several crystals of potassium permanganate onto the cut of a raw potato. As a result of observations, it was found that the smell of orange spread throughout the room in a few seconds, it took a little more time for the tea to color the water, and the molecules of potassium permanganate diffused only a few millimeters into the potatoes in a couple of hours. The results obtained indicate that diffusion is faster in gases, slightly slower in liquids and very slow in solids. The fact is that in gases and liquids the main type of thermal motion of particles leads to their mixing, but in solids, in crystals, where atoms make small vibrations around the position of a lattice site, this does not happen.
The diffusion process accelerates with increasing temperature. Let's turn to experience. Water was poured into two glasses, but cold into one and hot into the other. They dropped tea bags into the glasses at the same time. It is easy to notice that in hot water, tea colors the water faster and diffusion proceeds faster. This happens because as the temperature increases, the speed at which molecules move increases. Therefore, before injecting the patient, the doctor slightly heats the cold injection solution to a temperature close to human temperature.
§2 Osmosis and dialysis - forms of manifestation of diffusion
In the world of living organisms, diffusion manifests itself in two forms - dialysis and osmosis. Dialysis is the diffusion of solute molecules, and osmosis is the diffusion of a solvent through a semi-permeable membrane.
The main role for diffusion processes in living organisms is played by membranes located on the surface of cells, cell nuclei and vacuoles and having selective permeability. The passage of a substance through a membrane depends on the size and some other physical properties of the solvent molecules, as well as on the properties of the membrane itself.
If a parchment bag is filled with a solution of sugar or salt and placed in a vessel with water, the molecules of the dissolved substance will diffuse through the walls of the bag until their concentration in the bag and in the vessel with water is the same. In this case, we can say that the pores of the membrane are large enough for the passage of solute molecules through them. This method is dialysis– often used to obtain pure preparations of proteins and other compounds.
Dialysis is also used in the artificial kidney machine. The device is a hemodialyzer in which the blood comes into contact with a saline solution through a semi-permeable membrane. From the blood into the saline solution, ions and molecules of metabolic products (urea, uric acid), as well as various toxic substances that must be removed from the body, pass through the membrane. The device is a system of flat channels separated by thin cellophane membranes, through which blood and a saline solution enriched with a gas mixture of CO 2 + O 2 slowly move in counter flows. The device is connected to the patient’s circulatory system using catheters. Dialysis lasts 4-6 hours. This achieves blood purification from nitrogenous wastes in case of insufficient kidney function, i.e. the chemical composition of the blood is regulated.
If you take a bag with smaller pores that allow only solvent molecules (for example, water) to pass through, but not sugar molecules, then the water molecules will diffuse into the bag, increasing the volume of the solution in it. In this case we are talking about osmosis. First osmosis observed by A. Nolle in 1748, but research into this phenomenon began a century later. The phenomenon of osmosis is observed in environments where the mobility of the solvent is greater than the mobility of dissolved substances. Osmosis preserves proteins inside the cell that are so important for the biological processes of living organisms.
§3 The role of diffusion in nature
The phenomenon of diffusion plays a big role in nature. For example, thanks to diffusion, a homogeneous composition of atmospheric air is maintained near the Earth's surface. The lower layer of the atmosphere - the troposphere - consists of a mixture of gases: nitrogen, oxygen, carbon dioxide and water vapor. In the absence of diffusion, stratification would occur under the influence of gravity: below there would be a layer of heavy carbon dioxide, above it - oxygen, above - nitrogen and inert gases.
K.A. Timiryazev said: “Whether we talk about the nutrition of the root due to the substances found in the soil, whether we talk about the aerial nutrition of the leaves due to the atmosphere or the nutrition of one organ at the expense of another, neighboring one - everywhere we will resort to the same reasons for explanation : diffusion".
Indeed, in the plant world the role of diffusion is also great. For example, the great development of the leaf crown of trees is explained by the fact that diffusion exchange through the surface of the leaves performs not only the function of respiration, but partially also nutrition. Currently, foliar feeding of fruit trees by spraying their crowns is widely practiced. Thanks to diffusion, the plant receives minerals and water from the soil.
Without this phenomenon there would be no animal world. Diffusion affects not only the physiological processes occurring in the body of animals: such as, for example, the regulation of salt balance. Thanks to diffusion, they find food for themselves. Sharks, for example, can smell blood from several kilometers away. Butterflies, fluttering between plants, always find their way to a beautiful flower. Bees, having discovered a sweet object, storm it with their swarm.
Diffuse processes play a major role in supplying natural reservoirs and aquariums with oxygen. Oxygen reaches deeper layers of water in stagnant waters due to diffusion through their free surface. To study how various substances on the surface of water affect the rate of evaporation of water and to draw a conclusion about the rate of diffusion, the following experiment was carried out.
Water of the same mass and the same temperature (37 degrees) was poured into the plates, then gasoline (5 ml) was poured into one plate, kerosene (5 ml) into the second, vegetable oil (5 ml) into the third, and the water remained clean in the fourth. . Vegetable oil in our experiment imitated petroleum. The time was recorded, and readings were taken every 15 minutes from thermometers placed in all liquids. The measurement results are recorded in the table.
|
Time |
Clean water temperature, 0 C |
Water temperature with gasoline, 0 C |
Temperature of water with kerosene, 0 C |
Water temperature with vegetable oil, 0 C |
|
14:15 |
37 |
37 |
37 |
37 |
|
14:30 |
33 |
34 |
34 |
35 |
|
14:45 |
30 |
32 |
32 |
33 |
|
15:00 |
26 |
28 |
28 |
31 |
When water evaporates, individual molecules fly out. Since water covered with a film of gasoline, kerosene and vegetable oil cools more slowly, we can judge that it is more difficult for oxygen molecules to penetrate into the water: fish and other aquatic inhabitants experience a lack of oxygen and may even die.
Thus, the presence of various substances on the surface of the water disrupts diffusion processes and can lead to undesirable environmental consequences.
Therefore, any restrictions on the free surface of the water are undesirable. For example, leaves or duckweed covering the surface of the water can completely stop the access of oxygen to the water and lead to the death of its inhabitants. For the same reason, vessels with a narrow neck are unsuitable for use as an aquarium.
§4 The influence of diffusion on human life
Many physiological processes occurring in the human body are based on the phenomenon of diffusion: such as breathing, absorption of nutrients in the intestines, etc. We can protect ourselves from many diseases by taking medications that are also absorbed by the body thanks to diffusion.
Diffusion is widely used in various fields of human activity. Diffusion welding of metals is based on this phenomenon. The parts are placed in a closed welding chamber with strong vacuum, compressed and heated to 800 degrees. In this case, intense mutual diffusion of material atoms occurs. Diffusion welding is used mainly in the electronics and semiconductor industries, and precision engineering.
The phenomenon of diffusion is also used to obtain sugar juice from beet chips heated with water.
Man has learned to use the properties of diffusion to ensure his own safety. The natural flammable gas we use at home is colorless and odorless. If there is a leak, it is impossible to notice it, so at distribution stations the gas is mixed with a special substance that has a sharp, unpleasant odor that is easily perceived by humans.
§5 Harmful manifestation of diffusion
Unfortunately, as a result of the development of human civilization, there is a negative impact on nature and the processes occurring in it. The diffusion process plays a big role in the pollution of rivers, seas, and oceans. Pollution of water bodies leads to the disappearance of life in them. In addition, chemical reactions occur in contaminated water, releasing heat. The water temperature rises, and the oxygen content in the water decreases, which is bad for aquatic organisms.
Due to the phenomenon of diffusion, the air is polluted with waste from various factories, exhaust gases, because of which harmful human waste penetrates into the soil, water, and then has a harmful effect on the life and functioning of animals and plants.
Conclusion
Based on the above, we can conclude that the phenomenon of diffusion is one of the main general conditions for the life of plants, animals and humans. Without this phenomenon, life on Earth would be impossible.
A person does not need to do anything special to improve the occurrence of the phenomenon of diffusion in living nature. We just need to exclude pollution of the environment through our activities, since due to human fault this phenomenon plays a significant role in the pollution of rivers, seas and oceans, soil and the atmosphere of the Earth.
In the flame of the Sun, in the life and death of distant stars, in the air we breathe, everywhere we see the manifestation of an almighty and universal diffusion.
Bibliography
1. Alekseev S.V., Gruzdeva M.V., Muravyov A.G., Gushchina E.V. Workshop on ecology. M. JSC MDS, 1996
2. Peryshkin A.V. Physics 7th grade. – M.: Bustard, 2005. – 189 p.
3. Prokhorov A.M. Physical encyclopedic dictionary. 1995
4. Ryzhenkov A.P. Physics Man Environment. - M.: Education, 1996. – 48 s.
5. Shakhmaev N.M. et al. Physics 7.M.: Mnemosyne, 2007.
6. Encyclopedia for children. T.19. Ecology: In 33 volumes/ Ch. ed. Volodin V. A. – M.: Avanta +, 2004 – 448 p.
7. http://www.Wikipedia.org
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Attention! The site administration is not responsible for the content of methodological developments, as well as for the compliance of the development with the Federal State Educational Standard.
- Participant: Bagirova Elmira Iskenderkyzy
- Head: Zhukova Natalya Vyacheslavovna
Target: expand knowledge about diffusion, explain the physical nature of the phenomenon of diffusion, confirm theoretical facts with experimental results, summarize acquired knowledge and draw conclusions
Diffusion is the mutual penetration of one substance between the molecules of another.
A major role in the life of living nature is played by diffusion processes that determine the normal metabolism between the organism and the environment, as well as between various parts of the organism itself. Nutrition and respiration are typical diffusion processes. During respiration, oxygen O2 and carbon dioxide CO2 diffuse through the wall of the pulmonary vesicle. To understand these processes, it is necessary to take into account the conditions that provide or impede diffusion. Thus, respiration - the diffusion of oxygen from the environment into the body through its integuments - occurs the faster, the larger the surface of contact between the body and the environment, and the slower, the thicker and denser the integuments of the body. From this it is clear that small organisms, in which the surface dimensions are large compared to the volume of the body, can do without special respiratory organs at all, being satisfied with the flow of oxygen exclusively through the outer shell (if it is sufficiently thin and moist). In larger organisms, breathing through the skin may be more or less sufficient only if the integument is extremely thin (amphibians); with rough coverings, special respiratory organs are required. The main physical requirements for these organs are maximum surface and minimum thickness and moisture content of the cover.
Undoubtedly, when analyzing this aspect of the life of all living beings, diffusion plays a huge role.
Let us conduct a series of experiments proving the practical importance of diffusion.
"Diffusion in Liquids"
(textbook “Physics. Grade 7” by A.V. Peryshkin, Bustard, 2012. Paragraph 10, “Diffusion in gases, liquids and solids”, Fig. 24, task after paragraph No. 2.)
Items and materials
- Test tube with water
Conducting an experiment
Let's drop a little iodine into the water and watch its behavior.
Hypothesis
Is it true that a drop of iodine will gradually dissolve in water, giving it the appropriate color?
Let's explain
Water, like iodine, consists of a huge number of tiny invisible particles the size of a hundred-millionth of a centimeter, called molecules. They all move continuously, constantly colliding with each other, like, for example, schoolchildren at recess. Due to the impacts of water molecules, the iodine molecules initially collected together scatter in different directions, so that the distance between them increases and the iodine spot spreads out. The spread of one liquid into another for this reason is called diffusion.
"Clutch of lead cylinders"
(textbook “Physics. Grade 7” by A.V. Peryshkin, Bustard, 2012. Paragraph 11, “Mutual attraction and repulsion of molecules”, Fig. 26.)
Items and materials
- Two lead cylinders
- Cylinder fixation device
Conducting an experiment
Before starting the experiment, it is necessary to thoroughly clean the lead surfaces of the cylinders with a sander. We install the cylinders into the fixation device, pressing them together with their cleaned surfaces using a clamping screw. Tighten the clamping screw. After waiting a certain amount of time, you can loosen the clamping screw and remove the coupled cylinders.
Hypothesis
Will two lead cylinders really be connected to each other?
Let's explain
Cleaning lead cylinders is necessary in order to level the surfaces as much as possible and clean them from oxidation. Thus, we achieve the tightest fit of one surface to another. At this stage, the manifestation of attractive forces between molecules is very clearly visible when they are very close to each other. But the longer the cylinders are linked and under some load, the mutual penetration of the molecules of one cylinder between the molecules of the other - diffusion - will become more and more pronounced.
“Dependence of diffusion on temperature”
(textbook “Physics. Grade 7” A.V. Peryshkin, Bustard, 2012. Paragraph 10, “Diffusion in gases, liquids and solids”, task after paragraph No. 1.)
Items and materials
- Glass with cold water
- Glass of hot water
- Sugar crystals
Conducting an experiment
Pour room temperature water into one glass and hot water into the other. Place one teaspoon of sugar in each glass.
Hypothesis
Does sugar really dissolve faster in a glass of hot water?
Let's explain
We know that at any temperature in a substance there are molecules that move quite slowly, and molecules whose speed is high. If the number of molecules of a substance having a high speed increases, i.e. the average speed of the molecules increases, this means that the temperature of the substance also increases. The faster water molecules move, the more often they will collide with sugar molecules, and the faster the process of mutual mixing of one substance with another will occur. With increasing temperature, the process of mutual penetration of water molecules between sugar molecules - diffusion - occurs much faster.
On practice
- cooking food
- heat treatment of metals (welding, soldering, cutting, coating, etc. Applying a thin layer of metals to the surface of metal products to increase the chemical resistance, strength, hardness of parts and devices, or for protective and decorative purposes (galvanizing, chrome plating, nickel plating). To give iron and steel parts hardness, their surfaces are subjected to diffuse saturation with carbon (cementation).The natural combustible gas that we use at home is colorless and odorless... If there is a leak, it is impossible to notice it, so at distribution stations the gas is mixed with a special substance that has a pungent, unpleasant odor that is easily felt by humans even at low concentrations. (Safety measures). In sugar factories when extracting sugar from beets. For welding materials. For tanning leather and fur. For dyeing fabric fibers.) For imparting to iron and steel parts the hardness of their surface is subjected to diffuse saturation with carbon (cementation). The natural flammable gas that we use at home has no color or odor... If there is a leak, it is impossible to notice it, so at distribution stations the gas is mixed with a special substance that has a sharp, unpleasant odor, which is easily felt by humans even in low concentrations. (Security measures). In sugar factories when extracting sugar from beets. For welding materials. For tanning leather and fur. For dyeing fabric fibers.
- use of drugs (More than 30 years ago, the German doctor William Kolf used the “artificial kidney” device. Since then it has been used: for emergency chronic care for acute intoxication; for preparing patients with chronic renal failure for kidney transplantation; for long-term (10-15 years) life support for patients with chronic kidney disease. The use of the artificial kidney device is becoming more of a therapeutic procedure, the device is used both in the clinic and at home. With the help of the device, the recipient was prepared for the world's first successful kidney transplantation, carried out in 1965 by academician B.V. Petrovsky.
The device is a system of flat channels separated by thin cellophane membranes, through which blood and dialysate - a saline solution enriched with a gas mixture of CO 2 + O 2 - slowly move in counter flows. The device is connected to the patient’s circulatory system using catheters inserted into the hollow (blood inlet) into the dialysate) and ulnar (outlet) vein. Dialysis lasts 4-6 hours. This achieves blood purification from nitrogenous wastes in case of insufficient kidney function, i.e. the chemical composition of the blood is regulated.) - in gardening, during budding and grafting of plants, callus is formed on sections due to diffusion (from the Latin Callus - callus) - wound tissue in the form of an influx in places of damage and promotes their healing, ensures the fusion of the scion with the rootstock.
- canning and pickling (pickling vegetables, cooking jams, preparing compotes and many other technological processes.)
- use of cosmetics.
In nature
- Absorption is the process of entry of various substances from the environment through cell membranes into cells, and through them into the internal environment of the body.
- Diffusion in respiration. (An example of diffusion in nature is a process that is fundamentally important for life - breathing. It is thanks to diffusion that oxygen from the lungs enters the blood, and from the blood into the organs and tissues of the body. Thanks to diffusion, the carbon dioxide we exhale does not accumulate around us, but dissipates in space and mixes with oxygen, so we can breathe calmly for a long time in a closed room without wind. However, from time to time it is still necessary to ventilate the room and let in fresh air saturated with oxygen, which, again thanks to diffusion, quickly spreads throughout the entire volume of the room.)
- The homogeneous composition of atmospheric air near the Earth's surface is maintained (in practice, you often encounter phenomena that at first you do not pay special attention to, but then, as you study at school, you understand and begin to explain phenomena that occur in everyday life, but which play a huge role in nature and life humans as part of nature. Thus, thanks to diffusion, a homogeneous composition of the atmosphere is maintained near the surface of the Earth, diffusion of salt solutions in the soil contributes to the normal nutrition of plants, diffusion occurring in the human body allows us to saturate the cells of our body with oxygen and nutrients.)
About 27 tons of cosmic dust falls to Earth every day. Over the course of a year, more than 10,000 tons of dust land on Earth.
From history Lucretius Carus writes: “Look: every time the sunlight penetrates into our homes and the darkness cuts through with its rays, You will see many bodies in the void, flickering, rushing back and forth in the radiant radiance of light. As if in an eternal struggle they fight in battles and battles, In the fight they suddenly rush into squads, not knowing peace...” In the ancient world, of course, they could not observe molecules, but they could observe diffusion! Lucretius Carus described it beautifully in poetry.
If very smoothly polished plates of lead and gold are placed one on top of the other and some weight is placed on them, then after 4-5 years they will penetrate each other by 1 mm.
In fairy tales, diffusion helps the heroes. An excerpt from the Assyrian fairy tale “King Zimaz”: “The king had a smart adviser Ayaz, whom he respected very much. As usually happens in such cases, Ayaz had enemies who slandered him before the king, and he, listening to them, imprisoned him. When Ayaz’s wife came to him, he ordered her to catch a large ant, tie a strong thread forty meters long to its leg, tie a rope of the same length to its free end and let the ant along the outer wall of the prison in the indicated place. As Ayaz said, that’s what the wife did. Ayaz himself crumbled sugar onto the window of the cell and the ant, following the smell of sugar, reached the cell where Ayaz was sitting.”
And proverbs are continuous diffusion:
- A fly in the ointment.
- Chopped onions smell and sting your eyes more
- A vegetable shop doesn't need a sign.
- Scent feeds the wolf
“How do ants find their way home?”
Ants mark their path with droplets of odorous liquid; they press their abdomen to the ground and transmit their smell to it. Some ants do not always run exactly along the intended path, but to the side of the route, because the smell is quite strong. Having lost the trail, they circle around again to find the “road” and hurry along it. Ant trails can be several meters long.
Thanks to diffusion, insects find their food. Butterflies, fluttering between plants, always find their way to a beautiful flower. Bees, having discovered a sweet object, storm it with their swarm.
And the plant grows and blooms for them, too, thanks to diffusion. After all, we say that the plant breathes and exhales air, drinks water, and receives various microadditives from the soil.
Carnivores also find their victims through diffusion. Sharks can smell blood from several kilometers away, just like piranha fish.
The ecology of the environment is deteriorating due to the release of chemicals and other harmful substances into the atmosphere, water, and all this spreads and pollutes vast areas. But trees release oxygen and absorb carbon dioxide through diffusion.
The principle of diffusion is based on the mixing of fresh water with salt water when rivers flow into the seas. Diffusion of solutions of various salts in the soil contributes to normal plant nutrition.
