Diffusion between solid and liquid matter. Diffusion in gases, liquids and solids

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Three states of matter

The dimensions of the molecule are about 10‾¹ºm

Let's repeat

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"I value one experience above 1000 opinions born of imagination"

M. V. Lomonosov

• Sources of physical knowledge

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Brownian motion

Robert Brown in 1827, observing a suspension of plant pollen under a microscope, discovered that the particles were in continuous motion, describing complex trajectories.

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Diffusion observed

• In gases
• In liquids
• In solids

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Aromatic oils and resins are widely used in the perfume industry, medicinal aromatherapy, and for church needs.

Diffusion of gases in gases

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Diffusion of gases in gases

• Aromatics
• Oils
• Resins
• Jasmine petals
• rose petals
• Myrrh
• incense tree

Slide 11

Who among us has not been struck by the smell of a spring night? We could smell the smells of bird cherry, acacia, and lilac. Flowers' scent molecules diffuse into the air.

Diffusion of gases in gases

Slide 12

Tea, coffee and cocoa are commonly consumed as tonic crops.

The homeland of tea is China, coffee is Africa, cocoa is America. The rapid spread of the aroma of these drinks is explained by the fact that the molecules of the odorous substance penetrate between the air molecules.

Diffusion of gases in gases

Slide 13

The most numerous way insects communicate is through olfactory chemicals, which animals use to protect themselves or attract attention.

• The transfer of odors occurs through diffusion.

Diffusion of gases in gases

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• Attractive
• Pheromones, hormones.
• Diffusion of gases in gases
• Fragrances
• Butterflies
• May beetles
• Ferrets
• Bedbugs
• Skunks
• Repulsive
• Repellents

Slide 15

Forests are the lungs of the planet, helping all living things to breathe.

Urban air contains a lot of gaseous substances (carbon monoxide, carbon dioxide, nitrogen oxides, sulfur) resulting from the work of the industrial complex, transport and utilities.

The process of air purification by forests can be explained by diffusion.

Diffusion of gases in gases

Slide 16

Natural flammable gas has neither color nor odor.

Diffusion of gases in gases

Due to diffusion, the gas spreads throughout the room, forming an explosive mixture.

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Ways to solve the environmental problem associated with air purification:

1) filters on exhaust pipes;

2) growing plants along roads and around enterprises that absorb harmful substances.

Diffusion of gases in gases

• Poplar

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Observation of the process of diffusion of air molecules and ammonia molecules (the indicator is litmus paper, which records the presence of an alkaline medium)

OUR EXPERIMENT

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Observing the dissolution of smoke from a fire in the air.

OUR EXPERIMENT

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OUR EXPERIMENT

Spreading the smell of air freshener in the room.

Slide 22

Bee venom is a colorless, transparent liquid with an aromatic odor and high biological activity.

The rapid penetration of bee venom is associated with biological processes in the body

(with the movement of poison molecules and their interaction with the intercellular fluid of the connective tissue).

DIFFUSION OF LIQUID IN LIQUID

Slide 23

To prepare tea, flowers and leaves of some plants are used: jasmine, rose, linden, oregano, mint, thyme and others.

DIFFUSION OF LIQUID IN LIQUID

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DIFFUSION OF LIQUID IN LIQUID

• Green
• Black

In the solid state, the color of the tea depends on how the leaves are processed.

Tea brewing is based on the diffusion of water molecules and the coloring matter of plants.

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OUR EXPERIMENT

We invite you for tea.

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OUR EXPERIMENT

Comparison of the rate of diffusion when brewing tea with cold and hot water.

The diffusion process accelerates with increasing temperature; occurs more slowly than in gases.

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Adding a slice of lemon makes the tea lighter.

OUR EXPERIMENT

The color of tea is brown only in a neutral environment (water).

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OUR EXPERIMENT

To saturate the color of the beets, acetic acid is added to the water.

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The smell of salt, the smell of iodine.

Impregnable and proud

Reefs stone muzzles

They are being taken out of the water...

Yu. Drunina

Every year, 2 billion tons of salts enter the atmosphere.

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Smog is a yellow fog that poisons the air we breathe.

Smog is the main cause of respiratory and heart diseases and weakened human immunity.

DIFFUSION OF SOLID IN GASES

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DIFFUSION OF SOLID IN GASES

Particles found in urban air.

• Plant pollen
• Microorganisms and their spores
• Dry sand
• Coal dust
• Cement dust
• Fertilizer
• Asbestos
• Cadmium
• Mercury
• Lead
• Iron oxide
• Copper oxide
• Particle radius, µm
• 20 – 60
• 1 - 15
• 200 - 2000
• 10 – 400
• 10 – 150
• 30 – 800
• 10 – 200
• 0,5-1
• 0,1-1
• 0,1-1

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How to explain the process of pickling vegetables?

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DIFFUSION OF A SOLID IN A LIQUID

Mushroom pickles

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Fruit pickles

DIFFUSION OF A SOLID IN A LIQUID

When salting, salt crystals break up into Na and Cl ions in an aqueous solution, move randomly and occupy the spaces between the pores of food products.

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Making jam and compotes.

DIFFUSION OF A SOLID IN A LIQUID

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Production of sugar from beets in industrial production

DIFFUSION OF A SOLID IN A LIQUID

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Dissolving potassium permanganate crystals in water.

OUR EXPERIMENT

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OUR EXPERIMENT

Dissolving sugar crystals in hot water.

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Dissolving the Mucaltina tablet in water.

OUR EXPERIMENT

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Making pickled cucumbers, sauerkraut, salted fish and lard at home.

OUR EXPERIMENT

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To impart hardness, wear resistance and ultimate strength to iron and steel parts, their surfaces are subjected to diffuse saturation with carbon (cementation)

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The English metallurgist William Roberts-Austin measured the diffusion of gold in lead by placing this cylinder in a furnace at a temperature of about 200 ° C for 10 days.

The gold atoms were evenly distributed throughout the lead cylinder.

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OUR EXPERIMENT

Observation of the phenomenon of diffusion of potassium permanganate and wax molecules.

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OUR EXPERIMENT

• Results in three weeks.
• Two months have passed.
• Molecules of solids diffuse the slowest.

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• The reason for diffusion is the random movement of molecules.
• The rate of diffusion depends on the state of aggregation of the contacting bodies.
• Diffusion is fast in gases, slower in liquids, and very slow in solids.
• The diffusion process accelerates with increasing temperature, with a decrease in the viscosity of the medium and particle size.

Slide 46

1. Which drawing most correctly shows a drop of water under a microscope at high magnification?

2. Having models of particles of two substances, show what happens in the substance when they spontaneously mix.

3. Choose a picture in which the direction of the arrows correctly indicates the direction of motion of two particles in a substance.

Describe how particles move in matter.

What dances or melodies can be compared with the movement of palm particles growing in Africa and cedar particles growing in Siberia?

Slide 47

Everyone knows how healthy onions are. But when we cut it, we shed tears. Explain why?

This is explained by the phenomenon of diffusion. The reason is the volatile substance lachrymator, which causes tears. It dissolves in the fluid of the mucous membrane of the eye, releasing sulfuric acid, which irritates the mucous membrane of the eye.

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Intermediate level: 1. In which brine - hot or cold - will cucumbers pickle faster?

2. Why can’t fabric painted with low-quality paint be kept in contact with light-colored linen when wet?

Sufficient level: 1. Why does the smoke from a fire, rising upward, quickly cease to be visible even in calm weather?

2. Will odors spread in a hermetically sealed basement where there are absolutely no drafts?

High level: 1. An open vessel containing ether was balanced on a scale and left alone. After some time, the balance of the scales was disrupted. Why?

2. What is the significance of diffusion for the respiratory processes of humans and animals?

Slide 49

1. Paragraph No. 9, questions for the paragraph;

2. Experimental task (describe the diffusion phenomena observed at home).

3. Answer the question in writing:

Why does sweet syrup taste like fruit over time? (intermediate level)

Why does salted herring become less salty after being left in water for a while? (sufficient level)

Why are liquid glue and molten solder used when gluing and soldering? (high level)

Slide 50

Slide 51

1. Semke A.I. “Non-standard problems in physics”, Yaroslavl: Academy of Development, 2007.

2. Shustova L.V., Shustov S.B. “Chemical foundations of ecology.” M.: Education, 1995.

3. Lukashik V.I. Physics problem book for 7-8 grades. M.: Education, 2002.

4. Katz Ts.B. Biophysics in physics lessons. M.: Education, 1998.

5. Encyclopedia of Physics. M.: Avanta +, 1999.

6. Bogdanov K.Yu. A physicist visiting a biologist. M.: Nauka, 1986.

7. Enochovich A.S. Handbook of Physics. M.: Education, 1990.

8. Olgin O.I. Experiments without explosions. M.: Chemistry, 1986.

9. Kovtunovich M.G. "Home experiment in physics grades 7-11." M.: Humanitarian Publishing Center, 2007.

10. Internet resources.

Literature

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Lesson objectives:

Educational: consolidate students’ knowledge on a given topic, teach them to understand and describe the behavior of molecules of a substance in various states of aggregation, explain the significance of the diffusion process in nature and human life.

Educational: continue to develop students’ ability to think scientifically.

Educational: to instill in students the ability to compare phenomena seen in nature with acquired knowledge about various physical laws.

Key terms:

State of matter is a state of matter that can be characterized by a set of certain properties (for example, preservation or inability to preserve volume, shape, etc.).

Diffusion

The concept of the state of aggregation of matter.

The world around us is complex and changeable. At the same time, we are able to notice that the limitless diversity of the world is not so limitless after all. We often see the same substances in different states.

The simplest example by which I can prove the veracity of my words is water. It is easiest to see in different states - it is steam or fog, it is ice or snow, it is liquid running from the tap in the kitchen. Whatever the characteristics of water in one form or another, it always remains water - its composition does not change. These are the same 2 hydrogen molecules and 1 oxygen molecule.

If we continue to use the example we took, we can see that these 3 states of water depend on certain external conditions. Thus, water freezes at 0 degrees, turning into ice, and water boils at 100 degrees, turning into steam. This photo clearly demonstrates all 3 states of water:

Rice. 1: 3 physical states of water

So, what conclusions can we draw after thinking carefully about the example we have given? They will be like this:

The state of aggregation of a substance is a state of a substance that can be characterized by a set of certain properties (for example, preservation or inability to preserve volume, shape, etc.) under certain conditions.

Not only water can be in three states of aggregation: solid, liquid and gaseous. This is inherent in all substances.

Sometimes, to the three above states of aggregation, a fourth is added – plasma. You can get an idea of ​​what plasma looks like from the following figure:

Rice. 2: plasma lamp

but you will learn about plasma in more detail in physics and chemistry lessons in high school.

Diffusion process

As we all have already learned, all substances consist of tiny particles - ions, atoms, molecules, which are in constant motion. It is this movement that causes the process of diffusion to occur.

Diffusion is a process involving the mutual penetration of molecules of substances into the spaces between molecules in other substances.

Let's take a closer look at diffusion in various states of aggregation.

Diffusion in gases

Let's give examples of the process of diffusion in gases together. Variants of manifestation of this phenomenon may be as follows:

Spreading the scent of flowers;

Tears over chopping onions;

A trail of perfume that can be felt in the air.

The gaps between particles in the air are quite large, the particles move chaotically, so the diffusion of gaseous substances occurs quite quickly.

Let's watch a video demonstrating this process:

Diffusion in liquids.

Particles of substances in liquids, and these are most often ions of substances, interact with each other quite strongly. At the same time, the distance between the ions is quite large, which allows the particles to mix easily.

The following video picture shows how the diffusion process occurs in liquids. Paint particles, falling on the surface of the water, easily diffuse, that is, penetrate into the water.

Rice. 3: Paint particles spread in the water.

You can observe the same process, but in dynamics, in the video using the example of the dissolution of potassium permanganate crystals:

Diffusion in solids.

Solids can have different structures and consist of molecules, atoms or ions. In any case, regardless of what microparticles the body consists of, the interaction of these particles with each other is very strong. Despite the fact that they, these particles, still move, these movements are very insignificant. The spaces between the particles are small, making it difficult for other substances to penetrate between them. The process of diffusion in solids is very slow and invisible to the naked eye.

Let's watch a video about this:

Having learned about the peculiarities of the diffusion process in various states of aggregation, we saw that the process is not equally fast. What does the rate of diffusion depend on? We already have one answer to this question - the rate of the diffusion process depends on the state of aggregation of the substance.

You and I also know that particles of substances begin to move faster with increasing temperature. Does this mean that the diffusion process will also accelerate with increasing temperature? The answer is obvious. To confirm, let's watch the video:

The intensity of the diffusion of one substance into another also depends on the concentration of these substances and on external influences (for example, if you simply drop a solution of iodine into water and if you also mix it, the rate at which the solution acquires a uniform color will be different).

Conclusions

1. The state of aggregation of a substance is a state of a substance that can be characterized by a set of certain properties (for example, preservation or inability to preserve volume, shape, etc.) under certain conditions. Not only water can be in three states of aggregation: solid, liquid and gaseous. This is inherent in all substances.

2. Diffusion is a process consisting in the mutual penetration of molecules of substances into the spaces between molecules in other substances.

3. The rate of diffusion depends on: temperature, concentration, external influences, and the state of aggregation of the substance.

It is difficult to overestimate the process of diffusion in human life. For example, the penetration of oxygen through the thinnest wall of the alveoli into the capillaries of the lungs occurs precisely due to diffusion. The walls of the alveoli are very thin; from a physical point of view, the alveolar wall is a semi-permeable membrane. The concentration of oxygen in atmospheric air is much higher than its concentration and capillary blood, which is why oxygen penetrates through the semi-permeable membrane - where there is less of it. Thanks to diffusion we breathe.

This process also partially ensures the penetration of nutrients from the digestive system into the blood and the effect of many medications.

The figure schematically shows how nutrients are absorbed in the human intestine.

Rice. 4: small intestine of a mammal

References

Lesson on the topic: “Diffusion in gases, liquids, solids”, author Selezneva A.M., Municipal Educational Institution Secondary School No. 7, Boyarka, Kyiv region.

Peryshkin A.V. “Physics 7th grade”, Moscow, Bustard, 2006

Rodina N. A., Gromov S. V., “Physics”, M., Mir, 2002

Edited and sent by Borisenko I.N..

Worked on the lesson:

Apply acquired knowledge and skills to solve practical problems in everyday life

Students complete the task, remember, achieve the goal using their own resources of memory and thinking. They compose an answer, express their own point of view, and come to a consensus.

Control their own time, the correctness and order of their own and their interlocutor’s statements during the work process

Diffusion in nature and technology

They work with the texts that each group will receive. The task of each group is to highlight the main points in the text and write a story about the application of the diffusion process in this area. There may be several speakers from a group.

Text of group 1. Diffusion in the plant world

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 very important. 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.
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. 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.

Text 2 groups. The role of diffusion in human digestion and respiration

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 m2. 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 m2, i.e. reaches 2-3 times the surface area of ​​the entire body. The process of absorption of nutrients in the intestines 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.
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. 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 m2, and the total The surface area of ​​human skin is about 2 m2, i.e., 45-50 times less. 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.

Text of group 3. Application of diffusion in technology.

Diffusion is widely used in industry. Diffusion welding of metals is based on the phenomenon of diffusion. The diffusion welding method is used to connect metals, non-metals, metals and non-metals, and plastics. 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 atoms occurs in the surface layers of contacting materials. Diffusion welding is used mainly in the electronics and semiconductor industries, and precision engineering.
A diffusion apparatus is used to extract soluble substances from crushed solid material. Such devices are widespread mainly in beet sugar production, where they are used to obtain sugar juice from beet chips heated together with water.
The process of metallization is based on the phenomenon of diffusion - covering the surface of a product with a layer of metal or alloy to impart to it physical, chemical and mechanical properties that differ from the properties of the metallized material. It is used to protect products from corrosion, wear, increase contact electrical conductivity, and for decorative purposes. To increase the hardness and heat resistance of steel parts, carburization is used. It consists in placing steel parts in a box with graphite powder, which is installed in a thermal furnace. Due to diffusion, carbon atoms penetrate into the surface layer of parts. The penetration depth depends on the temperature and holding time of the parts in the thermal oven.

Text for group 4. But diffusion is not always good for humans. Unfortunately, it is necessary to note the harmful manifestations of this phenomenon. Chimneys of enterprises emit carbon dioxide, nitrogen oxides and sulfur into the atmosphere. Currently, the total amount of gas emissions into the atmosphere exceeds 40 billion tons per year. 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 diffusion process 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.

The text of the work is posted without images and formulas.
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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. An example of a positive impact is maintaining a uniform composition of atmospheric air near the Earth's surface. Diffusion plays an important role in various fields of science and technology, in processes occurring in living and inanimate nature. It influences the course of chemical reactions.

With the participation of diffusion or when this process is disrupted and changed, negative phenomena in nature and human life can occur, such as extensive pollution of the environment with the products of human technical progress.

Relevance: Diffusion proves that bodies are composed of molecules that are in random motion; Diffusion is of great importance in human life, animals and plants, as well as in technology.

Target:

prove that diffusion depends on temperature;

consider examples of diffusion in home experiments;

make sure that diffusion occurs differently in different substances.

Consider the thermal diffusion of substances.

Research objectives:

Study scientific literature on the topic “Diffusion”.

Prove the dependence of the diffusion rate on the type of substance and temperature.

Study the influence of the diffusion phenomenon on the environment and humans.

Describe and design the most interesting diffusion experiments.

Research methods:

Analysis of literature and Internet materials.

Conducting experiments to study the dependence of diffusion on the type of substance and temperature.

Analysis of results.

Subject of research: the phenomenon of diffusion, the dependence of the course of diffusion on various factors, the manifestation of diffusion in nature, technology, and everyday life.

Hypothesis: Diffusion is of great importance for humans and nature.

1.Theoretical part

1.1.What is diffusion

Diffusion is the spontaneous mixing of contacting substances, occurring as a result of the chaotic (disorderly) movement of molecules.

Another definition: diffusion ( lat. diffusio- spreading, spreading, dissipation) - the process of transferring matter or energy from an area of ​​high concentration to an area of ​​low concentration.

The most famous example of diffusion is the mixing of gases or liquids (if ink is dropped into water, the liquid will become uniformly colored after some time).

Diffusion occurs in liquids, solids and gases. Diffusion occurs most quickly in gases, slower in liquids, and even slower in solids, which is due to the nature of the thermal movement of particles in these media. The trajectory of each gas particle is a broken line, because During collisions, particles change the direction and speed of their movement. For centuries, workers welded metals and produced steel by heating solid iron in a carbon atmosphere, without having the slightest idea of ​​the diffusion processes occurring during this process. Only in 1896 began studying the problem.

The diffusion of molecules is very slow. For example, if a piece of sugar is placed at the bottom of a glass of water and the water is not stirred, it will take several weeks before the solution becomes homogeneous.

1.2. The role of diffusion in nature

With the help of diffusion, various gaseous substances spread in the air: for example, the smoke of a fire spreads over long distances. If you look at the chimneys of businesses and the exhaust pipes of cars, in many cases you can see smoke near the pipes. And then he disappears somewhere. Smoke dissolves in the air due to diffusion. If the smoke is dense, then its plume stretches quite far.

The result of diffusion can be equalization of the temperature in the room during ventilation. In the same way, air pollution occurs with harmful industrial products and vehicle exhaust gases. 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, which is easily perceived by humans even at a very low concentration. This precaution allows you to quickly notice the accumulation of gas in the room if a leak occurs (Figure 1).

Thanks to the phenomenon of diffusion, 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, inert gases (Fig. 2).

We also observe this phenomenon in the sky. Dispersing clouds are also an example of diffusion, and as F. Tyutchev accurately said about this: “Clouds are melting in the sky...” (Figure 3)

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.

Diffusion plays an important role in the life of plants and animals. Ants mark their path with droplets of odorous liquid and find out the way home (Figure 4)

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 (Figure 5).

Diffusion processes play a major role in the supply of oxygen to natural reservoirs and aquariums. Oxygen reaches deeper layers of water in stagnant waters due to diffusion through their free surface. 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 (Fig. 6).

It has already been noted that there is much in common in the meaning of the phenomenon of diffusion for the life of plants and animals. First of all, it should be noted the role of diffusion exchange through the surface of plants in the performance of the respiratory function. For trees, for example, there is a particularly large development of the surface (leaf crown), since diffusion exchange through the surface of the leaves performs the function of respiration. 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" (Figure 7).

Thanks to diffusion, oxygen from the lungs penetrates into the human blood, and from the blood into the tissues.

In the scientific literature, I studied the process of one-way diffusion - osmosis, i.e. diffusion of substances through semipermeable membranes. The process of osmosis differs from free diffusion in that at the border of two contacting liquids there is an obstacle in the form of a partition (membrane), which is permeable only to the solvent and not at all permeable to molecules of the dissolved substance (Fig. 8).

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 water penetrates into the grain and gives life to the plant.

1.3. The role of diffusion in everyday life and technology

Diffusion is used in many technological processes: salting, sugar production (sugar beet chips are washed with water, sugar molecules diffuse from the chips into the solution), jam making, fabric dyeing, washing clothes, cementation, welding and soldering of metals, including diffusion welding in a vacuum (metals are welded that cannot be joined by other methods - steel with cast iron, silver with stainless steel, etc.) and diffusion metallization of products (surface saturation of steel products with aluminum, chromium, silicon), nitriding - saturation of the steel surface with nitrogen (steel becomes hard, wear-resistant), carburization - saturation of steel products with carbon, cyanidation - saturation of the steel surface with carbon and nitrogen.

The spread of odors in the air is the most common example of diffusion in gases. Why does the smell spread not instantly, but after some time? The fact is that while moving in a certain direction, molecules of an odorous substance collide with air molecules. The trajectory of each gas particle is a broken line, because During collisions, particles change the direction and speed of their movement.

2. Practical part

How many amazing and interesting things are happening around us! I want to know a lot, try to explain it myself. It was for this reason that I decided to conduct a series of experiments, during which I tried to find out whether the diffusion theory is really valid and whether it is confirmed in practice. Any theory can be considered reliable only if it is repeatedly confirmed experimentally.

Experiment No. 1 Observation of the phenomenon of diffusion in liquids

Target: study diffusion in liquid. Observe the dissolution of pieces of potassium permanganate in water at a constant temperature (at t = 20°C)

Devices and materials: glass of water, thermometer, potassium permanganate.

I took a piece of potassium permanganate and two glasses of clean water at a temperature of 20 °C. She put pieces of potassium permanganate into glasses and began to observe what was happening. After 1 minute, the water in the glasses begins to color.

Water is a good solvent. Under the influence of water molecules, the bonds between the molecules of the solid substances of potassium permanganate are destroyed.

In the first glass I did not stir the solution, but in the second I did. By stirring the water (shaking), I made sure that the diffusion process occurs much faster (2 minutes)

The color of the water in the first glass becomes more intense as time passes. Water molecules penetrate between the potassium permanganate molecules, breaking the attractive forces. Simultaneously with the attractive forces between the molecules, repulsive forces begin to act and, as a result, the crystal lattice of the solid substance is destroyed. The process of dissolving potassium permanganate is over. The experiment took 3 hours and 15 minutes. The water turned completely crimson (Figure 9-12).

It can be concluded that the phenomenon of diffusion in a liquid is a long-term process, as a result of which solids dissolve.

I wanted to find out what else the speed of diffusion depends on.

Experiment No. 2 Study of the dependence of the diffusion rate on temperature

Target: study how water temperature affects the rate of diffusion.

Devices and materials: thermometers - 1 piece, stopwatch - 1 piece, glasses - 4 pieces, tea, potassium permanganate.

(experience of preparing tea at an initial temperature of 20°C and at a temperature of 100°C in two glasses).

We took two glasses of water at t=20 °C and t=100 °C. The figures show the progress of the experiment after a certain time from the beginning: at the beginning of the experiment - Fig. 1, after 30 s. - Fig. 2, after 1 minute. - Fig. 3, after 2 minutes. - Fig.4, after 5 minutes. - rice 5, after 15 minutes. - Fig. 6. From this experience we can conclude that the rate of diffusion is affected by temperature: the higher the temperature, the higher the rate of diffusion (Figure 13-17).

I got the same results when I took 2 glasses of water instead of tea. One of them contained water at room temperature, the second had boiling water.

I put the same amount of potassium permanganate into each glass. In the glass where the water temperature was higher, the diffusion process proceeded much faster (Fig. 18-23.)

Therefore, the rate of diffusion depends on temperature - the higher the temperature, the more intense the diffusion occurs.

Experiment No. 3 Observation of diffusion using chemical reagents

Target: Observing the phenomenon of diffusion at a distance.

Equipment: cotton wool, ammonia, phenolphthalein, test tube.

Description of the experience: Pour ammonia into the test tube. Moisten a piece of cotton wool with phenolphthalein and place it on top of the test tube. After some time, we observe the coloring of the fleece (Fig. 24-26).

The ammonia evaporates; molecules of ammonia penetrated the cotton wool soaked in phenolphthalein, and it became colored, although the cotton wool was not brought into contact with the alcohol. The alcohol molecules mixed with air molecules and reached the cotton wool. This experiment demonstrates the phenomenon of diffusion at a distance.

Experience No. 4. Observation of the phenomenon of diffusion in gases

Target: study of changes in gas diffusion in the air depending on changes in room temperature.

Devices and materials: stopwatch, perfume, thermometer

Description of the experience and results obtained: I studied the time of propagation of the smell of perfume in the office V = 120 m 3 at a temperature t = +20 0. The time was recorded from the beginning of the spread of the smell in the room until obvious sensitivity was obtained in people standing at a distance of 10 m from the object under study (perfume). (Figure 27-29)

Experiment No. 5 Dissolving pieces of gouache in water at a constant temperature

Target:

Devices and materials: three glasses, water, gouache of three colors.

Description of the experience and results obtained:

They took three glasses, filled with water t = 25 0 C, and threw identical pieces of gouache into the glasses.

We began to observe the dissolution of the gouache.

Photos were taken after 1 minute, 5 minutes, 10 minutes, 20 minutes, dissolution ended after 4 hours 19 minutes (Figure 30-34)

Experiment No. 6 Observation of the phenomenon of diffusion in solids

Target: observation of diffusion in solids.

Devices and materials: apple, potato, carrot, green solution, pipette.

Description of the experience and results obtained:

Cut the apple, carrots, and potatoes into one of the halves.

We observe how the stain spreads across the surface

We cut at the point of contact with the brilliant green to see how deeply it has penetrated inside (Fig. 35-37)

How to conduct an experiment to confirm the hypothesis about the possibility of diffusion in solids? Is it possible to mix substances in such a state of aggregation? Most likely the answer is “Yes”. But it is convenient to observe diffusion in solids (very viscous) using thick gels. This is a dense solution of gelatin. It can be prepared as follows: dissolve 4-5 g of dry edible gelatin in cold water. Gelatin must first swell for several hours, and then it is completely dissolved by stirring in 100 ml of water, lowered into a vessel with hot water. After cooling, a 4-5% gelatin solution is obtained.

Experiment No. 7 Observation of diffusion using thick gels

Target: Observation of the phenomenon of diffusion in solids (using a thick solution of gelatin).

Equipment: 4% gelatin solution, test tube, small crystal of potassium permanganate, tweezers.

Description and result of the experiment: Place the gelatin solution in a test tube; quickly insert a crystal of potassium permanganate into the center of the test tube with tweezers in one motion.

Potassium permanganate crystal at the beginning of the experiment

Location of the crystal in a vial with gelatin solution after 1.5 hours

Within a few minutes, a violet-colored ball will begin to grow around the crystal, and over time it becomes larger and larger. This means that the crystalline substance spreads in all directions at the same speed (Figure 38-39)

In solids, diffusion occurs, but much slower than in liquids and gases.

Experiment No. 8 Temperature difference in liquid - thermal diffusion

Target: Observation of the phenomenon of thermal diffusion.

Equipment: 4 identical glass vessels, 2 paint colors, hot and cold water, 2 plastic cards.

Description and result of the experiment:

1. Add a little red paint to containers 1 and 2, blue paint to containers 3 and 4.

2. Pour hot water into vessels 1 and 2.

3. Pour cold water into vessels 3 and 4.

4. Cover vessel 1 with a plastic card, turn it upside down and place it on vessel 4.

5. Cover vessel 3 with a plastic card, turn it upside down and place it on vessel 2.

6. Remove both cards.

This experiment demonstrates the effect of thermal diffusion. In the first case, hot water appears on top of cold water and diffusion does not occur until the temperatures are equal. And in the second case, on the contrary, it is hot at the bottom and cold at the top. And in the second case, hot water molecules begin to tend upward, and cold water molecules begin to tend downward (Figure 41-44).

Conclusion

In the course of this research work, it can be concluded that diffusion plays a huge role in the life of humans and animals.

From this research work, it can be concluded that the duration of diffusion depends on temperature: the higher the temperature, the faster the diffusion occurs.

I studied the phenomenon of diffusion using various substances as an example.

The rate of flow depends on the type of substance: it flows faster in gases than in liquids; in solids, diffusion proceeds much more slowly. This statement can be explained as follows: gas molecules are free, located at distances much greater than the size of the molecules, and move at high speeds. The molecules of liquids are arranged as randomly as in gases, but much denser. Each molecule, surrounded by neighboring molecules, moves slowly inside the liquid. Molecules of solids vibrate around an equilibrium position.

There is thermal diffusion.

List of used literature

Gendenstein, L.E. Physics. 7th grade. Part 1 / L.E. Gendenshtein, A.B., Kaidalov. - M: Mnemosyne, 2009.-255 p.;

Kirillova, I.G. Reading book on physics for 7th grade secondary school students / I.G. Kirillova.- M., 1986.-207 p.;

Olgin, O. Experiments without explosions / O. Olgin. - M.: Khimik, 1986.-192 pp.;

Peryshkin, A.V. Physics textbook, grade 7 / A.V. Peryshkin.- M., 2010.-189 p.;

Razumovsky, V.G. Creative problems in physics / V.G. Razumovsky.- M., 1966.-159 p.;

Ryzhenkov, A.P. Physics. Human. Environment: Supplement to the physics textbook for the 7th grade of educational institutions / A.P. Ryzhenkov.- M., 1996.- 120 p.;

Chuyanov, V.A. Encyclopedic dictionary of a young physicist / V.A. Chuyanov.- M., 1984.- 352 p.;

Shablovsky, V. Entertaining physics / V. Shablovsky. S.-P., Trigon, 1997.-416 p.

Application

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Solvent particles (blue) are able to cross the membrane,

solute particles (red) are not.

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Physics is one of the most interesting, mysterious and at the same time logical sciences. She explains everything that can be explained, even how tea becomes sweet and soup becomes salty. A true physicist would say differently: this is how diffusion occurs in liquids.

Diffusion

Diffusion is the magical process of penetration of the smallest particles of one substance into the intermolecular spaces of another. By the way, such penetration is mutual.

Do you know how this word is translated from Latin? Spreading, spreading.

How does diffusion occur in liquids?

Diffusion can be observed during the interaction of any substances: liquid, gaseous and solid.

To find out how diffusion occurs in liquids, you can try throwing a few grains of paint, ground lead or, for example, potassium permanganate into a transparent vessel with clean water. It is better if this vessel is tall. What will we see? At first, the crystals will sink to the bottom under the influence of gravity, but after a while a halo of colored water will appear around them, which will spread and spread. If we do not approach these vessels for at least several weeks, we will find that the water will become almost completely colored.

Another clear example. In order for sugar or salt to dissolve faster, they need to be stirred in water. But if this is not done, the sugar or salt will dissolve on its own after some time: the tea or compote will become sweet, and the soup or brine will become salty.

How diffusion occurs in liquids: experience

In order to determine how the rate of diffusion depends on the temperature of the substance, you can conduct a small but very indicative experiment.

Take two glasses of the same volume: one with cold water, the other with hot water. Pour an equal amount of instant powder (for example, coffee or cocoa) into both glasses. In one of the vessels the powder will begin to dissolve more intensely. Do you know which one exactly? Can you guess? Where the water temperature is higher! After all, diffusion occurs during the random chaotic movement of molecules, and at high temperatures this movement occurs much faster.

Diffusion can occur in any substance; only the time of occurrence of this phenomenon differs. The highest speed is in gases. That is why you should not store butter in the refrigerator next to herring or lard, grated with finely chopped garlic. Next come the liquids (from lowest to highest density). And the slowest is the diffusion of solids. Although at first glance, diffusion does not exist in solids.