Открытый урок "Diffusion"

Topic "Diffusion"

Lesson type: Combined.

Goals.

1. Formation of the concept of diffusion as a phenomenon

• spontaneous mixing of substances in solid, liquid and gaseous states,

• Continuous and chaotic motion of molecules.

2. Formation of the concept of the value of diffusion.

3. Formation of logical thinking, generalize skills.

4. Development of cognitive interest of students.

Demonstrations:

1. Air freshener "Coffee", (or any other freshener, on which the name "Lemon", "Orange", "Coniferous" is signed)

2. Crystals of iodine on glass under a layer of paraffin.

3. Diffusion in a liquid.(Vessels, a solution of copper sulf

During the classes.

1. Organizing time

• Welcome

• Checking the availability of educational supplies

• Checking the people present

2. Repetition

1. At the board:

• The structure of matter.

• Molecules.

2. In the field all:

The physical dictation "Believe - you do not believe"

(On the table sheets with the text of the physical dictation (1-2 option).Students write down the appropriate number "yes" if they consider this statement true, or "no" if they consider it incorrect)

Option 1.

1. The substance consists of the tiniest particles hardly visible to the naked eye. (No)

2. The substance consists of the smallest particles that can be seen on the screen of an electron microscope. (Yes)

3. The volume of the gas increases with heating, because Each molecule becomes larger in size. (No)

4. Atom - the smallest particle of matter. (No)

5. The molecule can have more than 1000 atoms. (Yes)

6. The steel ball when heated increases in volume, since the gaps between the molecules become larger. (Yes)

7. The oil film, spreading over the surface of the water, can occupy any area. (No)

8. Molecules of water are exactly the same as the molecules of ice.(Yes)

9. The volume of a body is equal to the sum of the volumes of its molecules. (No)

10. Atoms consist of molecules. (No)

Option 2.

1. The substance consists of the tiniest particles visible in an optical microscope. (No)

2. The body volume decreases with heating. (No)

3. The volume of the liquid decreases with cooling, since the gaps between the molecules become smaller. (Yes)

4. A molecule is a tiny particle of matter.(Yes)

5. There can not be more than 100 atoms in the molecule. (No)

6. Water vapor molecules are different from water molecules. (No)

7. When the gas is compressed, the size of the molecules decreases. (No)

8. A four-liter vessel can be filled with gas from a two-liter vessel. (Yes)

9. The volume of the body is greater than the sum of the volumes of its molecules. (Yes)

10. Atoms consist of elementary particles. (Yes)

3. The main material.

1.diffusion:

• in gases.

I begin the lesson with spray freshener; In case the student smelled, he must stand up. Thus, gradually, in a couple of minutes, all the students of the class will stand up. They will unmistakably determine what kind of freshener was sprayed. Slide 1

In the conversation the students come to conclusions: liquid, freshener, turns into steam; The molecules of the gas are in motion; The velocity of gas molecules is significant; Between the molecules of gases, of which air is composed, there are gaps; Substances can be mixed due to the movement of molecules.

• in liquids

I have two liquids on my table in the tall glass: a blue solution of copper sulfate from the bottom, water above; Between them a sharp border. If vitriol and water are capable of spontaneous mixing, the boundary between them should disappear. I suggest that students follow this boundary between liquids. Slide 2

• in solids

Well-cleaned and tightly pressed to each other plates of gold and lead diffuse to a depth of 1mm for 5 years.

Demonstration of the diffusion of iodine crystals on glass under a layer of paraffin.

(The paraffin around iodine crystals turned brown)

Teacher: So, what happened during this time in the first two experiments?

Teacher: But look what happened in the glass, where you gently poured vitriol and water a week ago.

Teacher: Formulate an answer that follows from observations and experiences.

Teacher: We met a new phenomenon, in physics it is known as DIFFUSION slide 3, 4

(Working with a textbook, writing a definition in a notebook.)

The phenomenon at which a spontaneous mutual penetration of molecules of one substance occurs between the molecules of another is called diffusion

Before the students put questions:

• What properties of molecules cause mixing of substances?

• Why is diffusion possible?

• What invisible processes occur with molecules during diffusion?

• How to explain the phenomenon of the penetration of one substance into another?

• Could it occur if the molecules were immovable and there were no gaps between them?

Frontal experiment.

Demonstration of the diffusion phenomenon on the model:

1. In a glass to fill up not up to a pea,

2. Add a glass with peas

3. Shake the glass gently.

(It is quite effective to see how the grains of millet penetrate into the intervals between peas)

After the experiment and discussions with the students, I emphasize that the phenomenon of diffusion occurs without interference from outside, due to the movement of the molecules themselves, i.e. Can be explained only by the fact that the molecules continuously and randomly move and collide.

Teacher: How will a small particle of an insoluble substance behave in a liquid if the molecules of the liquid surrounding it continuously and randomly move?

(Demonstration using the "Brownian Motion Model" device)

The phenomenon of random motion of suspended insoluble matter particles in a liquid or gas is called Brownian motion.

Whence such name, you learn at home from the textbook. Observe the Brownian movement can be done under a microscope, everyone can do this at a change.

The difference in the rate of diffusion of solids, liquids and gases is explained by the students.

• Gases are the fastest molecules.

• Liquids - the velocity of molecules is less than in gases.

• Solids - molecules can barely oscillate around their position.

2.The importance of diffusion in nature and production practice.

• Due to the diffusion of the gas, the air composition at the Earth's surface is homogeneous;

• Diffusion is essential in the nutrition of plants and other organisms;

• The phenomenon of diffusion is used in sugar plants when sugar is extracted from beets;

• The phenomenon of diffusion is based on pickling vegetables, boiling, making compotes and many other technological processes;

• Diffusion of molecules of solids is used in technology: to give iron and steel parts of considerable hardness, their surface layer is subjected to diffuse carbon saturation (carburization).

3.Dependence of diffusion on temperature.

• Diffusion accelerates with increasing temperature: with increasing temperature, the velocity of the molecules increases.

4.Fastening.

Explain why:

1. Wash clothes of different colors, soaked together, painted?

2. Cucumbers a few days after they were put in a brine, became salty?

3. Is natural gas, if used improperly, can rupture the cylinder in which it is located?

4. Does the ball swell when it is filled with gas?

5. When making herbarium plants are dried?

5.Lesson results

1. What did we learn about the molecules?

2. What is diffusion?