What is diffusion Is there an explanation of diffusion in the middle school textbook Thank you

Junior: Principles of Gas Diffusion.

Gas exchange of CO2 and O2 in tissues, cells and lungs during respiration] fluid diffusion. Water absorption and water loss of roots].

Summary: The concentration is large to the concentration is small.

High school? : Diffusion: The phenomenon of spontaneous migration of matter due to the thermal movement of particles (atoms, molecules, or groups of molecules) is called "diffusion".

The phenomenon of material migration due to the thermal motion of particles (atoms, molecules, or groups of molecules) spontaneously occurs and is called "diffusion". Diffusion can take place in one phase of the same substance or between solid, liquid, and gas phases. It can also be carried out between different solids, liquids and gases.

It is mainly caused by concentration difference or temperature difference. Generally, it spreads from the area with a large concentration to the area with a small concentration until the concentration of each part of the phase reaches uniformity or the concentration between the two phases reaches equilibrium. When substances come into direct contact with each other, it is called free diffusion, and when diffusion is carried out through isolated substances, it is called osmosis.

In nature, the phenomenon of diffusion plays a big role. It keeps the same composition of the atmosphere near the entire Earth's surface; The diffusion of various salt solutions contained in the soil is convenient for plants to absorb and facilitate growth. In addition, diffusion is applied in many industries such as semiconductors and metallurgy to achieve its goals.

Diffusion, heat conduction, and viscosity are commonly known as transport phenomena, which move matter (mass), heat energy, and momentum from one location to another, respectively, to achieve uniformity of concentration or temperature.

This is a quote from the Internet, which may be helpful.

Diffusion: The embodiment of the irregular movement of molecules in a never-ending manner. The diffusion of molecules is related to external environmental factors. Of course, it will also be affected by the temperature.

The phenomenon of one substance coming into contact with another substance and entering into each other.

In the chapter 15 of the junior high school physics textbook (p. 120).

Preliminary talk of "diffusion".

The teacher defined it as a phenomenon in which molecules of matter enter each other.

In junior high school books, it was mentioned that diffusion is a part of molecular kinematics.

The basic content of molecular kinematics:

1) Objects are made of molecules;

2) the molecules never stop moving in an irregular motion;

3) There are interacting gravitational and repulsive forces between molecules.

Diffusion is a concrete manifestation of the never-ending irregular movement of molecules.

Definition of diffusion: The phenomenon of migration of molecules from a denser place to a less dense place in solids, liquids, gases and other substances is called diffusion. Until the densities of the parts within the object are alternate.

For example, "a cup filled with cold water and hot water is dripped, and the glass of water is red after a while" can clearly conclude that the higher the temperature of the liquid, the faster the liquid will diffuse, which further indicates that the speed of molecular movement is related to temperature, that is, the diffusion of molecules is related to temperature

The phenomenon in which different substances enter each other when they come into contact with each other is called diffusion. For example, in the place where the other party's coal is located, after a long time, the soil below will be black, indicating that the coal and the soil have spread and entered each other. When you pass by the restaurant, you will smell the fragrance, and it is also diffusion.

Particles are in constant motion. When two objects are close to each other, particles enter each other, which is called diffusion.

It is molecular motion, the process of molecular motion of one substance into the interval of molecules of another substance.

In its simplest understanding) molecules leave each other with each other.

The object diffuses from a high concentration to a low concentration.

The gas-solid catalytic reaction on a porous industrial particle catalyst generally consists of the following steps: the reactants diffuse from the gas stream to the outer surface of the catalyst particles; The reactants diffuse from the outer surface to the inside of the pores of the catalyst; The catalytic reaction is carried out on the inner surface composed of the internal pores of the catalyst; The product diffuses from the inner surface to the outer surface; The product diffuses from the outer surface to the body of the airflow. The first and fifth steps are called the outer diffusion process, the second and fourth steps are called the internal diffusion process, and the third step is the intrinsic kinetic process.

The internal diffusion process and the intrinsic kinetic process on the inner surface of the catalyst are carried out simultaneously, so it is also called the diffusion-reaction process.

Hello, free diffusion is a type of diffusion.

Diffusion in living things.

It is divided into active transportation and assisted diffusion. Active transport is divided into: free diffusion, assisted diffusion.

Free diffusion and assisted diffusion are transported by high concentrations to the bottom (along the concentration gradient), which does not consume energy, and free diffusion does not require energy, so the transported substances are gaseous solvents and fat-soluble substances; Energy is required to assist in diffusion, and the example of such a transport of substances is "glucose into red blood cells" (you just need to remember this);

The active transport of substances is from low to high concentrations (inverse concentration gradient), so carrier proteins are required on the cell membrane, so that the transported substances are molecules and ions the size of monosaccharides, amino acids, and nucleotides.

After reading your question, if there is a carrier protein on the semi-permeable membrane, it can assist in diffusion, otherwise it can't, but it can spread freely.

Proliferation includes both free proliferation and assisted proliferation.

Whether energy is required, forward gradient and reverse gradient.

Hierarchical diffusion is a way of expanding diffusion, which refers to the diffusion of a certain culture that is divided into hierarchical levels, and it is necessary to pay attention to the changes in the diffusion process or scope into several levels. For example, the spread of computer technology in China began with scientific and technological workers learning from developed countries, then opened classes in colleges and universities, and finally spread to primary and secondary schools and social training institutions, and this diffusion was promoted by intellectuals to the level of ordinary people.

Spread refers to the way in which a person who has mastered a culture spreads to those around him who are eager to accept it. This kind of diffusion mainly emphasizes the "surrounding", that is, it spreads through the influence of the proximity, and when it is received, it has the meaning of "hearing and seeing". For example, if computer learners are instructed and trained by teachers in front of the computer in the classroom, this kind of cultural transmission is contagious.

The key to distinguishing between the two is to focus on one large and one small.

Diffusion mechanism: As long as there is oil and gas generation, especially for natural gas, there is a difference in hydrocarbon concentration in space, and the hydrocarbon molecules will appear in the diffusion and migration of free phase or water-soluble phase. It became one of the most prevalent transport mechanisms.

However, the diffusion rate of hydrocarbon molecules is extremely slow and the diffusion direction is not strong, which only promotes the accumulation of oil and gas under certain conditions, and in most cases, leads to the escape of oil and gas.

Vacancies mechanism, gap mechanism, and other diffusion mechanisms such as gap filling, annular factor, atomic transition characteristic, d=1, 6f, a, square are the migration frequency.

The phenomenon of water moving from a system with a high water potential through a semi-permeable membrane to a system with a low water potential is called osmosis.

Diffusion is the way a substance moves in and out of a cell through the plasma membrane.

Diffusion is the transport of molecules from high concentrations to low concentrations. With or without a semi-permeable membrane.

Semi-permeable membranes are required for infiltration, and there should be concentration differences between the two sides of semi-permeable membranes. Diffusion includes infiltration.

Infiltration, as the name suggests, a substance passes through one layer (such as thin film, coating, etc.) and transitions to the other side, which is called zhi osmosis, and the meaning of diffusion is relatively wide.

DAO pan, diffusion is from point to surface, however, I guess you are confusing this concept biologically, for example, glucose through the lipid layer is called diffusion, but this is also a manifestation of osmosis... My personal understanding is this... Huh...

Diffusion: The movement of solvent molecules into another substance. With or without a semi-permeable membrane.

Permeation: Semi-permeable membrane is required. It is the movement of solute molecules through a semi-permeable membrane into another substance.

1. The definition of bai is different.

1. Diffusion: du

Expanded dispersal: Cancer cells have spread. This message must not be spread outward.

A phenomenon in which the molecules (or atoms) of a substance are continuously dispersed in response to thermal motion. Solid, liquid and gaseous substances have diffusion properties. Gaseous substances diffuse the fastest.

2. Permosis: two gases or two liquids that can be mixed with each other through a porous film.

The liquid penetrates through the tiny voids of the object: the rain penetrates the soil.

A metaphor for the gradual entry of a thing or force into something else (mostly used for abstract things): economic infiltration. In every construction project, the efforts of designers and workers are infiltrated.

Second, the source is different.

1. Diffusion: Source: Mao Dun "Midnight" 9: "A stream of heat gradually spread from her chest, and her face turned a little red. ”

2, infiltration: source: Zhou Erfu "Morning in Shanghai" Part 1 6: "She nervously continued to take her head, and beads of sweat continued to seep out of her forehead. ”

3. The synonyms are different.

1. Diffusion: dispersion and dissipation.

2. Osmosis: secretion, exudation.