Collect
Check out my collection
0
Useful +1
Molecular thermal motion
(Thermal Motion) means that all microscopic particles (including molecules, ions, atoms, etc.) are constantly in irregular motion. The speed of temperature shift affects the thermal motion of microscopic particles,
temperature
The higher you go, the more intense the thermal motion. There are many examples of the hot movement of microscopic particles in life, such as salted eggs and salted vegetables that we eat, all because of the continuous movement of chloride ions and sodium ions, and enter the eggs or dishes to make them salty.
- Chinese name
- Thermal motion
- Foreign name
- thermal motion
- Subject classification
- thermodynamics
- occurrence
- Brownian motion, molecular diffusion
- applicability
- All matter
The irregular motion of a large number of microscopic particles in an object is called thermal motion.
The test for molecular thermal motion is
Brownian motion
. (Molecular thermal motion is not Brownian motion.)
Brownian motion shows the irregular movement of water molecules through the irregular movement of pollen in water, that is, the thermal movement of molecules, rather than the thermal movement of pollen.
Brownian motion
It is the irregular motion of a particle suspended in a liquid or gas, not the motion of a liquid or gas molecule, but an indirect proof of the irregular motion of a liquid or gas molecule. Therefore, the Brownian motion cannot be called thermal motion, but it can only be said that Brownian motion confirms the thermal motion of molecules.
Typical phenomena such as the diffusion of fragrance in daily life and so on.
The molecules that make up gases are very mobile. For example, jasmine, once in bloom, you can smell the fragrance; When fish and meat are rotten, they stink all over the place. The molecules that make up liquids are also very mobile. Put a drop in a glass of water
Ink
The ink will slowly disperse and mix completely with the water. This means that molecules of one liquid went into another liquid. Or the liquid molecules are in constant motion. Solid particles are also moving. For example, if the surface of a very smooth and clean lead plate is pressed tightly on the gold plate, it can be found that after a few months, lead atoms have run into the gold plate, gold atoms have run into the lead plate, and in some places even into the depth of 1 millimeter. After five years, gold and lead will join together, and their molecules will enter each other by about one centimeter. For example, the corner and the ground where coal is stored for a long time have a rather thick layer that has turned black, which is the result of the entry of coal molecules.
The most famous experiment to prove the disorderly motion of liquid and gas molecules was discovered by English botanist Brown
Brownian motion
.
In 1827, Brown put garcinia powder into water, and then took a drop of this suspension under a microscope, and found that small garcinia particles in the water constantly moving, and the direction and speed of each particle change quickly. If the suspension of garcinia powder is sealed up, Brownian motion can be seen at any time, day or night, summer or winter, and this movement will not stop no matter how long it is observed. Brownian motion can also be observed in the air, where particles suspended in the air, such as dust, also move irregularly.
It's made up of liquids or gases
Molecular motion
. For example in
Normal temperature
At normal pressure, the average speed of air molecules is 500m/s, and each molecule collides with other molecules 50 billion times in a second. Random molecules strike small suspended particles from all sides, sometimes larger in one direction, sometimes larger in another, and the result is that the particles are forced to move forward and back, left and right, in an irregular manner.
although
Kinetic theory of molecules
It continued to develop, but ruled throughout the 18th century
heat
The field is still
Caloric theory
After entering the 19th century, the debate between the theory of molecular motion and the theory of heat and matter became increasingly fierce. Around 1848,
joule
The experiments of the thermal equivalent of J.PJoule and, later, the frictional heat generation observed by Rumford in the machining of the barrel dealt a fatal blow to the thermal theory. In the second half of the 19th century, the theory of molecular motion developed rapidly until it was fully established in physics in the 20th century.
[1]
Due to the internal molecules, atoms, electrons, etc
Microscopic particle
The thermal movement of the object, and the composition of the material does not occur macroscopic displacement, the heat from the high temperature region to the low temperature region is called thermal conduction.
[2]
Pour one cup of hot water and one cup of cold water, then put a drop of red ink into each cup. The red ink in the hot cup will spread faster than in the cold one. This shows that the temperature is high, the speed of molecular movement is large, and it increases with the increase of the temperature of the object, so the movement of molecules is also called thermal motion.
Heat conduction
Is in solid
Heat transfer
The main way. In a gas or liquid, the heat transfer process often occurs at the same time as convection.
All kinds of matter can be transmitted
Heat conduction
But of a different substance
Heat transfer
Different skills. Substances that are good at transferring heat are called
A good conductor of heat
Substances that are not good at transferring heat are called
A poor conductor of heat
. All kinds of metals are good conductors of heat, of which silver is the best at heat transfer, followed by copper and aluminum. Porcelain, paper, wood, glass and leather are all poor conductors of heat. The least good at heat transfer are wool, feathers, fur, cotton, asbestos, cork and other soft substances. Liquids, except mercury, are not good at heat transfer, and gases are even less good at heat transfer than liquids.
Convection is in liquids and gases
Heat transfer
The main way, gas
Convective phenomenon
More obvious than liquids.
When using convection heating or cooling, two conditions must be met at the same time: one is that the material can flow, and the other is that the heating method must be able to promote the material flow.
Radiant heat is emitted from an object in a straight line and is called radiation.
The transfer of heat by radiation does not require any medium. So, radiation can be in
vacuum
In progress.
The Earth receives the heat of the sun, which is transmitted by the sun through radiation.
In general,
Heat transfer
The three modes (conduction, convection, radiation) are often simultaneous.
In some dietary propaganda, there is often some implicit knowledge of the phenomenon of diffusion. For example, an advertisement slogan promoting stinky tofu, "notorious, fragrant", very vividly describes the characteristics of stinky tofu "odor" and "fragrance", and "far" and "floating" are the spread of stinky tofu odor and fragrance; Describing the mellow degree of wine, "wine is not afraid of the alley deep", this sentence indirectly proves that this wine is a good wine, showing that no matter how deep the alley, it can not block the aroma of wine, floating out of the alley, people drink. The wine evaporates and the molecules move through the air so that even people farther away from where the wine is hidden can smell it.
[3]
In the room, the strong sunlight into the room, we can see the floating dust along the light, which is in the windless environment, the gas molecules in the air are constantly moving, impacting the small particles of dust suspended in the air, so that we can see that the small particles of dust are doing irregular movement.
[3]
