The process of evaporation requires endothermy, but why does it refrigerate?

Hehe, your explanation is good! Junior high school students, it's rare to be able to give such an explanation. However, there are many inappropriate words (concepts) in it, so help you change it for your reference.

1.The fluidity of water does not need to be considered, and in the general evaporation process, water does not flow. Generally speaking, the flow is macroscopic (simply understood as visible to the naked eye), and I guess what you might really want to express is the irregular movement of water molecules, which is microscopic motion, which is invisible to the naked eye.

2.There is no "heat" in the water. Water has only energy, and water that does not flow has only internal energy (gravitational potential energy is not considered).

There are two main parts of internal energy, one is the kinetic energy of the irregular movement of a large number of water molecules, and the other part is the gravitational potential energy between molecules. To get rid of the gravitational force between molecules is to increase the intermolecular potential energy to zero (the intermolecular potential energy was originally a negative value), and to increase the potential energy must have energy**, which is the kinetic energy of other molecules (there is no other**).

3.The vaporization process is roughly as follows: when the kinetic energy of some water molecules on the surface increases after being hit by other molecules, they may break away from the gravitational attraction of the surrounding molecules and run out of the water surface to become free gas molecules (the gravitational force between the molecules in the liquid is zero, and the potential energy reaches the maximum that is, zero), and in this process, the kinetic energy of the gas molecules decreases.

The kinetic energy of the other molecules that originally hit these gas molecules is also reduced, so that the average kinetic energy of the molecules left behind in the liquid is reduced. We say that temperature is a sign of how intense a molecule is moving, or rather a measure of the average kinetic energy of a molecule. The average kinetic energy decreases, which means that the temperature decreases and the liquid becomes colder.

4.Further understanding of heat: heat is the energy absorbed or emitted by an object, and after absorption, it becomes the kinetic energy or potential energy of the molecule, that is, the internal energy, so there is no heat in the object.

For heat, it can only be said that it is absorbed and released, that is, it is endothermic and exothermic. It cannot be said how much heat the object has.

To look at this problem, whether it is heat absorption or refrigeration, it satisfies the first and second laws of thermodynamics relative to two or more media.

Evaporation is endothermic.

Evaporation is the process of heating a solution to vaporize and remove some of the solvent, thereby increasing the concentration of the solution, that is, the solution is concentrated. Since most of the evaporated solutions are aqueous solutions, the evaporation process is to use water vapor as a heating agent to produce water vapor, and in order to distinguish it, the water vapor as a heat source is called heating steam or primary steam.

Principles and characteristics of evaporation:

Water is made up of a large number of water molecules that attract each other and are constantly dangling so that they retain their liquid shape. Because the molecules are constantly dangling, sometimes, there are individual molecules on the water surface that happen to be hit by a relatively large impact, so that they have a relatively large kinetic energy, so that it can get rid of the attraction of other water molecules and fly out. The molecules fly out one by one, and fewer molecules remain in the water, and the water evaporates like this.

However, there will always be water vapor on the surface of the water, and these water vapor molecules will also dangle and swim in space. Some water vapor molecules will also fly into the water surface, and if there are enough water vapor molecules on the water surface to make the molecules flying out of the water surface and the molecules flying into the water surface basically equal, a dynamic equilibrium will be formed.

It's like in a tightly closed bottle, we can't see the decrease in water, but in fact there are water molecules coming out of the water, and water molecules are constantly coming out of the air on the surface of the water and entering the water. If we use the wind to blow away the water vapor on the surface of the water, then fewer water molecules enter the surface of the water from the air, and the evaporation of water will be accelerated.

When water evaporates, it is endothermicIt cannot evaporate without heat absorption, so when water evaporates, it absorbs heat energy from the surrounding objects, so when water evaporates, it will make people feel cool because part of the surrounding heat is absorbed, which is often referred to as the cooling effect. However, over time, when the temperature of the water decreases, it begins to release heat, and part of this heat is transferred to the air, and the other part is transferred to the evaporation process.

Difference Between Water Evaporation and Boiling

1. The location of occurrence is different: evaporation is a vaporization phenomenon that only occurs on the surface of the liquid, while boiling is a violent vaporization phenomenon that occurs both inside and on the surface of the liquid;

2. Different temperature conditions: evaporation can occur at any temperature, while boiling occurs at a certain temperature;

3. The temperature change may be different: the liquid needs to absorb heat when it evaporates, and the temperature may decrease; Whereas, heat is absorbed during boiling, but the temperature remains the same;

4. Different degrees of intensity: evaporation is relatively gentle, while boiling is very violent.

: Liquid evaporation does not need to absorb heat from the outside, but it cannot be understood as "heat absorption from itself".

From the point of view of the essence of evaporation: because molecular bending is an irregular movement without stopping, there are always some molecules with high delay energy on the surface of the liquid, which can get rid of the attraction of other molecules and directly (escape) into gas molecules, which is evaporation.

If the energetic molecule escapes, the average kinetic energy of the remaining liquid molecules decreases, and the temperature of the liquid decreases. Therefore, evaporation does not need to absorb heat from the outside and evaporation can take place at any temperature. Yard positive wheel.

Similarly, sublimation is a phenomenon in which molecules on the surface of a solid are directly transformed into gas molecules.

The melting of the crystals needs to reach the melting point and continue to absorb heat.

In conclusion, evaporation, melting, and sublimation are all endothermic processes. If there is no heat absorption from the outside, evaporation and sublimation will occur.

The essence of evaporation is a change in the state of motion of molecules. There are many influencing factors, and it is not necessary to absorb heat. Theoretically, as long as the ambient temperature is above absolute zero (-273), evaporation will occur all the time. So this question is wrong.

For example, if a basin of water is placed in a closed room temperature and constant temperature environment, the water will always evaporate and condensation will always exist, but the evaporation rate is greater than the coagulation rate. Wait until the space is saturated with steam, and then the evaporation rate and condensation rate are in equilibrium. The evaporation and condensation rates are the same, but they still keep happening, and at this time, there is no endothermic phenomenon.

The same goes for melting and sublimation. It is a phenomenon in which the macroscopic state of matter changes. External conditions are only factors that accelerate this phenomenon.

From the point of view of energy, any matter has energy as long as it is above absolute zero degrees.

There are generally three manifestations of energy changes: 1. Energy transmission; 2. New substances are generated; 3. Change of exercise status. On the other hand, as long as there are these three phenomena, it means that there must be a change in energy.

Evaporation can absorb heat from the outside, if it does not provide heat during the week, then it can consume its own internal energy, evaporative heat absorption makes the wide void vertical and the temperature lower, providing evaporation energy. Melting from a solid state to a liquid state requires energy from the outside world, and sublimation of the solid state to become a cautious state requires energy from the outside world, and it does not provide much by itself, and external heat is the main thing.

It can also absorb heat from itself.

In general, evaporation, melting, and sublimation all require heat absorption from the outside. However, there are exceptions, such as a chemical reaction that emits heat inside the liquid brother, or work that can also convert heat and transport dust.

Evaporation does not lose heat from the outside world, not from itself. For example, when water evaporates into water vapor, its enthalpy increases, and this increased heat comes from the outer space realm. The same goes for melting and sublimation.

melts, absorbing heat from the outside. Sublimation absorbs heat from the outside world or from itself.

Evaporation does not absorb heat from itself, unless there is workmanship. Most of it is still heat absorption from the outside.

The evaporator can absorb heat from the outside as well as from itself, and I think of course, because I think this is really the case with evaporation.

Naturally, there is a heat source. I think the problem you raised is that you ignore the cause of the ambient temperature, and that it melts and sublimates from the heat absorbed by the high temperature environment.

Can hair growth agent evaporator be able to absorb heat from the outside or from itself? Of course, evaporation is an endothermic process.

Evaporation is a physical process in which the movement of material molecules intensifies, the kinetic energy increases the bond, and the total energy is also increasing.

When the liquid evaporates, the molecules that run out of the liquid work work by overcoming the gravitational pull of the molecules on the surface layer of the liquid. These molecules can do work because they have enough kinetic energy. Molecules with greater than the average kinetic energy fly out of the liquid surface, molecules with higher velocity fly out, and the molecules that remain inside the liquid have less average kinetic energy.

Therefore, during the evaporation process, if the outside world does not replenish the liquid with energy, the temperature of the liquid will drop. In this case, it draws heat from the surrounding objects through heat transfer, thus cooling the surrounding objects.

Categories: Education, Science, >> Learning Aid.

Problem description: I wonder why a liquid absorbs heat from itself, is it possible?

Analysis: When the liquid evaporates, it should absorb heat from itself and the surrounding environment, so that the liquid and the surrounding environment are cooled down due to exothermy, and at the same time, the internal energy of the vapor formed by evaporation increases after heat absorption, so that the molecular movement is more intense! Therefore, instead of "liquid endothermy", it is "evaporative endothermy", and then the vapor takes away the heat it absorbs, which cools the liquid and the surrounding environment.

The evaporation process is endothermic (refers to the evaporation process itself must absorb heat, otherwise it cannot evaporate), gaseous water contains more energy than liquid water (equal mass, equal temperature), so when liquid water becomes gaseous water, it must absorb energy from the outside world (endothermy), otherwise energy conservation cannot be achieved! (Just like a person who changes from a poor person to a rich person, although he is a person, but his state changes, the amount of money on his body changes, and the poor person must earn money from elsewhere (absorb heat) in order to become rich.) (If the body is wet, the wind will feel very cold, because the evaporation of water is accelerated, and this process absorbs heat from your body, it is the decrease in heat in your body, and the manifestation of a decrease in temperature, so it is cold).

It is true that the temperature of the water decreases because of exothermics, but to whom is this heat released, obviously it is released to the endothermic evaporation process, one endothermic and the other exothermic to ensure the conservation of energy (energy can neither disappear out of thin air nor be generated out of thin air).

The heat released is not only transferred to the evaporation process, but also to the air (hot water is hotter than air, and heat is always transferred from high temperature to low temperature) This is also an exothermic process.

As long as the energy contained in an object decreases, usually in the form of a decrease in temperature, it undergoes an exothermic process.

It is endothermic because evaporation changes from a liquid state to a gaseous state.

The evaporation process is endothermic (refers to the evaporation process itself must absorb heat, otherwise it cannot evaporate), gaseous water contains more energy than liquid water (equal mass, equal temperature), so when liquid water becomes gaseous water, it must absorb energy from the outside world (endothermy), otherwise energy conservation cannot be achieved!

It is endothermic because the substance absorbs heat up, for example: water evaporates into water vapor, and water needs to be heated by heat absorption from liquid to gaseous state.

Evaporation is endothermic. Because the substance changes from a liquid state to a gaseous state during evaporation, the distance between molecules becomes larger, and the thermal motion of molecules increases. It needs to absorb heat to change. So evaporation is endothermic.

In the process of evaporative endothermy, because the degree of movement of gas molecules is more intense than that of the liquid state, the energy contained in the gaseous state is higher than that of the liquid state, so the liquid state is converted into gas in the state of the molecule unchanged to absorb heat.

Endothermy Just take a simple example to understand that when boiling water, if you don't care about it, the water will dry out and eventually disappear, and the water will evaporate in the process.

Evaporation is endothermic. Because the energy of gases is higher than that of liquids! Evaporation is the process by which a liquid becomes a gas. So it's endothermic!

Evaporation is endothermic and evaporation occurs when snow melts. It is often felt that snow melts colder than when it falls, and this is because snow melts and absorbs heat.

Evaporation is the transformation of liquid into gas to be exothermic, and condensation of water vapor into water to endothermic ......Problems of energy conversion in high school physics.

Of course, it is exothermic, and the evaporation of water vapor will also take away the heat, do you think about how boiling water becomes cool? (except for thermal radiation).

Evaporation is endothermic, the liquid state is stable relative to the gaseous state, absorbs energy, and turns from stable to active.

Evaporation is endothermic. That is, water absorbs heat and turns into water vapor, which is evaporation.

Decalescence! The distance between the absorbed energy molecules can be large, and it can become a gas...

Endothermic • Liquid becomes gas to absorb energy and destroy intermolecular forces • Exhibits endothermy.

When the energy contained in an object decreases, it undergoes an exothermic process.

Water is endothermic during evaporation, and the temperature decreases when the liquid evaporates, indicating that it has to absorb heat from the surrounding objects. Therefore, liquid evaporation has a cooling effect.

Introduction to evaporation: The vaporization process that occurs on the surface of a liquid when the temperature of the liquid is below the boiling point can occur at any temperature. Factors that affect the speed of evaporation: temperature, humidity, surface area of the liquid, air flow on the surface of the liquid, etc.

The amount of evaporation is usually expressed in millimeters of the thickness of the water layer that has been evaporated. In addition to denoting a physical phenomenon, "evaporation" is also called "evaporation" by its original meaning through association.

Meteorological processes. 1. The moisture in the atmosphere is often in a state of unsaturation, so both the ocean and the land are slowly carrying out the moisture from the underlying surface"Evaporation"and the physical processes that enter the atmosphere. The phenomenon of evaporation in nature is quite complex, and the main factors affecting the evaporation rate are: water source; Heat; saturation difference; Wind speed and turbulent diffusion intensity.

Headwaters. There can be no evaporation without water, so open water, snow, ice or moist soil, and plants are the basic conditions for evaporation to occur. In the desert, the evaporation potential is high, but the actual evaporation is very small, because there is almost no water to evaporate.

2. Heat source. Evaporation must consume heat, and if there is no heat supply during the evaporation process, the evaporation surface will gradually cool, so that the water vapor pressure on the evaporation surface will be reduced, so that the evaporation will slow down or gradually stop. Therefore, the rate of evaporation is largely determined by the heat supply.

3. Saturation difference. All other factors being equal, the evaporation rate is directly proportional to the saturation difference. Strictly speaking, the saturated water vapor pressure here should be calculated from the temperature of the evaporation surface, but it is usually replaced by the saturated water vapor pressure at a certain air temperature.

4. Wind speed and turbulent diffusion. When there is no wind, the water vapor on the evaporation surface is diffused by molecules alone, and the water vapor pressure decreases slowly, and the saturation difference is small, so the evaporation is slow. When there is wind, the turbulence intensifies, and the water vapor on the evaporation surface is rapidly dispersed to the vast space with the wind and turbulence, and the water vapor pressure on the evaporation surface decreases and increases rapidly, the saturation difference increases, and the evaporation accelerates.

5. In addition to the above-mentioned basic factors, evaporation on the continent should also take into account the structure of the soil, humidity, vegetation characteristics, etc. Evaporation on the ocean should also take into account the salinity in the water. Among the factors that affect evaporation, the temperature (heat) of the evaporation surface is usually the factor that determines the evaporation capacity.

Since the temperature of the evaporation surface (land surface and water surface) varies annually and diligently, the amount of evaporation also varies annually and diligently. The global average is approximately 1 m per year for the water layer that evaporates from the underlying surface (ocean, land, ice sheet).