Evaporation Definition and 215 Threads

Evaporation is a type of vaporization that occurs on the surface of a liquid as it changes into the gas phase. The surrounding gas must not be saturated with the evaporating substance. When the molecules of the liquid collide, they transfer energy to each other based on how they collide with each other. When a molecule near the surface absorbs enough energy to overcome the vapor pressure, it will escape and enter the surrounding air as a gas. When evaporation occurs, the energy removed from the vaporized liquid will reduce the temperature of the liquid, resulting in evaporative cooling.On average, only a fraction of the molecules in a liquid have enough heat energy to escape from the liquid. The evaporation will continue until an equilibrium is reached when the evaporation of the liquid is equal to its condensation. In an enclosed environment, a liquid will evaporate until the surrounding air is saturated.
Evaporation is an essential part of the water cycle. The sun (solar energy) drives evaporation of water from oceans, lakes, moisture in the soil, and other sources of water. In hydrology, evaporation and transpiration (which involves evaporation within plant stomata) are collectively termed evapotranspiration. Evaporation of water occurs when the surface of the liquid is exposed, allowing molecules to escape and form water vapor; this vapor can then rise up and form clouds. With sufficient energy, the liquid will turn into vapor.

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  1. ATT55

    Energy Required to Evaporate Water

    Energy required to evaporate water. Given 3 evaporating scenarios: 1. Glass filled with 50cc of water at 20C; the water is heated to 60C 2. Glass filled with 50cc of water at 20C; the water is heated to 100C 3. 50cc of water at 20C wiped over a large plate to create 50micron thickness layer...
  2. J

    B Cooling effect of evaporation occurs even if the surroundings are colder?

    I was studying the principles of air conditioning and came across some questions. In an air conditioner, the refrigerant absorbs heat while evaporating indoors, thereby lowering the temperature, and releases heat while condensing outdoors, thereby raising the temperature. According to the second...
  3. askingask

    Vacuum by condensation causes water to boil?

    So basically if I have a closed container with a valve, and inside the container there is water. Now i heat the container and boil the water. The valve is open so steam escapes form there. I now close the valve and cool the container causing the steam to condense inside. Inside the container is...
  4. K

    B Question about Hawking Radiation and Iron Stars

    So, I was thinking, the most massive black holes are expected to evaporates in roughly a googol year. Fine. But I was reading that if protons are stable, every planet and non black hole star remains are basically expected to turn into iron star from quantum tunneling after mind numbing time on...
  5. E

    Can detergent also evaporate beside water?

    Hi PhysicsForums, My bed has 4 small plastic footing at each corner, and each footing is soaked in middle of small container of water with detergent (about 4 inches square container) to avoid ants from crawling up the bed in any footing. Can the detergent in the water also evaporate polluting...
  6. D

    I What is the Limiting Mass at the Final Stages of Black Hole Evaporation?

    As Hawking radiation does away with black holes in the eons of time it takes to evaporate, what is the limiting mass at the final stages of the black hole evaporation? Is it Planck mass? or some fractional mass of the initial BH?
  7. jaketodd

    I Hawking's latest contribution, is this an implication?

    Does this mean that everything, including us, will turn into photons/electromagnetic waves some day? Sounds fun! A universe of matter converted entirely to light! I couldn't find any papers yet on this on scholar.google.com Here are some good articles though...
  8. R

    I Atomization and Evaporation: Understanding the Energy Exchange

    Oh, also, I know that it takes a lot of energy to phase change a liquid to a gas, but what if you force the liquid through a small hole that atomizes the liquid. Does the atomized liquid draw the same amount of heat from the surrounding area as its forced to become steam?
  9. M

    Finding how much heat released by evaporation of water

    For this, Dose anybody please know where they got the 120W from? Many thanks!
  10. S

    I Kerr & Nordström Black Hole Evaporation: Q&A

    When a Kerr black hole evaporates, what will the Kerr parameter do? Stay constant at initial value? Approach zero? Approach unity? Approach a target value somewhere between zero and unity? Also, Nordström black holes in practice (with matter around) would have a strong tendency to attract...
  11. H

    I Black holes to explode due to evaporation?

    according to Hawking a black hole slowly evaporates and shrinks (when not feeded from outside with matter falling in). as I understood there comes a moment when it explodes and the singularity disappears. Is this true and if so, how is this triggered? and is there something such as a critical...
  12. kyphysics

    Science of Evaporation - General & Personal Questions

    Wasn't sure where to categorize this thread, but thought chemistry would be the most appropriate (mods: feel free to move as you see fit). I have some questions on the science of water evaporation - first in general terms and then within the context of something that happened to me. General...
  13. dario2

    How does evaporation generate cooling? Swamp coolers edition

    I looked for other related threads and read through them, but I didn't find one where I could add replies, so I made another one. This issue came to my mind as I'm thinking about the benefits and detriments of swamp coolers given a hot climate and moderate to high relative humidity. 1) Some...
  14. S

    B What causes the drop of latent heat at lower temperatures in liquid helium?

    The dependency of liquid He latent heat of evaporation on temperature shows a conspicuous maximum. https://www.nist.gov/system/files/documents/srd/jpcrd551.pdf for 4He. Section 16, pages 1264-1266 on pages, 48-50 on pdf. From fig. 16.1 and table 16.3, the maximum is around 3,1 K and 94 J/mol. At...
  15. Melbourne Guy

    Writing: Input Wanted Black holes as weapons - easy way to calculate the evaporation blast

    I've decided my latest novel uses black hole bombs, which aliens create by a mechanism unknown, and which are small enough to quickly evaporate to blast ships in the vicinity. Knowing it is sci-fi and doesn't have to be perfect, about how fast do BHs evaporate? Alternatively, if I need them to...
  16. Youssef Ellakany

    A Enthalpy of Evaporation at Zero Kelvin | Understanding Enthelpy Basics

    What's the enthalpy of evaporation at zero kelvin?
  17. Will26040

    Equation for the Diameter of a Dryer

  18. Kostik

    B Paradox about black hole evaporation

    Paradoxical scenario. Suppose Jack and Jill are sitting safely a kilometer above the event horizon (EH) of a large black hole. Now suppose: Jack decides to head toward the center of the black hole, traveling at an easy pace (say 10 km per hour). Jill sees Jack (with her ultrasensitive infrared...
  19. Marilyn67

    B Black hole horizon and Hawking evaporation

    Hello, I take the example of two observers : - A distant observer - A falling observer For the distant observer, the formation of the horizon is not part of his future cone of light, we agree. For the falling observer, the consensus says it is crossing the horizon. First question: the...
  20. StoningTree

    How does humidity affect air cooling?

    First i calculated the latent heat of vaporation: h_vap(15°C)= 2465.4 kJ/kg In the next step i calculated how much water is already in the air: x=0.622*j*ps/(p-j*ps)=0.00988 kg/kg where: j=50% ps=0.03171 bar p=1.01325 bar Now that i know that i can calculate the enthalpy of humid air: h_hum =...
  21. B

    Field Evaporation of Contact Charged Spheres: Exploring Possibilities

    If you were to positively contact charge a small ~1 mm diameter sphere using a Van de Graaff generator, and were to charge it sufficiently high enough that field evaporation began to occur, what would happen? Would the rate of evaporation increase exponentially as the field strength would...
  22. Z

    Still water droplet evaporation rate (help using Maxwell's formula please)

    So I've observed the animal I am studying dry it's self (a survival mechanism called anhydrobiosis) to avoid freezing (laseration by ice crystals). Life forms given time produce a number of protectants in order to survive. Trehalose a sugar is produced to 2-4%. This will act as an antifreeze to...
  23. V

    Mathematical Modeling of an evaporator for evaporating water

    I am trying to model an evaporator which evaporates water to steam in Matlab/simulink. Are there any governing equations i need to know and follow when modelling the evaporator mathematically? Please let me know.
  24. Y

    Low-Temp Liquid Helium System: Evaporation Heat & Temperature

    We consider a system composed of liquid helium in equilibrium with its vapor at very low temperature T, each phase being considered extensive. We neglect the mass of the gas compared to that of the liquid, as well as the heat capacities of the gas and the walls compared to that of the liquid...
  25. felipeborges

    Estimating the Evaporation Rate

    So I must define the problem stated above. I must define the variables and the error associated with each one of them. Any Formula, Articles, Insight would be of great help! Thanks in advance.
  26. F

    B Why does matter always escape while antimatter falls into black holes?

    Summary: I don't get it, why can we be sure, that black holes evaporate My simplified imagination about Hawking radiation is that when the vacuum fluctuation creates a matter-antimatter particles pair at the event horizon, thay are ripped appart by the tidal force and do not manage to split...
  27. SpinzTronics

    Help searching for SAMs (self-assembling monolayers) for a project

    Does anyone know of a self-assembling monolayer that can bind to triethylamine,deposit onto graphene/TMD by evaporation, and that has "low toxicity" (that I could use in the lab)? P-dopants could only help dope one side of the material and TEA would react on the other but that is very hard to...
  28. Z

    I Non-Linear Evaporation: Explained for Beginners

    Hello to you all, Can someone please explain non-linear evaporation to me. I have not studied physics and it was a very long time ago that I learned chemistry and maths at school. So please explain it to someone with no prior knowledge of physics. A small glass tube is filled with the liquid...
  29. Guilherme Franco

    How volatile is urea in a water mixture?

    I'm seemingly having problems of having too much evaporation of urea in the preparation of a gel. The gel is formed by drying the components in a water mixture, and it takes hours to dry at 70 ºC and dries much faster at 100 ºC (also produces a gel with better consistency), but at 100ºC it seems...
  30. G

    Physics of Light/Infrared for Solar Stills Research

    Hi, I am doing my dissertation for Mechanical Engineering on Solar Stills and my mentor has suggested it would be a good idea to research the physics of light/infrared absorption, transmission, water evaporation and condensation. I am wondering if anyone has good book recommendations for me to...
  31. Buzz Bloom

    I Question regarding Evaporation of galaxies

    I recently looked at https://www.physicsforums.com/threads/will-temperature-go-down.104791/ and then looked at the link http://math.ucr.edu/home/baez/end.html . My question is related to a quote from this link. (It may seem odd that first the galaxies form by gravitational attraction of matter...
  32. EEristavi

    I Is Energy Partially Spent on State Change Below 100°C?

    In the normal conditions (sea level) water evaporates at 100 C. In thermodynamics, we say: the amount of energy Q, can raise temperature of the liquid by the formula Q1=cm(t2-t1); when the liquid reaches the boiling point (100 C), we write Q2=Lm. Q2 is entirely spent on changing liquid state...
  33. J

    I Evaporation under vacuum; surface area

    I run a vacuum distillation unit that is used to distill ethylene glycol. The old glycol is subjected to 25Hg of vacuum at a temp of 275 degrees F. There are burner tubes submerged in the glycol to heat it up. The vessel has a diameter of 36 inches and is 124 inches long. We fill the vessel...
  34. A

    What are the dimensions/units of Evaporation?

    I am just starting with hydrology, does anybody know what the dimension is of evaporation? I see L/T in some of the slides, but I can't figure out what it stands for. L/Time, I assume. But what is the L? And in what dimension? Thanks heaps!
  35. V

    How calculate the Heat flux requiered to evaporate sub cool water

    Homework Statement I was trying to validate a calculation I didusing ANSYS fluent, it's about a flow of water that enters a tube, the tube is 16m long and is being heated with a Heat Flux of q'=1077328,47 [W/m^2], now after the simulation runs and I check the results I find out that the steam...
  36. H

    Heat of Evaporation: Melting Ice to Boil Nitrogen

    Homework Statement A 0.035 kg ice cube at its melting point is dropped into an insulated container of liquid nitrogen. How much nitrogen evaporates if it is at its boiling point of -196 C? Nitrogen has heat of vaporization of 200000 J/kg Ice's specific heat is 2100 J/kg*C Homework Equations...
  37. C

    Calculate the moisture content of air

    Homework Statement (Simplified) During tests at cliffside power station, the following data was recorded from the cooling tower. A cooling tower has a 9 cell draft design, each diameter is 10m. Data D_o = 10m V_exit = 14.4 m/s T_exit(15 celsius) = 288.15K Ambient conditions : T(15 celsius) =...
  38. D

    How to avoid boiling/bubbling effect under vacuum?

    I have a process problem where my product is mixed with water and needs to be separated under low temperature range 5-10 deg C. I hope evaporation under vacuum is the only solution but the boiling effect is creating splash and want to avoid it. Prefreezing or lyophilization is not an option...
  39. S

    I Why do quantum physicists claim that particles can tunnel out of a quantum well?

    Hi everyone,Every time I read an article about black hole evaporation through Hawking radiation, it seems to me that the writer didn't bother to connect all the dots so it will be clear for dummies like me.In many articles, I find 2 contradictory statements:1. Black hole emits a radiation (i.e...
  40. DaveC426913

    Dish soap and water evaporation

    I want to keep a small space (oh, say, about the size of a chest humidor - call it 2 cubic feet) humid to a level of about 70% to 80%. I don't feel like using the whole humidity technology that you have to fill all the time, so I've just stuck a gallon bucket of water in there. I was wondering...
  41. neil63

    Recycled acidic water evaporation / condensation

    I would like to recycle a source of used water at work. The water is contaminated with an acid solution and other chemicals used in a powdercoating process. My question is -- if I were to evaporate the water and then turn it back to condensate, would the water be pure? or would the acid and...
  42. Adrianus

    What heat capacity is needed to evaporate water in oil

    Homework Statement In an industrial fryer is f.e. 400 kW. Heating capacity installed. The fryer may contain as much as 1.450 ltr of oil. I can fry 2.000 kg of chicken nuggets per hour in that. These products loose 7% of moisture/water in this process. That water can only escape from oil in gas...
  43. Galbi

    Water evaporation by negative pressure and 0% of RH

    Greetings! I'm trying to evaporate water in some samples. I'm trying 3 methods. Baking samples with 100°C, normal air pressure, and normal RH. Put the samples in 0% RH, 23°C, and normal air pressure. Put the samples in container of -15 psi air pressure, 23°C, and normal RH. The total amounts...
  44. S

    Clothes Drying (Evaporation) Equation

    I am trying to find the most efficient way to dry clothes indoors with different evaporation factors 1. Heat/Temperature 2. Airflow 3. Humidity 4. Light (Electromagnetic energy) But I am not sure what equation to use. (mass loss rate)/(unit area) = (vapor pressure - ambient partial...
  45. Umar Awan

    Fractional distillation calculations

    Say I have got a super cooled cylinder of half hydrogen and half helium. This cylinder has a pressure of 100,000 Pascal's. At this pressure, hydrogen boils at 20 Kelvin and helium at 4.21 Kelvin. I hope to separate helium by cooling gas down to 4.21 Kelvin but I know that even at the...
  46. A

    Acetone and Petrol- Evaporation Rate

    < Mentor Note -- thread moved to HH from the technical physics forums, so no HH Template is shown > Need a bit of help here: Which has higher rate of evaporation :- Acetone or Petrol?
  47. C

    Understanding Evaporation at the Molecular Level

    I have been reading a bunch of different explanations of evaporation- and now I am confused. Hopefully someone can help clear this up in my head so that I can sleep tonight. I am interested in what is happening at the molecular level as well. Let's take a look at a body of water. In a body of...
  48. jmarkwalker

    Evaporating water using heat and reducing vapour pressure

    I want to reduce the amount of water present in the digestate coming out of my Anaerobic Digester. The traditional method would be to boil it until I've removed as much off as I want. However, this is expensive from an energy consumption point of view. There's a great video on Youtube showing a...
  49. T

    Water evaporation in semi-open system

    Hello guys! I'am having trouble getting my head around the physics of evaporation in quite specific situation. So i have a closed container with opening in the bottom (cross-section in picture below). Let's say that water has a constant temperature of 80°C and container has a temperature 90°C...
  50. Alfreds9

    Water evaporation, temperature, wind and heat capacity?

    Hi, I'd like to know how I'd put together, either elegantly or at least in physical terms, that surely water evaporation in a large pool of V volume and S surface is influenced by wind (increased by it as opposed to having side barriers), temperature (increased by direct sunlight as opposed to...
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