What is Evaporation: Definition and 212 Discussions

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. L

    Air pressure dependent water evaporation

    Imagine a water basin, surrounded by air. How does evaporation speed of water change if the air pressure of surrounding air is 1.000Pa, 10.000Pa, 100.000Pa, 1.000.000Pa, 10.000.000Pa. What is an order of magnite of the evaporation speed change. Where can I read more about that? Regards.
  2. K

    Heat loss due to Evaporation in a closed environment

    I am working on an incubator/shaker for laboratory use. I am trying to work out a temperature failure and repair it, but that is besides the point here. I was looking through the user manual to try to get some clues about the failure and I came across this: "Depending on various conditions...
  3. Saladsamurai

    What drives evaporation and diffusion?

    Hello all, I am reading through Stephen Turns' An Introduction to Combustion. The third chapter is essentially a crash course on mass transport. In it, he talks about "the Stefan Problem" as it pertains to diffusion and Fick's Laws. I am understanding most of it, but I am realizing that I...
  4. K

    Evaporation and heat transfer coefficient

    Hai I have a problem with heat transfer coefficient estimation. Please help Here is the problem: Two experimental scenarios are compared. Case 1: I have a well defined rectangular area in a silicon wafer. Water is completely spread over it. The mass of water is known. Air is blown over...
  5. K

    Evaporation in a silicon film

    Hai.. I have a problem with my heat transfer coefficient estimation during my evaporation measurements. Here is the problem: Two scenarios are compared. Case 1: I have a well defined rectangular area in a silicon wafer. Water is completely spread over it. The mass of water is known. Air is...
  6. A

    Question about proton decay and black hole evaporation

    Just to start, let me reassure you that I am not an LHC alarmist. I understand and agree with the cosmic ray explanation, i.e. earth, the sun, jupiter, and everything else would be a BH if they didn't evaporate. Anyway, I was reading around a little on wikipedia and came to this page...
  7. T

    Evaporation of water and escaping particles

    Homework Statement The heat of vaporization is approx the product of the average energy of the escaping molecules (E) and the # molecules per gram, N I want to know, is this is as simple as it sounds Homework Equations so H=E*N? Q=mH The Attempt at a Solution I'm supposed to...
  8. C

    Understanding Black Hole Evaporation with Hawking Radiation

    With the theory of Hawking Radiation, people generally say to imagine that the black hole has a temperature, so it must radiate heat. But, this really is not how it is said to work. The means by which the black hole evaporates is not that particles are actually coming out of it, or that it is...
  9. R

    Black Hole Evaporation: Exploring Mass Loss

    black holes evaporate, i know that it sounds like it defies all rational elucidation but i think that black holes evaporate. see black holes emmit black body radiation they also emmit hawking radiation and hawking radiation as far as I am informed shrinks black holes it causes them to lose mass...
  10. N

    Calculating heat loss by evaporation (water)

    Feet first... How do I calculate heat loss by evaporation from the surface of a swimming pool, at a range of temperatures and given a range of conditions? Any help gratefully received! Nick
  11. A

    How does evaporation work at the molecular level?

    The moderators here decided my explanation of evaporation was wrong, but they failed to explain why. They simply said I was an idiot and locked my thread. So... I ask the gods of physics here that moderate this board: How does evaporation work at the molecular level? Say you have a body...
  12. J

    Evaporation of liquid-metal alloys

    Hi everyone This is my first post, please be kind! I am part of a research group at Oxford University, UK. We are investigating ways to make multicrystalline Si solar cells more efficient. One of the characterisation techniques we use is electron beam induced conductivity (EBIC)...
  13. T

    Exploring Water Evaporation Rates in a Vacuum: Equations and Insights

    I am new to this site and would like to find some equations for water evaporation? I would like to understand more fully how placing water in a vacuum effects the rates at which it will evaporate? Any help would be greatly appreciated
  14. T

    Water Evaporation Rates: Equations & Vacuum Effects

    I am new to this site and would like to find some equations for water evaporation? I would like to understand more fully how placing water in a vacuum effects the rates at which it will evaporate? Any help would be greatly appreciated
  15. J

    How is boiling different from evaporation?

    Thinking about this, I would say that there really is no difference. When water evaporates, surface molecules gain enough kinetic energy to change state (if it even makes sense to talk about state in the thermodynamic sense when dealing with discrete molecules). During boiling, you are giving...
  16. D

    Formula for rate of evaporation of water

    My sister and I are working on a project in which we need to know the rate of evaporation of water... I know that there are a lot of variables to this equation, but we aren't sure exactly where we will end up completing it, so does anyone know a formula to calculate the evaporation rate of...
  17. R

    Was Energy Balance Overlooked When Examining Evaporation from Solids?

    I am curious. Maybe I don't understand something, but many articles I come across perform an energy balance on a solid and on a liquid. **I assume evaporation acts on the remaining liquid and not directly on the substrate. Correct?** They always include heat loss due to evaporation as...
  18. E

    Evaporation of gold circuit

    Dear all, I have a quite easy plan: W want to evaporate a gold circuit on a Brass plate. Between this copper and gold I need to make an isolating layer to prevent short-currents. i thought to make this layer of Silicon-oxide. Is the possible to evaporate and what source can I use this for...
  19. J

    Evaporation from a swimming pool

    Homework Statement A) How much energy is required to evaporate all the water in a swimming pool of area 119 m2 and depth 2.4 m on a typical summer day? (Please note that the temperature of the water in the lake stays the same.) (For latent heat of vaporization use 2200 kJ/kg.) B) The...
  20. ~christina~

    Evaporation of organic solvent and leftover residue

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  21. A

    Understanding Water Evaporation Process

    The question: If you fill a shallow dish with water at room temperature the water will, under normal conditions, evaporate completely. It is easy to believe that some of the more energetic molecules can escape from the water surface but how can all of them eventually escape? Many of them do...
  22. R

    Water evaporation using solar reflector dishes

    Hi, we are running experiments with solar power; any inputs on below problem are highly appreciated. TNX Robby Project: We are experimenting how to maximize evaporation, using Solar Power. We have set up parabolic dishes with a fixed focus (Scheffler Reflectors). Each reflector can...
  23. marcus

    Where are the particles created in BH evaporation?

    This thread is about a Bill Unruh article ("Where are the particles created...?") and an article on the same theme by Unruh and Ralf Schützhold ( http://arxiv.org/abs/0804.1686 "Origin of particles in BH evaporation") and Schützhold's participation in the LQG-BH workshop taking place this month...
  24. R

    Evaporation and condensation problem

    Hi, I'm now studying evaporation and condensation and I have a question. Why even when water boils, its temperature doesn't exceed 100 C? Where did the energy gotten from environment go? What was it used for? Examining structure of water and vapour molecules are given as a hint, but I see no...
  25. N

    Water Evaporation Rate at 80°C, 1 atm

    For stirred, maintaining temperature at 80 and at atm pressure thx ..
  26. U

    The rate of evaporation at high temperatures

    To whom it may concern I'm a University of Portsmouth student in the UK and have a conundrum for one of my projects. I'm trying to evaporate a reservoir of water at the bottom of a venting system to cool down the airflow in a gap between two membranes for a period of time. The reservoir is...
  27. C

    Rate of evaporation of a spherical drop

    Homework Statement The rate of evaporation of a spherical drop of liquid is proportional to its surface area. Derive R(t) assuming constant density, where R(t) is the radius of the drop as a function of time. Homework Equations I know that the surface area of the sphere is A = 4 \pi...
  28. S

    Salt crystal forms after 3 days of evaporation

    If a salt crystal forms after 3 days of evaporation, and the crystal mass is 30 mg, how many Na+ and Cl- ions was added to the crystal each second (average). How do I solve this?
  29. Orion1

    What is the Solar Evaporation Time?

    An interesting equation derived from Classical General Relativity: Solar evaporation time: \boxed{t_{ev} = \frac{ m_{\odot} c^2}{P_{\odot}}} m_{\odot} = 1.98892 \cdot 10^{30} \; \text{kg} - Solar mass P_{\odot} = 3.846 \cdot 10^{26} \; \text{W} - Solar Luminosity \boxed{t_{ev} = 1.473...
  30. R

    Surface area vs rate of evaporation

    Two vessels of the same volume, in the same location and open to the atmosphere. One is tall and of a small diameter, the other is short and is of a larger diameter. Each vessel supplied with an identical heat source. Each vessel filled with an equal volume of an identical liquid. The goal...
  31. R

    What factors determine the rate of evaporation?

    And if I'm heating a liquid that contains things that evaporate at different temperatures, will I have an increasing amount of trouble separating these things as I increase the amount of heat applied?
  32. T

    Evaporation of Water: Error in Formula?

    I am trying to calculate the rate (g/m2) of water evaporation given Temperature, Humidity, Air Speed, elevation. The best source of an equation for this I have found is from engineeringtoolbox.com, but I have found a possible error in their calculation. (I am in a far off land with no access...
  33. O

    How Can I Calculate the Evaporation Rate of Water in My Decorative Pond?

    Not sure where this posts needs to go, as I am not familiar with engineering, so if it needs moved, please do so. I build decorative ponds, and one of the conversations I end up with is the evaporation rate of the water in a pond setting. I do know there are formulas out there on the rate of...
  34. Z

    Black Hole Evaporation: Charged Particle Energy Effects

    in classical electromagnetic a charge can make energy. Now consider Howking radiation effect: if an anti-particle fall into the BH the volume of BH will reduce. But if that particle be a charged particle, this charge can make positive energy and increase the volume. Is that right?
  35. D

    Exploring Black Hole Evaporation and Its Explosive Effects

    If it is indeed true that black holes (eventually) evaporate, then once they lose enough mass do they then return to become a normal body of matter? I would assume that once this happens there would be an enormous explosion due to constraints of relativity disappearing.
  36. belliott4488

    How does black hole evaporation end?

    Someone asked me what happens when micro-black holes evaporate, and I have no idea, not really knowing anything about the theory of black holes, other than what you learn in a first course in GR. What he was asking was whether the black hole just keeps emitting energy (in the form of Hawking...
  37. M

    Solving Methanol Evaporation Problem

    Hey guys, I was wondering if anyone could help me out with this problem? If you place 10.0L of methanol (CH4O) in a sealed room that is 3 m long, 1.75 m wide, and 2.5 m high, will all the methanol evaporate? If some liquid remains, how much will there be? The vapor pressure of methanol is...
  38. S

    Understanding Entropy: Diffusion, Evaporation, Mixing, Melting, Separation

    entropy increases? entropy decreases ? no change in entropy? diffusion, evaporating, mixing, melting, separation i think diffusion - increase evaporation - increase mixing - increase melting - increase but what about separation :S? and if anyone thinks any others are...
  39. H

    Evaporation of the tube-side coefficient in a heat exchanger

    I've got a problem. I'm trying to design a reactor with internal cooling provided by water flowing through tubes directly within the reactor. Basically, it's like a shell and tube heat exchanger with an internal heat source. The problem is that the cooling water is to be evaporated within...
  40. B

    Evaporation of Water on a Jogger

    The latent heat of vaporization of H2O at body temperature (37.0°C) is 2.38E+6 J/kg. To cool the body of a 71.9 kg jogger [average specific heat capacity = 3550 J/(kg*°C)] by 1.10°C, how many kilograms of water in the form of sweat have to be evaporated? Q=cmt Q=mL...
  41. A

    Hawking Radiation and Black Hole Evaporation

    I've been trying to discover a qualitative description of Hawking Radiation and Black Hole evaporation and haven't been able to find one yet. I figured this board might offer some insight. Can someone explain to me how a 'virtual' pair differs from a 'real' pair? It seems to me that no...
  42. A

    Does Black Hole Evaporation Result in Visible Emission and Directional Output?

    According to the Black Hole evaporation theory, Hawking Radiation is emitted from the black hole. My first question is: Does it emit in one single direction or at polar opposites, and my second is: What happens when enough matter is emmited, does the black hole suddenly become visible again...
  43. P

    How Much Water Do You Lose Through Perspiration While Running?

    When you jog, most of the food energy you burn above your basal metabolic rate (BMR) ends up as internal energy that would raise your body temperature if it were not eliminated. The evaporation of perspiration is the primary mechanism for eliminating this energy. Determine the amount of water...
  44. G

    Question: Evaporation - beyond boiling point

    Hi, I've been wonderring what happens to a substance once boiling point is reached, in particular the rate of evaporation. Am I right in thinking that further energy will cause the rate of evaporation to increase, while temperature of substance remains constant? Is there a point where if...
  45. Integral

    Calculating Water evaporation rate

    Could someone link me up with some information, either text or web based, concerning evaporation rate of water, in a slightly reduced pressure environment. I need to design a settling tank for a vacuum system to separate a fine oxide powder from water. We produce the slurry at a rate of about...
  46. I

    Is Fick's Law related to the mass transfer coefficient in water evaporation?

    I guess this would go under chemistry. At least I leared what thermodynamics I know from my chem class. Here's the situation: My dad wants to know if the decreacing water level in the jacuzzi is due to a leak or evaporation. The pool guy told us to fill up a bucket with water and compare...
  47. daniel_i_l

    Why Does Evaporation Cool You Down If It Uses the Sun's Energy?

    I know that the conventional explanation for this is that the water needs energy to evaporate so it conviniantly takes the heat energy from your body in order to do this. But first of all, why does the water need to evaporate in the first place? Because of the sun? Then it should be getting...
  48. A

    Kinetic explanation of evaporation of boiling/Melting.

    Hi guys I am slightly confuse about a statement in the kinetic explanation for evaporation as well as melting. Firstly for the evaporation: "Thus the latent heat supplied in causing evaporation represents the potential energy gain of the escaping molecules plus the work needed to expand...
  49. S

    Rate of evaporation physics help

    I am in my first year of the IB Diploma and I have chosen Higher Physics and want to do my extended essay in Physics. Is fluid dynamics (or fluid mechanics i.e. how things fall in water and why) better or is analyzing the effect of colors on the rate of evaporation better? This essay has to be...
  50. D

    Understanding Evaporation and Cooling: Physics Problem Explained

    Hey. If i jump out of a swimming pool, into a breeze, i feel cold. Is this because the breeze is moving the more moist air away from my body, allowing more evaporation to occur, cooling the water, and since two substances of different temperatures naturally want to equalize in temperature...
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