Questions tagged [evaporation]

The process of a liquid changing to a gaseous state

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150
votes
9answers
24k views

Why are the wet patches on these floor tiles circular?

My friend's 3-year-old daughter asked "Why are there circles there?" It had either rained the night before or frost had thawed. What explains the circles? Follow-up question: Ideally, are these ...
71
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4answers
310k views

How does water evaporate if it doesn't boil?

When the sun is out after a rain, I can see what appears to be steam rising off a wooden bridge nearby. I'm pretty sure this is water turning into a gas. However, I thought water had to reach 100 ...
51
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6answers
7k views

Because things smell, is everything evaporating?

Everything, in theory, can have a smell, but that is not the whole point of this question. My main query is, since things do smell, does that mean that everything is slowly evaporating (or, ...
44
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4answers
7k views

Why is water evaporated from the ocean not salty?

I am wondering about this. When salty water in the ocean evaporates we are getting the clean distilled water. Why is that? I was trying to think on this and maybe the comparative size/mass of water ...
43
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11answers
7k views

Why does moving air feel colder? [duplicate]

If temperature is just the average kinetic energy of particles, why would moving air feel colder rather than warmer?
35
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3answers
6k views

Why does a blackboard dry very quickly?

When you have made some stupid mistakes on a blackboard, you quickly want to erase it with a wet sponge before anyone sees them. So you clean the blackboard and within a minute the blackboard is clean ...
34
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9answers
128k views

How can water evaporate at room temperature? [duplicate]

Boiling point of water is 100 degree Celsius. The temperature at which water in liquid form is converted into gaseous form. Then how it possible for water to evaporate at room temperature?
32
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7answers
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How is a 25-year-old can of soda now empty without having been opened or poked? [closed]

I just discovered in my parents' basement a Sprite can from 1995* and also a Coca-Cola can probably from the same year. Both cans are unopened and have no visible damage or holes. The Coca-Cola can ...
31
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5answers
11k views

How are water vapors not visible?

This site says that water vapor isn't visible. However, take a look at this picture: Isn't that water vapor?
31
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4answers
6k views

Lengthwise or widthwise. Which towel will dry faster?

So I was putting towels on drying rack and I had extra space. Should I hang towels lengthwise to speed up drying? If we have a standard, rectangular towel. Say like this: Which will dry sooner? ...
28
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1answer
3k views

Why does a water drop on a hot plate at 150°C evaporate faster than on a plate at 200°C?

I recently read that: A drop of water landing on a hot plate at 150°C (300°F) evaporates in a few seconds. A drop of water landing on a hot plate at 200°C (400°F) survives a whole minute. How ...
27
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10answers
8k views

Can a fan cause a liquid to cool below room temperature?

I enjoy the occasional hot drink, but place it below a small fan in order to cool it to a drinkable temperature. Unfortunately, as expected, I commonly forget about my drink, and it ends up very cold. ...
20
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7answers
84k views

Does wrapping a wet paper towel around a glass bottle really speed up the cooling process?

There are claims like this one that you can improve the cooling speed of beverages when you put them wrapped in a wet paper towel inside the refrigerator/freezer. I've just tried it by myself and it ...
18
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4answers
11k views

Why does water feel cooler than air?

My first assumption was based on "evaporation causes cooling" but I realized that it is not the case as it is cooler even if I am submerged under it. Are all liquids generally cooler than air ? Just ...
18
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2answers
952 views

Stripeless cleaning of windows

Cross post: https://chemistry.stackexchange.com/q/4377/22 Last week I was discussing with a friend how we thought the stripeless cleaning of windows is achieved when using a cleaner like Windex Glass ...
16
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1answer
1k views

Why doesn't breath condense around poop of flies on the window's glass?

One day it was raining outside and I was breathing on the glass of my window. I noticed that around the spots of fly poop there is a circle where vapor does not condense. With time the circle becomes ...
15
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1answer
5k views

Why do I feel cold air in the shower?

Our house has a glass sliding door to the shower. The shower has the dimensions of about 2 feet wide, 5 feet long, and 6 feet high. Above the door (and shower head) there is about 1 foot of open space ...
14
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5answers
4k views

What is the real cause of the boiling (forming of bubbles) of water?

I've got a question about the boiling of water. I'm a first year physics student and from the Netherlands. I've searched alot about the boiling of water and this confused me. Everyone said something ...
14
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4answers
5k views

Why is there a hiss sound when water falls on a hot surface?

Why is there a hiss sound when water falls on a hot surface? I have searched a lot, asked my teachers but none of them seem to give me the logical answer to it.
13
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5answers
88k views

Does placing a lid on a pot affect the rate of boiling?

On the subject of cooking, someone once told me "If you have too much water in your pot after cooking a dish, just turn up the heat and let it boil without a lid for a few minutes". Now I've thought ...
11
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3answers
55k views

How does an earthen pot keep water cool?

I understand that evaporative cooling takes place thanks to small pores contained in the pot and that allow some water to go through and evaporate. However I couldn't understand clearly whether water ...
10
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3answers
11k views

Can ice melt in a perfectly closed container?

If I have an ice cube of, let's say, for example (15$\times$15$\times$15 cm), it was put inside a container of internal dimensions (15$\times$15$\times$15 cm), and the container is strong so ...
10
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2answers
6k views

Why do clothes dry at room temperature? [duplicate]

When I leave wet clothes in the open air, they will get dry over time by themselves even at room temperature. I know that somehow the water becomes vaporized; it's not "disappearing". For that, it ...
10
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2answers
3k views

Does Uchimizu (watering streets in summer) help reduce temperature in an area?

It appears that in Japan, there is an old custom called Uchimizu. The name is a combination of words "road" and "water". The essence of it is moisturizing small parts of populated areas like sidewalks,...
10
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2answers
19k views

Why do liquids boil when their vapor pressure equals the ambient pressure?

Given that the boiling point of a liquid is the temperature at which the vapor pressure is equal to the ambient (surrounding) pressure, what significance does a liquid's vapor pressure have in the ...
9
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1answer
1k views

Why can water evaporate? [duplicate]

Why can water evaporate below 100°C? Or, more in general, what is the mechanism behind the evaporation process in liquids?
9
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2answers
2k views

Water evaporation problem. Exercise from Feynman's lectures

I read lectures of Richard Feynman and try to solve problems and I have some trouble with a problem on water evaporation. A glass full of water is left standing on an average outdoor window in ...
9
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0answers
347 views

A theoretical model for evaporation occurring when wind is blowing over the surface of water

I've recently done an experiment in which I was studying the variation of the cooling rate of hot water in a draft (wind). The air was blown directly over the surface of the water (kept in a ...
8
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5answers
3k views

What keeps water molecules in air from falling down?

I was thinking about evaporative cooling, how the particles in water with the most velocity fly out of the water, leaving it colder. But then I thought, how come these water molecules stay in the air ...
8
votes
1answer
64 views

Time for which a drop stays in the leidenfrost point

Is there any way to find out the time required for a drop of given dimensions to vaporize after attaining Leidenfrost point?
7
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4answers
9k views

Sauna thermodynamics

Why does it get hotter (feel hotter) in a sauna when one pours water over the hot stones? Wikipedia says that the water condenses onto the skin, but the actual air humidity is so low that I doubt ...
7
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0answers
920 views

Can a substance have zero vapour pressure above absolute zero?

According to this Reddit thread, the answer is no, vapor pressure can't be zero when temperature is above absolute zero. I suspect the answer might actually be yes according to a precise definition I ...
6
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3answers
588 views

atmospheric phenomenon? What causes condensation trails to converge?

This air plane just caught my eye. Two contrails apparently are flowing backward, slightly off-centered and then ultimately converge, giving the overall shape of a very narrow rhomboid parallelogram, ...
6
votes
2answers
625 views

Does adding cold water to evaporative air coolers actually produce colder air?

Or should it be the other way around, because hotter water evaporates easier than cold water? I know this sounds stupid, so just hear me out. I use an evaporative cooler and add normal room ...
6
votes
2answers
328 views

What causes the milk to suddenly rise up & spill out if not stopped?

Well, when milk is heated in a container its temperature starts rising & water vapor bubbles rise up through it. This initially causes a little and slowly rise in level of milk. But after certain ...
6
votes
3answers
9k views

Does evaporation decrease entropy?

I have a container of water in thermal equilibrium (there are no temperature fluctuations inside the container). Some molecules will evaporate out of the container of water thus decreasing its ...
6
votes
3answers
5k views

Acer saccharum (Sugar Maple) Sap & Freezing

This may or may not be the appropriate scientific discipline to ask this question of, but I'll give it a shot. I'll happily invite chemists to chime in as well. It's time to tap sugar maples in the ...
6
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2answers
1k views

If water evaporates at below 100 degrees then why not stone?

I have asked this question recently: Why does evaporation take place? and I got a satisfactory answer, that temperature is macroscopic and is the average temperature of the object. That said, why ...
6
votes
3answers
14k views

How to calculate the evaporative cooling rate needed to protect a house from forest fire

Recently in our area there has been a large forest fire and I've been looking into home defense from such things. I am not a physicist - but can do some basic math. I was wondering how I could ...
6
votes
1answer
165 views

Can you prove the interesting relation in equilibrium thermodynamics?

Problem and background I noted the following interesting relation in a paper discussing the liquid-vapor phase change, in which it was given directly without any derivation and reference: $$d\ln p^\...
5
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1answer
628 views

Is evaporation a kind of phase transition?

When liquid is heat up to a critical temperature $T_{c}$, it starts boiling and converting to gas. In statistical mechanics, we learn that it is a phase transition. We studied all the properties near ...
5
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2answers
5k views

Why does evaporation take place? [duplicate]

I was looking at at puddle when I thought that this puddle will evaporate tomorrow but then it occurred to me that the boiling temperature of water (aka to turn into gas) is $100$ degrees under 1 ...
5
votes
1answer
4k views

Can water evaporate when frozen?

If an ice cube is stored in a freezer could it evaporate given enough time? Is there a temperature below which water cannot evaporate (even just a little)?
5
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2answers
2k views

Does the temperature of water determine how much heat will be removed from air used to evaporate it?

This is a question about evaporative cooling as used in residential evaporative cooling appliances. This type of cooling uses the heat in the ambient outside air to evaporate water and remove the heat ...
5
votes
1answer
121 views

Simple question about molecules leaving a liquid at a temperature below the boiling point

My textbook asks the question why a liquid cools down when partial evaporation occurs just below the surface at a temperature below the boiling point. The answer is of course that only those ...
5
votes
4answers
3k views

Why does saliva on the finger give correct direction of wind?

When we lick a finger and put it up in the air, the side that is cooled is the one facing the direction from which the wind is blowing. But consider this, if we take a cross section of the finger, ie ...
5
votes
1answer
285 views

Why does salt ions is not exist at vapor when the water is boiled and evaporated?

I would like to understand when the water is boiled only pure vapor is produced and ions do not exist with vapor. Why? Can't the ions stick to water vapor? And Are Na+ and Cl- have boiling points? ...
5
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2answers
5k views

Which way the water evaporate faster?

-Hello everyone, Yesterday I was preparing some tomato sauce and, in order to remove some water from the sauce, I put it in a pot on the burner and waited until it started to evaporate. When I sow a ...
4
votes
3answers
1k views

Dumping hot liquid water in sink [closed]

When I make pasta or potatoes, I dispose of the hot water (around 80-100°C) in a metal sink. Am I justified to first pour regular hot tap water on the sink to reduce the amount of steam generated, or ...
4
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2answers
2k views

Does a glass of water at room temperature emit (infrared?) radiation

While reading the introduction to Feynman's lectures, it's mentioned how a glass of water cools down through evaporation, when some molecules get a bit extra energy and break free. If it's not a ...

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