Questions tagged [evaporation]
The process of a liquid changing to a gaseous state
322
questions
1
vote
1answer
32 views
Finding the equilibrium vapor pressure of two solutions(of different concentrations) enclosed in a vessel
The saturated vapour pressure above
an aqueous solution of sugar is known to be
lower than that above pure water, where
it is equal to $p_{sat}$, by $\Delta p = 0.05p_{sat}c$.
where c is the molar ...
1
vote
1answer
32 views
Does the amount of water vapor air can “hold” depend on the temperature of the 'water' or the temperature of the 'air'?
The amount of water vapor that the air in a large region (say a suburb) can hold should be dependent on the average temperature of the liquid water within that region. Not the air temperature of that ...
3
votes
2answers
187 views
Why don't clouds gradually evaporate and never come down as rain?
Clouds are present in the troposphere . So the radiation from the Sun first needs to pass this layer of the atmosphere to come down which means that the clouds above are constantly being radiated from ...
0
votes
0answers
13 views
What determines if an element can melt in vacuum conditions (UHV and below)?
As part of my work, I grow thin films via thermal evaporation. However, I am still very new to it. I have noticed at under UHV conditions ($\sim~ 10^{-8}\, \rm{mbar}$) that some elements like Sulfer, ...
2
votes
1answer
29 views
How exactly does air accommodate water vapor?
I would like to have clarity on how air accommodates water. When water vaporises, does the water molecules just squeeze into the space between already existing molecules of nitrogen and oxygen? From ...
4
votes
1answer
162 views
What does 'saturated' air actually mean?
I'm having some problem in getting an insight on what 'saturation with vapor' actually means. The question is asked in the context of atmospheric air becoming saturated with water vapor and beginning ...
1
vote
1answer
20 views
My fish pond I was wondering if the water will evaporate quicker with the water fall running and blowing air into the pond with an air stone
Hi I keep thinking that my pond has a leak I have just emptied and cleaned the pond and made sure there was no leaks as I could see. When running the pond water is being pumped through sealed ...
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 ...
2
votes
2answers
55 views
Why atmospheric pressure does not influence vapor pressure of water but only temperature does?
We know vapour pressure is dependent on temperature. But why it is not dependent on atmospheric pressure or pressure applied on the gas surrounding vapour-water equilibrium?
Pressure does influence ...
0
votes
1answer
60 views
Relighting a candle from its smoke, and being burned?
Having been extinguished, a candle can be relit from the resulting trail of smoke, even from meters away.
However despite this apparently high level of heat, paper, bystanders, etc… are never ...
0
votes
1answer
22 views
Liquid nitrous oxide released from gas cylinder
Say you have liquid nitrous oxide in a standard gas cylinder (about 55 bar) at room temperature. Normally the cylinder sits upright and gas is released via valve.
Now let's assume you released liquid ...
0
votes
1answer
74 views
Will water in vacuum stop boiling?
Will water in vacuum chamber (low pressure chamber(around 0.02 atm)) stop boiling when the remaining air gets saturated? Or if the walls of the chamber are cold enough the water vapor condensates and ...
0
votes
1answer
43 views
Why does adding salt to the water in a humidifier increase the amount of steam it makes?
Rather than "it decreases the latent heat of vaporization", can you explain why?
0
votes
0answers
10 views
How (or where) to look up vapor pressure of a material at ultra-high vacuum pressure?
Is there a way to look up the vapor pressure of a given material (usually binary compounds or simply elements) at ultra-high vacuum (usually near $10^{-9}$ Torr). For example, if I want to know the ...
3
votes
1answer
29 views
Why use partial pressure, not chemical potential, to describe vapor phenomena?
I have been looking up the basics on evaporation, boiling, humidity, and the dew point, in order to try to understand these everyday concepts with precise physics. I have noticed that "vapor ...
1
vote
1answer
22 views
Vapor pressure in a closed box
If there is a closed box at room temperature with water inside after a certain point there will be an equilibrium condition where some water is liquid and some is vapor. So there will be a certain ...
0
votes
0answers
26 views
Given a molecule, can you calculate its heat of vaporization?
Let's take water for example. How can we calculate the heat (enthalpy) of vaporization from first principles?
The enthalpy of vaporization $ \Delta H_v$ is
$$ \Delta H_v = \Delta U_v + p\Delta V$$
...
0
votes
0answers
15 views
Steam in boiler from evaporation not boiling
Vapor pressure inside a closed container keeps building up and the boiling point of water become higher. What if the steam is required to reach say , 30psi, and the pressure in the boiler is that ...
1
vote
1answer
16 views
Moisture evaporation from paper
Is there a way to calculate moisture loss from a piece of paper in contact with a heat source.
If you have roll of paper 1 meter wide of infinite length the paper weight is 130g paper per m2 with 8% ...
2
votes
1answer
72 views
Why does mist on glasses disappear when you go back outside in freezing weather?
This evening after a walk in the cold weather, about -5 degree Celsius, my glasses were misting up when I got back into the warm house, about +20 degree Celsius.
However, shortly after I went outside ...
1
vote
1answer
80 views
Rate of evaporation of water vs temperature. Where can I find data?
The story
If there is an easily understandable problem that fascinates me compare to apparently how hard it is to model and solve accurately, and how little it has been studied, the time to cool down ...
1
vote
5answers
182 views
Will liquid nitrogen evaporate if left in an unopened container? [closed]
SOS! I left work today and got a horrible feeling that I forgot to put the lid back on a large container of liquid nitrogen which contains many racks of frozen cells in it. If this did happen, how ...
0
votes
2answers
28 views
How can the moisture of a peace of wood can be reduced to below 10% if the surrounding air humidity is over 50%
This question just came to my mind and I hope this is the right Stack Exchange to ask it.
How can the moisture of a peace of wood can be reduced to below 10% by storing it outside surrounded by air ...
0
votes
1answer
29 views
Calculating indoor humidity — do I need to account for pressure?
I'm developing a calculation that converts an outdoor temperature, pressure and relative humidity into an indoor relative humidity (for a given indoor temperature).
E.g. if it's 39°F outdoors at 87% ...
2
votes
2answers
42 views
Saturation vapour pressure and the effect of ambient gas other than water vapour
Water (or any liquid/solid for that matter) has a saturation vapour pressure (SVP) that follows the curve given by Clausius-Clapeyron. At room temperature the SVP of water is about $0.023$ bar, so in ...
0
votes
1answer
26 views
Doubt about why to consider partial pressures in calculating vapour pressure [closed]
I am confused as to why the partial pressure is considered while calculating whether a liquid will evaporate in atmosphere or not.
But doesn't the reasoning given of molecules colliding also consider ...
0
votes
1answer
18 views
Will an evaporation water cooler work better if the water in the reservoir is cool?
I d like to find out if a evaporation water cooler works better or worse if you cool the water in the reservoir.
Let's suppose that the water in the reservoir is at some 10°C, will the cooler deliver ...
1
vote
1answer
35 views
How is coke missing from a sealed can?
This question has actually been asked but my scenario involves different circumstances. I have a can of Coke from 2016, that I was keeping because it was a promotional one. Once, after a about a year ...
3
votes
1answer
78 views
Why does wind blowing across a bird bath cause the water to freeze even though the ambient air temp is 39 - 40 degrees F?
Frequently, after cold frontal passage, a strong NW wind blows across the open marsh and through our back yard. With ambient temps still well above freezing, the surface of the water in our concrete ...
0
votes
1answer
58 views
Evaporation and boiling: are they the same thing when only one substance is involved?
Another way to put it: Is evaporation possible when only one substance is involved?
Consider a closed vessel with water in gas and liquid state, in equilibrium. At the interface, the same amount of ...
0
votes
0answers
19 views
Calculating the evaporation rate of water
I'm tying to calculate how much water would evaporate when air of particular temperature and humidity and flow rate is forced on a surface containing water at a particular temperature and calculate ...
0
votes
0answers
34 views
How much heat (solar-energy) is required to evaporate water?
I was wondering how to calculate the mass of water that evaporates and the amount of energy it demands if I were to expose the water to the heat irradiate from the sun given by Q. Q=1360KJ/m^2 is the ...
0
votes
2answers
51 views
Why liquids evaporate completely when heated at their boiling points?
I'm confused about why the boiling of liquids happen. The boiling point of a liquid is defined as the temperature in which it's vapor pressure is equal to the pressure of the gas above the liquid( for ...
0
votes
0answers
32 views
Extracting other mineral from salt in evaporated seawater
I recently stumbled upon this news,
seawater contains 47 minerals and metals. Starting with the most abundant and proceeding to the least abundant, these are chloride, with a concentration of 18 980 ...
0
votes
0answers
13 views
How does a capillary pressure drop affect evaporation?
Normally phase changes are said to occur at a constant pressure, but in situations with a capillary pressure drop (like a heat pipe as shown in the picture below) there is a difference in pressure ...
0
votes
1answer
10 views
Liquid water “evaporation” or diffusion mass transfer?
Is the disappearance of liquid rain water at < 100 deg C (< 212 deg F) @ atmospheric pressure after it stops raining and the sun comes out an example of evaporation and/or diffusion mass ...
0
votes
1answer
90 views
Calculation of humidity ratio by vapor partial pressure
I've been looking around for a way to calculate the humidity ratio by the partial vapor pressure and the atmospheric pressure of the environment.
I found a procedure for such calculation on ...
1
vote
3answers
67 views
What does the definition of boiling actually mean?
Boiling point is defined by wikipedia as:
The boiling point of a substance is the temperature at which the vapor pressure of a liquid equals the pressure surrounding the liquid and the liquid changes ...
1
vote
2answers
238 views
Why water molecules at the surface of water have higher kinetic energy than the bottom ones?
It's written multiple times in my textbook that
Some molecules at the surface of the liquid have kinetic energy more than those in the bottom, so they can escape from the surface.
But what causes ...
2
votes
3answers
125 views
What is the real reason for evaporative cooling?
I have read two different explanations for evaporative cooling. The first is from my physics textbook:
"As heat is transferred to a liquid, the average kinetic energy of its molecules increases. ...
2
votes
1answer
57 views
Is it possible to cool down air with warm water?
Is there some condition in wich the water evaporation can cool down the air even if the water is hotter than the air?
0
votes
2answers
47 views
Vapour pressure at the steady state
I came across a question today about vapour pressure, it was as follows :
$2$ flasks $X$ and $Y$, each containing liquid water, joined by a tube connecting their mouths (no vapour could escape) having ...
0
votes
1answer
77 views
How long and how much water will boil at room temperature in a vacuum chamber
Let's say, I have a vacuum chamber of diameter D and height h. I have filled 1/10th of the chamber with water. Now I have two questions:
1.How long and how much water will boil or evaporate if the ...
2
votes
4answers
76 views
How to quantify evaporative cooling?
Water has a latent heat of vaporization equal to $2,260\ \mathrm{kJ/kg}$. While ethyl alcohol has a latent heat of vaporization equal to $846\ \mathrm{kJ/kg}$.
Even though ethanol's latent heat is ...
0
votes
1answer
37 views
Why is the saturation decreasing with temperature?
As you can see below, I'd like to know why the saturation is decreasing with the temperature while the absolute amount of water remains constantly.
The image is taken from a description of a ...
0
votes
2answers
147 views
After sweating ,why do our body cool down faster under a fan?
The sweat on our body evaporate taking energy from our body in the form of heat.the temperature of our body decreases and we feel cool. Thus sweating cools down our body.
Now why does our body cool ...
1
vote
4answers
1k views
How much heat is required to evaporate water
I was wondering how to calculate the mass of water that evaporates if I were to expose the water to some amount of heat given by Q. $Q=ml$ ($l=2.26\times10^3kJkg^-1$) is the standard way to calculate ...
2
votes
2answers
113 views
Why has warm air a higher water saturation than cold air?
I've wondered about that for a while but all I read is commonly just "Warm/hot air has a higher energy so when it hits the surface of a liquid, it has a higher probability to transfer energy, ...
1
vote
2answers
683 views
How much energy is required to boil and maintain boiling water temperature for a set time period? [closed]
I am trying to calculate the amount of energy required to bring 1 litre of water up to boil (from 20 degrees C to 100 degrees C) and to maintain the water temperature at 100 degrees C for a period of ...
2
votes
2answers
84 views
Why don't ionic liquids evaporate in a vacuum?
Proposals exist for a rotating liquid mercury telescope on the Moon, using ionic mercury. Pure mercury has a triple point at 312 K and 0.2 mPa, but the Moon's surface pressure is far lower than this.
...
