Hot answers tagged evaporation
8
It actually gets a bit complicated, since several effects are involved:
Evaporating water does require heat, which comes primarily from the hot stones. So throwing water on the stones does cool them down.
(This is where the claim one occasionally hears, that "throwing water on the stones makes the sauna colder", comes from. Technically it's true, if one ...
4
Evaporative cooling works by removing the high-velocity tail of the kinetic energy distribution. That is, only the fastest molecules escape the liquid, leaving the rest to thermalize at a lower temperature. If there is capillary action taking water to the outside of the pot and that is evaporating, then the pot cools down as it is losing heat to the leaving ...
4
I will make it an answer instead of a comment.
My guess is that the convergence is an optical illusion. This plane is flying at a level where the relative humidity is small.This means that the trail evaporates, it will evaporate faster from outside (the trail itself is humid) and finally what is left is merged the dissolution giving the impression of ...
3
what is the surface area of a liquid?
The surface of a liquid is the interface between the liquid and (usually) the air surrounding it. The surface area is the amount of that liquid that is exposed to the air, or touching the air.
And also that why the rate of evaporation increases with increase in surface area of the liquid?
If more liquid is ...
3
All aircraft producing lift have a wake, because the wing deflects the air downward, while the air further away is not deflected. This takes the form of a pair of "wingtip vortices".
Since they transfer energy to the surrounding air as they dissipate, they expand in radius, because momentum is conserved. So they capture the condensation trails from the ...
3
I'd be very surprised if this was crystal formation. It looks to me as if the goo at the bottom of the glass formed a film, then as the film dried it shrank and fractured. The pattern of lines you're seeing are stress fractures in the film not crystals.
The fracture pattern looks very symmetrical, but then you have a circular boundary condition due to the ...
3
Your instincts are right -- this is indeed crystallisation. Your original cocktail was a solution of lots of non-volatile components (sugar, Splenda, citric acid from the lemon juice, and many many other things...) in some rather more volatile solvents (ethanol and water). Only a limited amount of any of the non-volatile compounds can dissolve in a given ...
2
Instead of temperature drop, we have to to consider amount of heat transferred to the building from the wildfire. The temperature of the structures will rise towards the ignition point depending on the temperature and closeness of the heat source. Cooling can then slow down the heating or in best case stop it completely.
The heat transfer is is a ...
2
Regarding your first question, yes, the evaporation rate is related to both the temperature of the liquid and that of the air. There is no single, universal equation describing the evaporation rate at an interface, because so many factors come into play. The simplest equation describing evaporation rate is probably that established by Langmuir:
You can ...
2
If you have water in an enclosed container with some air, then the evaporation will gradually slow down towards zero. That is because the rate that liquid water molecules gain energy and become water vapor will be balanced by the rate at which water vapor molecules lose energy and become bound to the liquid. The point at which that occurs is called the ...
2
If you are just standing on the ground and looking up, you will be able to see the base of the cloud. I suggest that your estimate for a cloud more or less directly overhead (and closer) will be more accurate than for distant clouds visible on the horizon. The altitude to the base of the clouds is called the ceiling, and can be measured using a instrument ...
2
Heat of vaporization is related to enthalpy change, while dew point is related to free energy change, i.e. enthalpy plus entropy. That's why they are very different concerning relative humidity.
The enthalpy of a gas is more-or-less independent of pressure or partial pressure, because gas molecules don't really interact with each other. At insanely-high ...
2
The vapor pattern that we can see on this pictures is due to the instability of trailing edge vortices. Here are some picture showing an instability of this vortices (in French for English see aslo this JFM). Different plane will have different trailing edge vortices resulting in different observable vapor pattern. On Wikipedia the trailing edge vortex are ...
2
Water vapour at the Earth's surface consists of molecules of water mixed up with molecules of oxygen and nitrogen. At room temperature 100% relative humidity is about 20g of water per kilogram of air (roughly a cubic metre), so about 4 molecules per 100 are water.
To get water vapour in a vacuum you just remove the air molecules and leave the 20g per cubic ...
2
A volume of water contains a gigantic number of molecules, each with different speeds. The ones with faster speeds are the ones that escape the surface boundary forces to evaporate into the air. Thus the remaining ensemble of water molecules has a lower average speed of movement = lower "temperature".
2
This answer was posted on chemistry.SE by @permeakra:
After quick digging I found, that glass cleaner solutions usually contain alcohols and surfactants. This additions reduce surface tension and allows the solution to interact with glass more easily, distributing the solution over the entire surface.
The white stripes visible after water dried are ...
2
In glass,there can be different types of staining based on how the stains form
http://www.britewayservices.com/resources/HardWaterSpots.pdf
Based on your nature of question I think you are talking about limescale staining.Sometimes stains are from due to chemical reaction between silicates and with the calcium and magnesium in hard waters.These minerals ...
1
Imho, this process is driven not by energy considerations but by kinetic considerations. That should be why it naively seems weird that water absorbs heat from a cooler object and evaporates. Note: This is an explanation I came up with on-the-fly and have no references to back up with.
Since the earthen pot has small pores, water "flows" through those ...
1
Latent heat of evaporation cools the pot in the same way it cools your skin. If the pot is then at a lower temperature than the water in it, heat energy will be transfered to the pot from the water in it by conduction.
Using plant xylem water for evaporative cooling, the desert cicada Diceroprocta
apache can maintain a body temperature as much as 5°C ...
1
Because in a liquid, the molecules are all about the same distance apart (since most liquids are not very compressible).
So the top surface of liquid in your coffee cup has a certain area and a certain number of molecules in that area.
Two cups of coffee will have twice as much area, so twice as many molecules, so twice as much evaporation.
Now connect ...
1
One or two sentences?
Heat is transferred to water, which therefore evaporizes, taking away the heat with it.
Latent heat is the amount of heat necessary to trigger a phase transition in a substance, and is not spent to increase or decrease the substance's temperature. So it is incorrect to say tha the water has removed the latent heate. I'd rather say ...
1
One can make an estimation. Consider the first part, liquid and its vapour in equilibrium. Let the vapour concentration be $n_0$ and temperature $T$ such that vapour can be treated as an ideal gas (that is there isn't much vapour).
Then the flow of molecules flying from vapour to liquid is
$$F(n_0) = \frac{1}{4} n_0 \langle v\rangle = \frac{1}{4} n_0 ...
1
It gets cooler. It feels hotter.
Saunas are generally around 80-110 degrees Celsius, and very low humidity (steam rooms are much lower temperatures, and very high humidity).
The temperature we sense is dependent on humidity. Putting water on the stones means that lots of energy from them goes into turning the water into steam & vapour. That's energy ...
1
Your body can increase its heat loss by evaporating water from its surface. Blood is then directed to the surface of your body to cool it, so that it can maintain an internal temperature of 36.8 Celsius, say. If the humidity is higher, your body cannot lose as much heat by evaporation. See here, say, or the Google search that got me there. So, you are hotter ...
Only top voted, non community-wiki answers of a minimum length are eligible
