How does evaporation REALLY work?

How do evaporation and condensation really work? What concepts to people often get wrong (even scientists) and why do we need to care about wet bulb temperatures? And is that cloudy stuff over a hot cup of coffee steam, water vapour, mist or smoke? And what simple thing can we do to take action about global warming? The chemistry and science of evaporation is explained in this video with 3D animations.
To join in some simple, practical and useful action against climate change, check out 350.org: 350.org/
Phase transition demo (small particles simulation) coded by Kristjan Kongas: kongaskristjan.github.io/2020...
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Three Twentysix Presenter/Project Leader: Dr Andrew Robertson
Production assistant: Es Hiranpakorn
Graphic Design: Maria Sucianto
This video was produced at Kyushu University and supported by JSPS KAKENHI Grant Number JP21K02904. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author and do not necessarily reflect the views of Kyushu University, JSPS or MEXT.

[@GetMeThere1]

As a child I once remarked to an "old timer" living in a rural area "This is a nice warm, sunny day. It should help the snow melt." He told me "Wind is what makes the snow go fastest."

[@TaserFish-qn2xy]

Well, sunlight or "radiative forcing", as environmental physicists like to call it, is usually one of the strongest indicators for evaporation. At least when the surface is dark like a leaf or the ocean - not so much for snow. The extra heat input will also produce convection (unless there is an inversion). And yeah, dry wind evaporates or sublimates snow and water real quick.

[@philipoakley5498]

While sun provides the energy, its the wind that moves it about. And where does the wind get it's energy to move the sun's energy about, well, it's back to square one... (Wind is the sun's energy redistributing itself, based on heating via conduction, convection and ultimately mass transport)

[@GuillotinedChemistry]

Really nice connection between kinetic energy of particles and evaporation. That's a good perspective on why evaporation is an endothermic process. Also didn't know about wet bulb temperatures... super interesting and great job again!

[@ThreeTwentysix]

Thanks again!

[@KhaoticDeterminism]

is it tho? isn’t it exothermic or else it wouldn’t happen? it’s useful to view it as one fluid (air) dissolving another one (water) at the surface interface kinda like dissolving sugar into water 🤔

[@GuillotinedChemistry]

@@KhaoticDeterminism good question. Just model it with your fists... The liquid particles are rolling over each other. The gas particles are bouncing all over the place. That second scenario requires more energy, hence it's endothermic. Think about how the evaporation of sweat feels... It cools you down because it's absorbing heat from you. I don't know enough about fluid mechanics to model water and air as to adjacent fluids but I bet somebody has... 😁

[@wayneyadams]

It's the same explanation any good Chemistry or Physics teacher would tell you, and I know because I was teaching both while he was still a squaling baby soiling his diapers.

[@nickflynn666]

Great explanation.I unexpectedly learned more about vapour pressure which is good. One thing I would say is that on a practical level you can always stay cool on an above 35C wet bulb day if you have access to water or any other large thermal mass. Tap water tend to be close to the ground temperature which is almost always cooler on a hot day. I've put my head in a bucket to cool down on hot days when working in high temperatures. Most of the cooling comes instantly as water is a good thermal conductor with a high thermal mass, the evaporative cooling is just a bonus and as you say wouldn't work on a +35C day. If I was trying to cool down someone who was disabled and couldn't put their head in water I would fill a bucket of water and put their feet in it. Even a large body of water such as a sea, lake river, or pond would almost always be cooler than the air temperature so would cool you down. The same is true of other thermal masses such as a large rock or anything connected to cooler ground temperatures such as the base of a building or even a cave.

[@ThreeTwentysix]

That's a very good point. But it does mean you need access to a large amount of clean water, which is not the case for most of the world population that's likely to be exposed to these wet-bulb temperatures.

[@SeattlePioneer]

I like your idea of putting your feet in a tub of water to cools down. Sounds a LOT more efficient than air conditioning a building. By and large, I prefer a fan to evaporate sweat and cool off my body. I have one turned on right now! But when it gets hot enough, that's no longer adequate, and the feet-in-tub method would be good to try at that point. I'll give that a try.

[@MadScientist267]

Of course there's a gotcha, you need to keep the water below body temp and the closer it is, the more of it you'll need and transfer efficiency goes thru the floor.

[@KaiHenningsen]

@@MadScientist267There's always a gotcha. Once the easy ways to get rid of thermal energy stop working, it gets more and more complicated, and even those methods will eventually stop working. Enough time, and you're looking at the heat death of the universe when the whole universe has the same temperature, and there's no more useful (non-heat) energy available. (But that's very far into the future.)

[@stevenverrall4527]

​@@SeattlePioneerSounds a lot more efficient, but isn't. Modern building AC systems are highly efficient.

[@jaimeduncan6167]

Not new to me, but a great refresher. It's also the best explanation I have seen online. The simple model it builds on people's minds is amazingly powerful. Thanks for devoting the time to creating this video.

[@marielizysurourcq]

Very instructive for having a whole picture of every day physics / chemistry. One often has roughly an idea about it but you are filling in the holes in our knowledge. So thanks and carry on, I subscribed.

[@ThreeTwentysix]

Thank you!

[@BabaBoee5198]

@@ThreeTwentysixbro, why don’t ya do a collab with marble science. That’s would so cool and I hope you and also marbleScience skyrockets in views and subs

[@Connect2discxnnect]

Totally agree. Great teacher here. It’s amazing to have teachers like this to help people understand science at a fundamental level. So many bad teachers that make things needlessly complicated and the students suffer because of it. Guys like this will become more and more valuable as American schools continue to decay.

[@matthewbartsh9167]

I like the way you used the term "thermal mass" instead of the more common (outside of the building trade), and technically proper, "heat capacity". "Thermal mass" is definitely a term that should be popularized. It's really appropriate. You have quite a way with words.

[@john-ic5pz]

fwiw, thermal mass is a common term in chemical engineering, as is specific heat capacity and heat capacity (Cp×m). cheers

[@matthewbartsh9167]

@@john-ic5pz I never heard "thermal mass" before.

[@jdata]

What I love about your videos the most is that they often align perfectly with my day dreams and musings about chemistry and physics. So many "what if" scenarios and "how does this really work" shower thoughts that you really nail on the head. I love it! I always felt like the practicality of understanding chemistry and physics comes from truly getting a grasp on what's going with molecules on an everyday basis. Thanks so much for your content.

[@aleonyohan6745]

I'm going to share this with my other Refrigeration Techs. Refrigeration is all about evaporation, condensation, superheat, subcooling and it's really nice to know the physics of what's going on. I'm probably going to watch your videos three or four times most of it sinks in. You do such a great job of explaining. You know you're good when you don't even need a chalkboard and you can explain it verbally with minimum graphics. Phenomenal videos thank you so much.

[@YashKumar-ij5rc]

Very nice explanation sir. Keep making chemistry videos, I am supporting you.

[@tuberroot1112]

He should stick to the chemistry instead of climate crap of which he has near zero knowledge. FIVE times more people die of COLD than die of heat. If you want MORE people to die, do all you can stop "global warming" and make essential fuels are unaffordable as possible.

[@TheNameOfJesus]

Finally! A great explanation about this. You could also cover freezing/melting in the same manner, as the principles are the same. I've been teaching these things to my friends and relatives for 20 years. I figured it all out for myself from contemplating the following simple thought experiment: "If I dropped two magnets from the roof of my house, what would be their speed when they hit the ground and sometimes separated? And how would their speed change if the magnetic charge holding them together was much stronger, or much weaker, than a typical magnet?" This thought experiment is really the same problem as molecules sticking together because molecules actually do stick together by magnetism. If I was creating your video, I would have spent more time explaining that heat is stolen from a pool of water when some of it evaporates, (i.e., it gets COLDER when a heat source is HEATING it causing evaporation) and that heat is added to any quantity water when water molecules in the atmosphere condense into it. The same is true of water and ice: the water in a lake gets WARMER when its surface is turning into ICE, and the same lake gets COLDER when the ice on its surface melts. Since that seems impossible to most people, I really enjoy explaining it to them.

[@johncartwright4041]

I live in Brisbane Australia and it is fairly humid in summer. Many people go out and buy evaporative coolers which are next to useless in high humidity. Perhaps you could do a video on cooling mechanisms and the conditions suitable for them. Like your explanations!

[@stevesedio1656]

In Los Angeles, with 5% humidity, evaporative coolers provide marginal cooling. Yucca Vally, with 5% humidity, they provide very cool, and much needed humidity.

[@andyjoiner8887]

Best explanation of evaporation at the molectular level I've found so far.

[@NejinPokharel]

this is by far the best explanation on youtube. Thank you for making this video

[@ecospider5]

I have generally understood vapor pressure but I always got confused with how the vapor pressure affects the environment if you go down to 1/10 atmosphere. I was confusing evaporation and boiling. I have know I was missing something for over 2 decades. You just explained what I was missing. Fantastic video thanks.

[@philipoakley5498]

An additional practical issue is damp elimination in house crawl spaces, why sometimes things just aren't working (see various US climate regions), why damp is worse in winter than summer, etc. The partial issue is the rate of replenishment of 'sensible' water/moisture at the sub-soil interface, and the thermal lag effects that creates and maintains wet areas as cold, so reinforcing the condensation from the atmosphere. Its and area that's not discussed other than in hand waving terms.

[@olahafs]

Why has this channel not blown up yet? It will I'm sure of it.

[@ThreeTwentysix]

Thanks. We're busy working on it!

[@tuberroot1112]

While making home made double glazing , always seal it on a cold autumn morning. If you seal if on a warm "dry" day it will be full of water vapour.

[@Bobik1998]

You are an incredibly good educator. Thank you.

[@DarthCalculus]

This is such a relief. I include an explanation of evaporation and condensation in my atmosphere unit for Earth science, including an experiment to investigate evaporation rates. My explanation of evaporation is consistent with this video. I was afraid I was going to have to overhaul my lessons 😅

[@wayneyadams]

Any good Physics, Chemistry, or science teacher will teach this same lesson, there is nothing special about this guy other than his animations. I taught high school Physis and A.P. Chemistry (I have degrees in both) for 33 years snd his lesson is nothing special.

[@javierlopezgarcia8855]

Great video! A truly masterclass! I´ve shared it with my two daughters who are in secondary school. I wish I could have had this sort of material when I was their age. It is so difficult to come up with a view like this just from traditional textbooks! Changes of phases have always fascinated me and never actually fully understood them. Thanks to this and its sister video, now I understand much better the equilibrium between a liquid and its vapor below its boiling temperature and why boiling happens at a certain temperature for a given pressure. But what about ice and liquid water? Why ice and water apparently can only be at equilibrium at 0 C (at 1 atm)? Why isn’t there a wider range of temperatures where ice and water can coexist, like water and vapor between 0 and 100 C? However, ice cubes at -25 C in the freezer tend to stick to one another over time and form big blobs. Is that a sign that even at those low temperatures there’s still some liquid water around the ice cubes shufling molecules around and getting them to re-freeze in the boundaries and gaps between the cubes? I guess this is kind of my letter to Santa asking him to bring me another video on the topic of fusion and freezing.

[@onlyeyeno]

As always an excellent video, though I would have liked if You had talked a little about ""relative humidity"" as I believe that is a concept that would "fit in well " in this context, and that is good to grasp as well. Best regards.

[@CraBundy]

Excellent video, the animations really helped alot with explaining at the molecular level. Thank you Could you explain the evaporation through various surfaces? Like a traditional building with solid brick construction and also thee evaporation method of >50mm cavity houses, its a good topic to explore, as vapour is key to these structures, aswell we reside in these places, good video topic. Again Thank You.

[@XRP747E]

Excellent explanation. Thank you.

[@sstolarik]

Well done. While this vid (and the boiling one) didn’t get down to an atomic level, at which I would _definitely_expect_ to learn something new, I was floored about the characteristics described in your video that explained behaviors that we normally don’t think about (e.g. why boiling temp isn’t exceeded). Great videos, just Subbed!

[@ThreeTwentysix]

Thanks.

[@gwhite618]

Just a quick question, at school we were taught that evaporation is at its greatest when there is a big difference in the air versus water temperature. Eg, say the water temperature in scenario A is 30 degrees celsius and the air is 10 degrees celsius, then in scenario B the water temperature is 30 degrees celsius and the air temperature is 40 degrees celsius. When would the most evaporation take place if the humidity and dew point of the air is the same in both situations?

[@justayoutuber1906]

So on your last example, could it be answered with the difference in the web bulb temp?

[@thatguy431]

the explanations here are just amazing man!

[@wayneyadams]

His animations are good, his lesson is nothing more than that any decent Physics or Chemistry teacher will teach. I taught high school Physics and A.P. Chemistry (I have degrees in both) for 33 years and am not that impressed.

[@user-tw5ch6pt6t]

@4:07 can we use centigrade and degree together? Very nice lecture please upload some on thermodynamics and chemical bonding from basic to advance because those two really bother me.

[@vspqrv9784]

Exactly what i was looking for thank you sir

[@BjerkeRobin]

Would we say that dissolved co2 in a solvent evaporates?

[@andersemanuel]

Thank you. Always a pleasure to learn from you. I don't agree on your climate thinking, but I think coal is only to be used if you can't afford anything else to survive. Mainly because of the particle pollution, not the CO2. Keep up the good work.

[@bevanthistlethwaite3123]

I'd like to hear more about the thermodynamics of ground and ocean evaporation and their effects on atmospheric conditions.

[@thelovertunisia]

amazing channel Dr. so informative.

[@tobsco2]

Could you do a video on relative humidity and the moisture content of absorbent materials like wood, and how an equilibrium gets reached?

[@chadchampion7985]

amazing video, amazing channel. what a great find!

[@cowboybob7093]

The thumbnail makes me want to vomit. Sounds like I'm missing out.

[@klapstekker]

Can you explain to me why a bucket of anhydrous ammonia of -33 degr C which is depressurized to atmospheric pressure may reach a liquid temperature of -60? Obviously the evaporation of the ammonia cools the remaining liquid in the bucket. But why does the ammonia keep evaporating? I hope you can explain.

[@3SPR1T]

Very nice video, can you explain the dew point chart in detail?

[@justayoutuber1906]

Question: In a bowl of hot soup is the coolest soup on the top of the bowl (surface) or the bottom? My friend says it is on the bottom because heat rises, but I thought the coolest would be on the surface nearest the cool air.

[@sparkysmalarkey]

You can run an experiment and observe the results for yourself. You just need a temperature probe and a laser thermometer. Put the probe in the soup to test the temperature from the bottom, and use the laser to check the temperature at the surface. Observe, track and record the data as it cools down. Thermal energy radiates in all directions towards areas with less thermal energy. The surface will be more efficient because of evaporation but it will go in and through the bowl as well. I would guess the middle of the soup would stay hot the longest.

[@triple_gem_shining]

I hope I get some great teachers like you in university

[@uheuheuheheu]

does relative humidity makes sense after 100°C? I've read somewhere the max RH actually drops with temperature... Can you help me understand?

[@pulsar22]

You are forgetting one thing about evaporation. Even if you reach a wet-bulb temperature of 35C, evaporation doesn't stop. And evaporation still cools down a surface albeit more slowly and at less efficiency. But if you have wind, natural or artificial, it would speed up that evaporation dramatically. And, you can still cool down by immersing your body completely in water (no evaporation but it combats global warming). So, making people fear of global warming is not good when this is easily solved even without air conditioning. Also, the human body is very adaptable. It is shown that physiological response of a person who lives in hot humid tropics is much different from northern temperate acclimatized person during stressful physical activity (you can google the study about this). And, one thing a lot of global warming alarmist forget is that the tropics is the least affected by global warming. Remember that global warming is the average of warming of the Earth. It is the Temperate zones that warm fast while the tropics stays relatively the same. The reason for this is that the tropics already bear the full brunt of the sun whole year round. It cannot heat up anymore that it already has. It is already the most humid areas in the globe. It cannot get any more humid (otherwise it rains out). Of the current global warming temp increase, only 1/3 is attributed to CO2. The rest is attributed to positive feedback of which water vapor is the #1 feedback. If the precipitation in the tropics is already maxed out, then CO2 will not have any additional effect on the tropics. Otherwise, the positive feedback of water vapor would have already made the Earth a hothouse. But that is not the case, therefore CO2 will not affect the tropics in anyway.

[@migueldelpozo3358]

does water condense in an open system ( a parcel of air in the atmosphere with no liquid water ) when it reaches its vapor pressure saturation at a given temperature ?

[@BrHck]

Can we affect liquids in a mechanical way, such as irradiating them with waves that resonate destructively with their internal vibration, thereby reducing their kinetic energy causing them to vaporize?

[@keithjurena9319]

Cloud equilibrium altitude is energy based. Saturated air surrounds clouds, absorbing nearly all outgoing long wavelength IR. This returns descending water particles to vapor state, creating buoyancy. The lapse rate causes heat loss at cloud tops, the IR is free to leave as humidity is less at cloud tops.

[@stephenkneller6435]

It is anecdotal, but I have had to work outside all day at temperatures at or above 35°, for years. I still do when I have to. I survived. I can see how those used to constant temperate temperatures would struggle. But they can most definitely adapt. So what am I missing? Saying people will die at 35° seems a little alarmist. And to date, more people a year still die from cold weather than hot weather.

[@wayneyadams]

The reason you survived is because his radical leftist scare tactics are deliberately misleading, a common tactic among radical leftist capitalist hating communists like him. 35°C is the wet bulb temperature of a device called a sling psychrometer, not an absolute outside temperature as he tries to make you believe, it is a lie of omission. Two thermometers one with a dry bulb and the other with a wet wick surrounding the bulb are swung around in the air. The water evaporates from the wick cooling the wet bulb thermometer. The difference between the two temperatures along with the dry bulb temperature are used to calculate relative humidity. The part that he DELIBERATELY leaves out is that the relative humidity plays a part in this. As long as the relative humidity is not 100%, a very rare occurnce, you will still be cooled by evaporation. There is an old saying when people are moving to hot climates like Arizona, "it's a dry heat." To be perfectly clear, the wet bulb temperature depnds on the outside temperature AND the relaive humidity, not just temperature alone. The temperature outside can be 45°C in an extreme heat wave, but you will still be cooled by sweating as long as the relative humidity is below 100%. The cooling will be less efficient as the relative humidity goes up meaning you have to scale back yor actvity, but you won't fall to the ground dying an agonizing death. This is a pathetic and common tactic radical climate alarmists (all are either communists or socialists) use to convince developed western nations to revert back to the stone age.

[@vikapavelitsa2393]

Perfect video! Thanks a lot! Could you please confirm, if I got it right, the intensity at which surface of something wet at the same temperature will cool down in the environment of different humidity will depend only on the rate of condensation? The closer the rate of condensation to the rate of evaporation the lower be the intensity of cooling? And the rate of evaporation doesn’t depend on humidity level at all?

[@ThreeTwentysix]

It's the NET rate of evaporation that counts. So there is the rate of molecules leaving the surface of the liquid, which is fixed by temperature, and there is the rate of entering the liquid from the atmosphere, which depends on both temperature and the vapour pressure of the water in the air. Higher vapour pressures correspond to higher humidities and so higher humidities mean a lower rate of net evaporation, which means a reduced cooling effect. At high enough humidities, the cooling effect is effectively reduced to zero.

[@vikapavelitsa2393]

@@ThreeTwentysix Got it! Thanks! ☺️☺️ It was important for me to find out, that the rate at which molecules leave the liquid depends only on temperature not on humidity.

[@carlbrenninkmeijer8925]

so clear !!

[@felixarroyo839]

Total pressure may not affect vapor pressure, but it will affect condensation rate since collision in the gas phase will transfer energy to the novolatizing pre-existing gas.

[@wedchidnaok1150]

Of course I've got questions. The speaker stated an answer (for one of the main initial questions, "more evaporation of water happening in the drying of wet clothes bathed: in cool dry air or in hot humid air?") depends on the differences of the variables; yet he didn't elaborate a sampled graph nor an guessed proportion in between the limited scenarios. Using "sheer words" is relevant to keep touch with our cultures, yet science also involves empirical & imaginative research: if the comparison between the two fictional scenarios resulted in the need to compare further scenarios of each of the two classes of scenarios, then it's reasonable to go for it. "It depends" "on variables" ain't no sciencing no, sir. Please raise the "sciencing frequency" varible then, aye? Such mistification of evaporation ain't making its features more visually watchable in this metaphorical case. Solid samples: that's what was shown in the water-in-container (various) examples. Nicely done, there. Explicitly, my metaquestion is "How's the variance of water-in-cloth evaporation between some iconic samples of surrounding atmosphere?" And by "iconic" I mean common points of "variable measurement" [cohering unit-of-measure-of-difference between 2, 3 or few more conditions of achieved precision with available knowledge and hand-reach] in a full set of crossed combinations (in the mentioned minimalized case, the duo "wet & warm" and "dry & cool" gets accompained by the misssing duo "same dryness & same warmness" and "same wetness & same coolness") (to track-in-mind, shaping a single tetrahedron might work fine, but training such "relativity frame" of 4 objects with 2 bi-variables each is makes the seeming complexity quite straight-forward in post-exercise abstraction). The "iconicness" can be improved by enmeshing further (relevant or irrelevant) variables in the combination set. It's similar to the "beverage evaporation in alternatively-sealed-atmosphere examples, such as the "imaginary submarine tale" or the "bottle simulated toon" or the "lidded and agitated becker-thingy". Thanks. May the humanly-proper coolness be with us. In all scales (of "us"). My cooly haired head is resting in an open refrigerator as I write this brief sentence. Warning is warmonging is warming, sometimes. Diplomatic befriendery rules humanity in ways undifferentiated pressure either compresses (lidded common ground) or mistifies (airs suggestive of dances). The evaporation as metaphor operates in-between said lids. While empty space is perenial, proportional space is relative. This video connects environments. Btw, another question is "What 'Three Twentysix' or/and 'San Nijūroku' stand for?" I've no background to guess the chosen id. Is there a story, a ratio, an expected reaction, a rhyme, a group of theses causes? Dunno; wanna know. What gives?

[@rfvtgbzhn]

7:10 that is valid under "normal" conditions, but not if you compress the gas a lot (like to 1/1000 of it's normal volume).

[@nicklockard]

I wish we would report weather and discuss it in wet bulb temps. This is because wet bulb reflects what you actually feel, more directly. Wet bulb temps measure heat sensible and latent enthalpy (heat).

[@rickkwitkoski1976]

Just found your channel. Thank you, YT algorithm. You are very good at explaining. Of course, I understand this stuff already but your scripts are well done.

[@waelfadlallah8939]

I couldn't say much more after i read all the beautiful comments other than very well explained 👏 I just have curiosity strongly related to this topic which is how clouds weighing several airliners (jumbo jets) stay uplift or floating as if they are feather wheight and also why they always reach a certain point to gather around or fully condense of a height of approx. 10km?

[@megasbaladoros]

Nice that you wander about those things. The weight of the atmosphere above any square meter near the sea level is more than 10 tones. Think about what this means for pressure. Also, if you want to double the pressure by diving into the sea, think about how deep you would have to go. To return to your question, if the atmosphere above is so heavy, perhaps you can make sense out of it holding so much weight of other stuff, like clouds or airliners.

[@waelfadlallah8939]

@@megasbaladoros thank you for the input, it was intresting. You know, i once heard it's due to another cause yet i didn't quite get the concept. Basically, within the cloud itself there is always an exothermic reaction occurring which of course releases heat and when heat is present it means less material density (in this case water particles) and the less dense a substance is the more likely it is to float just like oil floats on water. I wonder about everything that i encounter on a daily basis, like for example something i hadn't figure it out yet is why in cases of carbonated drinks the bubbles coming of (some of them) get stuck to the side of the container (in cases of glass)

[@jodiegreen7980]

Yes. Even though I knew this 'in theory' it still wasn't until I read the first harrowing chapter of Kim Stanley Robinson's book 'Ministry for the Future' that I really 'got' what exceeding safe wet-bulb temperatures and humidities means for living things on a large scale.

[@SakibHasan-ks2fe]

Great vid!

[@matthewbartsh9167]

I liked the way the vid called the cloud of droplets of water in the air near a kettle, "mist". I haven't heard that before. I always used to just say "steam", knowing I was talking nonsense, and feeling slightly bad about it. Did the author think of that way of putting it, himself?

[@thelovertunisia]

Humid weather: here in Tunisia we have very hot and humid days and nights in summer and often it is hard to sleep.

[@mariojcjr]

Como que vaporizadores funcionam? Pois eles não aquecem a água.

[@HansLemurson]

326 supports 350 to reduce wet bulbs reaching 35?

[@ThreeTwentysix]

Yes, we want to do a 180 on fossil fuels!

[@matthewbartsh9167]

Good video, as usual. But why do you always pull a fast one? In "How to triple the effects of caffeine" the answer turned out to be to switch decaff, at the end of the video. This time, a puzzle is posed (which will dry faster), but no proper answer is given. Is the deeper lesson that we should be unscrupulous?

[@SeattlePioneer]

> I noticed that as well. I'm supposing that is left to the viewer as a way to apply what is in the video. My answer to that question is that raising the temperature in a humid environment will dry clothes faster. Applying what's in the video, there is ALWAYS opportunity for a liquid to evaporate. The hotter the liquid, the faster the evaporation. Applying that same principle, liquid will evaporate from clothing when the clothing is cool, too. But it will do so s-l-o-w-l-y in comparison with the higher temperature. I line dry my clothes. Last night I hung out two towels that were very damp. In the cool overnight temperature with no sun adding radiant heat, they were still quite damp this morning. During the day, with hotter temperatures and sun adding radiant heat to the clothing, the towels will dry rapidly. (Actually, the towels are shaded from direct sunlight) Looking at overnight humidity levels, they increased to a maximum of 76% at 0753 hours, when the temperature was 63 degrees F. Now at 1153 hours, the temperature is 77 degree F and the relative humidity 47%. So most of the drying has taken place when humidity was lower and temperature higher. That doesn't prove my conclusion that the temperature is the driving factor, but I still think that it is! I invite further discussion ----especially if I'm right!

[@matthewbartsh9167]

@@SeattlePioneer There will be no further discussion.

[@jezzamobile]

I think he's teaching us to fish, rather than giving us a fish 🐟😹

[@Lundy.Fastnet.Irish_Sea]

@@SeattlePioneerthere are lots of other factors to consider though, when we're drying clothes outside. Wind and humidity for example.

[@ricardovencio]

Excelent video

[@naeemchanna5633]

i have a question that where do electrons get energy to spin?

[@ThreeTwentysix]

It's important to understand that they're not actually spinning in the common understanding of the word. There are a few good videos on KZbin about the meaning of spin for electrons, but it's very quantum mechanics, so don't worry if you don't follow it.

[@markotrieste]

I've learned all this stuff at the university, but it's nice to listen again. The concept of vapor pressure is not easy to grasp, you did a good job in explaining it. Further topic: the three ways to reduce humidity at home: heating, dehumidifier or split air conditioner. People really mess this all too often.

[@ThreeTwentysix]

Thanks for the idea, I'll keep it in mind.

[@TimRobertsen]

Interesting video! :) If I was to ask for anything, it would be for more/different examples of vapour pressure: substances with low and substances with high vapour pressure.

[@ThreeTwentysix]

How about liquids with ZERO vapour pressure?

[@TimRobertsen]

@@ThreeTwentysix Gasp! Unvapourable liquids? :o (or am I getting vapour pressure wrong:p)

[@ThreeTwentysix]

Nope, that's exactly what they are.

[@TimRobertsen]

@@ThreeTwentysix From one Robertsen to another Robertson: this subject needs a video :)

[@rahimarunu8945]

Thanks ❤❤❤

[@geolyst]

Dear Professor Robertson and fellow KZbinrs, with great interest I watched your KZbin video on Evaporation. I am trying to transfer the knowledge to meteorology and in reverse, i.e. condensation. But somehow I am struggling to find the same logic. When you have an air "package" with a certain moisture content that gets lifted up due to temperature differentials, then a wetter air package cools down LESS than a drier air package (dry vs. wet adiabatic cooling). What I don't understand is, where the heat/energy comes from that causes this. If I have a water molecule wizzing around in air with a certain amount of kinetic energy and it gets condensed into an already existing water droplet, then yes, maybe the water droplet gets slightly warmer, but the whole air package itself will have one molecule and all its kinetic energy less (since it is now bound in a water droplet). Therefore: shouldn't it get cooler? How can it then be that the air package itself is getting warmer (or at least less cool) just from condensation? Maybe you can shed some light on where the missing piece is I am overlooking, or even better do a follow-up on the evaporation topic, where you go more in depth on condensation. Thank you !! :)

[@ThreeTwentysix]

It's easier to visualise if we just simplify a complex variety of interactions to a simpler model. 'Hot' fast-moving water molecules don't condense, they just bounce off each other and any water droplets. In order to condense, they have to lose their kinetic energy first. How does that happen? By a simple Newtonian collision with a 'cold' nitrogen/oxygen molecule. That makes the water molecule cold (and susceptible to condensation) and the 'air' molecule hot. Taken together, heat is transferred from the water molecules to the air molecules. The energy hasn't come from nowhere, it was always present in the water molecules whizzing around.

[@geolyst]

@@ThreeTwentysix Thanks for the reply. I am still struggling to tie this with the video. In the video you explain that the water is cooled down from evaporation because they wizz off into the air, which is made hotte because now it flies around in there with kinetic energy. So: evaporation = cooler water = hotter air. Is this right? If yes, how can condensation ALSO lead to hotter air (as you explain in your comment)? And is then the condensed water molecule still having an effect on the existing water droplet? If yes, is it cooling it or heating it? Since it is going it, I would expect it adds kinetic energy, and thus also heating it. So: condensation = hotter water = hotter air. Seems weird. In isolation I understand your comment, but in detail not :-/

[@triffid0hunter]

The standard method of keeping cool in the Australian summer seems to be drinking enough to sweat ethanol…

[@easteregg-ch5jg]

Loved the video,found the channel and subscribed though I rarely subscribe😅, Again very thankful to you for the video

[@goonimann5028]

This has to be one of the greatest KZbin channels I’ve found in the last 5 years. Amazing videos!

[@niccolo99]

My god you are so immersive

[@Lundy.Fastnet.Irish_Sea]

watching your inorganic chemisty professor slowly turn into a popular KZbinr is truly a bizarre experience. Regardless, people deserve to understand the mundane phenomena around them, and I can’t think of anyone better to teach them, Doctor.

[@ThreeTwentysix]

If I knew who you were, I'd write something more personalised.

[@Lundy.Fastnet.Irish_Sea]

@@ThreeTwentysix My name is on my profile. It was Basic Chemistry class actually. We did the rats-on-a-grid analogy for Gibbs Free Energy.

[@aaronh1372]

That was tricky... Wind dependent.

[@fredrickemp7242]

when water evaporates and it is a cloud then what is the definition of steam?.

[@davidrussell8927]

when water evaporates [it is steam] and [where that steam is condensing in air,] it is a cloud..

[@BarrieHughes]

Not very light molecules but molecules with weak intermolecular bonding eg alcohol/ether are much heavier than a water molecule but much better at evaporative cooling.

[@fariesz6786]

airconditioning? _•laughs in German•_ to be fair though, most of Europe experiences comparatively dry heat and very hot days or heatwaves are not guaranteed events. that being said, i'm still really annoyed when people here keep pretending heatwaves were just freak occurrences and weren't getting more and more common. 2018 had a really hot summer with at least two 7ish-day stretches of "tropical nights" (defined as those nights where temperature won't dip below 20°C, usually isolated events) in a row. and i was unfortunate enough to be in hospital on the top floor of the building and the temperature never really got lower than 27°C - they had to hook some people up to a drip just to make sure they would stay hydrated enough. and that was a research-adjacent hospital, and the building wasn't exactly old (1980s or 90s i reckon). i feel at least hospitals should somehow be required by law to make sure their rooms can stay below a certain temperature, either just by virtue of being shaded by trees or by some smart architecture that keeps them sort of cool. and yes, they also have to be able to stay warm enough in winter. i totally get that this is a pretty hard task, but those are both required in "inland temperate climate" like we have. and technically heat pumps could be an amazing solution for this bc they can be (and by some manufacturers are) produced so that they are able to shove thermal energy both ways; most manufacturers though only produce them as heat pumps here, and only as AC in other countries (where they will shoehorn an oil heater or something like that in for when it's cold.. even in climates that only only ever go down to temperatures easily covered by a heatpump)

[@davidgipson7140]

This is more of a question than a comment. You mentioned discouraging investors from investing in coal. I was under the impression most coal burning was for the production of electricity. Do you suggest nuclear plants as a replacement or for example investing in scrubber technology. Since even though cutting back on electrical usage may slow the problem with a growing population the problem will still grow?

[@Sugar3Glider]

Scrubber tech is a pipe dream. Nuclear is burdened by scare mongering. Degrowth is what we need, but dont discuss.

[@theplatypen1959]

I saw in Siberia that they put their clothes outside to freeze and then bring them inside to unfreeze and like magic they're dry. Wonder what's happening there. I now do the same with my clothes after hunting and it works

[@HiroshimaMS]

So the bubbles that form inside the cold water are not the microbes breathing like I thought it was (laughs) but it is the water evaporating?

[@DaveE99]

I’m no longer 37 years old, I’m 37 revolutions through. And temperature is no longer temperature, it’s now kinetic energy level of organic chemistry or just kinetic level outside. I shall be labeling my kineticometer and existentially we might as well..after all.. aparently tomatoes are a berry and I now call those lava berries.

[@AK-vx4dy]

Super cool and clear explanation !!! But second part... fuuuu

[@lansonfloyd4687]

Nice right up to the point where you bought into global warming. Unfortunately you will find that is not the case. Just plot the temp graphs on a longer timeline (one that does not fit the "carbon tax initiative" goals and you will see that we are nowhere near a global warming scenario. But otherwise good vid.

[@Dream-jn1sx]

Oh my god thats nice.

[@ThreeTwentysix]

Thanks!

[@geschwarz]

I need a solution. It’s my understanding that only gasoline vapor burns and that droplets do not burn. I am designing an intake manifold for my internal combustion engine, how can I ensure that all of the gasoline that enters the combustion chamber is vaporized, with no droplets. This is a Mazda rotary engine, which is known for poor fuel economy because it exhausts unburnt gasoline. That unburnt gasoline gets burned in the exhaust system, not in the combustion chamber, which is wasteful. My theory is to have the air/fuel mixture in the intake manifold pass through a sufficient mesh or grill like structure upon which the mixture can impinge on the surfaces in a turbulent manner, adding kinetic energy to the liquid gasoline, and by increasing the surface area of the droplets over the surface of the mesh structure to maximize evaporation. Thoughts anybody?

[@ThreeTwentysix]

If you haven't already checked out Engineering Explained's awesome videos on rotary engines, you should: kzbin.info/www/bejne/qZWZoX2qh5mDl7ssi=rlkotEcfrn794vIT

[@ecospider5]

Once the outside temperature is way above body temperature you need to insulate your self from the heat. But in a way that still allows your sweat to evaporate. As he said when the wet bulb temperature hits 35 Celsius you are in big trouble. You insulate yourself from the heat but your body burning calories produces heat. So inside your coat you begin to heat up. Then you sweat but the sweat can’t evaporate so you just keep heating up until you die. I have a feeling people without AC at the equator are going to start digging down to make man made caves that are at a livable temperature.

[@fredrickemp7242]

I asked what Alexa what comes off of a hot cup of coffee and it says steam the hot molecules hitting the colder air molecules, making a visible white cloud

[@Richardincancale]

Stop press! MIT confirmed the photomolecular effect, published end October 2023, whereby light interacts with water at the air/water boundary and causes very significant evaporation without thermal input! New video please 😊!

[@catbertsis]

those spheres could use more polygons

[@sfertonoc]

Is not the warming the problem, but weather instability. And the more measures to correct it, the more unstable you risk it becoming and get crop failures.

[@KalebPeters99]

The instability will lead to more extremes. Including extreme warming.

[@davehalliday9399]

Wait, a gas can evaporate? I've never heard that statement made before in my life until now. I've heard of a gas diffusing, or a solid sublimating into a gas, or a gas coming out of or going into a solution, but a gas evaporating? I need an explanation of that please.

[@theEVILone0130]

He's talking about gas as the liquid in your cars fuel tank.

[@davehalliday9399]

@@theEVILone0130 yea no, he was talking about the gas coming out of a coke can deep under water diver environmental habitat.

[@KalebPeters99]

​@@davehalliday9399you mean the CO2? It's in liquid solution before it evaporates. Gasses don't evaporate. And I think he misspoke when talking about ice evaporating too, it would technically 'sublimate' from solid to gas.

[@prins1991]

Whichever has a greater vapor pressure deficit dries wet clothes faster.

[@luciangg1553]

A cold humid day sounds like hell for my por wet clothes

[@alberthamilton8251]

Tell me about ice on a pond

[@stevenverrall4527]

The predominant cause of excessive wet bulb temperatures is urbanization. The solution is to implement policies to reduce population densities, rather than vice versa. Excessive wet bulb temperatures will still be just as problematic once we achive net zero GHG, which we need to do for several other reasons. People in developing countries need to be enouraged to move away from major urban areas instead of into them.

[@keithjurena9319]

Anthropogenic carbon dioxide release is about 35 G tons per year. This causes a 2.5 ppm rise in carbon dioxide per year, representing only a 13 G ton increase per year. Nature sequesters 22 G tons per year. Net zero isnt needed, net 60% would stabilize current levels. Net zero would cause carbon dioxide to fall under 200 ppm in 60 years, this would be catastrophic to all agriculture.

[@januszlepionko]

Reading the video title I thought the video had something to do with 1984.

[@rickkwitkoski1976]

Evaporation... In the tropics, it could take 2 days for a washed pair of denims to dry when it was hot and HUMID. When it was dry out... a couple of hours only. I once dried a wet towel in the hot and humid time by holding it out the window of a car while driving down a highway. I wasn't driving! It dried in about 20 mins. Without the "wind" it would have taken about a day.

[@dadesway]

Andrew, as a retired chemistry teacher I greatly appreciated the clarity and energy of your presentation. Oh, how dearly I would have loved to have had use of the computer kinetic model; so much better than the clear plastic tube containing ball bearings being energized from the bottom by a motorized cam hitting the rubber base . . that I used to use. However, I was dismayed when half way through you mentioned the issue of high humidity reducing the effectiveness of sweating to cool the human body and did not mention the use of fans (Japanese or otherwise) but rather launched into a "carbon dioxide catastrophically heating our planet" polemic and fueled (pun intended) the fear porn. Such a shame.

[@KalebPeters99]

The fear is warranted. As a retired chem teacher I'd hope you'd know better...

[@dadesway]

@@KalebPeters99 Kaleb . . . The problem is that I do know better; and I know better because, as a scientist, I understand how to look at evidence and also judge the quality of the evidence. Evidence such as pitiful rise in temperature over the past 150 years (

[@cadamham]

Climate deaths are on the decrease. More people die of cold exposure than heat exposure. We can also grow more food in colder climates.

[@farcydebop7982]

Maybe water evaporates at any pressure, but can it do it on a cold rainy night in Stoke?

[@varshneydevansh]

Pedro Pascal of Science