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.

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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.

[GetMeThere]

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."

[rockapedra]

Why doesn't this channel have millions of subs? It's so thorough and clear!

[JoshJoshman]

Excellent explanation of evaluation, well done!

I could not follow the political solution however at the end.

Mom always told me "close the door, the AC is on, are you trying to cool the great outdoors!?"

Fact: more humans die from cold than heat

Fact: homeostasis is the bodies' process of adapting to environmental conditions (like temp regulation)

As mentioned in the video, humans need the resources to adapt to their environment.
I'm with you so far . . but the climate change focus seems misplaced given the desired outcome.

Cheap energy makes this possible for the poor.
All things being equal we all want clean and efficient energy, of course but if the political action makes energy more expensive for the poor then . . . people will die.
The devil is in the details of course with any mitigations or purposed solutions, but the simplistic solution = "cooling the 'great outdoors'"

Doesn't it make more sense to give the poor access to affordable energy rather than attempting to 'fix' the planet **if your concern is for people?**

This is not an excuse to harm the planet, and long term focus is required, but the argument in favor of human well-being was poorly made.

To be fair, the focus of the video is evaporation, so a dedicated video on climate mitigation would be ideal to consider all factors pragmatically.
My objection is that a simplistic solution is offered to a complex problem and there's no nuance provided.

[pulsar]

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.

[matthewbartsh]

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.

[thyandyr]

Below freezing is typically very low RH. If you have a sunny day, even clothes that are frozen solid, will dry nicely. Also even without the sun, just abit slower.

[andyjoiner]

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

[RobertoHernandez-gpgu]

Nope.

You totally forgot of boundary layer.

In your model, there are not air molecules punching the surface of the water.

One of the most important factors in evaporation: ATMLSPHERIC PRESSURE!!!

[vikapavelitsa]

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?

[stephanierusch]

I live in the north of Sweden, and in winter we are able to dry the clothes. Dry weather in -25C degrees, freezes the clothes, you just to break the ice and get dry clothes :)

[jodiegreen]

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.

[RahmatAbdullateef-db]

How do waters become steam is it by magic well that's amazing

[BjerkeRobin]

Would we say that dissolved co2 in a solvent evaporates?

[rickkwitkoski]

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.

[farcydebop]

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

[DANGJOS]

This video mostly confirmed things that I've already intuited and worked out from what I know. It's good to know that it was pretty much entirely correct since things I intuit are sometimes wrong.
The only thing I'm not clear on is the interchanged use of vapor pressure and evaporation rate. My understanding is that they're not the same and that one of them can be affected by pressure. I'll have to look it up to see.

[XsmaelTheBest]

I'd like to also understand how does wind or airflow cause evaporation. On a molecular level like you explained here and comparison with evaporation by temperature

[triffidhunter]

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

[tedarcher]

Your illustration is wrong at the beginning. If a molecule needs 10 quanta to break all bonds and has 11, it will have 1 left after evaporating. That's why water misters cool the air.

[उस्तादGaming-mq]

@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.