Lecture 4: Introduction to evaporation and latent heat
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- Опубліковано 9 лют 2018
- UPDATE: I'm making materials available for all of my lectures on my website (melstrong.org) for either those bored folks stuck at home due to the virus or teachers looking for online content. For this lecture I have an experiment that you might be able to conduct at home, plus some written questions regarding evaporation and latent heat. With answer key.
This was originally part of the Blue Planet lecture series at the University of New Mexico. If you are interested in weather, this lecture is now part of my "weather short course" playlist, where there are another ~15 videos similar to this one.
I am a pilot and these weather courses are so incredibly useful. You are helping far more people in many more ways than you may know
These lectures are helping me *a lot* with studying for a basic meteorology/weather exam I've had a grand total of 2 days to prepare for. You explain things so intuitively, never skipping over a subject or concept thinking the listener is already familiar with it, and you repeat things over and over and don't make them sound more complicated than they have to be. It takes the pressure off from trying to _memorize_ each term just for the sake of passing the exam, and instead focuses on the conceptual understanding of what's actually going on which is a much better way to study imo... This is a great way to teach (and to learn!), so thank you for being so good at it haha.
Mel Strong you have been blessing for me, such a clear basics concepts for climate change student. Thank You!
I'm from Brazil and I fully understand what you say. You speak so clear! Thank you for the classes, I'm understanding much better the world around me
Thanks I'm glad you are getting something out of these!
This is be best and clearer explanation I’ve even had about latent heat. THANK YOU!!!
I'm hooked with these videos. I understand more of the weather in general thanks to your intuitively video classes. It has even made me understand why the raining days, clouds and the sun has not come out for a few days when planning outdoor activities and, not to take it by bad luck. Thanks for sharing this weather knowledge sir.
Thank you a million times over! Truly. You are a very clear explainer/speaker.
Hi! I just want to let you know that I have been LOVING your videos. This is not my field but I am very intrigued by weather and the skies and nature around me and I have found most material to be dry and not exactly what I want to watch or read after a day of work, but your videos check every box for me. You are an incredible teacher, straight to the point yet providing enough pertinent examples for understanding, your tech setup is ideal (video, image, sound, etc), and of course, your lovely cats make me immensely happy :) Thank you for sharing this with people like me, who otherwise might not get to learn about all of these wonderful things!
Thank you very much! I really appreciate that you took the time to write such a long comment. It is very nice for me to read after a hard day! The kitties send their love...
Glad you enjoyed my comment!!! It is nice to get feedback, I get it. I am currently in my end-of-semester at school in something else but I am devouring these in my free time. I have been sharing snippets with my friends, too - things I find very cool, or bits that made me laugh. They are enjoying the cats as well :)
Wow! Im really enjoying your videos Mel. Im 53 and learning about the weather. Your explanations make the science easier to understand and you are a natural born teacher. Thank you for enriching the world with your knowledge.
I am amazed by the way You explain it, Thank You so much
I live in central Arabia, one the driest areas in the world where RH in summer in 10-20% range, evaporative coolars are working very good especially if mixed with AC (you cannot rely on evaporative cooler only if temperature around 48 C or 122 F)
Sometimes we get humid weather in the middle of summer, I can tell that the weather outside is humid when I notice the evaporative cooler is barely cooling.
Thank you professor Mel for your intereting lectures
Beautifully well explained!!! 😆
I'm so glad I found your video about weather! Your a great teacher and I look forward to learning more. Thanks for taking the time to make these. Its much appreciated Mel!
Thanks I hope you are learning something. Almost nobody watches this one...I guess latent heat sounds boring to people...
Very informative and interesting, thanks!
Hello from rainy England! For the last two years I've been studying for the 13 professional flying exams and now just have two subjects left, Meteorology and General Navigation. I must have watched hundreds of different educational youtube creators over the last 24 months but none come close to the standard of your videos Mel. They are so so good, and I think thats an understatement. Thankyou!
Thank you Sir, Very well explained.
Australians used to have a device called the Coolgardie safe which used the same principle as the swamp cooler. A wooden box with hessian or burlap layers that were kept wet. Evaporation cooled the box and your meat, butter and the like would stay cool. Good 'ealth, John Warner. Australia
Great explanation! Thanks 🙏
Great series of info. THANKS! Swamps cooler are used in the part of the country were there are no actual swamps - Have to laugh at the English language.
Amazing lectures,greetings from Belarus
Love this lecture series! Down south of Abilene Tx we used evaporative coolers in our farm house- worked very well here too, and easier on electricity and environment. I grew up near the gulf, doubt it would work there. Even a/c units had a tough time there.
I'm quite surprised they would have worked at all in Abilene!
Your lectures are wonderful, at last I am beginning to understand the weather. Thank you
Thank you glad they are helpful!
The cat makes me want to learn it all... best teaching!
Beautiful explanation brother 😍😍😍
Binge-watching your videos for acing my qualifier exams! Thanks a ton!
If you failed....I refuse to be held accountable....LOL
@@MelStrong hahahahha :D
Nice and wonderful explanation..
I have an exam tomorrow on weather and climate. I haven’t studied enough and today the anxiety is high. This playlist is very good, I understand things I hadn’t before and it’s good to take it all from the beginning. Probably going to have to re-do the exam after Christmas, so this will probably be my December playlist 😅 I’m doing a candidate in biology, which includes some geology courses and I’m sooo lost.
Are you sure it's anxiety? Being nervous before a big exam is normal. I'm generally curious how the majority of humans suffer from anxiety now. 30 years ago it's was just referred to as being "nervous" about something or other and it helped us grow by facing these challenges. Saying you have "anxiety" seems like a trend and it's cool to say you suffer from something. All I am saying is that you are a lot stronger than you think you are. It's all in your head. You are not a victim. No more crying about it. Stay strong push through it and you will be proud of yourself later. Good luck to you.
@@joshntn37111 it sounds like you are blessed with a life without much anxiety, which is a good thing. There is a big difference between nervousness and anxiety, and I know it well. I mean anxiety when I say it, and I’m not going to go into more detail than that about my mental health with a stranger on the internet.
Great lecture! Thanks
Thank you so much, you are great!
nice work buddy. keep it up
Now after I watched this video I understood why ice has less density than liquid water.
Because in ice the molecules has less vibration but have high distance between each other than liquid water.
Yes the crystalline structure of ice has more 'open space' than the liquid
For deciding where to use evaporative coolers, the best map would be one that weights humidity toward the warmest days. However, at the same time, I would not expect that distinction to significantly change the threshold of decision.
Thanks again for these excellent lectures! Four decades ago I had learnt thermodynamics at universty. I wish, I have had a professor like you at that time. Now I am learning just for fun and not to get my graduation. 👨🏼🎓
NIIIIIIIIIICE STUFF... THANKS
Thaaaaaaanks
This presentation made me think about something I never considered before. Suppose you have a cup of water sitting outside, and the relative humidity is exactly 100%. There will be no net evaporation at all. Does that mean that cup of water will just sit there forever, and the amount in the cup will never change? I don't think so. That would be too neat. Water molecules will be constantly escaping from the cup, and others will be condensing into the cup. As many molecules must condense as there are evaporating. But I don't think the condensation will all be into the cup. Gradually, the cup will lose water, but there will be condensation around the cup. I expect the cup to eventually be empty, and there will be a pattern of condensation around the cup. The condensed water will eventually spread more and more, as time goes on, until no drops can be detected anywhere, because the water has spread too widely. But just how this proceeds will be governed by some physics that could get quite complex.
Does anyone have a quantitative analysis of this kind of thing?
A cup of water at 100%RH will not evaporate, but there will be constant exchange of water molecules with the atmosphere. If you had a way of labeling each water molecule in your cup, you would notice that over time your original water molecules have been leaving and new ones have joined. This type of experiment can be done with stable isotopes, where the isotopic composition of water in the cup starts out different than the composition of the water vapor in the atmosphere. Over time the isotopic composition in the cup will approach that of the atmosphere. The rate at which this happens depends on temperature.
@@MelStrong I still say the water in the cup would slowly disperse over the surrounding environment, just due to entropy. If all the water in the cup were to stay the same forever, I think I'd consider that as evidence that maybe I really am living in a simulation.
What is the difference when dew is formed and fog is formed?
Sorry, maybe i am not fully connecting the dots, but why is relative humidity correlated with the evaporation rate?
At 100% relative humidity, each water molecule that enters the air must be balanced with one molecule that is removed from the air - because the air is at saturation. So a puddle of water that sits in air of 100% RH will never evaporate. At the extreme opposite, if you had a puddle of water sitting in air of 1% RH, there would be a huge flux of water molecules leaving compared to those entering, and the puddle would be evaporating rapidly.
So no concept of thermodynamics for students at this level? Unfortunate.