wow u have 30 likes rn lol I would like this comment but I dont want to ruin the 30. If you lose or get a like ill like it but dont forget to reply to this comment or I wont remember ;)
I know this is an older video, but it was new to my 4th grade Science students. They loved it! Your videos are a regular part of my lessons and I wanted to let you know how much we love you and your content.
Hypothesis on soapy bubbles in the coffee: Coffee 🍵 (& oil based paint 🎨!) is a naturally oily liquid. Soap washes grease from skin and other surfaces by trapping the grease in little bubbles and allowing the water to rinse off the soap-trapped oils where water doesn't mix with oils naturally (over-simplification without going into chemistry diagrams). The soap (or soapy film) must be trapping the oils of the coffee into bubbles temporarily which then roll across the surface of the oily coffee bean steeped water. An interesting experiment to test this would be experimenting with different concentrations of coffee steep and seeing if the affect is made more dramatic when more oil is present in the liquid. My thoughts. Thank you for filming!
Ha les tensions de surface, c'est vrai que c'est marrant, j'imagine déjà une future vidéo e-penser en français cette fois sur le sujet en élargissant peut-être à ce qu'on peut observer dans la nature (les insectes qui marchent voire même courent sur l'eau par exemple). Enfin je dis ça, je dis rien :P
C'est vrai que c'est génial et me fait même penser aux expériences du Dr Nozman en France. Par contre je comprends pas grand chose >< vu mon niveau de compréhension orale
Huge improvement in video quality! Camera Upgrade? If so, what kind did you get? I've been looking into cameras lately... super expensive and I'm kind of at a loss on what I should get. It's a lot of money to spend on potentially the wrong camera. Unfortunately, I have no one around here that can help even with good suggestions. P.S. Good video :-) I've only tried some of these myself. I'll have to try the others soon.
Hello Diana- Love your work! Thank you! 2 comments about your surface tension vid...you can do the screen over the jar with just a square of screen held over the mouth of a drinking glass just like you do with a paper. No need to attach it with the lid. Just make sure that the screen is only a bit larger than the diameter of the glass and that it is quite flat, not bowed. And...make a paperclip holder out of another paper clip to place the first one on the surface tension of the water. To do this, unfold a paperclip and bend the ends to make 2 parallel "arms". Place the place the new paperclip onto the arms and slowly lower it into the water., and,...shaboom! The unbent clip will float on the surface tension. I have found that the metal clips work just as well with this method as do the plastic-coated clips! Happy Science-ing! (yes...I stole it form you. I'm not proud about it, but there it is.) -Ian
In Fluid Mechanics, there's a dimensionless number that measures the importance of Surface Tension relative to Gravitational Forces, it's called the Bond Number. A very high Bond Number means that Surface Tension is not important. A low Bond Number (lower than 1) means that Surface Tension dominates. This is what happens with small bubbles of fluid because Bond Number is proportional to the square of the characteristic length in the geometry.
About soapy droplets: aip.scitation.org/doi/abs/10.1063/1.2335905?journalCode=phf If there are capillary waves then air cushion below droplet is replenished. Surface tension makes wavelength longer : en.wikipedia.org/wiki/Capillary_wave. So tiny vibrations keep replenishing the air cushion below the droplets.
For the second experiment, I might have an idea. I did a bit of research on that and found that soap contained some oils. But since soap seems to mix with water, I tried to find out how oil mixed with water. After some research (which is a few minutes of googling) I found that if you put detergent/soap into water, it is attracted to both oils and water, so it can help them combine to help form something called an emulsion. But that didn't explain why there were those circles floating on top of the water. So I though maybe by flicking something onto the surface, you could separate the water and the oils inside the soap again, so the oil would float on top. But then the detergent/soap would combine the two liquids once more. It may be a long explanation, but that was what I found. Hope it helped!
I use a Chemex pour over to make my coffee in the morning. As the last bits of coffee fall out through the filter they make those spheres on the surface of the water and skid around for a while before plopping into the coffee (I usually watch it for a minute or too). I only wash the Chemex with soap about once every two weeks so I have a feeling that the effect is possible with only coffee. I wonder if the freshness of the coffee changes the effect-- as I grind decently fresh roasted beans-- and whether or not the cream/milk you added to it changed it at all. Regardless, these were all neat demos, and I guess I have more to think about when making coffee. Thanks!
If you have soap in a polar liquid (like water and by extension coffee) the unpolar part of the soap molecules will point outwards because the polar parts "want to be in the water". So you have a hydrophobe layer on top of the coffee. My guess is that the bubbles are basicly soap bubbles that are created by the stirring and have their polar sides on the outside, so that the unpolar film on the coffee rejects the bubble.
Well, I think +TheNerubin is correct in calling them soap bubbles in the #coffeee. +axxization: a minor correction: Micelles are (strictly defined) soap-water interface structure (www.dataphysics.de/2/start/understanding-interfaces/basics/surfactants-and-critical-micelle-concentration-cmc/) while bubbles are soap-water mixtures with air interface (en.wikipedia.org/wiki/Soap_film), more like the coffee. @PhysicsGirl is AWESOME.
The last one is actually the Leidenfrost effect. The pan is so hot that during the impact, a vapor layer is formed between the droplet and the pan, which makes it possible to "levitate" the water droplet. The droplet and the pan don't have any contact. Pretty amazing! Nice video!
Oh God, I've discovered #2 last year while drinking coffee as well! I've wondered for a bit about it, thought it has something to do with surface tension but that's where my knowledge and resources ended. I got so excited when I saw it on your video! Hopefully answers will come!
Very nice. You should try touching the underside of the screen on your inverted jar with the soapy Q-tip. Interested to see how quickly it pours out. Or maybe it doesn't- perhaps the water that beaks out where the surface tension is broken takes the soap away and then it's stable again. Or maybe the vacuum sucks up air where the surface tension is broken and thereby mixes the soap through all the water and it all runs out. I'd love to know which but don't have a bit of screen.
your coffee-soap demo is due to you mechanically lifting small amounts of the coffee surface which has the hydrophobic ends of the soap molecules at the coffee to air interface so when a drop falls from the stirrer it is a drop of coffee with a "coating" of the hydrophobic ends around it, when it falls back to the coffee in the cup electrostatic repulsion keeps the drops "floating" on the surface.
This is a great series of experiments that are more about observation than trying to explain things. Observation is what initially motivates working scientists and the rest is a lot of hard work trying to figure out what's going on that eventually results in an exciting explanation that maybe nobody knew before. But first, you have to hook a potential scientist and this set of activities does the trick. There's evidence to support that in the other comments here. Thanks, Physics Girl! Another awesome job!
From 0:43 to 0:48 notice that the larger bubbles absorb the smaller bubbles: the air pressure in the smaller bubble is larger, pushing air from the smaller to the adjacent larger bubble (through the membrane separating them). See Discrepant Balloons by FlinnScientific. The same happens to connected soap bubbles (see my "Unit 5 Fluid Experiments" at 5.40 min) and to the foam bubbles on top of carbonated drinks.
The pressure changes caused by the stick causes sudden waves and displaces the molecules in the uppermost layers of the film since they are relatively loosely bound as compared to those in the lower layers.These molecules are consequently replaced by the molecules from lower layer. The molecules form their own spheres due to surface tension which float over the film and move in the direction of net resultant waves.
I am unable to find my brain after i saw your last experiment .....1 . amazing 2. mindblowing 3.fantastic hoping for more new videos from the best youtube channel
+1 for "penny dropper" hahaha. I do have one question; if soap breaks the surface tension, why does the addition of soap *allow* you to make bubbles? It would also be cool to talk about the vapor barrier created on the hot pan and how the air is a less efficient conductor of heat (so it remains in a liquid state). Great video, but more science is always better! :)
Cool video! I was doing a poster on surface tension and had never seen the water upside down trick done with a screen before. I tried it out and it worked! Really cool. Also tried floating paper clips on water. Then i put a soapy cotton swab in and the paper clip sank, just like it is supposed to. BUT when i tried the water upside down experiment with soapy water or poking a soapy needle into the screen, it still worked. Even with more soap mixed in the water, then turning it upside down, it still worked. Shouldn't the lowered surface tension cause the water to spill? Maybe the air pressure difference still plays the bigger role than the surface tension in this experiment? I could try it again with alcohol mixed in the water, that should also not work.
Pretty awesome stuff! I'd seen a few before, but others were new to me... Would love a video on what surface tension is, and how those experiments actually work. Also, how soap affects the tension in the water.
The only thing I could possibly imagine happening as far as the "antibubbles" is that when you put soap in the drink you create and incomplete hydrophobic layer across the top. The ball stays on top until it finds a hole in the hydrophobic layer then falls through. It lasts longer when you have a lot of motion because it's harder to find a hole. I could be wrong but that's using my education as far as organic two. And my bio classes thus far. I thought the penny trick was interesting I thought I was the only one that found that cool I did it all the time as a kid. Anyway as a new subscriber great videos!!! It makes me slightly less apprehensive about physics next semester. Thank you so much.
When I was a about 12 I was sitting in a row boat on a slow moving river and my nose started to bleed. I hung my head over the side of the boat and the drops of blood landed on the water and formed small balls on the surface, like those on your coffee, The drops of blood drifted away from the boat and after a while burst, at which time they disolved into the river. It was a fascinating moment.
perhaps the motion of the drops plus the internal fluid dynamics keep the drops from breaking the surface tension of the original fluid? maybe the flick of the straw keeps the drop moving on the inside fast enough? awesome videos keep up the great work!
Hi there, thanks for these experiments, I've tried them all and they've all been very interesting in helping understanding how surface tension works. Couple of questions on the milk one though: 1) how many attempts did you do before a perfect one like the one in the video showed up? 2) how deep was your plate? Is it correct my assumption that the more shallow the better? 3) and this is the most important: why milk? My only guess is that food coloring tends not to mix with milk, unless you stir it, and it's quite visible, way more than in water. But apart from these reasons, milk has fats, which I've read somewhere are supposed to lower the surface tension, so the effect should be less visible than in water. Any help? Thanks!
0:30 Попробую объяснить по-русски :когда ты резко прикосаешься трубочкой к поверхности кофе воздух по инерции опускается под воду плюс он имеет кинетическую энергию , направленную в бок, поэтому когда ты поднимаешь трубочку пузырь движется под водой паралельно( приближенно)плоскости данной поверхности ,сила Архимеда стремится выталкнуть его наружу но сила поверхностного натяжения не даёт это сделать,таким образом и объясняется данное явление,причем в обычным кофе сила натяжения настолько большая,что пузыри крайне нестабильны и сразу лопаются( that was russian) i think you wouldn't expect to see russians here ,i can understand english clearly but I can't write it so yeah if you have some questions - write me them ,kirill kasimov ,russia ,15 years old)
Bro let me tell you the secret of last one That was because when water hit the hot surface the first little of it immediately vapourised.Now when other drops fall on the small amount of vapour. The vapour started trying to get up because it is lighter than water. Thus the small amount of vapour makes the water dance on hot surface.
I just have to say, your videos are amazing and i love them. When i saw the email that said you had this video i was so happy, but sad because i couldn't watch it, because i had to take a quantum mechanics quiz (Which also made me happy)! :)
Thanks a lot Dianna!! I really appreciate your interest and enthusiasm to teach science in a very interesting way. I just love your videos.. Waiting for more of them.
Hey! With respect to the coffee experiment. I think the soap is concentrated at the top of the coffee, forming a layer (or part of a layer, depending on how much soap you ingested haha), and in the layer the non-polar ends are pointing up. When you steer it, you curve the layer, and if you steer it faster you may create little drops of coffee. These drops will be surrounded by a layer of soap with the non-polar ends pointing outward. These effectively 'repel' the water outside of the drop and the drop rolls around as if it were a hydrophobic surface. Then I guess instabilities in the shape of the droplet grow, until the area of the drop is more than the area that may be covered by a layer of soap. When a "non-protected" part of the drop touches the rest of the coffee, it's done. Happy physicsing! :)
in numer 2 i think the increase in surface tension makes posible to agglomerate less dense material into a sphere. And the sphere falls down when is heavy enough
Surface tension also applies to circuit board manufacturing. SMT. Surface mount technology. The solder paste is controlled during reflow (oven) to keep the liquefied short and components in place. I love Physics Girls channel. : )
Your mother is a natural with the camera. The rooster is just trying to hog your screen time. Another great video. BTW, the e-mail updates for your new vid releases work great!
The little spheres are little droplets of liquid sitting on top of the large liquid. it takes them a while to sink in due to the surface tension. you can see this as well with rain drops. they actually bounce on the surface of water several times before they actually form with it
#2 is hydrophobic water lol I did that when washing dishes a lot and have a video of it with soapy water in a bowl. I think what's happening is caused by differences in surface tension and also the soap has a polar and non polar side, so when the soapy water molecules attach, the polar end are facing inward making a bubble of water with a lipid layer on the outside, marking it hydrophobic and allowing it to float on the surface tension of the water. When those bubbles hit other non polar facing molecules it tears the barrier away and mixes together. I'm sorry if I'm not using the proper terms, but hopefully it makes sense and is at least somewhat correct. lol
My thoughts, for the spheres ontop of the slightly soapy water, is that the soapy film on the surface of the water, would likely have its hydrophobic end (oily end) pointing away from the water below. When you flick the surface you might be flicking some pure water from below the soapy film which will then sit ontop this hydrophobic (oily) layer. Therefore the tiny droplets of pure water would try and maximise its interaction with itself (i.e. form little balls) rather than spread out over the hydrophobic (oily) layer. Eventually the droplet would What I'm not sure of is why stirring the water would make these little droplets last longer (and one would imagine that stirring would break the hydrophobic layer and intermix the soap film with the water below). One other possibility, considering that both of the examples you showed contained milk (the coffee seemed to have milk in it!), that it instead might have something to do with the folding of the milk proteins (which presumably may have different folding in a hydrophobic and hydrophillic environments). I tried to reproduce the experiment using water + detergent (specifically Fairy liquid and a hand soap) and milk + detergent. In the water I wasn't able to get anything like spheres that you observed, in the milk + detergent I believe I was (though it was hard to tell due to the lack of contrast). There could also be a temperature dependence and liquid : detergent relative composition dependence. So, I guess my question would be: Do you see it in coffee without milk? Do you see it in water without any coffee or anything like that? (if yes then it is nothing to do with the proteins in the milk). As you heat the liquid + detergent does it become easier or harder to make these spheres (higher temperatures lead to lower surface tensions, and should also increase the dissolving of the soap into the water / milk), similarly can the same thing be achieved with an oil (e.g. cooking oil) - soap will lower the surface tension of the water, oil shouldn't affect the surface tension as they do not intermix (to test whether it is the hydrophobic layer or the effect on surface tension that is causing this). Perhaps going even further and looking at acetone mixed with hexane (very polar and very non-polar solvents) or even better dimethyl sulfoxide and hexane (massive difference in density) to see if you can get the same effect.
David Duncan This effect has been observed in fluids other than those containing milk. Indeed even in distilled water: www.ncbi.nlm.nih.gov/pmc/articles/PMC3208511/ As previously linked by Saṃdīp Īśa.
You can also create #2 using a water filtering bottle. Mine is the Brita brand, and if you watch water drop from the filter to the surface, small round drops of water will bounce around if the surface of the filtered water is close enough to the filter outlet.
With the coffee, can I ask if you handwash your crockery? I noticed alot of things that come out of a dishwasher (most likely like at your local cafe) still have soap residue left on them...you can see if it you rinse with higher pressure water as all the bubbles quickly rise, and then rinse off after a few seconds - easier to get off with hot water. So i'm thinking that maybe you either have a dishwasher that has a really good rinse cycle, or you wash by hand (I don't think the normal dish soaps are anywhere near as harsh as the dishwasher tablets)...so it rinses better, so doesn't end up in your coffee/cereal. Maybe....
I would say the spheres on the coffee are either air bubbles or a water droplets floating on the liquid. I've noticed it while having water pour from a faucet onto water in the sink. On closer inspection I remember determining that they were just weird bubbles, but yours look like actual liquid drops on the surface of the coffee so I don't know.
#5 I use a second paper clip (which I bend) to place the floating paper clip onto the surface. That way my hand's natural trembling (amplified by being nervous in front of my students) doesn't affect the positioning as much.
Usually the soap bubbles we see has air on the inside in a soap water container floating in the air . But the ones you made has soap water on the inside but in a container of air and floating in the water .
Spheres in the coffee cup (+ little bit of soap) experiment is in fact anti-bubble. These anti-bubbles jump and move on the parent surface. Researchers are trying to understand the behaviour of wave and particle motion by oscillating the parent liquid. There is a nice video on this though I don't remember the link. I forgot to thank you for nice demos. Cheers.
I think that the bubbles form because the soap and coffee have a higher concentration making it heavier and when you flick it you get air into it but the soap holds it thus because it's lighter it sits on top of the solution
I know this video was posted almost a year ago, are the droplets on the coffee not just a sign of a dirty cup? residue dishwashing liquid or grease could create a film on the top of the drink right?
Okay, so the one with the jar was really awesome, I actually sat here with my mouth open :D do you know how big the mesh holes can get before the surface tension isn't strong enough to hold the water...?
I think the little balls that formed when you added soap are there because soap is like blowing bubbles they are similar substances in that they both trap air that's why it's soap is so sudsy so when you're mixing it in air was getting trapped underneath the little droplets of coffee
If the coffee/water is vibrating, drops of water/coffee can remain in droplet form. When you played around with the coffee, you were creating vibrations in it, so to speak. So if you put speakers under a water container, the droplets will stay on top of the water permanently, until they clump up and get too heavy of course
I think I know what was in your coffee that day. Soy. Soy proteins can do the same thing as the soap in your home experiment.
and also some kinds of oily flavours (like the ones on starbucks)
yeah, i noticed it in my tea too just today. maybe the temperature helps with that?
Thank goodness I haven’t drank soap for years.
Or any other kind of emulsifier
If you put water or milk in very hot pan these drops appear then to
Today is my first day as a Teacher's Assistant and I'm sharing some of these experiments with the students. Thank you so much! This video was fun!
I asked my mom for adult supervision to try this. All she said was you're 30!!!
wow u have 30 likes rn lol
I would like this comment but I dont want to ruin the 30. If you lose or get a like ill like it but dont forget to reply to this comment or I wont remember ;)
Emperor Kosi peep peep like bait
now you have a stack of likes
@@kidskpadonou894 okay, like now
What? Why talk about age??
crisp and clear video which has no irritating intro and wast of time
hats off!!!
I know this is an older video, but it was new to my 4th grade Science students. They loved it! Your videos are a regular part of my lessons and I wanted to let you know how much we love you and your content.
Hypothesis on soapy bubbles in the coffee: Coffee 🍵 (& oil based paint 🎨!) is a naturally oily liquid. Soap washes grease from skin and other surfaces by trapping the grease in little bubbles and allowing the water to rinse off the soap-trapped oils where water doesn't mix with oils naturally (over-simplification without going into chemistry diagrams). The soap (or soapy film) must be trapping the oils of the coffee into bubbles temporarily which then roll across the surface of the oily coffee bean steeped water. An interesting experiment to test this would be experimenting with different concentrations of coffee steep and seeing if the affect is made more dramatic when more oil is present in the liquid. My thoughts. Thank you for filming!
The thing I find most fascinating about surface tension is how, at small scales, the major force acting on life is not gravity, but surface tension.
niiiiiice...
Ha les tensions de surface, c'est vrai que c'est marrant, j'imagine déjà une future vidéo e-penser en français cette fois sur le sujet en élargissant peut-être à ce qu'on peut observer dans la nature (les insectes qui marchent voire même courent sur l'eau par exemple). Enfin je dis ça, je dis rien :P
C'est vrai que c'est génial et me fait même penser aux expériences du Dr Nozman en France. Par contre je comprends pas grand chose >< vu mon niveau de compréhension orale
Hehe pas mal!
C'est pas mal la réactions des liquides.
Sinon tu feras une vidéo sur les liquides non newtoniens? C'est drôle comme truc ;)
Loïck Del Heureusement elle utilise un vocabulaire simple.
ZEL0D Ouais mais l'anglais à l'oral j'y arrive pas. Autant à l'écrit ça va bien mais l'oral...
Huge improvement in video quality! Camera Upgrade? If so, what kind did you get? I've been looking into cameras lately... super expensive and I'm kind of at a loss on what I should get. It's a lot of money to spend on potentially the wrong camera. Unfortunately, I have no one around here that can help even with good suggestions.
P.S. Good video :-) I've only tried some of these myself. I'll have to try the others soon.
***** Heya. Nope, still using the same camera from the last year or so. It's a Canon 7D. I've just gotten better at using it lately. :)
Physics Girl Nice! :-) Super expensive camera, although not too far off from what I was figuring I'd have to spend.
The Science Asylum great
Hi crazy
You are great Science Asylum
Love your explanations.
Hello Diana-
Love your work! Thank you!
2 comments about your surface tension vid...you can do the screen over the jar with just a square of screen held over the mouth of a drinking glass just like you do with a paper. No need to attach it with the lid. Just make sure that the screen is only a bit larger than the diameter of the glass and that it is quite flat, not bowed.
And...make a paperclip holder out of another paper clip to place the first one on the surface tension of the water. To do this, unfold a paperclip and bend the ends to make 2 parallel "arms". Place the place the new paperclip onto the arms and slowly lower it into the water., and,...shaboom! The unbent clip will float on the surface tension. I have found that the metal clips work just as well with this method as do the plastic-coated clips!
Happy Science-ing! (yes...I stole it form you. I'm not proud about it, but there it is.) -Ian
In Fluid Mechanics, there's a dimensionless number that measures the importance of Surface Tension relative to Gravitational Forces, it's called the Bond Number. A very high Bond Number means that Surface Tension is not important. A low Bond Number (lower than 1) means that Surface Tension dominates. This is what happens with small bubbles of fluid because Bond Number is proportional to the square of the characteristic length in the geometry.
About soapy droplets: aip.scitation.org/doi/abs/10.1063/1.2335905?journalCode=phf
If there are capillary waves then air cushion below droplet is replenished. Surface tension makes wavelength longer : en.wikipedia.org/wiki/Capillary_wave. So tiny vibrations keep replenishing the air cushion below the droplets.
For the second experiment, I might have an idea.
I did a bit of research on that and found that soap contained some oils. But since soap seems to mix with water, I tried to find out how oil mixed with water. After some research (which is a few minutes of googling) I found that if you put detergent/soap into water, it is attracted to both oils and water, so it can help them combine to help form something called an emulsion.
But that didn't explain why there were those circles floating on top of the water. So I though maybe by flicking something onto the surface, you could separate the water and the oils inside the soap again, so the oil would float on top. But then the detergent/soap would combine the two liquids once more.
It may be a long explanation, but that was what I found. Hope it helped!
The last one we have always seen , while making “dosa” in India 😂
😂😂😂yes
Yasss😂
Yea
😂😂😂😂😂😂
I use a Chemex pour over to make my coffee in the morning. As the last bits of coffee fall out through the filter they make those spheres on the surface of the water and skid around for a while before plopping into the coffee (I usually watch it for a minute or too). I only wash the Chemex with soap about once every two weeks so I have a feeling that the effect is possible with only coffee. I wonder if the freshness of the coffee changes the effect-- as I grind decently fresh roasted beans-- and whether or not the cream/milk you added to it changed it at all. Regardless, these were all neat demos, and I guess I have more to think about when making coffee. Thanks!
If you have soap in a polar liquid (like water and by extension coffee) the unpolar part of the soap molecules will point outwards because the polar parts "want to be in the water". So you have a hydrophobe layer on top of the coffee. My guess is that the bubbles are basicly soap bubbles that are created by the stirring and have their polar sides on the outside, so that the unpolar film on the coffee rejects the bubble.
TheNerubin That is what I was thinking, but you said it better than I could. Kuddos!
+TheNerubin It's called forming micelles.
Well, I think +TheNerubin is correct in calling them soap bubbles in the #coffeee. +axxization: a minor correction: Micelles are (strictly defined) soap-water interface structure (www.dataphysics.de/2/start/understanding-interfaces/basics/surfactants-and-critical-micelle-concentration-cmc/) while bubbles are soap-water mixtures with air interface (en.wikipedia.org/wiki/Soap_film), more like the coffee. @PhysicsGirl is AWESOME.
Exactly
what about the fact that they only stay while moving and pop when they stop?
Thanks so much for creating and sharing this educational and entertaining video.
I hope that each day you are feeling better than the day before 🙏
I love all your videos, they're great. It's such an important thing to be doing: making learning about science entertaining.
The last one is actually the Leidenfrost effect. The pan is so hot that during the impact, a vapor layer is formed between the droplet and the pan, which makes it possible to "levitate" the water droplet. The droplet and the pan don't have any contact. Pretty amazing!
Nice video!
For 2, the soap decreases the surface tension to allow "thicker" bubbles to form, which can hold more opaque compounds such as lactose or cocoa.
Oh God, I've discovered #2 last year while drinking coffee as well! I've wondered for a bit about it, thought it has something to do with surface tension but that's where my knowledge and resources ended. I got so excited when I saw it on your video! Hopefully answers will come!
Nice channel, very cool stuff. I've created the water spheres you did in your second demo using acoustic disturbances in one of my own videos.
Welcome to the internet.
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cody ko
Very nice. You should try touching the underside of the screen on your inverted jar with the soapy Q-tip. Interested to see how quickly it pours out.
Or maybe it doesn't- perhaps the water that beaks out where the surface tension is broken takes the soap away and then it's stable again.
Or maybe the vacuum sucks up air where the surface tension is broken and thereby mixes the soap through all the water and it all runs out.
I'd love to know which but don't have a bit of screen.
Cool video! Studying for my chemistry test and found this. Cool video and sure as hell made this a lot more interesting than my Chemistry teacher.
your coffee-soap demo is due to you mechanically lifting small amounts of the coffee surface which has the hydrophobic ends of the soap molecules at the coffee to air interface so when a drop falls from the stirrer it is a drop of coffee with a "coating" of the hydrophobic ends around it, when it falls back to the coffee in the cup electrostatic repulsion keeps the drops "floating" on the surface.
This is a great series of experiments that are more about observation than trying to explain things. Observation is what initially motivates working scientists and the rest is a lot of hard work trying to figure out what's going on that eventually results in an exciting explanation that maybe nobody knew before. But first, you have to hook a potential scientist and this set of activities does the trick. There's evidence to support that in the other comments here. Thanks, Physics Girl! Another awesome job!
From 0:43 to 0:48 notice that the larger bubbles absorb the smaller bubbles: the air pressure in the smaller bubble is larger, pushing air from the smaller to the adjacent larger bubble (through the membrane separating them). See Discrepant Balloons by FlinnScientific. The same happens to connected soap bubbles (see my "Unit 5 Fluid Experiments" at 5.40 min) and to the foam bubbles on top of carbonated drinks.
Good to see how the channel is growing.
My absolute best regards for filming to Mom.. Great job there.. Salute! :)
All your videos are fascinating and fun! Thanks for helping me love physics even more! I hope you feel better soon
The pressure changes caused by the stick causes sudden waves and displaces the molecules in the uppermost layers of the film since they are relatively loosely bound as compared to those in the lower layers.These molecules are consequently replaced by the molecules from lower layer. The molecules form their own spheres due to surface tension which float over the film and move in the direction of net resultant waves.
I am unable to find my brain after i saw your last experiment .....1 . amazing
2. mindblowing 3.fantastic
hoping for more new videos from the best youtube channel
the last experiment was mind bending!!!! thumbs up!
Can I know the reason for the last experiment's observation?
i discovered your chanel with E-penser. You are doing a super job. I'm going to improve my physics and english knowledges with you.
I love this channel. That is all.
Hi are u alive
+1 for "penny dropper" hahaha.
I do have one question; if soap breaks the surface tension, why does the addition of soap *allow* you to make bubbles? It would also be cool to talk about the vapor barrier created on the hot pan and how the air is a less efficient conductor of heat (so it remains in a liquid state). Great video, but more science is always better! :)
Thank you for doing the experiments in such a lovely way
Cool video! I was doing a poster on surface tension and had never seen the water upside down trick done with a screen before. I tried it out and it worked! Really cool. Also tried floating paper clips on water. Then i put a soapy cotton swab in and the paper clip sank, just like it is supposed to. BUT when i tried the water upside down experiment with soapy water or poking a soapy needle into the screen, it still worked. Even with more soap mixed in the water, then turning it upside down, it still worked. Shouldn't the lowered surface tension cause the water to spill?
Maybe the air pressure difference still plays the bigger role than the surface tension in this experiment? I could try it again with alcohol mixed in the water, that should also not work.
This channel's growing! So exciting :D
Pretty awesome stuff! I'd seen a few before, but others were new to me...
Would love a video on what surface tension is, and how those experiments actually work. Also, how soap affects the tension in the water.
Thanks for these. They'll help me plan experiments for home education group next week.
Making a point to watch every Physics Girl video that comes up in my stream. Hoping you get better soon!
So glad I fell into this! Informative and funny! ❤
The only thing I could possibly imagine happening as far as the "antibubbles" is that when you put soap in the drink you create and incomplete hydrophobic layer across the top. The ball stays on top until it finds a hole in the hydrophobic layer then falls through. It lasts longer when you have a lot of motion because it's harder to find a hole. I could be wrong but that's using my education as far as organic two. And my bio classes thus far. I thought the penny trick was interesting I thought I was the only one that found that cool I did it all the time as a kid. Anyway as a new subscriber great videos!!! It makes me slightly less apprehensive about physics next semester. Thank you so much.
When I was a about 12 I was sitting in a row boat on a slow moving river and my nose started to bleed. I hung my head over the side of the boat and the drops of blood landed on the water and formed small balls on the surface, like those on your coffee, The drops of blood drifted away from the boat and after a while burst, at which time they disolved into the river. It was a fascinating moment.
OMG thank you so much I really needed this video for a science experiment I am analyzing. THANK YOU!!!!!
soo awesome...m definitely gonna try these experiments in an upcoming science fair. Thank u so much wonder girl!! Oops i mean physics girl :)
perhaps the motion of the drops plus the internal fluid dynamics keep the drops from breaking the surface tension of the original fluid? maybe the flick of the straw keeps the drop moving on the inside fast enough? awesome videos keep up the great work!
Another great video Physics Girl! I might just have to try a few of these experiments myself sometime! :D Keep up the good work!
Hi there,
thanks for these experiments, I've tried them all and they've all been very interesting in helping understanding how surface tension works. Couple of questions on the milk one though:
1) how many attempts did you do before a perfect one like the one in the video showed up?
2) how deep was your plate? Is it correct my assumption that the more shallow the better?
3) and this is the most important: why milk? My only guess is that food coloring tends not to mix with milk, unless you stir it, and it's quite visible, way more than in water. But apart from these reasons, milk has fats, which I've read somewhere are supposed to lower the surface tension, so the effect should be less visible than in water. Any help?
Thanks!
Cool, thanks! The paperclip is awesome. But the screen holding up the water is mindbending.
wordsnwood Agreed. It's hard to believe that it actually works until you try it!
I tryed the milk firework and It WORKED!!! So cool
Wow you got a new symbol for Physics girl. Anyway when did you going to explain all these phenomenon?? Cant wait for those video. !!!
0:30 Попробую объяснить по-русски :когда ты резко прикосаешься трубочкой к поверхности кофе воздух по инерции опускается под воду плюс он имеет кинетическую энергию , направленную в бок, поэтому когда ты поднимаешь трубочку пузырь движется под водой паралельно( приближенно)плоскости данной поверхности ,сила Архимеда стремится выталкнуть его наружу но сила поверхностного натяжения не даёт это сделать,таким образом и объясняется данное явление,причем в обычным кофе сила натяжения настолько большая,что пузыри крайне нестабильны и сразу лопаются( that was russian) i think you wouldn't expect to see russians here ,i can understand english clearly but I can't write it so yeah if you have some questions - write me them ,kirill kasimov ,russia ,15 years old)
Thanks for posting. :) I needed to find the paperclip experiment and this was the only video I have found!
i was much hoping for an explanation but anyways the video was good
Bro let me tell you the secret of last one
That was because when water hit the hot surface the first little of it immediately vapourised.Now when other drops fall on the small amount of vapour. The vapour started trying to get up because it is lighter than water.
Thus the small amount of vapour makes the water dance on hot surface.
Me too
Keep up the good work!!! Love your videos!!!
Man, if back at school I had a teacher like this, I wouldn't have that much problems with physics lol
I just have to say, your videos are amazing and i love them. When i saw the email that said you had this video i was so happy, but sad because i couldn't watch it, because i had to take a quantum mechanics quiz (Which also made me happy)! :)
Noah Blacker Hope the quiz went well!
Superb prestantion ❤❤
I loved it
Thanks a lot Dianna!! I really appreciate your interest and enthusiasm to teach science in a very interesting way. I just love your videos.. Waiting for more of them.
Loved your experiments💥💥👏👏👏
Hey! With respect to the coffee experiment. I think the soap is concentrated at the top of the coffee, forming a layer (or part of a layer, depending on how much soap you ingested haha), and in the layer the non-polar ends are pointing up. When you steer it, you curve the layer, and if you steer it faster you may create little drops of coffee. These drops will be surrounded by a layer of soap with the non-polar ends pointing outward. These effectively 'repel' the water outside of the drop and the drop rolls around as if it were a hydrophobic surface.
Then I guess instabilities in the shape of the droplet grow, until the area of the drop is more than the area that may be covered by a layer of soap. When a "non-protected" part of the drop touches the rest of the coffee, it's done.
Happy physicsing! :)
Wow! Nice work!
this channel is totally awesome
in numer 2 i think the increase in surface tension makes posible to agglomerate less dense material into a sphere. And the sphere falls down when is heavy enough
Great stuff on Surface Tension.
Hi. You are such an inspiration
The water droplets in the pan at the end is so cool! but i don't understand why it works!! can you tell me Physics Girl?
Surface tension also applies to circuit board manufacturing. SMT. Surface mount technology. The solder paste is controlled during reflow (oven) to keep the liquefied short and components in place. I love Physics Girls channel. : )
oopps...typo. liquefied solder.
Your mother is a natural with the camera. The rooster is just trying to hog your screen time. Another great video. BTW, the e-mail updates for your new vid releases work great!
Glad to hear that!
Have you tried the coin one with a ring? it looks pretty cool
Love these experiments!! We tried the soap in milk effect and my son named them “soap minions”. Thought you might like that!
The little spheres are little droplets of liquid sitting on top of the large liquid. it takes them a while to sink in due to the surface tension. you can see this as well with rain drops. they actually bounce on the surface of water several times before they actually form with it
DarthMaskar the soap makes the droplets take longer to sink in as well
Nice video! The first one was fascinating!
#2 is hydrophobic water lol I did that when washing dishes a lot and have a video of it with soapy water in a bowl. I think what's happening is caused by differences in surface tension and also the soap has a polar and non polar side, so when the soapy water molecules attach, the polar end are facing inward making a bubble of water with a lipid layer on the outside, marking it hydrophobic and allowing it to float on the surface tension of the water. When those bubbles hit other non polar facing molecules it tears the barrier away and mixes together. I'm sorry if I'm not using the proper terms, but hopefully it makes sense and is at least somewhat correct. lol
My thoughts, for the spheres ontop of the slightly soapy water, is that the soapy film on the surface of the water, would likely have its hydrophobic end (oily end) pointing away from the water below. When you flick the surface you might be flicking some pure water from below the soapy film which will then sit ontop this hydrophobic (oily) layer. Therefore the tiny droplets of pure water would try and maximise its interaction with itself (i.e. form little balls) rather than spread out over the hydrophobic (oily) layer. Eventually the droplet would What I'm not sure of is why stirring the water would make these little droplets last longer (and one would imagine that stirring would break the hydrophobic layer and intermix the soap film with the water below).
One other possibility, considering that both of the examples you showed contained milk (the coffee seemed to have milk in it!), that it instead might have something to do with the folding of the milk proteins (which presumably may have different folding in a hydrophobic and hydrophillic environments).
I tried to reproduce the experiment using water + detergent (specifically Fairy liquid and a hand soap) and milk + detergent. In the water I wasn't able to get anything like spheres that you observed, in the milk + detergent I believe I was (though it was hard to tell due to the lack of contrast). There could also be a temperature dependence and liquid : detergent relative composition dependence.
So, I guess my question would be: Do you see it in coffee without milk? Do you see it in water without any coffee or anything like that? (if yes then it is nothing to do with the proteins in the milk). As you heat the liquid + detergent does it become easier or harder to make these spheres (higher temperatures lead to lower surface tensions, and should also increase the dissolving of the soap into the water / milk), similarly can the same thing be achieved with an oil (e.g. cooking oil) - soap will lower the surface tension of the water, oil shouldn't affect the surface tension as they do not intermix (to test whether it is the hydrophobic layer or the effect on surface tension that is causing this). Perhaps going even further and looking at acetone mixed with hexane (very polar and very non-polar solvents) or even better dimethyl sulfoxide and hexane (massive difference in density) to see if you can get the same effect.
David Duncan This effect has been observed in fluids other than those containing milk. Indeed even in distilled water:
www.ncbi.nlm.nih.gov/pmc/articles/PMC3208511/
As previously linked by Saṃdīp Īśa.
You can also create #2 using a water filtering bottle. Mine is the Brita brand, and if you watch water drop from the filter to the surface, small round drops of water will bounce around if the surface of the filtered water is close enough to the filter outlet.
With the coffee, can I ask if you handwash your crockery? I noticed alot of things that come out of a dishwasher (most likely like at your local cafe) still have soap residue left on them...you can see if it you rinse with higher pressure water as all the bubbles quickly rise, and then rinse off after a few seconds - easier to get off with hot water. So i'm thinking that maybe you either have a dishwasher that has a really good rinse cycle, or you wash by hand (I don't think the normal dish soaps are anywhere near as harsh as the dishwasher tablets)...so it rinses better, so doesn't end up in your coffee/cereal. Maybe....
I tutor ochem and one of the first concepts is surface tension. I like showing videos as examples of chemistry. Thanks
I love the milk fireworks one! I tried it on my own and it was so cool!
Thanks! I love seeing experiments like this!
I would say the spheres on the coffee are either air bubbles or a water droplets floating on the liquid. I've noticed it while having water pour from a faucet onto water in the sink. On closer inspection I remember determining that they were just weird bubbles, but yours look like actual liquid drops on the surface of the coffee so I don't know.
#5 I use a second paper clip (which I bend) to place the floating paper clip onto the surface. That way my hand's natural trembling (amplified by being nervous in front of my students) doesn't affect the positioning as much.
Usually the soap bubbles we see has air on the inside in a soap water container floating in the air . But the ones you made has soap water on the inside but in a container of air and floating in the water .
Spheres in the coffee cup (+ little bit of soap) experiment is in fact anti-bubble. These anti-bubbles jump and move on the parent surface. Researchers are trying to understand the behaviour of wave and particle motion by oscillating the parent liquid. There is a nice video on this though I don't remember the link. I forgot to thank you for nice demos. Cheers.
This Physics Girls is fun and delightful and interesting. More power to you, Physics Girl! :-)
I think that the bubbles form because the soap and coffee have a higher concentration making it heavier and when you flick it you get air into it but the soap holds it thus because it's lighter it sits on top of the solution
2. It is small droplet of that liquid floating above it caused by surface tension. Most of them use to be small in water ( if it's made in water).
Hey physics girl I think they are antibubble
By the way your videos are awesome and much more interesting than others thanks for making such videos
I know this video was posted almost a year ago, are the droplets on the coffee not just a sign of a dirty cup? residue dishwashing liquid or grease could create a film on the top of the drink right?
I've done the last one before..it's actually fun😁
Okay, so the one with the jar was really awesome, I actually sat here with my mouth open :D do you know how big the mesh holes can get before the surface tension isn't strong enough to hold the water...?
I don't know! I suggest trying it!
ViolettaSachra That would depend on a lot of things I think. Shape of the holes, amount of water pushing down, impurities, local gravity :p
Physics Girl You mean, doing experiments?!
Peter Bonnema
I know :D I thought maybe there was a way to calculate this..?
I think the little balls that formed when you added soap are there because soap is like blowing bubbles they are similar substances in that they both trap air that's why it's soap is so sudsy so when you're mixing it in air was getting trapped underneath the little droplets of coffee
Awesome videos!
What type of Mesh are you using?
If the coffee/water is vibrating, drops of water/coffee can remain in droplet form. When you played around with the coffee, you were creating vibrations in it, so to speak. So if you put speakers under a water container, the droplets will stay on top of the water permanently, until they clump up and get too heavy of course
I love all your vdeos, they are . always interesting and fun to try ourselves.
What kind of mesh is good for the water suspension trick?
it is the property of surface tension to have minimum surface area and hence those small spherical balls appear as sphere has the least surface area