I applied for a program for a university that I really wanted to get into and I had to write a supplementary application for admission. One of the questions was to discuss who is my favourite scientist and why he is my role model. I talked about Professor Poliakoff and how he is so passionate in learning about science everyday and I got into my program! Thank you Professor Poliakoff and Brady for being such inspirations in my life!
I always took science class in school even when it wasn't compulsory and i failed yr 12 science miserably (i was horrible at math) but i loved learning and knowing the concepts and the physics behind what happens on earth. Great video and keep it up!!!
If you read the video description (still don't understand why people don't do this as a first reaction to having a question, just /before/ commenting), you'll see that it says "From the School of Chemistry at The University of Nottingham" and includes a link to the department.
Fascinating. I've been a submarine cook for the last 12 years and I have noticed that water takes longer to boil the deeper we go. We also operate with a slight pressure on the ship. Would that also contribute to water taking longer to boil?
Hi, I have got an idea about a new chemistry series for you: can you do a weekly episode where you chronologically mention the highlights of each decade (starting at some arbitrary point, and highlighting one decade per episode). Thus, It will be a series about the history of chemistry, and how things got to where they are today. Thank you!
Not sure if you received an answer or not, but what happens is that because there is no pressure- or next to no pressure- in space, then the water boils instantaneously. But oddly, because of how cold it is in space, that now gaseous water freezes very rapidly afterwards. You can do something like this at home by boiling water on a cold winter day, then going outside and tossing it into the air. It should finish boiling and turn into snow rather quickly.
If you get below the triple point of pressure with some liquids (water in particular), you will find ice sublimating directly to water vapor without going through a liquid phase. Admittedly if the substance is already a liquid it will immediately boil in a vacuum as well, so you are somewhat correct. It is just that such liquids need to form in higher pressure locations in the first place.
What interests me in this context, is how much the pressure changes the other phase transitions. And how much difference is there from water to other fluids. I always hear that water is pretty unique in many ways.
But you also have to say that the PTC/NTC Sam is using is also not exact to the point, because every measuring instrument has a bit of failures. I also need a little help on the freezing temperature here, Because i also have seen water not frozen at -4 degrees at our place (but i have to say it was no constant cold of many days just 2 hours) and also you can see the water in the lake is rather sludgy than fluid ( i mean about to freeze) soo... please don't be too harsh :) Nice video as always!
Yes, the plate is a unique number registered to that car. Not the owner. It is possible to transfer the plate to another car but only if the plate is the same year or older than the car you want to transfer it to.
Isn't anyone else curious about what the correct boiling point is for each of the altitudes in the first video and what it would be a the top of Everest (~8848). I believe it should be possible to calculate it at standard pressure for a given altitude. One of the things that Prof didn't mention is that air pressure varies at any given altitude depending on depth of the air mass above that spot. It varies as a function of air movements and air temperature.
I got super excited to see supercritical fluids when he mentioned the concept in the video. A quick search on TH-cam of course landed me right back at the professor showing off a supercritical fluid demo rig he has in his office. You really should link to that video. I can't believe you made it back in 2008 and here we are looping back to the subject. It's here, by the way: /watch?v=yBRdBrnIlTQ
Dear Brady, Professor Poliakoff said that the pressure on top of the mountain is less than on sea-level and you proofed that with boiling water. my question is, how does the low-pressure envirnoment affect the solid water on top of the mountains, also shown on your Video footage. is there a simmilar abnormality in melting or something compareable like the boiling water? Thanks
ERGO. Just because water is boiling, DOES NOT MEAN it is hot. It only means the water molecules have enough energy to leave the water body into the "atmosphere". So to be scientifically correct, when someone asks you: "Why (when) does water boil?" You would have to answer, see above. Love it
... Martyn was as patient as a saint explaining the most basic experiment ... boiling water ... No suprise the signature tie was black and diffused ... 372 C is acceptable Proffesor ... too hot for tea ... well done all ...
It's very nice of Poliakoff to explain GCSE level physics. And yes, stream water will contain minerals, amongst other things, slightly reducing the freezing point of water.
I always thought it will solidify, or freeze, if you want. It's metal after all, and normal state for metals is solid. I mean, the melting poing of mercury is quite close to water (-38 deg. C), but the boiling point is much, much higher (357 deg. C). And it's very dense, so the gas that forms inside can't go out as easily as water vapor. That's why i'm interested in it - both versions are plausible, but only one can be true.
gibbs free energy will tell us the value of the equillibrium point at which the two phases can exist or above or below the temparature that one will be stable,it does not come in handy when we want to measure the conversion points at various pressures and temparatures..that is why Dr.Gibbs himself made the Phase rule(F=C-P+2) and perferctly described phase transitions..at normal single temparature cases though you are correct :D
yes, it would be quite explosive. Maybe some liquid water will remain because evaporation cooling cools down a small amount quickly enough, but most of it would blow explosively. So far above boiling point, you can just consider water to be a gas, it would be similar to instant decompression of any pressurized gas container.
I think I learned something new. At about 3:16 in, is the professor saying that a big component of the heat of vaporization is due to work being done against the atmosphere? I had assumed that it was an entropy thing like the heat of fusion or am I reading too much into it. Thanks
Thank you! I didn't understood that all the molecules don't have the same energy. But if I understand well, the boiling point is just the temperature when half of the molecules have enough energy to become gazeous? It seems a much more precise way to define the boiling point. (Sorr for my english...i'm french)
Hmmm you must be misinterpreting the diagram. Freezing point starts at 0C, 1 Atm yeah? Then take the Freezing point at 0.01C (0.006 Atm). The freezing point is only increasing along that line. At no point can the freezing temp drop below 0C until you get below 0.006 Atm, well below any pressure experienced on a mountain. All good?
This got me thinking about what the chemical process is that results in salt preventing water from freezing below 0 degrees centigrade. Based on what he said about impurities in water affecting its boiling point, I'm curious if that's the same thing happening with salt. But then, why does salt cause snow and ice to melt? Or does it just accelerate the melting once it's already started?
Chiara's correct for a pure water system. Look up "water phase diagram" and you'll be able to understand better what she has said. As the professor said however, this water is possibly (probably in my opinion) impure.
No, the freezing point will go higher to the triple point at 0.01 C and below the pressure for that it would be eventually gas not liquid at -4C since below the triple point liquid is impossible. But the triple point is only 10 millibars are 1% of an atmosphere which would be impossible on that mountain top because as you could clearly see the guys up there didn't die!
To deep fry, you use oil heated to around 180 - 200"C. I would hypothesize that you could indeed deep fry a turkey, under high pressure at 374"C it would cook really really fast. The dangerous thing would be removing the lid on the pressure cooker. Would be a cool experiment.
at around 2:13 he says that in an enclosed space there is an equilibrium between gaseous and liquid water, and that causes a pressure ( called vapor pressure), but later on the he says that when the vapor pressure is equal to the ambient pressure it boils. How can that be if the space is enclosed? Does he mean that the water is encapsulated by the air?
Air pressure does not change how much we weigh. There is pressure from air pushing down on us, but there is also air pressure pushing up one us, so they cancel each other. We will weigh slightly less, just because we are farther from the centre of the earth, but the effect is negligible because the earth is so large that the change in distance from the centre is also negligible.
They spoke of boiling water and pressure, but never mentioned latent heat of vaporization. With the changes in elevation and air pressure I think this would have been a good experiment to display this concept.
Generally yes. You might get the problem if you put the metal into a vacuum-chamber to lower the boiling point that it starts subliming instead (going directly from solid to gas, like dry ice does)
You may think that water in the solid and liquid phase doesn't sublimate or evaporate, but have you ever spilled some water and wiped it? Leaving that tiny trace that even though at room temperature: evaporates. The average kinetic energy (definition of temperature) of the solid water (system) in frozen food may by 0 degrees Celsius, but a tiny little fraction of water molecules may have such great kinetic energy that they enter the liquid or even gas phase, and therefore sublimating.
Well, i have no idea. That's why i've asked :D But still, you can't operate just pressure and temperature, it seems to me that other things matter too. Like density, volume and initial temperature of mercury before it was put in space. If you look only at temperature and pressure - any substance should sublimate right away, but it doesn't happen. And i'm not good enough with physics to find the approach to this problem.
A steam engine works by harvesting energy from the pressure difference between the steam and the atmosphere (or a condenser if it's closed cycle). Trying to boil more water by lowering the pressure would just give you less pressure difference to do work.
I can't wrap my brain around this many things well enuf, so I'm prolly making a mistake here, but.. Isn't the lower temp of the liquid glacier actually correct according to your 'splanation? If water can boil at a lower temp, doesn't it make sense that it can retain a liquid state at a lower temp as well. It's only one state removed. The entire temp range (both top and bottom) for liquid simply moves down as the pressure goes down. What am I missing?
Sorry for the possible bad english btw let me make sure i don't want to be overly protective or mocking somebody (if it sounds like this) I am doing chemistry projects too at a local shool and the worst part of the protol is always the failure evaluation at the end, where you have to find possible failures in the process of the experiment and you have to be really critical about yourself. Sorry for textboming!
A question for the professor; This has be hunting me for a while. Why does hot (90*C) water freeze 'faster' than RT temperature water? And if so, does the crystal of the ice difference between them?
Hey Prof, I am not sure how car license plates work in the UK. Is there a way to keep the number, say by buying it? Nonetheless I would suggest that u get a new car. Cars that are too old post a danger to the driver.
it's always relieving to hear someone say "gaseous water" or "water vapor" instead on "steam" when referring to boiling water. steam would burn someone's hand terribly if they put it over steam, but when you boil water you can put your hand over the vapor and be fine. steam is not the same as vapor.
The pot calling the kettle gay. Wait a minute, that's not right...
11 ปีที่แล้ว
Wait, I didn't understand the part about the freezing point however. :( So the water just COULDN'T have been -4º C ? Melting point doesn't change with pressure as boiling point does?
I applied for a program for a university that I really wanted to get into and I had to write a supplementary application for admission. One of the questions was to discuss who is my favourite scientist and why he is my role model. I talked about Professor Poliakoff and how he is so passionate in learning about science everyday and I got into my program! Thank you Professor Poliakoff and Brady for being such inspirations in my life!
"I thought 'critical temperature of water - I must buy that car!'"
Oh man I love you, Poliakoff :D
This is probably the best explanation of the concept of boiling I've ever seen.
Cool story about the car, btw.
this dude is epic
Professor: pointing out all the flaws in Brady's experiment was super-critical of you.
amazing footage of Brady at Everest.
Super critical is also called "super heated".
i love watching these videos even if i already understand the topic. You guys just make it interesting.
he got a haircut!
This guy is awesome! I'm addicted to his videos now and will probably watch them all.
The Professor is such a nice and engaging person I swear I could listen and easily learn whatever he would teach.
i SOOOO wanna go to that school, just because of him. the professor is AWESOME! he actually makes chemistry so much more interesting and fun.
Dustin, Prof, Brady all are awesome people to watch
Thank you for making your videos, they teach me so much and i really enjoy them. Keep doing what you do!
Thank you for explaining this! My chemistry teacher never explained it very well.
I always took science class in school even when it wasn't compulsory and i failed yr 12 science miserably (i was horrible at math) but i loved learning and knowing the concepts and the physics behind what happens on earth. Great video and keep it up!!!
Wow, I learned something awesome today.
I'd LOVE to hear more about your water research as I am an Environmental Engineering student. Thank you.
"Brady bashing" by "el proffo" GREAT STUFF!
Awesome video! Even on topics that I think I completely understand, these videos always make me see it in a new way, and usually learn something
omg science is a real man
dear prof. poliakoff, you are awesome.. the best videos on youtube.. I love the way you explain things. Thank you great sir.
If you read the video description (still don't understand why people don't do this as a first reaction to having a question, just /before/ commenting), you'll see that it says "From the School of Chemistry at The University of Nottingham" and includes a link to the department.
Fascinating. I've been a submarine cook for the last 12 years and I have noticed that water takes longer to boil the deeper we go. We also operate with a slight pressure on the ship. Would that also contribute to water taking longer to boil?
Hi, I have got an idea about a new chemistry series for you: can you do a weekly episode where you chronologically mention the highlights of each decade (starting at some arbitrary point, and highlighting one decade per episode). Thus, It will be a series about the history of chemistry, and how things got to where they are today. Thank you!
I missed the videos! glad they are back (:
Not sure if you received an answer or not, but what happens is that because there is no pressure- or next to no pressure- in space, then the water boils instantaneously. But oddly, because of how cold it is in space, that now gaseous water freezes very rapidly afterwards. You can do something like this at home by boiling water on a cold winter day, then going outside and tossing it into the air. It should finish boiling and turn into snow rather quickly.
Such a nice bloke. Thanks
If you get below the triple point of pressure with some liquids (water in particular), you will find ice sublimating directly to water vapor without going through a liquid phase.
Admittedly if the substance is already a liquid it will immediately boil in a vacuum as well, so you are somewhat correct. It is just that such liquids need to form in higher pressure locations in the first place.
Great explanation, thanks. I'll use this video for my students for sure :)
What interests me in this context, is how much the pressure changes the other phase transitions.
And how much difference is there from water to other fluids. I always hear that water is pretty unique in many ways.
Talking about thermodynamics in a cool way. That is rare ! Would have been super nice if you talked about the Triple point though
Love periodicvideos! Currently studying HND in Chemistry :)
But you also have to say that the PTC/NTC Sam is using is also not exact to the point, because every measuring instrument has a bit of failures. I also need a little help on the freezing temperature here, Because i also have seen water not frozen at -4 degrees at our place (but i have to say it was no constant cold of many days just 2 hours) and also you can see the water in the lake is rather sludgy than fluid ( i mean about to freeze) soo... please don't be too harsh :) Nice video as always!
Yes, the plate is a unique number registered to that car. Not the owner.
It is possible to transfer the plate to another car but only if the plate is the same year or older than the car you want to transfer it to.
You should make a video about water's Critical Point. That sounds very fascinating!
I really enjoy these videos!
Isn't anyone else curious about what the correct boiling point is for each of the altitudes in the first video and what it would be a the top of Everest (~8848). I believe it should be possible to calculate it at standard pressure for a given altitude. One of the things that Prof didn't mention is that air pressure varies at any given altitude depending on depth of the air mass above that spot. It varies as a function of air movements and air temperature.
The properties of water never cease to amaze me.
I got super excited to see supercritical fluids when he mentioned the concept in the video. A quick search on TH-cam of course landed me right back at the professor showing off a supercritical fluid demo rig he has in his office. You really should link to that video. I can't believe you made it back in 2008 and here we are looping back to the subject.
It's here, by the way:
/watch?v=yBRdBrnIlTQ
Dear Brady,
Professor Poliakoff said that the pressure on top of the mountain is less than on sea-level and you proofed that with boiling water. my question is, how does the low-pressure envirnoment affect the solid water on top of the mountains, also shown on your Video footage. is there a simmilar abnormality in melting or something compareable like the boiling water?
Thanks
At first I thought your question was crazy, but then I got to thinking and now I'm really curious!
holy crap i learned something! 374, must remember
ERGO. Just because water is boiling, DOES NOT MEAN it is hot. It only means the water molecules have enough energy to leave the water body into the "atmosphere".
So to be scientifically correct, when someone asks you: "Why (when) does water boil?" You would have to answer, see above. Love it
11 years ago. Where has my life gone 😵💫
Fascinating... Great vid!
... Martyn was as patient as a saint explaining the most basic experiment ... boiling water ... No suprise the signature tie was black and diffused ... 372 C is acceptable Proffesor ... too hot for tea ... well done all ...
It's very nice of Poliakoff to explain GCSE level physics. And yes, stream water will contain minerals, amongst other things, slightly reducing the freezing point of water.
The professor has lost his winter coat in preparation for summer.
thanks allot your comment really helped me to answer my question. thanks again and best wishes.
I always thought it will solidify, or freeze, if you want. It's metal after all, and normal state for metals is solid. I mean, the melting poing of mercury is quite close to water (-38 deg. C), but the boiling point is much, much higher (357 deg. C). And it's very dense, so the gas that forms inside can't go out as easily as water vapor. That's why i'm interested in it - both versions are plausible, but only one can be true.
please post some videos on the sixty symbols also...good work...thankyou!!
Where you can enjoy your tea for 10 seconds before it becomes iced green tea. ;)
You deserve more thumbs up
gibbs free energy will tell us the value of the equillibrium point at which the two phases can exist or above or below the temparature that one will be stable,it does not come in handy when we want to measure the conversion points at various pressures and temparatures..that is why Dr.Gibbs himself made the Phase rule(F=C-P+2) and perferctly described phase transitions..at normal single temparature cases though you are correct :D
yes, it would be quite explosive. Maybe some liquid water will remain because evaporation cooling cools down a small amount quickly enough, but most of it would blow explosively. So far above boiling point, you can just consider water to be a gas, it would be similar to instant decompression of any pressurized gas container.
I think I learned something new. At about 3:16 in, is the professor saying that a big component of the heat of vaporization is due to work being done against the atmosphere? I had assumed that it was an entropy thing like the heat of fusion or am I reading too much into it. Thanks
The extra footage of this is set to private!
Thank you! I didn't understood that all the molecules don't have the same energy. But if I understand well, the boiling point is just the temperature when half of the molecules have enough energy to become gazeous? It seems a much more precise way to define the boiling point. (Sorr for my english...i'm french)
Hmmm you must be misinterpreting the diagram. Freezing point starts at 0C, 1 Atm yeah? Then take the Freezing point at 0.01C (0.006 Atm). The freezing point is only increasing along that line. At no point can the freezing temp drop below 0C until you get below 0.006 Atm, well below any pressure experienced on a mountain. All good?
I'm not sure what your question is; but a pot 'with a lid on' is a pressure cooker.
This got me thinking about what the chemical process is that results in salt preventing water from freezing below 0 degrees centigrade. Based on what he said about impurities in water affecting its boiling point, I'm curious if that's the same thing happening with salt. But then, why does salt cause snow and ice to melt? Or does it just accelerate the melting once it's already started?
Chiara's correct for a pure water system. Look up "water phase diagram" and you'll be able to understand better what she has said. As the professor said however, this water is possibly (probably in my opinion) impure.
Martyn at his best: Exited about a number plate :-)
I guess, when this car vanish, he will put the licences plate into his office.
Should the professor really give out his license plate like candy? That's a nono in my book.
No, the freezing point will go higher to the triple point at 0.01 C and below the pressure for that it would be eventually gas not liquid at -4C since below the triple point liquid is impossible. But the triple point is only 10 millibars are 1% of an atmosphere which would be impossible on that mountain top because as you could clearly see the guys up there didn't die!
Is there any way we can get in touch with the professors? Like a Q and A of sorts?
BZ! I love this channel BTW.
So did you guys get new lighting or is this the first time you shot a video on a sunny day?
More on pressure and boiling, Brady! Maybe power plants or something?
To deep fry, you use oil heated to around 180 - 200"C. I would hypothesize that you could indeed deep fry a turkey, under high pressure at 374"C it would cook really really fast. The dangerous thing would be removing the lid on the pressure cooker. Would be a cool experiment.
Would very much like to attend his lectures.
at around 2:13 he says that in an enclosed space there is an equilibrium between gaseous and liquid water, and that causes a pressure ( called vapor pressure), but later on the he says that when the vapor pressure is equal to the ambient pressure it boils. How can that be if the space is enclosed? Does he mean that the water is encapsulated by the air?
Air pressure does not change how much we weigh. There is pressure from air pushing down on us, but there is also air pressure pushing up one us, so they cancel each other.
We will weigh slightly less, just because we are farther from the centre of the earth, but the effect is negligible because the earth is so large that the change in distance from the centre is also negligible.
They spoke of boiling water and pressure, but never mentioned latent heat of vaporization. With the changes in elevation and air pressure I think this would have been a good experiment to display this concept.
Generally yes. You might get the problem if you put the metal into a vacuum-chamber to lower the boiling point that it starts subliming instead (going directly from solid to gas, like dry ice does)
You may think that water in the solid and liquid phase doesn't sublimate or evaporate, but have you ever spilled some water and wiped it? Leaving that tiny trace that even though at room temperature: evaporates. The average kinetic energy (definition of temperature) of the solid water (system) in frozen food may by 0 degrees Celsius, but a tiny little fraction of water molecules may have such great kinetic energy that they enter the liquid or even gas phase, and therefore sublimating.
Well, i have no idea. That's why i've asked :D But still, you can't operate just pressure and temperature, it seems to me that other things matter too. Like density, volume and initial temperature of mercury before it was put in space. If you look only at temperature and pressure - any substance should sublimate right away, but it doesn't happen. And i'm not good enough with physics to find the approach to this problem.
Only the professor can make boiling water interesting
Watching this 11 years after release I’m wondering if the professor still has the same W374 car?
A steam engine works by harvesting energy from the pressure difference between the steam and the atmosphere (or a condenser if it's closed cycle). Trying to boil more water by lowering the pressure would just give you less pressure difference to do work.
Instructions: Boil Water.
WHAT AM I A CHEMIST?
Thanks you for the answer and the lip.
I can't wrap my brain around this many things well enuf, so I'm prolly making a mistake here, but..
Isn't the lower temp of the liquid glacier actually correct according to your 'splanation? If water can boil at a lower temp, doesn't it make sense that it can retain a liquid state at a lower temp as well. It's only one state removed. The entire temp range (both top and bottom) for liquid simply moves down as the pressure goes down.
What am I missing?
Your TAs are right. But it's not always gonna decrease boiling point, as far as I know. Sometimes, BP would even increase.
Water at -4ºC is less dense than water at 0ºC. That might be the reason why the thermometer read -4ºC, since the frozen layer floated upwards.
Love the vids Brady. Could you do one about partial pressure of O2, related to altitude? I can't get my tiny mind around it!
So was it a total or partial immersion thermometer?
Sorry for the possible bad english btw let me make sure i don't want to be overly protective or mocking somebody (if it sounds like this) I am doing chemistry projects too at a local shool and the worst part of the protol is always the failure evaluation at the end, where you have to find possible failures in the process of the experiment and you have to be really critical about yourself. Sorry for textboming!
you should do some a video on other interesting things about supercritical fluids and their properties etc
A question for the professor; This has be hunting me for a while. Why does hot (90*C) water freeze 'faster' than RT temperature water? And if so, does the crystal of the ice difference between them?
Look up a phase diagram for water. It changes from solid to liquid at pressures that low, so technically it doesn't boil, it sublimates.
Hey Prof, I am not sure how car license plates work in the UK. Is there a way to keep the number, say by buying it? Nonetheless I would suggest that u get a new car. Cars that are too old post a danger to the driver.
1:33. Suddenly, and simply because its Poliakoff, I got excited about a glass of water.
it's always relieving to hear someone say "gaseous water" or "water vapor" instead on "steam" when referring to boiling water. steam would burn someone's hand terribly if they put it over steam, but when you boil water you can put your hand over the vapor and be fine. steam is not the same as vapor.
I have finally understood what the critical point is! ...and I thought watching a video about boiling water wouldn't be interesting
The pot calling the kettle gay. Wait a minute, that's not right...
Wait, I didn't understand the part about the freezing point however. :( So the water just COULDN'T have been -4º C ? Melting point doesn't change with pressure as boiling point does?
Apparently the rig extras video is set to private...
I do love professor P.