Thank you so much for your videos ! I am taking my GCSEs at the moment but I hate only getting half explanations of everything so you have been a huge help in understanding what is actually going on instead of just memorising a textbook! EDIT - just watched another one of your videos about Patreon - I'm really sorry I don't have a job at the moment.. but i'm not planning on giving up on learning science anytime soon so I look forwards to supporting you on Patreon in the future!
I knew I was wrong, but I didn't know the process was that long. I don't recommend this to any SHS students like me who is watching this w/o background knowledge ab heat capacity and enthalpy. Go watch how to solve heat of capacity and enthalpy first and come back, it will make much more sense. You're still gonna get it wrong but at least you understand how it works
I don't understand how the last comprehension check we were expected to do mathematically. How did you know when to use what? What does the s stand for in s_water and s_ice, etc...?
it stands for specific heat, check out the one or two tutorials prior to this one in the playlist, about heat capacity and calorimetry and thermochemistry
The video is OK, but why the hell would you round to the correct sig figs for every partial answer, and then not round the final answer? Final answer should be 104 kJ. If you round before you get to the very end, your answer will be skewed.
for the heating portions it's the q = ms delta T where heat exchanged is equal to the mass of the sample times its specific heat times the change in temperature. for melting and boiling it's just the heat of fusion or vaporization times the mass of the sample. but keep in mind that water has a different specific heat depending on what phase it is in!
I have a sticking point I'm a little confused about. Say I have 2 kg of ice, I begin applying heat energy, and the heat begins overcoming the phase bonds, and I melt half the ice. As I continue to apply heat to the sample, now 1 kg ice and 1 kg liquid water, does the existing water begin heating up while the energy put into the ice continues being used to break bonds? Will it take more heat than I put into the first half to melt the second half because of the presence of the already melted liquid water, or is the effect nil or negligible? Thanks.
I always recommend using an external source as well. Double check your comprehension with learning from another source as well for full comprehension! and then come back !
im constantly learning from 3-4+ sources to make sure Im getting the full picture and not missing anything. Theres zero shame in doing this to make sure you understand all steps!
Ok so i have a question, how many height meters do a mountain need, for these rules to apply? In my hometown, there is a mountain which is accurately, 1100meters above sea level. In this top, during the summers of norway (15-25 degrees celsius), the snow here doesnt melt until way late, past midsummer, i think some of it never melts. Is it safe to assume that this snow has lower pressure at 1100m above sea level, that it sublimates, which probably is slower, than just melting to water? Just a curious question.
hmm i'm not sure of the precise numbers! the higher you go in altitude, the lower the atmospheric pressure certainly, and the lower the boiling point of water, and also it gets colder of course, so that's a factor. but i'm not sure of the quantitative specifics.
4:23 I am doing some research & need the temperature enthalpy diagram for various materials, mostly high temperature ceramics. Can you give me a reference that would have this information? I also need the optical properties of materials. Any help there?
hello professor Dave! Thank you for this concise explanation. I understand that when heating a liquid after it has reached the boiling point the energy being given to the sample goes towards breaking the intermolecular forces of the sample rather than adding to its kinetic energy. I find this very interesting and cannot see why that happens. Could you tell me why the system behaves this way? Why not have the energy input increasing the kinetic energy and breaking the intermolecular forces at the same time? If anyone has any idea about it, it would be appreciated!! Thank you!!!
while heating water at (example:30 c) the energy given is used to increase the kinetic energy until the pressure reaches the surrounding pressure. As equilibrium states are more favourable here , the energy is used to change the state rather that increasing the kinetic energy (equals increase in pressure).
Not sure where I got this from but I always thought that when you look at a kettle boiling the steam you see is actually tiny water droplets and that the gaseous form was invisible. Same with dry ice. Is this not true?
well you can't see individual molecules, so if you steam then certainly some molecules are coagulating to some extent, but it's not in the liquid phase, nor is the vapor emanating from dry ice in the solid phase, it's gas.
Professor .. one question always comes to my mind! 😅 As the water bottle is an air tight container .. it can't even leak! But what makes the water droplets swoosh out the container.. in case if de-freezing a solid iced bottle? (I am not that good at english , but please try to understand) Always love yours videos professor! You became my saviour!!🙏 Clearing such sweet lil' concepts .. in the best way!! #short_and_effective! Thanks loads!!🌟🌈🙏 #👑
Water droplets on the outside of cold water bottles are usually condensed water droplets from the air around the bottle. So the water vapor in the air touches the outside of the bottle, cools, and forms the liquid water. I hope that helps.
What you're talking about is condensation. The water from inside the bottle isn't going through the bottle. The bottle is cold, and is making water vapor (water in the air, yes, there is a little) become a liquid. The cold water slows down the molecular moment of some of the water vapor enough to make it become a liquid, and it builds up on the outside of the bottle. Evaporation is different. Evaporation is the process of water doing what is essentially boiling. But evaporation can happen much slower though. For example, if you leave a cup of water out for months, slower, little by little, the water will become gas and go into the air. This is because small amounts of the liquid water have high enough energy (are moving fast enough) to leap from the liquid and go into the air, and become a gas. People often get condensation (what you asked about) and evaporation mixed up. I used to.
there is always an equilibrium between liquid water and water vapor, even at room temperature. some molecules have enough kinetic energy to enter the gas phase, and some molecules will re-enter the liquid phase. the boiling point is when the vapor pressure equals atmospheric pressure, or when all of the molecules will enter the gas phase.
I didn't know it, about always having liquid and vaporized water at the same time! is it true for every substance? thank you! btw in the phase diagram of water, the line between solid and liquid is bent backwards because of the hydrogen bonds, right? Thank you again!
@@gabriels2395 Good question. The heat to vaporize water at room temperature, comes from the thermal energy of the air into which it evaporates, causing it to cool adiabatically. The water is nowhere near 100 Celsius to boil directly, but it is above its own boiling point at its partial pressure in the air/water vapor mixture. Consider a dry desert with air at 35C and 15% relative humidity. Water's boiling pressure at 35C is 0.0555 atm. This means, up to 5.55% of the air molecules can be water vapor (3.54% by mass). At that point, we'd say its relative humidity is 100% for saturation. For the dry desert air, 15% relative humidity means that only 0.8% of the air molecules are water vapor (0.5% by mass). Now we evaporate the water from liquid to gas, until saturation. It will cool to 18C. At that condition, the water vapor is 2% by molecule population, or 1.2% by mass. Given 1 kg of desert air, it will evaporate 7 grams of water as it saturates. The air loses 17 kJ of heat and the water gains 17 kJ of heat as it transitions from liquid to gas. You can check that this is consistent with water's enthalpy of vaporization at 18C of 2.46 kJ/g and air's constant pressure heat capacity (1 kJ/kg-C).
We had the same given but my calculator didn't match with the answer in 4:19, i checked the given thrice and it's right. I think he used other constant enthalpy change (of fus and vap) and/or the specific heat capacity (of ice, water, and steam). Because the given enthalpy and specific heat capacity constant in the video are rounded off to the nearest hundredth. Edit: Btw, I got 108,847.55J or 108.35kJ. Not so far with the answer in the video but since the constants were not the same with the constants which I used (which are given in this video) are not the same, our answers were not exactly the same, as well.
Wtf 😂 whats happening haha (35.3g)(2.06J/g °C)(20°C)= 1454.36 J Howd you get 1450? (35.3g)(334 J/g)= 11790.2 J How did you get 11,800J? through rounding up? Im so confused rn😭 I think my Calculator is broken🤷♀️
I thought I understood everything clearly until I was asked to solve a problem at the end.
the problem at the end was indeed enough to comprehend the concepts
lol me too i was like wait thats so easy until the problem came and I was like oh wait lemme watch the video again ahhahah
same
ugh same
ua-cam.com/video/o2kYyvxtAAQ/v-deo.html
Thankyou for the video on Phase Changes, Heats of Fusion and Vaporization, and Phase Diagrams.-Alexis Kironde
When your teacher gives you this video for digital learning day
Krinkle same
Just now😕
same bruh.......
Thank you so much for your videos ! I am taking my GCSEs at the moment but I hate only getting half explanations of everything so you have been a huge help in understanding what is actually going on instead of just memorising a textbook!
EDIT - just watched another one of your videos about Patreon - I'm really sorry I don't have a job at the moment.. but i'm not planning on giving up on learning science anytime soon so I look forwards to supporting you on Patreon in the future!
awesome! happy to be of help and no worries! my content is for everyone and if you ever can manage to support one day i'll be grateful then :)
ua-cam.com/video/o2kYyvxtAAQ/v-deo.html
Thank you! The visuals are awesome.
Damn 7 years ago!!!❤
Thanks prof!! Really wasn't getting this until I realized that phase change per mol/g is for STEPS, not the entire equation!!! Now time to practice :D
This brings back so much nostalgia, I remember watching this in grade 6 in class
Rodrigo Góes, is this you guy?
Making science videos on UA-cam?
Lord be praised, man! You’re everywhere!
Thank you so much for the videos! Professor Dave :)
I think I understood this well enough with the last tutorial still in memory, but I forgot to include the fusion and vapour differences
I knew I was wrong, but I didn't know the process was that long. I don't recommend this to any SHS students like me who is watching this w/o background knowledge ab heat capacity and enthalpy. Go watch how to solve heat of capacity and enthalpy first and come back, it will make much more sense. You're still gonna get it wrong but at least you understand how it works
4 mins vs 55 mins and you killed it
I LOVED the scream-yodeling Mountain Man!!!! You explain things in a fun and informative way!! Way to go!!!!
In the first part of the comprehension problem, how did you get 20.0C?
thank you so much for sharing your gifts
Why does density matter in the way the lines point in the phase diagram?
professor dave you deserve it all
for the heat of vap and formation in the comprehension, aren't you supposed to use mols?
btw im in APChem
I don't understand how the last comprehension check we were expected to do mathematically. How did you know when to use what? What does the s stand for in s_water and s_ice, etc...?
it stands for specific heat, check out the one or two tutorials prior to this one in the playlist, about heat capacity and calorimetry and thermochemistry
I HAVE AN ONLINE TEST ON SOME THESE TOPICS AND MORE IN 10 MINUTES AHHHH ILL UPDATE
WHERES THE UPDATE
@@Valeria-pq7hx he died
How much heat, in kJ, must be removed to condense 25.71 g of steam at 100.0°C to liquid
water at 100.0°C?
if you watch this you'll know how to answer that!
I wanted to learn about phase change to plasmas… consider adding it to a video later please.
Congrats on 2 mill
Thanks sir. I get the concept now
The video is OK, but why the hell would you round to the correct sig figs for every partial answer, and then not round the final answer? Final answer should be 104 kJ. If you round before you get to the very end, your answer will be skewed.
Could you remind me what formula you were using for the checking comprehension in this video?
for the heating portions it's the q = ms delta T where heat exchanged is equal to the mass of the sample times its specific heat times the change in temperature. for melting and boiling it's just the heat of fusion or vaporization times the mass of the sample. but keep in mind that water has a different specific heat depending on what phase it is in!
you saved the day once again. Thanks boss
Thank you very much
just 2k left to cross 1 million
HARDWORK is the key of SUCCESS
I like the intro
very helpful. thank you so much for sharing your talents.
Why line between water solid and liquid slants up and left is because solid form is less dense than liquid form?
correct!
I have a sticking point I'm a little confused about. Say I have 2 kg of ice, I begin applying heat energy, and the heat begins overcoming the phase bonds, and I melt half the ice. As I continue to apply heat to the sample, now 1 kg ice and 1 kg liquid water, does the existing water begin heating up while the energy put into the ice continues being used to break bonds? Will it take more heat than I put into the first half to melt the second half because of the presence of the already melted liquid water, or is the effect nil or negligible? Thanks.
Hello! I didn't quite understand the chek comprehension portion of the video. What exactly did you use to calculate the energy?
I always recommend using an external source as well. Double check your comprehension with learning from another source as well for full comprehension! and then come back !
im constantly learning from 3-4+ sources to make sure Im getting the full picture and not missing anything. Theres zero shame in doing this to make sure you understand all steps!
hello sir ,sir what formula is used to calculate the energy to melt the ice?
Ok so i have a question, how many height meters do a mountain need, for these rules to apply? In my hometown, there is a mountain which is accurately, 1100meters above sea level. In this top, during the summers of norway (15-25 degrees celsius), the snow here doesnt melt until way late, past midsummer, i think some of it never melts.
Is it safe to assume that this snow has lower pressure at 1100m above sea level, that it sublimates, which probably is slower, than just melting to water? Just a curious question.
hmm i'm not sure of the precise numbers! the higher you go in altitude, the lower the atmospheric pressure certainly, and the lower the boiling point of water, and also it gets colder of course, so that's a factor. but i'm not sure of the quantitative specifics.
its like noah kahan is helping me with chem
Professor DAVE YOU ARE AMAZING
I have seen some videos where they convert grams to moles in q2 and q4 but u didn’t y?
So Helpfull thank U
I like your lectures
4:23 I am doing some research & need the temperature enthalpy diagram for various materials, mostly high temperature ceramics. Can you give me a reference that would have this information?
I also need the optical properties of materials. Any help there?
hello professor Dave! Thank you for this concise explanation. I understand that when heating a liquid after it has reached the boiling point the energy being given to the sample goes towards breaking the intermolecular forces of the sample rather than adding to its kinetic energy. I find this very interesting and cannot see why that happens. Could you tell me why the system behaves this way? Why not have the energy input increasing the kinetic energy and breaking the intermolecular forces at the same time? If anyone has any idea about it, it would be appreciated!! Thank you!!!
while heating water at (example:30 c) the energy given is used to increase the kinetic energy until the pressure reaches the surrounding pressure. As equilibrium states are more favourable here , the energy is used to change the state rather that increasing the kinetic energy (equals increase in pressure).
ua-cam.com/video/o2kYyvxtAAQ/v-deo.html
What happens to the kinetic energy and potential energy during the phase change?
I think during phase change potential energy increasees
Can someone please explain the question at the end to me?
q_Total = \sum{q} + \sum{\delta{H}}, right?
Nice video. Between Specific latent heat of fusion and vaporization for substances generally, which is greater?
Generally, the latent heat of vaporization is greater.
hello prof dave. isn't that supposed to be (35.3)(2.02)( *115* ), not 15 in comprehension?
once it's a gas it's already at 100, only 15 degrees left to go!
oohh ok. thanks prof!
Hi, thanks for your tutorials please I need physics tutorial for grade 11 especially on the topic WAVES I am writing my exam this year thanks
Is there any word ablimastion
Not sure where I got this from but I always thought that when you look at a kettle boiling the steam you see is actually tiny water droplets and that the gaseous form was invisible. Same with dry ice. Is this not true?
well you can't see individual molecules, so if you steam then certainly some molecules are coagulating to some extent, but it's not in the liquid phase, nor is the vapor emanating from dry ice in the solid phase, it's gas.
1:23 it’s a normal time stamp no need to see what it is
how can making holes change the colour of a plastic sheet
Hello professor David and thank you for your videos. Where I can get the values of heat of fusion for stable noble gases isotopes? Thank you.
ua-cam.com/video/o2kYyvxtAAQ/v-deo.html
there are a million holes each of one nano meter
i think he is great .............. isn't him???
English is a good language
@@yannick5068 🤣🤣🤣
Ok I understood
Is 35.3g the weight of ice or water?
prolly
Wait on the solving part why did you use 15.0 C instead of 115 C
the third part only involves heating up the steam from 100 to 115
Professor Dave Explains Oh ok thx cuz my chem teacher doesn’t tell us to do that!!!👍🤗
Professor .. one question always comes to my mind! 😅 As the water bottle is an air tight container .. it can't even leak! But what makes the water droplets swoosh out the container.. in case if de-freezing a solid iced bottle? (I am not that good at english , but please try to understand)
Always love yours videos professor!
You became my saviour!!🙏
Clearing such sweet lil' concepts .. in the best way!! #short_and_effective!
Thanks loads!!🌟🌈🙏 #👑
Water droplets on the outside of cold water bottles are usually condensed water droplets from the air around the bottle. So the water vapor in the air touches the outside of the bottle, cools, and forms the liquid water. I hope that helps.
What you're talking about is condensation. The water from inside the bottle isn't going through the bottle. The bottle is cold, and is making water vapor (water in the air, yes, there is a little) become a liquid. The cold water slows down the molecular moment of some of the water vapor enough to make it become a liquid, and it builds up on the outside of the bottle.
Evaporation is different. Evaporation is the process of water doing what is essentially boiling. But evaporation can happen much slower though. For example, if you leave a cup of water out for months, slower, little by little, the water will become gas and go into the air. This is because small amounts of the liquid water have high enough energy (are moving fast enough) to leap from the liquid and go into the air, and become a gas.
People often get condensation (what you asked about) and evaporation mixed up. I used to.
Your English is indeed not very good...tbh its a little crappy
@@jagruti_rs now see that would be "a" critic....thank me later.
where from do water molecules get enough energy to get vaporized at room temperature?
there is always an equilibrium between liquid water and water vapor, even at room temperature. some molecules have enough kinetic energy to enter the gas phase, and some molecules will re-enter the liquid phase. the boiling point is when the vapor pressure equals atmospheric pressure, or when all of the molecules will enter the gas phase.
I didn't know it, about always having liquid and vaporized water at the same time! is it true for every substance? thank you! btw in the phase diagram of water, the line between solid and liquid is bent backwards because of the hydrogen bonds, right? Thank you again!
@@gabriels2395 Good question. The heat to vaporize water at room temperature, comes from the thermal energy of the air into which it evaporates, causing it to cool adiabatically. The water is nowhere near 100 Celsius to boil directly, but it is above its own boiling point at its partial pressure in the air/water vapor mixture.
Consider a dry desert with air at 35C and 15% relative humidity. Water's boiling pressure at 35C is 0.0555 atm. This means, up to 5.55% of the air molecules can be water vapor (3.54% by mass). At that point, we'd say its relative humidity is 100% for saturation. For the dry desert air, 15% relative humidity means that only 0.8% of the air molecules are water vapor (0.5% by mass).
Now we evaporate the water from liquid to gas, until saturation. It will cool to 18C. At that condition, the water vapor is 2% by molecule population, or 1.2% by mass. Given 1 kg of desert air, it will evaporate 7 grams of water as it saturates. The air loses 17 kJ of heat and the water gains 17 kJ of heat as it transitions from liquid to gas. You can check that this is consistent with water's enthalpy of vaporization at 18C of 2.46 kJ/g and air's constant pressure heat capacity (1 kJ/kg-C).
Good 'ol Jesus
sir, pls tell me what is mean by phase change
when a substance changes from one phase of matter (solid, liquid, gas) to another
Thanks prof Dave ❤
I watched this about 15 times I guess I’m just dumb, goodbye grades
Good vidio
Sorry to be that person, but its video.
But, I understand that water boils at a higher temperature at higher altitudes due to low pressure.
It is the opposite way
شرحك رائع
I thought I understood until I saw that question 💀💀💀
when your so slow that you cant understand simple chem
sobbing
"Enthropy"
We had the same given but my calculator didn't match with the answer in 4:19, i checked the given thrice and it's right.
I think he used other constant enthalpy change (of fus and vap) and/or the specific heat capacity (of ice, water, and steam). Because the given enthalpy and specific heat capacity constant in the video are rounded off to the nearest hundredth.
Edit: Btw, I got 108,847.55J or 108.35kJ. Not so far with the answer in the video but since the constants were not the same with the constants which I used (which are given in this video) are not the same, our answers were not exactly the same, as well.
i felt so smart until that confusing meme
I was confused he looks like indian actor Ranbir Kapoor 😮😮😮😮😮😅😅😅😅😅
Wtf 😂 whats happening haha
(35.3g)(2.06J/g °C)(20°C)= 1454.36 J
Howd you get 1450?
(35.3g)(334 J/g)= 11790.2 J
How did you get 11,800J? through rounding up? Im so confused rn😭 I think my Calculator is broken🤷♀️
U look like Ranbir Kapoor
anyone else from India🇮🇳
Mee😎😎
Who agree he looks like Ranbir Kapoor 😅😅😅
can you be my sugar daddy
ads
i think my calculator is broken :'(
Looks like ranbir kapoor if he is shorten his hair
He is Ranbir Kapoor bonly style vof hair is different
1:23 bruh what was that