@@nathanwidjaja3652 why do so many freshmen take chem. At my school, freshment take bio and then after that u can choose (among other things) either chem or physics, so sophomores usually take chem
I had to miss a class on this yesterday. What I watched in this 4 minutes taught me almost everything that my classmates learned in 2 two hours. Thank you so much!
That's because lecturers have no experience in anything to do with learning and cognition - so they are robots - they just write or read notes which you take down.
I owe so much to your channel, Professor. Your videos are direct and very easy to understand. I'm studying for an admission test and you have been such a big help.
@@pbower4378 I love making comments like these, and I've actually gotten a few people to respond, even after a decade! Good luck on your upcoming exam. I'd say that if you'd be so inclined, asking questions and engaging in the comments on educational videos might help prepare a bit for it 😃
I'm going back through material to study for my ACS exam for GenChem II, and he has been an incredible help. He explains concepts and equations so simply I don't feel like I have to spend hours trying to figure it out. Thanks Professor Dave!
I did already take it. It went well. I’m not sure exactly what I made, but it was a big part of my grade and I ended up bringing my grade from a C to a B!@@PunmasterSTP
01:13 Heat is NOT a FORM of energy. Heat is a PROCESS. Heat is the TRANSFER of energy due to a difference in temperature. Please read Peter Atkins: "Four Laws that drive the Universe", p.30.
@@efhi lol - OR you could completely ignore me and keep repeating your error! To a certain level of education, that's what you've been told. However, physics is richer than that.
Not sure why I need to attend school anymore? I just learnt more in 58 seconds than I have all semester. Thanks for being the awesome science teacher that don't have!
Very informative series. The men like PROFESSOR DAVE are the essence of the humanity. If he continues to lots of other chemical topics he will be welcome. May God bless him time and enthusiasm to teach many other difficult topics in physical, inorganic, organic and applied chemistry.
Shouldn't the 2nd answer at 3:10 say that the delta H is -1780.6kJ, not kJ/mol? It is still -890.3kJ/mol regardless of how many moles you combust, correct?
@@sebastianriedel8627 Actually good either way in this example because talking about methane (CH4), of which there is only 1 mol. When providing molar enthalpy it should always be absolutely clear from the context or question which substance it is referenced to. In other words, because the question is talking about methane and the balanced equation indicates only one mol of methane, the enthalpy could be listed in kJ or kJ/mol (of methane). But if the question had asked about producing 10.0g of water, you would have to use -890.3 kJ for the equation, as balanced, or -445.2 kJ/mol (of water produced)
At 0:52 onward it would have been easier to understand, in my opinion, if the order was reversed, eg reactants to products and dH positive =products required energy = endothermic reaction
Thank god there are people like professor Dave who can actually explain the material eloquently and in an interesting way and not bore you to death like my stupid chemistry teacher in school.
im currently a student living off of subsidies but i promise! when i get my first paycheck when im graduated! i WILL make a donation to you to THANK YOU!
Yeah, I don't get it either. He didn't say anything about it in the video. Apparently you just divide the mass you have by the mass of your substance in one mole and multiple it by the enthalpy given...
you probably have figured it out 2 years later lol, but because the enthalpy is in units of KJ/mol, by knowing how many moles are actually being used in the reaction will give us a multiple to know how much of that energy (enthalpy) (which is per mol), is actually released. take this for example, though not precise, say i have a pizza of 4 slices, and that pizza gives me 800 calories for a whole pizza. now, one may wonder how many calories for 2.5 slices of pizza. I must divide the amount i want to know by the total amount per pizza, then multiply that by the energy for 1 whole pizza. boom, there's your answer
2:30 You need to have "enthalpy" or "heat" at the top of the background when you are giving definitions/units..i kept having to rewind to see what you were referring to.. every "slide" should have what you're referring to so that each slide can be standalone.
2:07 "When T,P are constant, Q=∆H". How is there a change in enthalpy/heat if the temperature is held constant? Are you saying that temp of entire system is held constant (but there is still a change in enthalpy within rhe system)? Im confused here. I also dont know how to visualize the difference in Heat Flux & Enthalpy. I wish somebody would give a concrete example and contextualize it in the real world.
I am not completely sure but as much i know, the heat is given to the system it either changes its temperature or its potential energy so i guess this is the reason for temperature not getting changed... but i am not completely clarified about it. You can correct me if i am wrong somewhere
If a chemical equation has a delta heat value given, if the heat value is negative, does that mean the reaction is exothermic? just double checking, it can be kinda confusing, i love your videos thanks!
My teacher is an absolute moron, I can confidently say that you Professor Dave, are a man among men and you deserve a place in the teachers hall of fame. Even ahead of many teacher!
Thank you Professor Dave for your explanation of enthalpy. Could you please make a video to explain effect of expansion valve in thermodynamics. what kind of effect it does on gases and gases take energy from surroundings.
The expansion valve, also known as a throttling valve, is a device that produces an irreversible drop in pressure, with no work or heat exchanged with the surroundings. It is known as an isenthalpic process. Unlike turbines that have a counterpart component like a compressor, that does the same, but in reverse, there is no counterpart to the throttling valve that raises pressure isentahalpically. Time would need to run backwards for such a component to exist. An application of the throttling valve, is the vapor compression refrigeration cycle that we use in refrigerators and air conditioners. From state 1 to state 2, we compress the vapor to high pressure; from state 2 to state 3, we condense the vapor to a liquid while it rejects heat; from state 3 to state 4, we expand the liquid through this valve to a 2-state mixture of liquid and vapor at a cold low pressure, and from state 4 to state 1, we boil the liquid in the evaporator so that it absorbs heat from the cold space. In concept, we could use a turbine from state 3 to state 4, but it wouldn't be practical to build such a turbine. To keep it simple, we use a throttling valve to drop the pressure. A throttling valve can also be controlled by a thermostat (called a thermostatic expansion valve) to govern the flow rate and differential pressure of an air conditioner.
0:39 Energy isn't stored in bonds. Common misconception, debunked in plenty of videos by other instructors here on RUclips. If energy WERE stored in bonds, why would you need to ADD energy in order to break bonds?
Good video. Could you please answer my question professor or anyone who is an expert? So if enthalpy of products is lower that means (u+p*rho) is lower. But the fact that heat is released and the temperature of products is higher means that "u" or internal energy must be higher! How do I reconcile these two ?
Wish I found these videos 3 months ago. This is so helpful! But quick question. Why do we keep a positive answer? If the Delta H is negative and its Exothermic, shouldn't we right the number as a neg? If the problem had stated that 890 were positive, would the 556 have been negative? Whats the relationship there in writing the answer with the correct sign(_/+)?
+William Rice oh the delta H would be negative, it's the semantics of how the question is worded, it asks how much energy is released. it doesn't make sense to say a negative amount of energy is released, the negative sign simply means that it is released, specifically 556 kJ of it.
Just to make sure, I thought that, if the energy of the bonds in the products is greater than the energy of the bonds in the reactants then it should be exothermic and viceversa would be endo. Am I wrong?
You are wrong. All of the chemicals in the reaction represent the 'system'. If you end up with more energy in the final state of the system...like in the bonds of the the products... then the system has gained energy from the 'surroundings' making the reaction endothermic with a positive enthalpy. Usually this is manifested as a temperature drop in the surroundings because the products take energy away from the surroundings.
Is the amount of heat denoted by q is the same as H (enthalpy) contained in the law of ΔH=Hp-HR In short, is the amount of heat q the same as the enthalpy H?
@@Paul-yd7eo n=m/M n=10g /16 g per mol It can also be written as: =10g × (1mol/16g) This is beacuse when we change sign ÷(/) into × then value inverts... This is how it's written in the video...
at 3:16 you say that when number of mol is doubled the enthalpy also doubles. shouldn't the value of enthalpy still be the same regardless the no of mol?
![Seungmin "그렇게, 천천히, 우리(As we are)" | [Stray Kids : SKZ-PLAYER]](http://i.ytimg.com/vi/kAzmhLHePqU/mqdefault.jpg)
I love how he explains things as if I were 7 years old but without it seeming insulting
Fr😂
do you know who has the video for the six year old?
@@caru3257 tyler dewitt but idk if he has vids about thermochemistry
Idk he’s pretty condescending
That's how one understands this well!!!
Most underrated science channel. College hack
college??? im a freshman in high school
@@nathanwidjaja3652 why do so many freshmen take chem. At my school, freshment take bio and then after that u can choose (among other things) either chem or physics, so sophomores usually take chem
@@Waiter1986 In my country this is taught in junior year of high school
@@bamb8s436 I learnt this in high school I was 16
@@gen2208 yeah same
I had to miss a class on this yesterday. What I watched in this 4 minutes taught me almost everything that my classmates learned in 2 two hours. Thank you so much!
Gabriella Underwood At which standard did you study this?
That's because lecturers have no experience in anything to do with learning and cognition - so they are robots - they just write or read notes which you take down.
@@deepakghugardare8453 tum 11th class m ho. Hain na? Lol
"I would drop this class, but it is the only place I can get any sleep."
I know it's been six years, but how'd the rest of your class go?
Dude you are a beast man. Your videos are short and sweet goes straight to the point, keep it going David Grohl.
I owe so much to your channel, Professor. Your videos are direct and very easy to understand. I'm studying for an admission test and you have been such a big help.
Did you already take the test, and if so, what was it and how'd it go?
I'm so glad I found this channel BEFORE my final exam! Cramming for a midterm tonight and I've learned so much in just one hour. THANK YOU!
I know it's been seven years, but I just have to ask. How'd the midterm and final go?
@@PunmasterSTPlol this comment actually made me giggle cause I was about to ask the same thing 😂 I have a gen chem exam in a week and I’m NERVOUS.
@@pbower4378 I love making comments like these, and I've actually gotten a few people to respond, even after a decade!
Good luck on your upcoming exam. I'd say that if you'd be so inclined, asking questions and engaging in the comments on educational videos might help prepare a bit for it 😃
Jesus coming to save me for my chem exam lmfao
🙏, You made me laugh
🤣🤣🤣
@@mikeoxlong2077 it's Jesus bruh
I had a test on this, I would pray.
HAHAHAHAHAHAAH AMEN😭🙏
I'm going back through material to study for my ACS exam for GenChem II, and he has been an incredible help. He explains concepts and equations so simply I don't feel like I have to spend hours trying to figure it out. Thanks Professor Dave!
Did you already take the ACS exam, and if so, how'd it go?
I did already take it. It went well. I’m not sure exactly what I made, but it was a big part of my grade and I ended up bringing my grade from a C to a B!@@PunmasterSTP
This taught me more in 4 minutes then my chemistry teacher has taught me all year
blud had about thermochemistry all year 💀
I know it's been a few years, but how'd the rest of your chemistry class go?
Your vids are making my MCAT prep more feasible. Thanks!
Did you end up taking the MCAT, and if so, how did that (and med school) go?
I watch the ads all the way through to make sure my chemistry Jesus gets his Adsense 🥺✨
my best disciple!
@@ProfessorDaveExplains : 11. Thou shalt not 'SKIP'
Sorry Dave, i've had add block on for a while so i sent you some patreon to make up for it. You can thank Aivarey for making me feel bad. : )
You explained this in a 4 minutes video better than a 2 hour lecture by my professor
I know it's been a few years, but I just came across your comment and was curious. How'd the rest of your chemistry class go?
At least ur Chemistry proffessor lectures
This man taught me thermodynamics in half an hour which my chem teacher couldn't in half a month. U r amazing sir ! Keep up the good work!!
How'd the rest of your class go?
01:13 Heat is NOT a FORM of energy. Heat is a PROCESS. Heat is the TRANSFER of energy due to a difference in temperature. Please read Peter Atkins: "Four Laws that drive the Universe", p.30.
Nope, heat is the kinetic energy of the particles of the system
@@efhi lol - OR you could completely ignore me and keep repeating your error! To a certain level of education, that's what you've been told. However, physics is richer than that.
2:32 Thanks Dave, this is the first time I learned the difference between dietary calories and chemistry calorie.
Not sure why I need to attend school anymore? I just learnt more in 58 seconds than I have all semester. Thanks for being the awesome science teacher that don't have!
Ever since I got into high school i can’t help but notice that teachers are so lazy
How'd the rest of your studies go?
when he said delta H is energy in bonds of product - reactant
that just saved my life
Very informative series. The men like PROFESSOR DAVE are the essence of the humanity. If he continues to lots of other chemical topics he will be welcome. May God bless him time and enthusiasm to teach many other difficult topics in physical, inorganic, organic and applied chemistry.
I love this guy videos. He can explain everything very clearly.
Thankyou for the video on Thermochemistry: Heat and Enthalpy.
Shouldn't the 2nd answer at 3:10 say that the delta H is -1780.6kJ, not kJ/mol? It is still -890.3kJ/mol regardless of how many moles you combust, correct?
oh man! what a dumb error. yes it should just be kJ. thanks for catching that!
why can delta H unit be Kj and Kj/mol?
And I believe in the comprehension example it is the other way round. KJ/mol and not kJ
@@sebastianriedel8627 Actually good either way in this example because talking about methane (CH4), of which there is only 1 mol. When providing molar enthalpy it should always be absolutely clear from the context or question which substance it is referenced to. In other words, because the question is talking about methane and the balanced equation indicates only one mol of methane, the enthalpy could be listed in kJ or kJ/mol (of methane). But if the question had asked about producing 10.0g of water, you would have to use -890.3 kJ for the equation, as balanced, or -445.2 kJ/mol (of water produced)
At 0:52 onward it would have been easier to understand, in my opinion, if the order was reversed, eg
reactants to products and dH positive
=products required energy = endothermic reaction
Studying for ap chem test this is really coming in clutch
Thank you.This video was helped me lot to clarify my answers.This is the best channel for science students.
i manifest that i will have 96 and above grade in advance chemistry, pls lord🙏🙏
Thank god there are people like professor Dave who can actually explain the material eloquently and in an interesting way and not bore you to death like my stupid chemistry teacher in school.
Yeah for real. Out of curiosity, how'd the rest of your chemistry class go?
Bill gates wants to recreate butter with this.
I finally understand enthalpy from ur 4min vid, and its better than those 40min or hour and a half crappy vids!
im currently a student living off of subsidies but i promise! when i get my first paycheck when im graduated! i WILL make a donation to you to THANK YOU!
2020 and he's still the best!
Professor Dave is the GOAT.
this was so clarifying and concise thank you sir
Binging your videos before my chem exam in two hours 🎉
at 3:45 why did you change delta H to a positive in the actual equation when it was originally a negative ?
Thank you so much for your videos sir, your videos have been very useful for both physics and chemistry in my current academic year.
How'd the rest of your year go?
Correct the unit of it :- ∆H = -890.3 KJ/mol
This is exactly the information I was looking for. Thank you!
Love from India professor your teaching is So Amazing
Dave knows a lot of stuff.
Thank you for existing
Your videos are my holy grail, thank you so much!~ You explain it so clearly & the visuals help so much.
the most important point in thermodynamics you said ,.. thanks Prof. Dave!!
Professor Dave, you're the man.
Thanks, you're better than my actual professor.
Chemistry Jesus. Thank you!
Thank u so much. So impressive and easy to understand
The explanations helped me a lot, however the "comprehension" I had trouble with because I learned it much differently
Yeah, I don't get it either. He didn't say anything about it in the video. Apparently you just divide the mass you have by the mass of your substance in one mole and multiple it by the enthalpy given...
you probably have figured it out 2 years later lol, but because the enthalpy is in units of KJ/mol, by knowing how many moles are actually being used in the reaction will give us a multiple to know how much of that energy (enthalpy) (which is per mol), is actually released. take this for example, though not precise, say i have a pizza of 4 slices, and that pizza gives me 800 calories for a whole pizza. now, one may wonder how many calories for 2.5 slices of pizza. I must divide the amount i want to know by the total amount per pizza, then multiply that by the energy for 1 whole pizza. boom, there's your answer
Thank you Proffesor for helping us😁 in this subject,
Seen once. Shall be seen again. Good vid.
Hi sorry but i dont understand how dix you find this result attend the end or thé video , can you please explain it ?
3:44
Maybe it helps to know that the -890 is kJ/mol
Thanks for this video!
Tbh I stil dont understand what I'm doing
Thank you Professor Dave
I LOVE YOU DAVEEEEEEEEE
😘😘😘😘
my saviour
I love this channel
Thank you, chemistry Jesus!!!!
Thank you so much for these great videos. Summing up with the comprehension check is awesome! Very very helpful! Thank you.
My freaking savior
Damn man your videos really helping out for jee
Mere bhi , bahut confusion tha isme
2:29 My mind just exploded
2:30 You need to have "enthalpy" or "heat" at the top of the background when you are giving definitions/units..i kept having to rewind to see what you were referring to.. every "slide" should have what you're referring to so that each slide can be standalone.
love that opening 😂
I think this is how professors should teach the first-year engineering students.
I love you professor dave
What is the difference between q and H when both are defind as energy
2:07 "When T,P are constant, Q=∆H". How is there a change in enthalpy/heat if the temperature is held constant? Are you saying that temp of entire system is held constant (but there is still a change in enthalpy within rhe system)? Im confused here. I also dont know how to visualize the difference in Heat Flux & Enthalpy. I wish somebody would give a concrete example and contextualize it in the real world.
I am not completely sure but as much i know, the heat is given to the system it either changes its temperature or its potential energy so i guess this is the reason for temperature not getting changed... but i am not completely clarified about it. You can correct me if i am wrong somewhere
Love your vid professor :D
Best "Guru" ever....
Go on Prof.
Hi can you please explain the comprehension part to me, I don't understand the method that you used?
I still don’t get it 🙃🙃🙃 is there any other topic I should know before this one to understand it better
BRO LOVE FROM INDIA 🎉
Thank you soooooooo much. SO SO SO SO SO SO SO SO SO much!
Heat and enthalpy? More like "Incredibly great and informative videos for me!"
If a chemical equation has a delta heat value given, if the heat value is negative, does that mean the reaction is exothermic? just double checking, it can be kinda confusing, i love your videos thanks!
Yes.
My teacher is an absolute moron, I can confidently say that you Professor Dave, are a man among men and you deserve a place in the teachers hall of fame. Even ahead of many teacher!
Please prof. Dave explain why there is 16.0g CH4 and it is coming from.
Molar mass
@@ProfessorDaveExplains ohh thanks
makan roti campur saos
parjamban siap ready nih boss
💃🏼 💃🏼💃🏼💃🏼💃🏼💃🏼💃🏼💃🏼
Sir u are the wonderfull teacher awesome sir
Thank you professor Jesus
Thank u so much 🤗🤗🤗🤗🤗
I love having Noah Kahan teach me chemistry
Very nice your teching .
Sir i just have one request can you please make a Playlist !!!
Thank you Professor Dave for your explanation of enthalpy. Could you please make a video to explain effect of expansion valve in thermodynamics. what kind of effect it does on gases and gases take energy from surroundings.
The expansion valve, also known as a throttling valve, is a device that produces an irreversible drop in pressure, with no work or heat exchanged with the surroundings. It is known as an isenthalpic process. Unlike turbines that have a counterpart component like a compressor, that does the same, but in reverse, there is no counterpart to the throttling valve that raises pressure isentahalpically. Time would need to run backwards for such a component to exist.
An application of the throttling valve, is the vapor compression refrigeration cycle that we use in refrigerators and air conditioners. From state 1 to state 2, we compress the vapor to high pressure; from state 2 to state 3, we condense the vapor to a liquid while it rejects heat; from state 3 to state 4, we expand the liquid through this valve to a 2-state mixture of liquid and vapor at a cold low pressure, and from state 4 to state 1, we boil the liquid in the evaporator so that it absorbs heat from the cold space. In concept, we could use a turbine from state 3 to state 4, but it wouldn't be practical to build such a turbine. To keep it simple, we use a throttling valve to drop the pressure. A throttling valve can also be controlled by a thermostat (called a thermostatic expansion valve) to govern the flow rate and differential pressure of an air conditioner.
Q = △H when T and P are constants ? Have just P as a constant is sufficient, no ?
THANK YOU!
0:39 Energy isn't stored in bonds. Common misconception, debunked in plenty of videos by other instructors here on RUclips. If energy WERE stored in bonds, why would you need to ADD energy in order to break bonds?
Thank you
Good video. Could you please answer my question professor or anyone who is an expert? So if enthalpy of products is lower that means (u+p*rho) is lower. But the fact that heat is released and the temperature of products is higher means that "u" or internal energy must be higher! How do I reconcile these two ?
Wish I found these videos 3 months ago. This is so helpful! But quick question. Why do we keep a positive answer? If the Delta H is negative and its Exothermic, shouldn't we right the number as a neg? If the problem had stated that 890 were positive, would the 556 have been negative? Whats the relationship there in writing the answer with the correct sign(_/+)?
+William Rice oh the delta H would be negative, it's the semantics of how the question is worded, it asks how much energy is released. it doesn't make sense to say a negative amount of energy is released, the negative sign simply means that it is released, specifically 556 kJ of it.
I was having the same problem.But now I am happy.
In this video I know all about chemistry
Thanks to prof. Dave
Stay blessed by Jesus
man, i LOVE that intro..lol
Thank you so much
Just to make sure, I thought that, if the energy of the bonds in the products is greater than the energy of the bonds in the reactants then it should be exothermic and viceversa would be endo. Am I wrong?
You are wrong. All of the chemicals in the reaction represent the 'system'. If you end up with more energy in the final state of the system...like in the bonds of the the products... then the system has gained energy from the 'surroundings' making the reaction endothermic with a positive enthalpy. Usually this is manifested as a temperature drop in the surroundings because the products take energy away from the surroundings.
@@sarabourke7081 That makes sense, thanks for the explanation.
Is the amount of heat denoted by q
is the same as H (enthalpy)
contained in the law of ΔH=Hp-HR
In short, is the amount of heat q the same as the enthalpy H?
Thanks . very nice teacher you
Watching this from France ! There's a mistake at 3:38 it's 16.0 g/mol and not g ! But thanks for helping me :)
no mistake! grams are on the bottom so as to cancel grams in the value we are working with. you'll notice one mole is on top.
But isn't that the formula : n=m/M ? 🤔
there's no formula here, i'm just doing a conversion. check out my tutorials on dimensional analysis and stoichiometry!
@@Paul-yd7eo
n=m/M
n=10g /16 g per mol
It can also be written as:
=10g × (1mol/16g)
This is beacuse when we change sign ÷(/) into × then value inverts...
This is how it's written in the video...
@@umairafatima5616 Thanks I was getting pretty confused
Any Indian here?
Yes
Yes
at 3:16 you say that when number of mol is doubled the enthalpy also doubles. shouldn't the value of enthalpy still be the same regardless the no of mol?
certainly not! twice the number of molecules, twice the number of bonds formed or broken.
Professor Dave Explains heat released wud be double but enthalpy should be the same right?
nope, change in enthalpy depends on the quantity of matter being transformed.