The First Law of Thermodynamics: Internal Energy, Heat, and Work

[@myron_jd1272]

Sometimes hearing the same information from a different person helps very much!

[@sadhanajoseph2320]

I agree with you.

[@سارة-ط6ق1ي]

يا رجُل ماهذا الشرح الجمييييل ، شرح مُبسط وجميل ♥️♥️♥️♥️👏🏻👏🏻👏🏻

[@abdulrhman.3742]

كملتي معه ولا ؟ عندي اختبار بكره.

[@cherylbauman9510]

Why couldn’t you have been my professor in college? You explain everything perfectly!

[@thanos5466]

U should do study My girl 😂😂

[@fishplayztoh]

Yes

[@jefrreyjeffery2192]

You study this in college. We study this is in 10th grade in asia💀☠️☠️

[@anuragchaudhary6307]

@@jefrreyjeffery2192 We study this in college too, we do more than this, but I'm coming back to the basics, Also Asian here.

[@Evangeline_Hansen]

​@@anuragchaudhary6307maybe you two live in two different countries/regions ,after all Asia is a big place

[@Sulfuricacid__140]

i want all Teachers as you. You explain a lot of things in few minutes.Thank you..

[@nischalchhetri7445]

I don't know if I have gotten this all wrong, but isn't the sign convention explained here wrong? 1) Work done by the system- (-w) 2) Work done on the system (+w) This is what I have learned. Please correct me if I'm wrong. Edit- So this tutorial was for physics, not chemistry. Anyways, it's more interesting to discover that we use different sign conventions in physics.

[@markvillacampa4314]

I am looking for a validation of my understanding of the work done on the system because I feel like what is in the video is wrong, and I found this comment hahahaha. I searched for the work done on the system in physics and, similarly in chemistry, they are positive. So the video is indeed wrong.

[@AR14SigmaGulfam]

Yes, video is telling wrong about the sign conventions.

[@abhi22]

@@markvillacampa4314 The video isn't wrong. He has changed the signs in the equations too. So the equations will always work. It's just a different perspective to look at.

[@borapadmanabham3676]

Yes work done on the system is positive, work done by the system is negative

[@legendaryx2k19]

Well the sign convention don't matter much as long as they are opposite in any case

[@Maxz-lg1et]

For those who are confuse, there's two perspective here System (mostly use in chemistry) and the Surrounding (mostly use in physics), W = Q + W (chemistry) (system's perspective) >When W is negative (-W) work is done by system, >When W is positive (+W) work is done on the system W = Q - W (physics) When W is negative (-W), work is done by the system When W is positive (+W), work is done on the system

[@Zempie]

you just wrote the same convention pair twice.

[@loreenzo2120]

@@Zempie not rly cuz the equation is different

[@Zempie]

@@loreenzo2120 I meant the description of the equation. it should be opposite for one of the scenarios

[@loreenzo2120]

@@Zempie huh, yeah, the signs should be flipped for the last one

[@maelscott7212]

Great video, one thing you missed that I think is important is if U = q - w or = q + w depending on which subject you're taking. I know that physicists and biomedical engineers use +w.

[@shreya_0412]

This is my confusion too... When to use which one?

[@wetworksyt4446]

​@@shreya_0412if work is being done on the system, w will be will be positive and the equation will be U=q+w. If work is being done by the system, w will be negative and the equation will be U=q-w.

[@aurickbiswas8233]

​@@shreya_0412 in chemistry work done by the system is negative and in physics work don by system is positive. Think of it like physics is oriented with profit and loss while chemistry is more about caring about the system like a baby😅

[@Rahul-hp5ie]

I swear to study thermodynamics eagerly if he's my professor.Deserves a lot of subscribers and likes.

[@TomBrooklyn]

As always, clear, and most importantly, concise. No wasted words or time. Well done, Professor Dave

[@MattMattMat]

Professor Dave is definitely still saving educational lives years later with these videos

[@heliumteam151]

Me watching this 5 min shit after studying this for 13 hours straight in a complex way and dreaming about this video to be enough for my exam ....

[@vaishnavipatil2972]

Best video for understanding the concept

[@WritersDigest-b8f]

Exhaust stroke & also intake stroke are adiabatic processes because no heat is added or removed in the processes and internal energy reduces in exhaust stroke and internal energy is added in the suction stroke. Accordingly work is done by the system reducing the internal energy in the exhaust process and accordingly work is done on the system to shoot up the internal energy in the suction process.

[@derrickdanso6631]

You're making me fall for thermodynamics. Thank you so much

[@tommysheehan2136]

Professor Dave helping me cram for the physics GRE, what a hero

[@v2sisters138]

Amazing video! But please specify that this is from physics' point of view. according to chemistry the signs are different. This kind of induces confusion. THANK YOU!

[@sychomadman]

thank you so much. i thought i was going crazy.

[@na-chan163]

@Mohamed Sherif how is that so?

[@fatimaisra9143]

@@na-chan163 the surrounding energy is the atmosphere's energy and the system's energy is the internal energy

[@na-chan163]

Fatima Isra work done by system (expansion) is negative for chemistry but positive for physics. Can you pls explain this?

[@fatimaisra9143]

@@na-chan163 it's positive in phyics because we are describing the system's actions on it's surroundings, and it's negative in chemistry because the system is "throwing" out work (idk if im completely correct but im sure this is a good way to think of it)

[@VishnooSpotlights]

We need more professors like you in India ...

[@skullmax3595]

Exactly

[@Unknown_Ooh]

I think I'm dropping thermodynamics

[@Traewing]

😂😂😂😂😂

[@cephasdn6576]

😂😂😂😂😂

[@bhumikaulangwar9056]

Good one 😂

[@LawsonHanson200]

😂😂😂😂

[@NoriousKumwenda]

😩😩😅😅😅😅

[@TheMultipower47]

I wish your channel was bigger

[@ProfessorDaveExplains]

me too, friend!

[@Lioooooooo1ooo7oooo]

It is now

[@unknown-gy8jz]

Now it's bigger than ever!!!

[@eyerus-uw7gt]

@@ProfessorDaveExplains that's amazing and could you explain why U become zero when temeperature is constant plz ?

[@benYaakov]

IUPAC said that work done by the system is negative and vice versa

[@baurzhanhydros9957]

expansion of the gas W < 0 and compression of the gas W > 0. Because in the first case, the system does work on the surroundings so it loses work while in the second case, the surroundings does work on the system so the latter gains works which will be positive

[@prishaendait8621]

Everyone wathing this video please do note that the sign convention used here is only valid for physics, it is the opposite for chemistry.

[@makeitmemorable__]

Sir you have done wrong here about sign convention work done by the system is negative and work done on the system is positive

[@ProfessorDaveExplains]

That's chemistry. This is a physics tutorial.

[@makeitmemorable__]

@@ProfessorDaveExplains okh sir my mistake actually I am in 11th class and a neet aspirant so I don't know it well and thankyou for replying

[@Mohith1111]

​@@makeitmemorable__ lol same

[@USArmyVeteranOIFandOEF]

Awesome visual examples and simplified to absorb the information being released, making understanding and keeping it in so much easier. Thank you, Prof. Dave!

[@Luke-t4f3x]

3:29 dude you're wrong bro... If work is done on the system, its sign is positive. If work is done by the system, its sign is negative.

[@Kyrmen-b4h]

Right 👍

[@prishaendait8621]

its because the sign convention used here is valid for physics but not chemistry and I think he made it from physics point of view.

[@minimidder2025]

Why does this channel have so few subscribers???!! You're amaze man! Thanks! ❤

[@kripashankarshukla4073]

You deserve to be a noble prize winner. Sir you are awesome you should get a noble prize!!!!!

[@rachellicari5964]

***My chemistry teacher has told me +w=work done on system, -w=work done by system

[@carultch]

Different disciplines will prefer different sign conventions. I'm accustomed to the heat engine sign convention, where work done by the system is positive.

[@BOLYANA]

3:49 isn’t if the work done by the system then it is negative?

[@khaledzainel-dein3766]

Thanks for your brilliant explanation

[@Vagdebrume]

You do an amazing job ♥ !

[@ziadyasser8888]

man... u r the best one explain this .........so thank u

[@devnaathpillai]

Isnt work negative when it is performed by the system or am i trippin?

[@devnaathpillai]

@ProfessorDaveExplains

[@B-MAN95]

I'm really impressed , the way of teaching, how u remember all those things, can u give me any tips to remember easily

[@nourhannenagy7666]

When work is done by the system W is negative when work is done on the system w is positive

[@nourhannenagy7666]

You said the opposite

[@ProfessorDaveExplains]

Chemistry and physics have opposite conventions. This is a physics tutorial.

[@Endless20162]

@@ProfessorDaveExplains ahh so that's why

[@EnricoMicheli-jo6bg]

Anyone else got exam today GL Guys also Professor Dave u a life savour

[@ayesha4599]

Professor Dave is amazing, honestly!

[@shahxad6533]

why was (150J) taken positive ??? In the Last Example.?

[@Juboury_20]

I think there are mistake in work subject

[@WritersDigest-b8f]

Professor Dave: could u do YT thermodynamics videos with examples of processes from IC engine, jet engines, rockets, compressors, gas turbines, steam turbines, boilers, refrigeration cycle, heat pumps. Thermodynamics concepts would stick to comprehension and memory by using heat engines as examples. This video was fantastic and not easy to forget now because u used mechanical examples. Thank u so much

[@EngineeringStudyMaterials]

Thank you for making this video. Well Explained. It Helps me a lot.

[@manoharapproach7178]

Thanks for the video, but am confusing a bit . If work done by the system that mean system loss energy to surroundings which decreases the internal energy of the system , so it should be negative. Please need more explanation

[@evelyntromp789]

I’m obviously not Prof Dave but I think it’s positive because the equation has a negative W, whereas most equations have a positive work (dU = Q + W)

[@Ice-yp4wg]

Question: Why must heat be represented by "Q" and internal energy is to be represented by "Delta U"?

[@heinzguderian9572]

delta U means the overall change in internal energy. delta U= U2 - U1

[@Ice-yp4wg]

@@heinzguderian9572 but why use U specifically?

[@heinzguderian9572]

@@Ice-yp4wg wdym? Specific internal energy? Sometimes questions want u to find out the internal energy of the system before it went under compression or expansion process

[@Ice-yp4wg]

@@heinzguderian9572 The letter U I mean

[@heinzguderian9572]

@@Ice-yp4wg no idea. But I guess it's because it's a good letter to use since other letters are used to define other properties such as temperature, pressure or enthalpy

[@muhamadabubakar7621]

Sir your way of explaining topic in detail is the #best.....

[@icelerez]

This is a great video! i just wish you wouldn't have used capital letters when referring to heat and work because they aren't state functions and should be lower case. Anyways thank you for helping a whole generation of students through college.

[@HarshaAbey]

thank you

[@AB-rj7vh]

Hey quick question for those interested. How much do you need to cool a solar cell operating at, let's say, 23% efficiency? My thoughts are that a solar cell should not change its internal energt U, so in other words deltaU or dU/dt should be 0. So 23% of the solar energy becomes electrical work, while the rest of the sun's power (1-0.23=0.77) is transferred as heat that, without cooling, would accumulate in the solar cell. In order for dU/dt (delta U) of the solar cell to be 0 you need to fulfill Q=W, so in other words you need to cool the cell to such an extent that the only heat that isn't cooled off equals the electrical power of the solar cell, in this case 0.54 times the power of the sun? Is this way of thinking correct? I would very much appreciate any input.

[@carultch]

Yes, indeed, that is correct. This is why the panels heat up, if you turn off the system and make them remain at open circuit. The lack of a destination for the power to go, means that they heat up to a temperature where they can radiate more energy to the background. This is counterintuitive, because most of the time, operating electrical equipment makes it heat up, rather than cool down.

[@ayushijain8671]

Excellent for revision, short and crisp, covers all points quite well. Thanks a bunch. I also love your organic chemistry and dna-rna videos.

[@333_studios]

Why does my textbook say deltaU= Q + W ?

[@mufakkirhussain2816]

333 Studios cuz you are Indian. You consider work done by the system +.

[@TheMWBooher]

Engineers and Chemists view work differently. As he explains, Work is positive if the contained volume does Work against the atmosphere, like the expansion of a gas in a piston assembly. Chemists view Work as positive if the environment does work on the contained volume, such as a compression of the gas.

[@Amityadav99.]

Mufakkir Hussain it is in physics but in chemistry this sign is reverse of W

[@v2sisters138]

Wrong, because he is studying chemistry, and you are studying physics.

[@ranjeetsohanpal752]

Even my textbook is saying work done on the system positive

[@jacobthonkuotamol4927]

I don't think there is someone like Professor Dave on the planet Earth. I am just waiting for your inventions or discoveries my Professor.

[@miniaturenature2507]

Amazing sir 👌 Wish you have more successful in life

[@crescencelee5112]

short and easy to understand thanks

[@sharingbeth5148]

you saved me Mr!lots of thanks from Ethiopia

[@captainldd]

I loved this video. so much good information!

[@tkub77]

Great video! This helped me a lot!

[@physics20246]

Exordinary, congratulations, Sir

[@muftiaaishasuhail3050]

Thanks a lot sir! You made it easy

[@Ali-cc3zz]

بارك الله فيك... God bless you

[@AyatMohammed-y1h]

thank you now i understanding therom esay.

[@karthikswaminarayan4278]

please make a video on carnot engine or carnot cycle

[@ProfessorDaveExplains]

that would be the second law, the one right after this!

[@fexofenadinaGenerica]

Awesome tutorial.

[@N3thStudios]

Thankyou Professor

[@bjalle3569]

Nice video Dave, really helped me and my buddy Johan learn thermodynamics :)

[@nokitosembrano3657]

how about isobaric

[@kjkitz]

Please note that you have incorrectly applied the signs for work. Work is (-) when it is done by the system on the surroundings. Work is (+) when it is done on the system.

[@ProfessorDaveExplains]

No, that's for chemistry. This is a physics tutorial.

[@ahmedelshazly4139]

awesome, great job professor . keep on

[@sajukgeorge3399]

thankyou sir, it is very useful for me

[@hja9157]

Love to hear more from you

[@siritelugutech2448]

3:27 Is it correct? Work done on the system is +ve And Work done by the system is -ve Correct me ...... If I am wrong

[@amitsmash]

Whn work is done on the system. The sign will be positive.

[@ProfessorDaveExplains]

nope, negative!

[@sbrightOzner]

Amit Kushwaha quite confusing. If work done on the system by the surroundings, therefore its positive. Same goes for work Done on the surrounding into the system. *head hurts* correct me if I'm wrong, thanks.

[@pravinshelar2146]

Work done on system by surrounding should be positive...

[@Dsc009]

In Chemistry, we are looking at it from the point of view of the "system" so work done on system is positive since system is gaining internal energy. In Physics, we look at it from the point of view of "surroundings" so work done on system is negative since the surrounding is losing that energy.

[@doctorbase2364]

@@Dsc009 so why prof Dave used -w ?! If in chemisty is +w and we are studying chemistry ?!

[@ViaDenglas-xz4th]

THANK YOU PROF!!!!!!!!!!!!!!!!

[@effasvt_]

isn't work done on the system is +ve

[@ziaulhaq5910]

Yes my text book says that work done by the system is negative

[@monkeybusiness673]

That is the usual statement, because it reflects what the sign on Q means and is therefore more coherent. That's why you usuall write (delta)U = Q+W instead of minus.

[@thandietania1785]

equation states delta U =Q - W ...the minus sign multiplied by the sign on work done...eg if work is done by its -ve, product of that with the minus sign u get +ve same goes for work done on..hope that helped

[@ziaulhaq5910]

thanks

[@TheMWBooher]

In chemistry, you're correct. Engineers view the sign of work opposite of the chemists, in the manner the video explains.

[@abdurrakib551]

very good expression sir!

[@ramb0077]

thank you very much and wish you good future

[@sajidkhan-rq8yw]

Hello Professor Dave, please make me understand how is the work done by the system positive? When heat is applied then gases expand against the downward force of the piston, so product of force and negative displacement is a negative work done. Isn’t it? I hope you got what I am trying to say.

[@majinDuu]

This is exactly why I came to the comment section. Work done BY the system is NEGATIVE and work done ON the system is POSITIVE

[@davidisaacgalang3000]

@@majinDuu yes, I was really confused too

[@carultch]

@@davidisaacgalang3000 It's nothing more than a sign convention. Different disciplines use different standards for the sign on heat and work, to keep track of them entering and leaving the system. It is just a language you translate back to words, to explain how the energy exchange happens. There is no reason work has to be positive when it is done by the system, other than "because we said so". I'm accustomed to the heat engine sign convention, whereby work done by the system is positive (that's the purpose of an engine), and heat added to the system is positive (that's the source of energy for a heat engine).

[@eshaan2500]

Mr. Dave, you are awesome

[@manishkanna532]

superb nd simple xplanation

[@amlansasmal]

you are awesome sir i was unable to understand this topic...again again.... but your way is very simple and very useful to me.... keep on sir...that has a positive effect on us...😀

[@Kate-em1kf]

Whew this is a lot to remember

[@bsatyam]

Why Q - W and not Q + W, but change the sign convention of work done to match that of Q?

[@shihanrahmi]

I really wish I had a physics tutor like this. Unlucky me

[@niceguy4801]

Thakyou professor dave!

[@محمدهشامعفيفي-ل3س]

From college of science azhar university ❤ from Egypt 🇪🇬 Thanks

[@Amityadav99.]

are in chemistry the concept of sign of W is reverse in physics

[@parpeez]

This is a really clear video buddy!

[@mohanraj-rw9du]

Good explanation

[@siddhantgupta3500]

Thanks dave

[@fatehazkhan]

I have a question. In class we're taught about four processes of thermodynamics. Isobaric Isochronic Isothermal and Adiabatic. Isovolumatric and Isochronic are the same. But you didn't mention anything about the Isobaric process. And we're not taught about the Isolated system as well. Or maybe I didn't pay proper attention. Could you help me understand?

[@johnrayrivas1375]

Great explanation... Thanks

[@aneeshaperera6680]

Thanks sir.we are hoping to a vedio on minerals .

[@WritersDigest-b8f]

Is bomb calorimeter similar to Explosometer that explodes a mixture inside a portable sealed box to detect possible hydrocarbon leaks in petrochemical plants. It’s replaced with sensors for detection. Thanks Isovolumetric process because heat transferred from the spark to just change the internal energy inside the box and the increase in temperature or no temperature increase is visible on the meter to the user.

[@leunam1leunam172]

Very great video

[@sadhanajoseph2320]

thank you sir.

[@charleshenryescuela6452]

the difference between changes in enthalpy and internal energy for the explosion of trinitrotoluene, TNT, at 25°C producing carbon dioxide, nitrogen dioxide gas and water vapor will be in what Joules?

[@MJ-gx9fi]

I didn't skip the ad😎😌

[@LarryWater]

Thank you so much!

[@ashensaranguhewa]

Thank you!

[@CalviNsiku]

Thinking I've understood and still failing comprehension question😭😂Lord do me Mercy 🤲

[@MohanySoliman]

Good

[@aicellealcala5653]

In checking comprehension, why the operation is addition?