Entropy and the Second Law of Thermodynamics
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- Опубликовано: 11 сен 2024
- Deriving the concept of entropy; showing why it never decreases and the conditions for spontaneous actions. Why does heat go from hot to cold and not the other way round?
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honestly I cant thank you enough. I used your videos for Alevels and now I am watching them as preparatory material for our first year lectures. all I can say is thank you.
This is the most coherent presentation of Thermo I have seen on line. He is the gift that keeps giving !
This has to be the most outstanding thermodynamics lesson ever. Brilliant!
KNOWLEDGE
summarized my whole thermo one class in 60 mins...awesome! thanks!
This video was so innocent, so purely abstract, and then subtly you ease into the revelation that for the past 49 minutes we had been proving that the Universe is on an uninterruptible path towards dark, meaningless, mathematically perfect disorder... And then I blink and we're back to math. That was magnificent.
I hope it was helpful.
It was
it was
You are AWESOME this is great level of knowledge u r giving us .🤟
As usual a magnificent lecture by a great teacher.
I'm a first year Chemical Engineering student, i have my Thermodynamics exam in 2 days... this video may have just saved my life. Thank you.
11 years later
I hope all is well in life for you 💙
I watched this 3 times to fully get it. I love how you condense all this cool stuff so well
The key point is that overall entropy increases. Or at the least it does not decrease. We can always find situations in which order is increased in a particularly local situation, for example if I build a sand castle. But at the end of the day the tide will come in and wash it away creating greater disorder. Particles which materialise and then annihilate leave the universe in the same state as before they were created in the first place.
I found each and every second informative. Thanks a lot. May God bless all of us!
Amazing from the beginning of the story to the end thank you again sir 👍👍👍👍👍
Thank you sir, Good job and excellent because I more understand the thermodynamics from derivations of the formula and the working principle of it 👍👍👍
Stuff with more energy does more stuff than stuff with less energy. And it keeps doing more stuff until it has no more stuff than all the other stuff. Then the system is all stuffed up and no more stuff can be done.
Is that what you were trying to say?
More or less.
Your videos are always excellent as you are an outstanding teacher. You are very methodical and it's a delight to follow your tutorials, but sometimes your script is difficult to follow as you tend to blend letters together. It just takes a little extra attention to follow but well worth it, given the quality of your lessons. Thank you.
After 10 years of under geaduate course passout, revisiting this lecture made the concept more clear. The lecture is excellent 👍
Very nicely explained
-At 8:22: Why can you bracket the differential teerm d out?
d(U+pV)= dU + d(pV) = dU + pdV + Vdp
What about this last term?
-At 13:45 could you link to a video/ressource where this application of the chain rule gets clarified?
-At 28:05: Why is the only way to the system to make it "do" work on the volume?
Thank you for this beautiful video:)
1. I think it's at constant volume, so dp=0.
2.
U(T,V):dU=(∂U/∂T)v dT+(∂U/∂V)t dV
V(T,p):dV=(∂V/∂T)p dT+(∂V/∂p)t dp
U(T,p):dU=(∂U/∂T)p dT+(∂U/∂p)t dp
Substituting dV from line2 into line1:
dU=[(∂U/∂T)v +
(∂U/∂V)t (∂V/∂T)p ]dT+
(∂U/∂V)t (∂V/∂p)t dp
Comparing the first term with line3:
(∂U/∂T)p =(∂U/∂T)v +
(∂U/∂V)t (∂V/∂T)p
3.
dU=Q+W and Q=0, so dU=W=-pdV
@@nychan2939 for the first, pressure should be constant, so that d q = d H, but teacher did not mention it
Yes, I made a mistake. But I really thought of constant pressure, so I wrote dp=0. Thanks.
52:00
S = Kb(ln(w)) Not dS.
You pulled over dQ = nRTdV/V and then used it in dS = dQ/T
However you integrated dQ into nRln(V2/V1) but left S as dS.
You would have to Integrate both sides, or leave it as dS = nR dV/V
Or dS = NKb dV/V
Just a small correction, Otherwise this video was very informative and well put together.
It gets a lot of information over in a short time and well explains the mathematical processes.
This is when you realize that the reason you did not understand something was not your fault. Teachers with Ph.D. make a difference. Thank you, sir.
it is very usefull ..... thank you from me - indonesia.
Thanks. Hope the exam goes well.
Thank you so much. You are a talented lecturer. Watching your video was a pleasure for me.
wow
I am going to hav my exam this evening!
Just in time to watch this!! Thanks a lot!!!!!
Oh man you're the God of physics!
salute for your hardwork sir. i specially like your quantum mechanics and atomic physics videos. could you possibly make a couple more of those please? a little bit on perturbation theory and hartry-fock approximation + some molecular orbital and density functional theory would be very helpful for chemistry students. thank you very much again..
where have you been all my life? THANK YOU!
great video. maybe the most succesful entropy explanation in earth!
but still i should watch a couple of times again to understand what's going on literally ! :D
Awesome, can't wait for A level physics :)
You sir, deserve my tuition.
Very nice video, love how I can follow the process of getting to it
A More mathamatical account could make it marvelous
anyways love you sir
Interesting video!
This is an invitation to see an artist theory on the physics of light and time!
This theory is based on just two postulates
1. Is that the quantum wave particle function Ψ or probability function represents the forward passage of time itself
2. Is that Heisenberg’s Uncertainty Principle ∆×∆p×≥h/4π that is formed by the w-function is the same uncertainty we have with any future event within our own ref-frame that we can interact with turning the possible into the actual!
Brilliant !!! Consice and clear !!! Thank you.
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One cannot help to surmise perhaps there's a link between entropy and the expansion of the whole universe. Just as entropy must always be increasing, so that universe must always be on the expanding, as if holding up the former law.
SIR, YOU ARE MY HERO!
Kelvin is just Kelvin -although equivalent in magnitude to a degree Celsius, the Kelvin is not in degrees-seems like a minor point but necessary to understand
Great revision Video for Thermodynamics up to Entropy part........Very useful and thank u very much for the video.
@4:00 dw = -P * dv ... Does P represent the pressure before or after the change? Also, shouldn't it be dP?
The video taught us how to get equations of thermodynamics. It is good. But It need more specific examples would be better. In addition, it can give us some pictures or graphs to help people understand easily. Because equations are difficult for some people to understand. They need strong math physics backgrounds to support people to understand. But the source of each equation is very clear. Many people who have some basic engineering knowledge could know them more easily. For me, it is good material to help me review equations of thermodynamics such as entropy and enthalpy equations.
This theory is based on just one equation (E= ˠ M˳C² )∞ the Lorentz contraction of space and time is between the energy and mass. The greater the energy the greater the contraction of space and the slower time will run. Mass will increase relative to this and each ref-frame can be seen as a vortex in space and time. The brackets represent the boundary condition of the ref-frame formed by the energy and the infinity symbol represents an infinite number of ref-frames that make up our Universe.
i wished you were my professor in thermodynamics, everything is much more clear now
Thank you for the video! It's always amazing how simple equations have so many secrets to teach us when we play with them!
I have a question. I've been watching videos that were vulgarising quantum mechanics and they were saying that in a vacuum particles were always popping in and out of existence and I was wondering how that could be satisfying the equation and the end of your video.
The reason given at 14:20 to take out the term (du/dv)T=const , is not valid. gas internal energy only depends on T, only when there is no work (constant volume process). Here when we talk about a general process, that argument cannot be valid anymore! Would you please clarify it?
Great video!!! Very helpful! Awesome job!!!
In a case where we wanted to prove that heat cannot go spontaneusly from colder reservoir to hotter reservoir ( T2 to T1) we had used condition delta S >= 0 , however this is a condition derived when describing Carnot process.
However in our example we don't have got Carnot process nor any engine, so why cannot we assume that delta S < 0 ???
Why are we prohibited to assume that delta S < 0 ?
Really Doctor, you are excellent ! we are lucky to have your great explanation ! we need more !
Around minute 4 :30 --- if no heat is flowing into the box dq=0 and du = - Pdv where P is compressing the gas.. This means the internal energy of the system decrease as more volume is compressed !!!! -- how is that possible as more work is put INTO the system the less the internal energy? It should be the other way . The du should be positive as the volume gets smaller and smaller. du = dq + dw and dq should be the heat INTO the system and dw should be work done ON the system. Am I missing something? Great set of lectures and very well thought out.
you are a wizard... ty
Beautiful, very compliment
how does the chain rule work to expand (du/dt)p at 13:10?
World gonna finish soon....entropy increasing , disorderness increasing , useful energy decreasing...btw nice video..
Great detail derivation. At 16:12, the subtitle is isothermal but actually you are explaining adiabatic since you make q=0 in the following derivation. Just want to check that I followed your content correctly.
At 14:40, when you explain chain rule of partial U / partial T at const. P, Are you explain Cp (h) or the partial of internal energy u respective to T at constant P. I lost when you expand the chain rule and conclude back to Cp=Cv+R.
I am wondering why Enthalpy was brought in. The connection between Enthalpy and second law didn't become very clear. But a great lecture, as usual.
Very methodical. I realy enjoyed this video
i think the chain rule you used is wrong, it should be (du/dp)(dp/dT) + (du/dv)(dv/dT), isn't it?
I imagine Atoms, Particle's must be a spatially extended locational spherical rings series compressing+4-0-4+decompressing eXpanding sphere's dissipating gravity same ratio information is being multiplied by inward spherical wave's of future probability generating electrical potential oscillating volume of a mass at the expense of entropy of gravitational potential.
Wave's must propagate non-linearly at the central region producing two coupling reasonances. We only see the eXpanding ripple's."
The fact that s2 is always greater than s1 makes its clearly
can u make a video explaining in detail what the last equation means? with an example?
Easy...when someone takes you through it step by step!
Fantastic video!
Great video! Can you say natural log, or something like that instead of just log, or simply clarify it, because I got confused about the base first time, other viewers may also get confused.
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Hello. First of all, thank you for your videos. In this video, after 17'', you use a formula (of dU) which allows a variation of the volume. My problem is that you have equalled this formula of dU with one that was derived by considering a fixed volume ( with Cp). Perhaps, i missed some explanations. Thank you for your lightening.
Where did the initial energy in the universe come from if it couldn't have been created in the first place?
Thank you so much for this.
Great work! Thanks
Sir, i am going to take alevel (A2 exams this may/jun). i studied physics at home from your channel.I am close to my alevel exam, so i wana skip the parts that arent in the syllabus. I cant find about entropy n the second law in the syllabus so can i skip it n move on????
great video just one question on the derivation of Boltzmans formula. Does it necessarily have to come from doubling the volume? What if you tripled the volume? would boltzmans formula still arise? yes but then it would be 3 to the N power, so is there alittle more to know about that?
I'm confused about the simple summation of change of entropy for heat Q transferred from the hot body to the cooler one. You have simply -Q/T1 + Q/T2. What confuses me is that presumably the temperature of each body changes as heat is transferred. Why can we simply use the starting temperature of each body?
I found web.mit.edu/16.unified/www/FALL/thermodynamics/notes/node41.html that gives some examples. It starts with the example I was confused about. It is simplified because they are both heat sinks that can provide or absorb heat without changing temperature. Example 4 shows what I was thinking of when a hot brick is brought in contact with a cold one. There the temperature of each brick changes to a medium temperature. Integrals are done with dT/T so end up with natural logs similar to what you did with the changing volumes. With C the heat capacity, H the high temperature, L the low temperature, and M the final middle temperature, the result is change in S = Cln(MM/HL). Why is this guaranteed to be larger than 0? It's not obvious to me that M squared is larger than HL.
it seems to me that all particles can randomly go to one part of the container (end of the video), but that is impossible according to the mathematics, not just improbable. Is it because of the way we look at gas in the gas law?
Having the same thought about the gas as you did, I supposed that the maths doesn't necessarily factor in the difference in rules that apply at the quantum mechanical level, which might fit the gap we observe in the simplified mathematical explanation causing us both to question it?
Hello Dr, that is a very nice video. Could you make some videos about Thermodynamics for open system, if you know it, please ? It will be awesome. :) Best wishes.
@35:00 Shouldn't the fact that you are integrating from C to D result in not needing the "-" sign before the integral?
@Dr. Physics. can you please explain the concept of entropy for non gaseous (like charging capacitors, magnetic or gravitational field) systems. where there is not a heat transfer but some other form of energy and work is done in different forms.
or if you already have, let me know the link or just guide to a book or notes that has dealt with such problems.
sir I'm your big fan ......sir please make videos on stastical mechanics ......
Rather good and informative video sir.
Relating to Thermodynamics, what are you views on the words of Dr.Wernher von Braun's conclusions; relating to the 1st and 2nd Laws of Thermodynamics (as it relates to the big bang theory? I found his observational conclusion rather refreshing. I would like to know your thoughts professor. Below is his statement. Good day to you.
The First Law of Thermodynamics states that the total quantity of matter and energy in the universe is constant. The Second Law of Thermodynamics states that matter and energy always tend to change from complex and ordered states to disordered states. Therefore the universe could not have created itself, but could not have existed forever, or it would have run down long ago. Thus the universe, including matter and energy, apparently must have been created. The "big-bang" theory of the origin of the universe contradicts much physical evidence and seemingly can only be accepted by faith.1 This was also the case with the past cosmogonies theories of evolutionists that have been discarded, such as Hoyle’s steady-state theory. The universe has "obvious manifestations of an ordered, structured plan or design." Similarly, the electron is materially inconceivable and yet it is so perfectly known through its effects," yet a "strange rationale makes some physicists accept the inconceivable electrons as real while refusing to accept the reality of a Designer." "The inconceivability of some ultimate issue (which will always lie outside scientific resolution) should not be allowed to rule out any theory that explains the interrelationship of observed data and is useful for prediction," in the words of Dr. Wernher von Braun, the renowned late physicist in the NASA space program.
DrPhysicsA
+Joe Chaplin a designer is not observable in the forming of the universe. my orginal point stands
Alexia Richardson neither is the big bang. My point stands as well.
Joe Chaplin big bangs effects are observed. Learn something before you try taking me on kk thanks
Alexia Richardson please state your claims with facts.
13:24 can u please tell me why ??????????????
Also, our base point is ideal gas law pV= nRT . The law was coined by Clapeyron well before molecular kinetic theory of gases. How did Clapeyron derive gas constant R ?
***** Sorry for the silly question, but aren't you using kinetic theory of gases? How did Clapeyron figured it out without this theory?
Appreciate that video Doctor!!
very good video, but talking about entropy in terms of disorder is very misleading (take crystallization for example). for a better understanding i think it's useful to talk about entropy in terms of statistical mechanics
Except most people who learn thermodynamics for the first time don't know, and probably aren't capable of learning, statistical mechanics. No?
Sir
Thanks very much for your clear explanation. But I have one confusion for it. As I understand Entropy equals to Qrev/T. Then do S1 and S2 you mentioned are the defination of Entropy or they are the Entropy Transfer.
Does entropy imply that the Universe is a closed system?
Thank you very much! It was very nice lecture and helpful.
DrPhysicsA can you do some videos on statistical physics too?
I have to study it this year and I got no clue what it is...
Hi Doctor, from my understanding：
When heat is added, gas particles gain more kinetic energy and therefore their internal energy increases therefore temperature increases. (considering it is an ideal gas and U= total kinetic energy of the particles). If so, why would temperature be constant when heat is added during isothermal expansion?
Also, if U increases that means there is a change in U therefore delta U is not going to be zero. However, for your theory that all heat is converted to work in an isothermal expansion, delta U must be zero so that Q = W (this is from delta U = Q - W)
So I am quite confused by these concepts. Please correct me if any of the above is wrong and could you explain these please?
Thank you so much and sorry for typing an essay...
+Samantha Yu As the gas expands work is done by the system on the surroundings and this means there is a decrease in internal energy (because work is done) which in turn causes a decrease in temperature in the system. To counteract this decrease in internal energy and temperature (so that the expansion is isothermal) heat is provided from an outside source (the candle). The net internal energy change will be zero and the temperature will be constant.
ΔU = q(heat from candle) + dw(work by system) (dw will be negative as work is done by the system and dq = -dw => dU=0)
+Andrey Thank youu :)
Sir, if you have time kindly make a video of processes and pure substance. Thank in advance 😊
Hello professor its good to in adiabatic process of carno cycle explain that the m(c) in constant v is infact the m(c) in constant p. Because there in no change in q so the pressure is in equibalance and this assuption is possible. At min 30
Why does heat go from hot to cold and not the other way? No, the differential in temperature is being eliminated......it is the differential that is important....open a container of high pressure gas in the environment and the differential in pressure is eliminated.
The derivation of s = k Ln W this way does *NOT GIVE THE BOLTZMANN EQUATION!* because W made equal to the total number of microstates in the system is only
(1) an approximation of the most probable macrostate (equilibrium) and secondly ignores internal structure ie it is only valid for a gas and
(2) misses the Boltzmann term W which is actually based on the number of microstates in a macrostate chosen by an observer for a state not at equilibrium.
thank you so much
@ 4:32 sir, internal energy is function of only temperature. how it will be function of (V) also.
what is dark energy and entropy relation...????useful energy will be vanish once in future so expansion will stop???bt it is accleraing day by day
never seen asuch a teacher like this
thanks much, now am not get bothered to attend lectures room. its just to click and find lecture i want.
I + F+ C = Like.
I like Fish and Chips.
Actually this doesn't seem too easy but it seems easier than GCE Science at school.
This is harder than A Level.
@@AlchemistOfNirnroot
Only joking!
do u hv more videos of thermodynamics?
i cannot understand why differential of enthalpy function is differential of heat dH=dq......
WHY YOU WROTE (T,V) FOR U WHILE (T,P) FOR H ?
Many Thanks
Sir Please upload a lecture about Gibb's free energy , Helmholtz free energy and Maxwell relation.
very nice lecture. thanks