Kinetic Theory of Gases - A-level Physics

[@itz_harman6106]

Those 28 dislikes are teachers, amazing video, really helps revision

[@namename3130]

What 28 dislikes, i see no dislikes. Isnt the world such a nice place without dislikes, everyone likes everything now. Fabulous

[@officials2t]

nah its bad this way cause imagine if we clicked on a trash vid but we had to wait a solid 5 mins to realise it rather than have the like dislike ratio tell us beforehand@@namename3130

[@JohnAlex5470]

I got my A-levels this upcoming October and I'm really glad that there are some people like this gentleman here who help students for free!! I wish the best for you teacher, and thanks a lot for the videos👌

[@joshmillar6398]

How did it go?

[@teamcori]

Thank you! In class I was just writing a bunch of equations not knowing where they came from and you derived it clearly 😊.

[@nairamid7835]

Your videos is the most helpful resource I have for physics. I would be lost without them truly. Thank you so much, I'm glad that you are here making these.

[@izazzubayer3233]

YOU SIR, ARE A LEGEND!

[@fakexpoxpose273]

i pray for ur well being and success in ur future endevours.. u are a legend and the unsung hero for many students.. keep making these videos for students like us to whom the text book or class lecturer doesn't seem to make any sense..

[@Chickenpop]

Best A2 physics gas derivation vid approval from S.Korea

[@richardstone5096]

These videos are so great thank you! It saves so much time rather than plodding through a textbook and it is really enjoyable listening to someone speaking and drawing nice diagrams.

[@troliverxx5351]

this is the day before my exam, this helped to get the derivation in my head, thank you

[@callumgrimes6789]

Anyone watching the night before the Paper 2 exam?

[@rhysyarde1549]

Callum Grimes guilty 😂

[@estherkirakawaii]

Same here. I have a strong feeling Gases will come up tomorrow

[@hrperformance]

Absolutely shitting myself Grimes XD! good luck ladies and gents!!

[@hannahstypayhoralikson4664]

me im super anxious

[@eligrossnass6804]

Hope this comes up the only thing I know😭😭😭😭

[@callumdryburgh1493]

dude you’re single handedly saving my physics a level thank you so much

[@ontheway5792]

Extremely detailed!! I've solved more than 25 exams in the past papers and they aren't ever that detailed!!

[@jasminbriffa9719]

I couldn't understand this trough notes and i searched for so many videos and i understood none until i got to this one. You put thermodynamics so simply into words, really well done and thankyou so much for your help!

[@bellanorton4808]

Many thanks learned this topic remotely over lockdown and I’m not gonna lie it made very little sense in the lessons so I tried reviewing the PowerPoint and it ended up just making me more confused but this really helped :))

[@weich1q2w]

These videos are some of the best and most clearly/thought out videos as it relates to physics as I have seen

[@productivity7587]

Raved is a life saver. Thanks

[@riley2476]

insane how easy you made this incredibly difficult topic to understand, thanks!

[@KarlaWilletts]

sat through this with my daughter...really helpful with derivation thanks

[@SadikKhan-wt8cs]

Sir, I love the video but there's just one thing I am confused about. Isn't force equal to the change of momentum over the "time taken *for* the collision", and not the time between two? I mean, if I am incorrect, please rectify my mistake. I'm just really confused about this part.

[@ScienceShorts]

Yes. But by using the time between collisions, we are calculating the average force a particle exerts as it goes from one end of the box to the other.

[@abbasmehdi2923]

​@@ScienceShortssir , the time between collisions should be l/u ? Why is it taken as 2l/u , please tell sir.

[@malicumalicious]

@@abbasmehdi2923 this might be late lol but its because we consider the particle going TO AND FROM the cube so it travels the twice the length

[@deustitties3589]

Have in mind 3 in kinetic gas theory stands for 3 translational movement vectors, each is perpendicular to each other (vectors along x, y, z) axes. This formula is only used in ideal gas systems, where a molecule is made from one atom

[@carultch]

Other types of gasses store energy in molecular rotation and vibration, which is why molar heat capacity isn't identical for all types of gas. Otherwise it would be.

[@geezer1024]

Thank you so much for the videos, A level physics is so hard but you make it easier for me

[@Ashley-uz2gw]

Great video. Just one problem though: the momentum of a gas molecule is p=mv, so the change in momentum is mv-(-mv). So that would be 2mv, I don't understand where the negative sign came from in the force equation. Edit: I realise you said that you get rid of the negative sign as it doesn't really matter too much, I was just confused.

[@Delboiix]

It's because change in momentum is calculated by momentum *after* - momentum *before* . So if a particle is initially travelling at v and ends up travelling at -v, then the change in momentum is (m)(-v) - (m)(v) = -mv - mv = -2mv. Hope that helps?

[@paulkim3585]

Change of any physical property is (after)-(before), so it is negative

[@AM-hn7gj]

I had the same question, thanks people in the replies :)

[@abbasmehdi2923]

​@@DelboiixHello , shouldn't time be l/u instead of 2l/u for one collision. Why 2 is there ? Also , if particle hits one wall , why are we taking whole area of six faces

[@deltha488]

I know this is probably going beyond the curriculum but does this only apply to gasses in a cuboid? What if the shape of the container is different? Is there a way of deriving this equation for irregular shaped containers?

[@ScienceShorts]

The cube is only to derive the formula. This can then be applied to any container.

[@RishiR]

Wouldn’t it be too huge an assumption if you consider the time to be 2l/u?

[@s.madheshkrishna3352]

Ikr

[@CRAZIOS]

That's literally what I was about to comment... Makes no sense to me :(

[@fbdjwjflac]

wtf this is so true

[@SightlineRecordings]

Pretty sure you just saved my life

[@999Tutorialz]

Best derivation I've seen so far, thank you!

[@abbasmehdi2923]

How time is 2l/u for one collision? Shouldn't it be for two collisions ? What about y and Z dimensions ? Please tell 😢😢😭😭😭

[@menime69]

Thank you for the explanation sir it is really helpful but at 7:56 how did you proceed to root mean square speed from mean square speed ?? please explain, I googled it but coudn't find any solutions

[@hammadullah1907]

Its not quite asked or useful the only questions asked are about what the symbol c means

[@StudyAlphaBita]

When the gas is in equilibrium , molecules moves entirely random. So all the direction of motions are equally probable. so , u(mean square)=v(ms)=w(ms)=( u^2+v^2+w^2)(mean)/3=c(ms)/3

[@yussefnoeman7794]

That was the best sum up of the kinetic theory. Kudos my friend

[@RishiR]

Why are you considering the area of the whole wall? Shouldn’t it be just the area of contact between the particle and wall?

[@jax8763]

i had the exact same question

[@jax8763]

well before anything i think he meant to represent the gas as a whole by just that one partical...but again he also mentioned that there are many other individual particals and he was clearly referring that while deriving the equation so i am as confused as you

[@AliKhan-zl2kk]

@Science Shorts This is in IGCSE physics for CIE; a whole section on this thanks!

[@amadif1793]

very clear explanation of the derivation... thanks

[@moezjadran6720]

Sir at 3:37 , can you explain me the -2mu/t part 😔

[@user-ej6we6ei7q]

Please if u alr done ur alevels and get this please pelase explain it to me, I keep rewatching it and I don’t get it

[@darvey8410]

@@user-ej6we6ei7q momentum is a vector quantity change in momentum would be final momentum - initial momentum consider momentum to the right as positive, then final momentum = -mu1, initial momentum is mu1 hence change in momentum = -mu1-mu1 = -2mu1 then rate of change of momentum = -2mu1/t

[@chijiokeokonkwo5238]

What happens when solid matter is crushed, smashed, grinded or broken in pieces? How can we explain it using particulate nature of matter?

[@adosar7261]

I can't understand why we use this time interval in order to find the force. Can you please elaborate? Thanks in advance.

[@ScienceShorts]

It gives the average force exerted by a particle.

[@Plank8642]

In the beginning of your derivation, what sets the first particle in motion? I understand the particle gets KE but from where?? What force causes this?? Im so confused

[@divyanshtripathi5309]

thanks for helping me get through A levels.

[@lucasmonks8529]

Thank you for this channel so helpful. saving my alevel fr

[@naheemahakinwale8403]

Sorry, I'm a little confused, at 10:20,why did you combine 1/3 and 1/2. 1/3 only relates to particles moving in the u(or v or w) direction whereas we are trying to find the kinetic energy of a single particle. So why?

[@inyoungbaek6426]

c (rms) is an average speed that takes into account of all 3 different directions🙃

[@umarkhalik6230]

i know its silly but do these teachers have to use these markers to write on paper? it makes me tingly and i get goosebumps throughout the whole video. its still a great video and explained the theory really well and i really appreciate that, just curious bout the markers.

[@jeenajayasankar1305]

Sir... U are too good in explanations

[@alexcuenca]

So based on the fact that we use for time the time that it takes to travel back and forth, this means that the force we obtained it is not the force during the impact but it's the AVERAGE Force that is felt during the whole back and forth translation, the force THAT is felt by the particle at every point during it's translation, is my understanding correct? Please answer.

[@ScienceShorts]

Yes, you've got it 😊

[@alexcuenca]

@@ScienceShorts cool thanks! 😊

[@user-ph9pm6fc7g]

at 9:50 you equated density to p = Nm/V or (#. molecules * mass)/Volume I'm confused where the #. of molecules comes from here, or if density is different for a gas?

[@StudyAlphaBita]

To get the total mass of all the molecules we do this.

[@RajVerma-lc6cc]

sir awesome work just fab

[@zmaxproductionsharry5806]

what do you mean when u say Duration of collisions is very short compared to time between them, do you mean the time it takes for the particles to collide?

[@yousufajaz7917]

Time of their actual collisions. While they are together colliding. Compared to time they are apart and not in a collision

[@axsharma1]

A container of volume 0.7m3 holds oxygen gas at a pressure of 4.0 × 105 Pa and a temperature of 288K. (Relative molecular mass of oxygen gas = 32.) Calculate: (i) the number of moles of oxygen gas in the container; (ii) the rms speed of the molecules. Someone help me and explain this please!!! Much appreciated

[@alii7520]

aavash devkota (I) : pV = nRT 4 x 10^5 x 0.7 = n R x 288 n = (4x10^5 x 0.7)/(R x 288) and just type that into your calculator

[@rawrrii1020]

1 year late.. lol but for the second part you can use equation pV=1/3Nm(crms)^2 Use the value of moles you got in part 1 nR=Nk Rearrange nR/K =N Then find mass of oxygen: Relative molecular mass x moles= mass Insert values into equation : (pV/(3)Nm) =(crms)^2 Square root answer And then you have (crms)

[@manhaabdellah3474]

excellent explaination

[@abdullahkhalil2493]

6:27 Don't agree with the statement "(u1^2+u2^2 +u3^2+...)" it suggests that there are infinite molecules which cannot be as that would require an infinite mass. Should it not be "(u1^2+u2^2+u3^2+...+un^2)" which would indicate that there are n molecules ?

[@Appilesh]

It's physics not maths

[@BeepingSheep]

Boo. Nerd. Go back to blackpenredpen.

[@jax8763]

wait i got so confused by a point...so why did you assumd that the area under force is the whole area of one face of the box which you suggested to be lz x ly. does that mean that one single partical is as big as the box which does not make sense at all?

[@ShahbazPanezai]

?

[@ScienceShorts]

No, it means the force exerted by one molecule on a face lylz.

[@ferdousreza6907]

@@ScienceShorts So if I punched a gigantic wall that gigantic area, does that mean the pressure I exerted is P=F/Area of the entire wall ? Contradictory to what we've learnt about pressure isn't it?

[@carultch]

@@ferdousreza6907 There's billions of gas molecules. This is simply the force on one face of the container, due to the "average" gas molecule. I.e. the gas molecule moving at the RMS speed specifically.

[@burry218]

Excellent work, Sir! Your work is very detailed and I appreciate that very much. Thank you!

[@peterkaka5281]

For the change in momentum over the change of time why do u use 2l when calculating the change of time? Shouldn’t change of time = to the time of impact not the time between two collisions on the wall. Really confusing.

[@ScienceShorts]

This is so we get the maximum time within which the collision happens. To get the average force, we need to take the change in momentum and divide by the total time this happens over, seeing as the impact time itself would be infinitesimal.

[@PatrickAndrewsMacphee]

​@@ScienceShorts I think he still deserves a clear answer to his question, especially given the emphasis placed on the fact that collision duration

[@paulg444]

The only step that is hard accept is the 2lx/u as the time per boundary collision, something tells me it should be on average lx/u

[@binhnguyenuc7494]

Thank you so much! I have a question, are we assuming that the container is a cube ?? because i think just so can (Vx)^2=(Vy)^2=(Vz)^2 = (1/3)(V^2)... if that really is the case, how can we still apply this equation in situation when lx are not equal to ly and lz (not a cube) ??. Somebody please explain, thank you!

[@ScienceShorts]

The cube is only a model we use to derive the equation. It still holds true for any container, as there will always be as many particles going up, down, left, right etc.

[@binhnguyenuc7494]

@@ScienceShorts Omg, thank you so much 😭 I was being stupid, I was looking at the equation for average Force overtime and wonder why on earth could F be equal in each x,y,z case if the length of each side is not equal. Turns out you were talking about Pressure and only after dividing the equation by Area did we generalize the velocity square average!! Thank you so much for the video and for your reply !!

[@bangscutter]

@@ScienceShorts I usually see this derived using calculus conventions, using dx, dy, dz differential elements instead. Your method is mathematically equivalent, without confusing students who may not be familiar with deriving things using calculus.

[@sagarpokhrel5240]

I am from nepal.And i also study science.Physics is a logical subject.So, it needs a lot of hardworking and concept.Thanks you sir for make this video and i am capable to study this.

[@davidwarui6924]

Thankyou sir its now well understood

[@ericsonofjohn9384]

Don't forget the subscript 1 next to the velocity

[@annie4005]

I like to use DINERS to remember assumptions: D - Duration of collisions negligible compared to duration between collisions I - no Intermolecular forces N - follows Newton's laws E - Elastic collisions R- Random movement S- ... in a Straight line

[@anisaahmad7586]

This was so useful! thank you!!!!!

[@jackyye0416]

I still don’t understand how you got to p=(-mv^2)/lxlylz. Why is the area xyz that should be Volume.

[@chaoyijing245]

If u look at 5:10 dimension lx is already included in the equation for force. Given that pressure=F/A, A=lylz and this combines with lx which is already in the force equation to give lxlylz which is the volume.

[@Ilya_012]

It is impossible to dislike

[@sobiasiddiqui6501]

So helpful, thanks a ton!

[@kamal3702]

wait why is distance twice the length of the box at 4:28

[@ryanalexander6858]

why is it minus 2mu? cant we just say positive 2mu from the start?

[@mrk2938]

idiot

[@Holly-ew7ps]

Can someone answer this please

[@inyoungbaek6426]

@@Holly-ew7ps cos change in p = final p - inital p. Initial p = mu, Final p = m(-u) = -mu (because the final velocity is in the opposite direction of 'u', thereby '-u') So change in p = -mu - mu = -2mu 🙃

[@saadtariq4723]

😇🤪🤭

[@ferdousreza6907]

@@mrk2938 LOOL

[@aadityaprakash139]

well explained

[@pratham9151]

Great video SIR☺

[@arik9112]

I still dont get3:08 duratuon part Why are we cobsidering 2l

[@patricknyamuswa]

Thank you sir

[@manaschaubey6364]

Do we have to learn this of by heart?

[@rt-viz954]

yeee

[@manaschaubey6364]

RT-Viz the kinetic theory model?

[@rt-viz954]

ManasChaubey for aqa yes

[@km4437]

no u dont, its given in the data sheet

[@jadkhoury6983]

why are we allowed to just remove the negative sign??

[@ScienceShorts]

We're only concerned with the magnitude.

[@maglondon]

Thank you very much for the help would failing without you very clear can u pls make a video on option topic of engineering physics would b great

[@bangscutter]

VADER is a better mnemonic to remember with!

[@ScienceShorts]

Woah! Why didn't I think of that?! 😄

[@shaunlastname391]

Proof my typewriter is not a calculator

[@garvgursahaney4650]

lmfao pls?

[@nabin6781]

can you explain to me why you said density= Nm/V and not m/V

[@Kyle-zv7gt]

m is the mass of the single molecule. so Nm is the total mass of the substance divided by V gives the density

[@nabin6781]

yea i just realised doing Np (p=density) gives the same as Nm/v

[@jirenthegray2570]

M/V here M is mass of gas which is equal to n×m(n=no of molecules,m= mass of each molecule) so nm/V= M/V

[@kaisharyislam8103]

Hi i have never seen the questions of edexcel board ask for equation like that of at 11:27. So I am a little confused as its not matching my specification.

[@MR2perfectable]

Kaishary Islam this for aqa

[@makimemeshikino8676]

these videos are the only way im gonna pass my A-levels lmaoo

[@sikanderkhan5745]

same

[@joannaholland1486]

so helpful, thankyou!!!!

[@ToxicZerp]

How can you possibly dislike the video unless you misclick the like button

[@productivity7587]

Superb

[@williamwest2832]

u r the best

[@saadtariq4723]

Thank u soo.. Much... Can u again tell me that why we neglected the sign (_) in _mu sqare

[@ScienceShorts]

Because we just care about the size of the force, not the direction.

[@krishnabhambhani5270]

@@ScienceShorts and why is that so pleasee??

[@peterwilde4022]

@@krishnabhambhani5270 We can account for dropping the negative sign using Newton's third law. -2mv/t is the force needed to change the momentum of the molecule and so is provided by the wall and acts on the molecule. The force on the wall, using Newton's third law. is equal in size and opposite in direction. This means that the force we want is positive.

[@krishnabhambhani5270]

@@peterwilde4022 so that means -ve force (due to direction) = +ve force? If relating to Newtons 3rd law??

[@krishnabhambhani5270]

And if yes how does it apply to the single moving particle's momentum because if the particle goes in a direction w momentum mv and comes back with the same momentum but with -ve momentum (-mv) wouldn't it be mv + (-mv) which is 0

[@wasanalharbi9264]

THANK UUUUUUUUUU

[@hildaascanta8742]

De hecho, entendí mas en este vídeo que en mis clases jajaja

[@ImaanYahya]

legend

[@joshvir262]

Day before exam cba to learn this just going to pray it doesnt come up

[@zeroixbb6831]

Imma just remember the cube ngl

[@ali24ssh58]

thanks buddy

[@UCSAdityaKumarChoudhury]

Listen science short I am ordering u - please make more such awesome Videos, these help me too much in my exams so u have to help me and make more vidoes or I will find u .....and beg u to do so

[@ScienceShorts]

Sir yes sir.

[@sahilsagwekar]

ARE YOU FROM KINGSMAN

[@sagarsingh4863]

I love you

[@adrienneclark-mcguire5662]

A brilliant video, thank you very much!

[@jeffreydaclan1035]

What do you mean time between them 1:49

[@1sac2012]

face reveal at 60K subs?

[@mrawesome6239]

Good Luck Guys !!!

[@f.s240]

Why is I find it easier to understand it from this ,than a book by the exam board?

[@shroomjak200]

Where did the 3/2 in 3/2KT come from?

[@JPKpretzelz]

If you multiplied the 1/3crms^2 = kT by 3, you get crms^2 = 3kT. so then you put crms^2 into the second equation, which is 1/2crms^2, meaning you halve the 3kt, making it 3/2kT. I'm not sure if I explained it well.

[@pratikchoudhury6777]

awesome

[@johnonal7774]

what are the chances of this actually coming up

[@Aixzyl]

if it does were all fucked :P

[@dickiefinehuman5269]

just memorize that shiyt bro

[@Appilesh]

@@Aixzyl No we'll be fine because we have Science Shorts :)

[@teamcori]

John Onal I think AQA might be horrible to us and put it on as a 5 marker 😂

[@sahilsagwekar]

you should try doing british accent tutorials too

[@mahfuzali2809]

5:44

[@KarlaWilletts]

I will add I am a chemistry teacher and I though it was fab

[@atharvambokar6187]

well, really nice explantion! I hope I would have watched this earlier.

[@tbobxtbob]

day before physics exam , speed = 1.5

[@sosman747]

How did it go

[@tbobxtbob]

@@sosman747 decent , thx for asking

[@RenaudAlly]

@@tbobxtbob bruh. Thanks for answering. Most just leave such comments and then don't respond