Ideal Gas Problems: Crash Course Chemistry #13

We don't live in a perfect world, and neither do gases - it would be great if their particles always fulfilled the assumptions of the ideal gas law, and we could use PV=nRT to get the right answer every time. Unfortunately, the ideal gas law (like our culture) has unrealistic expectations when it comes to size and attraction: it assumes that particles do not have size at all and that they never attract each other. So the ideal gas "law" often becomes little more than the ideal gas estimate when it comes to what gases do naturally. But it's a close enough estimate in enough situations that it's very valuable to know. In this episode, Hank goes through a bunch of calculations according to the ideal gas law so you can get familiar with it.
Pssst... we made flashcards to help you review the content in this episode! Find them on the free Crash Course App!
Download it here for Apple Devices: apple.co/3d4eyZo
Download it here for Android Devices: bit.ly/2SrDulJ
Table of Contents
Large Size + Attraction to Others 3:36
Mendeleev to the Rescue 2:30
The Hindenburg Disaster 6:19
Helium vs. Hydrogen 7:33
Making Fire with Cotton and Your Fist 10:15
Crash Course is on Patreon! You can support us directly by signing up at / crashcourse
Want to find Crash Course elsewhere on the internet?
Facebook - / youtubecrashcourse
Twitter - / thecrashcourse
Instagram - / thecrashcourse
CC Kids: / crashcoursekids

[@crashcourse]

Pssst... we made flashcards to help you review the content in this episode! Find them on the free Crash Course App! Download it here for Apple Devices: apple.co/3d4eyZo Download it here for Android Devices: bit.ly/2SrDulJ

[@jsherer9616]

At 6:05, I did the calculations and got 22.414007031828275. And you're right Hank, it was boring. I also did the calculations for the Hindenburg using ATM instead of 100 kPa and got 9,199,570.179161146 moles of hydrogen gas, or 9.2 x 10^6 mol H2. If I get enough thumbs up, I'll find a more exact measurement by using a better estimate for the temperature on that date.

[@shadow81818]

"... the ideal gas law, much like our culture, has really unrealistic expectations when it comes to size and attraction." Nice.

[@scorpiaflueman8344]

I always write Avogadro as Avocado in my Chem notes,

[@poonamjagtapfc3254]

I hope David comes here and says " I know you exist Hank"

[@blueberrymilc]

+RushaanPlays Your wish has been granted

[@poonamjagtapfc3254]

+Caleb Linscombe ahahahahahahahah are you fucking serious ahahahh

[@The_NthGineer]

To all students watching this: In the workplace, unless you're shooting a rocket or operating a particle accelerator, the Ideal gas law is correct 99.9% of the time.

[@galaxyswift7835]

What if I hit the 0.01%?

[@shivangisingh7632]

flash reference

[@JamesSmith-zx1vg]

Shooting a rocket’s equation p=ma P=the force applied to the rocket m=mass of bullet a=deceleration of bullet when it hits ship

[@smallbeanmusic2187]

Shivangi Singh ??? Particle accelerators r real u know

[@priyasarov5541]

Must be why the particle accelerator exploded in Flash

[@JustMeZeed]

Hank says: "The Ideal Gas Law often becomes little more than the Ideal Gas Estimate when it comes to what gases do naturally." My interpretation of this: Perfect world: "Ideal Gas Law" The real world: "Ideal Gas Flaw"

[@swaggerflamingo5875]

Valter Fallenius nice pun👌🏾

[@CoalChrome]

nice

[@EmergencyTemporalShift]

It would be so cool if David Tennant commented on this video.

[@lucasstraub6695]

I started CourseCourse preferring john, after this 13 episodes I'm team Hank all the way. But as the old monk said "why compare?"

[@kabigailt]

Same as me lol! At first, I liked John. I didn't like Hank at all. Because of his biology videos. But, now I like Hank more. Welp, Life changes.

[@hellohope12]

This taught me more in 11 minutes than my chemistry teacher has taught me in 3 months..

[@ZeroKage69]

"and attraction, so far that's never gone away" Well Hank, you can blame that on all your damn charisma lol

[@aqeel220]

I would just like to take this moment to thank Hank Green for helping me pass my 11th grade chemistry class.

[@skippy7865]

David Tennant must know you exist Hank. You're as internet famous as he is.

[@RosaSteltenpool]

The english subtitles are so messed up: '100 kilopascal' gets written down as '100 kill about scouts'

[@alexwang982]

Rosa Maria lol.

[@omarabdelkadereldarir7458]

Why are you using the auto-generated ones, then?

[@tuamigafannybirds3993]

omg

[@Archiegirl7]

These videos are great! I'm Biology/ Pre-Med and they help me so much with class! Is there any chance you could do a Crash Course in Organic Chemistry? That would be awesome.

[@Mieraz22]

"yes i'm looking at you robert BOYLE" xDD

[@WaldyrImbroisi]

Man, these videos are just amazing. The amount of content expressed in ten minutes is formidable. I think it is the most brilliant material available for learning Chemistry. I graduated in Literature/Linguistics and have the bulk of my readings in Human Sciences / Arts, and, even so, I'm learning like hell. It's absolutely didactic. Thanks for this amazing work and congratulations. I'll keep following until video 46 and over :)

[@ashumanchauhan1410]

u r doing an awesome job man....here in India nobody teaches us that interstingly...keep u the good work

[@eshaansprollylost5886]

yes true that, if only teaching in India could be more than just rote memorization

[@danielvanhorne1973]

That moment when your teacher tells you to watch this video, instead of actually teaching you...

[@melc7516]

Daniel Van Horne not everyone has the skills, and maybe there was nobody better to hire who wanted to teach

[@nafrost2787]

David Van Horne that's a good teacher

[@FroMaestro]

This was your best video yet, IMO. The inclusion of calculations (which I was compelled to double-check) made learning actually happen. I'd suggest including more calculations wherever possible b/c it'd take these videos to the next level of utility. Earning you praise beyond the ranks of the numerous 'my teacher sucks, but you're so amazing' comments that I believe less and less each day.

[@PatrickStaight]

I'm sure there's some common ground between chemistry and physics. Also I'm really interested in physics as well as chemistry. I imagine PV=nRT can tell us many interesting things about Neptune. If gravity is holding the gas together instead of the wall of a balloon and it's at 1×10^−4 Pascals at the outer edge there has got to be some way of figuring out the pressure at some point in the middle.

[@oopiekloha]

00:07 Is your cartoon figure playing Settlers of Catan? That makes me so happy.

[@Katiegurrl97]

Love the Doctor Who reference!

[@davidtennant237]

I know you exist Hank.

[@josephgarcia7030]

+David Tennant hold on, tell me true, are you the real david tennant or not? and please be honest. if you are not then no hard feelings

[@josephgarcia7030]

thats what I expected, but it doesnt hurt to ask.

[@creamypeanutbutterjellygir3321]

lol

[@ornateoutdoors6431]

IF David Tennent WERE to comment, I doubt he'd have 3 followers...

[@audreyandremington5265]

Hank always reminds me of David Tennant's doctor.

[@rachy__.]

isn't R=8.314 only supposed to be used for joule calculations? atm is supposed to be 0.08206....

[@blooblis642]

Rachel Yeung Yeah, he used R=8.314 because he was using kPa instead of atm...but STP is 273.15 K and 1 atm, NOT 100kPa

[@Thought-Cafe]

They're meant to be ;)

[@levyxx1]

I'm writing the Avogadro chemistry contest this week and I've missed a lot of Chem classes because of other commitments. Crash Course is saving my life!

[@chrishammock4544]

I used this video all day today in my class. I am very bummed that I have always felt that Hank and John were just friends I haven't met yet... Now John has to go and write books that my students are carrying around. AND THERE's A MOVIE!!! Now, I am no longer this unique little flower that loves Hank and John. Now, I'm just another part of the noise that is John and Hank's fame. Oh for the golden days a few years back when it was just me and these cool videos my "not yet met" friends were producing.

[@jakeanderson3625]

+Chris Hammock I feel your pain. I didn't know who they were until they were both pretty much super stars...I still feel like we would have been best friends...

[@shontzu]

Seriously i love y'all SO much your videos are so fun to watch and they're short, entertaining, and highly informative compared to other channels. Full support from me!!

[@JustMeZeed]

The Ideal Gas Flaw??

[@vaishnandurkar9772]

LOL love it hahahah

[@mharth6594]

Demonstrating that increasing P will increase T was great. I’ve always had a hard time believing that until now.

[@TrollOfReason]

The makers of the Hindenburg not only filled it with hydrogen gas, but they also coated it with a mixture of iron oxide and refined, reflective aluminum powder. This mixture, as some might know, it also known as "solid rocket fuel." Which explains why it suddenly burst into flames as soon as the mooring cables touched the ground, and the craft's static charge was released. Now thumbs up for science and history, because you just learned several somethings.

[@ScholarOfImagination]

DAVID TENNANT AT MY HOUSE TO PLAY BOARD GAMES AND PUPPIES TO CURE CANCER!!! I'M IN!!!

[@enricoalessio5434]

PETA don't like when you use puppies to cure cancer

[@bonndell]

am I the only one who finds his intelligence so freaking attractive? it makes me tremble and want to hear him talking more like wtf is that love ? xD

[@swerdfish1005]

You're both right. Stanley Devastating didn't show a difference in his notation, but there is a problem with the video. The graphic around 2:50 effectively shows P*(V/n)*T = R when it should show PV/(nT) = R. Hopefully crashcourse will add an annotation or something to correct this soon.

[@EInc1000]

Its like as soon as I start to get it, something I forgot are don't understand shows up! Back to the first video I guess.

[@thdj4326]

6:29 "Hank Green and Crash Course are slammed by Wall Street Journal for Using Nazi Imagery in their videos"

[@PatrickStaight]

Wow! thank you, these are some great terms I will look up right away. Originally I was trying to figure out the total volume of Neptune as it sits in space but I quickly realized that unless I think of space as having an extremely low pressure instead of thinking of it as a vacuum I was going to be dividing by zero. So I instead bounded the question at an altitude Wikipedia had some data about.

[@DrDeeDot]

You'll definitely need to know about hydrostatic equilibrium to explore your curiosity. As for the pressure being 1x10^-4 Pa "at the outer edge", it really depends on how one defines the "outer edge". From your comments, I think what you're interested in is the scale height of Neptune's atmosphere. Check out the wikipedia article on scale height.

[@Lance_Lionroar]

I watch this to help me out and I just feel dumber.

[@wailrimouch4973]

you wouldn't if you actually studied high school

[@manjitthind672]

Lance Lionroar dude I am eleven

[@gideonleezhongsheng8808]

Lance Lionroar I WATCHED THIS SINCE I WAS SEVEN

[@thetruthfulchannel6348]

These videos are amazing.

[@motlypunk13]

I wasn't looking at the screen and all of a sudden I heard the Tardis and literally freaked out. I thought the Doctor came for me finally. :(

[@ester9261]

you have saved my life before chemistry exams a few times now xD Thanks for the videos :)

[@NeedsEvidence]

Despite the little flaws in the video (tell Heiko or the editor of the equations) I like the style of these series (chemistry and history alike) as it helps to reach out to a layman audience.

[@NakanoHitori]

I love STP. Dead and Bloated is my favorite song.

[@pantopia3518]

Loved the experiment and the one when you crushed the can it was Kwl.

[@MansionByBeach1]

Thanks for reminding me about all these things after 12 years. I scored extremely well in high school chemistry. But never used it after, because I chose a different line of work.

[@Tenocticatl]

Same thing. The order doesn't change the outcome. I learned it as PV/T = nR. That's why it remains useful (even at university) to be good at basic arithmetic, it means you don't have to dwell on those conversions.

[@gbiota1]

"carl sagan would be immortal" -agreed

[@courteneyskye5690]

"resident house elf Amadeus Avogadro"

[@dominicwynter4805]

Hi Hank! If your reading these comments. I just wanted to let you know that I really enjoy these videos. Please continue to make them.

[@TheVergile]

something I never quite understood: If we imagine a closed container filled with 1 mol of a molecular gas and these molecules then split into 2 smaller molecules each, thus raising the number of gas particles from 1 to 2 moles - the ideal gas equation would suggest that the pressure of the whole system would increase. However: if we look at a single molecule it seems that the temperature must drop. One heavy molecule at speed x produces two lighter molecules which - due to conservation of momentum - should still have the same speed. but since their mass drops the average kinetic energy per particle (and thus temperature) should drop considerably. Also: while it is true that we do have more collisions at the same time due to the increased number of particles, the particles also got lighter by that amount. Is the solution simply that (excluding energy given to or taken out of the system due to the endothermic/exothermic nature of the reaction itself) temperature will drop and pressure stays constant?

[@falnica]

Thanks, this video will help through the ages

[@michaellim204]

where have fire pistons been all my life? xD

[@yojuls]

Thank you for getting me to focus on studying for my chemistry final tomorrow.

[@rocksheezh4906]

2:57 shows that [PV=(nR)/T]

[@shaunmorgan4997]

This guy's got a wee bit of hate for Boyle :)

[@aasthasharma3820]

just a bit

[@benlyman7880]

Long Johnson Well he was a scumbag

[@aasthasharma3820]

ehhh... i guess so

[@melc7516]

Ben Lyman How so? / How do you know?

[@bleh8892]

You don't say

[@AleksandarStoianof]

David Tennant might know you exist

[@joshhyyym]

We always use SI units for these equations, that is to say metres, and pascals as apposed to litres and kilopascals... It always seems more fundamental, although if we wanted fundamental we ought to be using planck lengths :L

[@shauryat5270]

In a series of experiments with his friend, Richard Towneley, Power discovered the relationship between the pressure and volume of a gas that later became known as Boyle's law. This relationship was outlined in "Experimental Philosophy." However, many may argue nevertheless that Boyle, after discussing the theory with Towneley and reading a pre-publication manuscript of "Experimental Philosophy" cited the hypothesis as the sole work of Richard Towneley. Boyle's mention of the theory preceded the publication of "Experimental Philosophy" by one year, which, combined with Boyle's promotion of the idea and his significant status as an aristocratic scientist, ensured the theory's moniker of "Boyle's Law." -Wikipedia paragraph

[@RoabertG]

HEH...... "The Ideal Gas Law, much like our culture, has really unrealistic expectations when it comes to size and attraction." Oh Hank, you dog you!

[@christopherrobinson193]

Who is Allison Kane??

[@Absenteeee]

probably someone he went to school with

[@GenderPranks]

A bonerific babezilla.

[@paulmcgowan8253]

Probably his wife he is married

[@Gkiranbala]

I wanna ig her now🙊🥰😂

[@anthonyred3991]

Well, 1 cm x 100 = 1m x 1000 = 1km & 1g x 1000 = 1kg etc. is just much more intuitive and straight-forward than miles, feet, inches, yards and other arbitrary units. You can be guided by principles in figuring out what these metric units mean and how they scale, whereas the others just have to be learned... Still, I agree with you on the point, that some people are being really whiny and annoying in bringing up this topic again and again.

[@pansai9983]

Oh wow!! This episode was super interesting, thanks for publishing it! :D

[@katepv275]

I am sure David Tennant knows you exist!

[@tnttiger3079]

someone should send this to him.

[@kirill2525]

That zeppelin was also painted with thermite.

[@fupar172]

+Kirill Obraztsov And the us made a huge fuss about it to damage Germanys ekonomy, also the us where the only ones that could make helium and they didn't want to sell it to the germans... Air ships are awsome not awfull!

[@samanthalee36]

Also, I was a bit confused by the insistence that 100kPa was STP, which led me to look up the value to find that this is the IUPAC definition. AP Chemistry and other US chemistry students should note that the NIST STP conditions are actually 1atm, which is the value used on the AP chemistry test. It would be nice if the team could mention that in a future video.

[@McKayLewis]

Anyone else notice that (PVT)/n=R magically turned into PV=nRT? I did get the point, love these videos.

[@Maria-zj9op]

They rearranged the equation. :)

[@TristanBanks]

The actual equation is PV/Tn=R temperature is not inversely proportional to P and V

[@liamfarrow4503]

Maria Suhail They rearranged it incorrectly though was what he was referring to.

[@crystalwaters6388]

we crushed marshmallows using that tool in chemistry class

[@Dradym]

someone tell david tennet that hank exists!

[@TemperanceRaziel]

Thank you for not soiling your videos with advertisements like some lesser science KZbinrs have.

[@Tenocticatl]

This is all pretty well established, and still very useful. So we learn about the people who first figured it out. As you get to the more advanced stuff, you'll come across more recent findings. Because the basic stuff has to be discovered first, that's what you learn about first when studying the subject.

[@beehappyy3548]

THANK.YOU.

[@lesilielesilie1662]

David Tennant playing board games :D

[@adampkalb]

There's a lesson that I've learned over and over and over again- from Codename: Kids Next Door's Future, from Phineas and Ferb's Phineas and Ferb Get Busted, from My Little Pony: Friendship is Magic's The Cutie Map, from Star vs. The Force's of Evil's St. Olga's Reform School for Wayward Princesses, from Captain Underpants's The Sensational Saga of Sir Stinks-A-Lot, and just from watching MacArthur alone on Total Drama: The Ridonculous Race, and that lesson is that being individual is a lot better than being ideal. Besides, Android also tells you to be together, not the same. March 4, 2016, 7:36am

[@Steelflex33]

it's more accurate, arguably, to use metric since Imperial measurements' definition depend on which country you are in. Which is why the metric system was made in the first place (The Kilogram is defined by a kilogram of iron in Paris, in conditions designed to minimise erosion, efforts which have been reasonably successful). The big disadvantage of metric though, is its inability to divide evenly into 3 or 7 evenly, which thanks to a mixed base Imperial units can.

[@TrueCourse]

No giggling.... I tried so hard not to. XD

[@musashi939]

TrueCourse well as a German, without that animation I wouldn't have giggled about that only due to his pronunciation of 'Die' which sounded like 'die' instead of probably something like 'Dee'.

[@wahidakhatun8889]

I'm sorry but who is David Tennant?

[@tgaontcon6515]

+Wahida Khatun David Tennant is an actor from doctor who. he plays the 10th doctor, one of the most beloved doctors of the show.

[@wahidakhatun8889]

9h ok thanks mate

[@wahidakhatun8889]

Meant to say oh

[@mellyvflo]

+Wahida Khatun Have you been living under a rock your whole life?

[@wahidakhatun8889]

No. I'm from a village

[@noldos]

The meter is nowadays defined as "the length of the path travelled by light in vacuum during a time interval of 1/299,792,458 of a second." Originally it was defined as "one ten-millionth of the distance from the Earth's equator to the North Pole at sea level". So yeah, it's sort of arbitrary but it's based on verifiable and repeatable measurements. The kg is the last truly arbitrary SI unit (still based on reference objects) in use and they're working hard on a solution to this.

[@StrikaAmaru]

7:15 "No giggling" Absolutely nobody succeeded.

[@ilikecakemehehe]

Well, puppies are helping to cure cancer now :D

[@frederickwang888]

The last experiment was basically the inside of a gun.

[@Browsing348]

The Doctor Who part made my day!

[@olamideiyanda2317]

U don’t understand how much this is helping

[@comprehensiveboy]

Written by Speedy Gonzales?

[@the_cosmic_alexolotl2282]

DAVID TENNENT

[@LivingTar]

May I request a video on instincts. I would like to know when a habit becomes an instinct, why some things become an instinct whilst others do not and if it's possible to loose an instinct. If you could it would be awesome. Keep up teh amazing work, DFTBA

[@lenabauer9242]

thank you so much for making these. i might be able to pass chemistry now.

[@annfabgirl7]

OMG THE TARDIS.

[@calvertnicholas2240]

at 2:57 shoudnt the equation be PV/nT=R..... Instead of PVT/n=R

[@surya8891]

+calvert nicholas i was thinking the same

[@ashleyteece4237]

Both are the same

[@ashleyteece4237]

Luke Johnson i never said it was

[@ashleyteece4237]

I see whats going on. sorry bout that by "PV/nT=R" i thought you ment P(V/n)T=R given thats what it shows in the video.

[@useablelobster]

Mathematician here; Simpler is better. The fact that the metric system uses much simpler conversion factors, and for more logical prefixes, as well as fitting SI units just makes it a lot easier. The maths can be hard enough without complicating things further

[@nickcameron4107]

I could see Tennet and Hank meeting at some convention and both of them asking for autographs

[@its.moonjc]

Can anyone tell me when do I use R = 0.0826 and R = 8.3145?

[@EBajnath]

it all depends on the units you are using!

[@dennischiu272]

Ellie.S Bajie I second this. :) R= .0826 when you are calculating using STP at 1 atm. R= 8.3145 when you are calculating using kPa. (My class uses atm, though we actually use R=.0821.)

[@Rowbust]

Yeah same we use .821 most of the time too. :P

[@aasthasharma3820]

this was posted on my birthday

[@_ashyou]

HBD

[@_ashyou]

Too late!

[@aasthasharma3820]

oh well, thanks anyways

[@_ashyou]

I saw your comments on many of crash course videos .Which exam are you preparing for? I am preparing for NEET

[@aasthasharma3820]

nothing, I just watch them for fun :) also, I am a bit obsessed with Hank and John Green

[@VAB0L0]

The whole equation, however, changes drastically when you take the Hindengerg's temperature at landing in consideration.

[@vwoxy1]

IUPAC has defined STP as 273.15 K and 100 kPa because actual conditions are irrelevant in the laboratory, so easy calculations are preferred. NIST uses ISO 10780 (273.15 K and 1 atm) as well as 20 °C and 1 atm because these reflect actual conditions at sea level, OPEC uses 60 °F and 14.73 PSI (probably because they always have), and the FAA uses 59 °F and 29.92 in Hg, probably because that's what some bureaucrat chose. Hank is using the IUPAC definition because he's teaching a Chemistry course.

[@lukasdanarm]

Thank you! Thank you! Thank you! You make Chemistry fun. Unlike my actual teacher. He is mean and I do not like him. He does not teach well. His Chemistry are boooooooorring

[@kabigailt]

It's actually- Thank you! Thank you! Thank you! You make Chemistry fun. Unlike my actual teacher. He is mean, and I do not like him. He does not teach well, and his Chemistry teaching skills are boooooooorring. (Sorry, I am a grammar Nazi)

[@Sapphairis]

I know someone will want to shoot me for asking this but who is Alison Cane?

[@Gkiranbala]

Let's IG her, actually 😂🥰🙊

[@NeedsEvidence]

High P and T would make the Ideal Gas mentioned in the video even a better representation of reality. You can see why if you look at the improvement known as "van der Waals" equation, see en(.)wikipedia(.)org/wiki/Van_der_Waals_equation (just look at the "Equation" section). The nature of the improvement is the inclusion of the effect of attraction between gas particles and the effective volume taken up by the particles. Both are additive corrections which matter less the higher P and T are.

[@MrPhoenixQuill]

This entire thing was fascinating, but allow me to explain the Hindenburg disaster. The Hindenburg had a cable sub structure running throughout the frame to help keep tension throughout the frame proper, these cables ran between the gas bags from top to bottom and side to side all the way down the ship. When the captain turned too sharp the increased tension snapped either a or several cables ripping a bag near the stern of the ship. When they dropped wet ropes to land, they made an electrical