The Big Idea Behind Avogadro's Number (That Most People Miss) 

We're a hot mess over here when it comes to measurements. 😂 We do force them to use SI in the lab, but you can't get anyone to use the metric system outside of science class. It does give us lots of practice converting units.

Chemists in USA have solutions & are skilled in both metric and English systems of units. NO PROBLEM!

@@jimvinson6046 no problem, but they lose time and energy. not to mention the risk of errors.

​@@GuillotinedChemistryThis is a useless use of your time.

​@@ChaineYTXF dealing with English/metric or responding to comments? (Or making RU-vid videos) 😂

Thank you for stopping by and leaving a comment!

I'd like to know who won first place.

@@stefanieallen4645 There was another entry that got about three times the 'likes'. You can see all the entries at the following link... (Although, given the fact that this video is still attracting views like yours, I feel like I won. 😄) www.flinnsci.com/chemistry-week/mole-day-contest/

@@GuillotinedChemistry thank you!!!

Maybe it would have done better if you actually described HOW Jean Baptiste Perrin found the value rather than just tell us he did.

@@KenFullman fair point! I cut a lot of stuff about the experiments used (Faraday, Millikan, etc.) to make the video a little more focused. To be honest, I remember Perrin's experiment wasn't the most intuitive of the bunch, but it was based on Brownian motion of the little spheres. Maybe a future video idea, though! 😄 Thank you for the comment!

Thanks for sharing that cool story. There definitely are times when you use the actual value for Avogadro's number. It's neat to see such a utilitarian example. 👍

NICE! One of the best Avogadro's number examples I ever heard was that a mole of basketballs would be about the same volume as the Earth. So a mole of avocados would be much smaller... maybe the size of the Moon (ish)? 🌛

That would be N_avocado, right? But if a mole avocados is the size of the moon, and the moon is made of green cheese, then what is N_gorgonzola?

Gooey @@lhpl

Thank you so much for the kind words. I've also enjoyed learning more about the chemical discoveries most of us never learned. I'm enjoying the privilege of sharing this content with the community. I appreciate you checking out some of my videos! More coming (slowly but surely). 🤘

Pretty much. Once Dalton defined hydrogen's relative atomic mass as one, it set the stage for the conversion between grams and his atomic mass unit. So if one atom of hydrogen was one atomic mass unit, then one gram of hydrogen would be the numeric conversion between grams and amus... Avogadro's number. They could've used any giant number, but Avogadro's number allowed the atomic mass in amu/atom and the molar mass in g/mol to be the same. Almost too clever. Thank you for the comment!

The real contest is at www.flinnsci.com/chemistry-week/mole-day-contest/. Vote daily, my physics brother!

Glad you found it helpful and glad you're thinking about it!

I used to dismiss Dalton's accomplishments as relatively minor accomplishments, but not anymore. I was wrong and he was a beast. Glad to be back and great to hear from you again, sir!

Ha! I'll take credit for it, but it was honestly unintentional! I wish I had thought of it. 😂

Glad to have you over here! We have better food! 😃

Couldn't have said it better myself! Super interesting... Super important historically, but if the number disappeared tomorrow from the face of the Earth, I think chemists would get along just fine. 😄 Thank you for taking the time to leave a comment!

Such kind words! Thank you and I hope the rest of my content proves equally valuable to your self education. Keep up the great work! 🎉

Huge Flinn scientific fan

@@oakleafwiffleleague looking for some more endorsements? 😁

Thank you so much! I really appreciate the kind words. Glad you got something out of it!

Thank you so much! Yeah, it's fascinating how valuable the concept was long before anyone ever figured out it's actual numeric value. I'm so happy you got something out of it. 😁

The best analogy of scale I ever heard was if you had a mole of basketballs you'd fill the Earth. I think if you then compare that to the fact that a mole of carbon atoms is a tiny pile in your hand, then the scale, in my opinion, is slightly appreciable. I'm fine with teaching students the value (in fact I insist my students memorize it). I just hope teachers don't stop there as it is tough to comprehend a number that big. How interesting would it be to try to teach the importance of Avogadro's ideas without once mentioning the numeric value, for example? Thank you so much for taking the time to watch and comment. I hope you check out the other videos in my 'best of' playlist and let me know what you think. 🤘

By definition, one coulomb of electric charge passes a point on a wire carrying an electric current of one amp in one second. The number of electrons in one coulomb is 6.242 x 10^18. If you had that many grains of sand, how much sand would it be? Spoonful? Truck load? Train load? Turns out, it would be a lot more. Assuming a beach at the ocean is 100 yards wide and filled with sand to a depth of 6 feet with really fine sand, the length of the beach would be over 650 miles. [90 m wide, 2 m deep, about 1,000 km] Avogadro's number is roughly 100,000 times that. Or the beach would be long enough to wrap around the earth more than 2,600 times. Truly unimaginable. Yes, I have no life.

I'm here 24/7! 😆

@@GuillotinedChemistry indeed.

I'll work to earn that final point! Thanks for stopping by!

@@GuillotinedChemistry I just subscribed your channal

@@kiberenigestsebez6633 Huzzah! Thanks for subscribing and I'm looking forward to you keeping me honest!

It is (the mole unit) intuitively obvious to chemists, we were born knowing things, and many more...

My pleasure! Thank you for taking the time to comment!

I truly appreciate you taking the time to leave such a comment. Thank you! 🌟

I appreciate such a kind comment! Thank you for stopping by and I hope you find some of my other videos equally enjoyable!

Exactly! Dalton struggled with the idea of diatomics. Thank you for the assist there. :)

Thank you, sir! Yeah, I learned a lot making this video and I'm glad the algorithm is choosing to share it more widely. I have some more videos with some historical sleuthing especially with nomenclature, if you're interested!

I absolutely agree with you and I'm speaking as one of those chem teachers. Textbooks have managed to distill interesting stuff down to dry algebra practice. The history and the struggles are way more useful in showing how science is done than just showing they can get the same answer in the back of the book, IMHO.

Yeah, I've always seen that experiment, but have never done it myself. Sounds like it was memorable for you... Do you think I should I look into if for my students?

Assuming the property that the stuff if diluted enough and if the dilutant vaporizes fast enough, you should be left with a mono-molecular layer, you can even then calculate the volume of the cylinder, and the average atom to atom distance in the carbon chain. It's these kinds of practical experiments, even if the setup looks dull with no fire or intense reactions, that stay with people.

@@shadeblackwolf1508 I might have to look that one up again. It's definitely a classic that deserves a second look. Much appreciated.

I hope to be Oakleaf level at some point! Thanks!

Not shabby at all!

Thank you, sir!

My favorite is called 'Alchemy Of Air', but I'm reading 'how to talk to a science denier' right now and it's good too. Of course I can't forget 'The Making of the Atomic Bomb'... That could be a textbook for an introductory course. Thanks for the question and the kind words!

@@GuillotinedChemistry How to talk to a science denier sounds extremely topical. Thanks for the recommendations!

@@GoatChease Go search RU-vid for Lee McIntyre and you can see a bunch of talks with the author. Extremely interesting.

You are the first person who ever said I had sexy handwriting. 😘

My last couple videos have been hitting on it unintentionally. Especially the nomenclature videos on bi vs di and hydro vs hypo. Let me know if you like them. I'm glad you like the history... A lot of stuff I never knew!

Take a look at Kathy Loves Physics and History on RU-vid. The lady can tell a good story.

Thanks for the compliment and that's a great question about Perrin. His experiment isn't the most easy thing to understand, but maybe you'll have better luck than me. 😃 I feel like I found his paper/ book on the topic... So if I found it, I bet you could too? I'll see if I still have my old notes on this video....

Good point, but remember the mass of the electron wasn't determined until around 1909. Thomson and others determined charge-to-mass ratios for it decades before, but not the actual mass, as I understand it. A lot of stuff happened pretty quickly around the turn of the century and I really need to dig into that more. Fascinating stuff and thank you for the insightful comment.

Thank you so much! So pleased that you stopped by!

I'll put on the list... But it's a very long list. 😭

An important question. As I understand it, Dalton looked at the way hydrogen and oxygen reacted and the data suggested 1 gram of hydrogen reacted with 7 grams of oxygen, which Dalton assumed was a 1:1 ratio of atoms. So an atom of oxygen would theoretically be 7x the mass of a hydrogen atom since the 1:7 mass ratio should scale down. Now those masses were off, but the concept was sound. For example 12 grams of carbon will react with 16 grams of oxygen to form carbon monoxide (CO). No matter how much you scale that up or down that 12:16 (3:4) mass ratio will always be there, be it pounds, tons, milligrams or Dalton's atomic mass unit... The relative mass of individual atoms. Thank you for the comment... Let me know if that helped at all. 😄

Hey, the algorithm has been very generous with this video for the last week or so... I'm 0.00000000000000000005% of the way there! But that also means everybody has to watch it 75,250,000,000,000 times, so you better get started on your part. Thank you for the kind comment! :D

You're right. The number on the periodic table is the average mass of the different isotopes based on their relative abundance. Higher percent dominates the average with its mass. You're also spot on that several elements have different averages depending on where you gather them (I feel like there are about eight like that?). I never looked into it beyond that, however. I'm assuming there are ways to determine the relative composition of the different isotopes of an element... I'll have to look into that. Thank you for the great question 🤘

So many fun examples! Thank you!

I'm sad to report, that a mole of bananas compared to the size of earth is off by a factor of 10: 156,1 cm^3 (size of banana) times N equals 9.4E12 km^3 almost ten times the size of earth at 1080 billion km^3 or 1.08E12 km^3

@@lisizecha9759 so close! My favorite is that a move of basketballs would be about the size of the Earth. Maybe you can check them out on that one too. 🖖

Thank you for the comment! So Avogadro never came up with a numeric value for the number of particles in a mole of something. His contribution was the idea that similar volumes of gas contain similar numbers of particles, regardless of the identity. There are lots of different ways to drive the value of what came to be known as Avogadro number. Perrin did a good job of summarizing some of the different techniques in the paper I referenced. As for determining the actual atomic mass of elements, that's a whole other thing. There were lots of disagreements about what the values should be or even if atoms existed. The whole concept of equivalents, for example, with an attempt to use some of the progress thay said made without officially condoning the existence of atoms. So that would be a lot for a comment section, but a good idea for an eventual follow up video. I hope you subscribe to the channel and see if anything else I have here is of interest to you! 🤘

There's a fairly widely known method that's based on the assumption that molecules (typically of a fatty acid) can take up so much space in 2 dimensions to form a monolayer -- and empirically there's good evidence that monolayer forms -- and then by taking the 3-dimensional bulk density of the substances (which can be measured easily) and dividing it by that 2-d surface area, you get the size of that single dimension. From that you can calculate the dimension of the molecule, and so how many of them there must be in that space. Amateurs can use this technique to determine Avogadro's number to amazing precision given the assumption involved.

So glad I went into teaching... I think I would've made a middling chemist myself. I think there was a 50/50 chance of me ending up either rich or dead as a chemist due to some lab mistake. 😂

I am sure there are uses for the number, but in first year chemistry, it is mainly used in trivia calculations (i.e. how many atoms are in 23 grams of copper, etc.) you don't really need to use it for any practical purposes in the lab (unless you're trying to find its value). It was important to find because it allowed atoms to be measured in grams as opposed to a relative weight. But I agree with what I think you're saying... It surprises students that we were doing pretty well without knowing its value.

Thanks for that insight! I've never heard of Hahnemann and I appreciate the introduction!

No, because then I won't be able to remember my anniversary! 😂

I have to remember that play on words.

Stop it.

@@GuillotinedChemistry why?

@@vincentrotunno1479 He's more than just a brand of guacamole at Trader Joe's.

@@GuillotinedChemistry ???? avocado is not a brand of guacamole???

@@vincentrotunno1479 Not JUST a brand of guacamole. He is, in fact, the face of their guac...

Ok I had to look this one up. 😂 Avogadro is slightly different from Avada Kedavra.

I hadn't heard that one. Awesome!

Yeah, I've read not everyone is thrilled that Avogadro's number is a fundamental SI unit (like the Boltzmann constant). Out of curiosity, why would Avogadro's number be temperature dependent if it defined as exactly 6.02214076 × 10^23 elementary entities?

@@GuillotinedChemistry This number is just a convenient way to express the large number of particles in a usual gas sample. Could be a dozen or a thousand. For actual gases, like Van der Wall, the ratio PV/kT is temperature-dependent. In general we have the virial coefficients. The relevant fact is that in the equation PV/kT = N, the number N is always a integer, denoting the basic atomic hipothesis, Likewise, Boltzman's constant is not a fundamental one, but just a energy converting factor.

@@josemarcos6441 I agree that Avogadro's number is an arbitrary number, but at its current value it allows the value of molar mass to mirror atomic mass so I guess it's a special type of arbitrary. 😂 Again, thanks for bringing up boltzmann's equation... I'll have to look more into that!

Thank you! (?) 🤔

Great question. I think a lot of teachers ONLY use Avogadro's number as a conversion between atoms and moles. which in my opinion misses the point. The concept of equivalent masses is extremely useful even without the number. Think about it... does a student need to know the exact number of atoms in a test tube or that the ratio is correct for a chemical reaction? Outside of trivia conversions, the first year chemistry student actually will never use Avogadro's number because the actual number of atoms or particles is certainty interesting, but irrelevant to a chemical reaction as long as they understand the ratios. But that's what I think. 😁 Thanks again for stopping by. I really appreciate it.

Yeah! I could do a whole video on how the value of constants have changed (which sounds like an oxymoron) ⚖️

@@GuillotinedChemistry I would like that. I know the definition of a foot was changed slightly a few decades ago to make conversions between imperial and metric more convenient, and I know the kilometer definition changed slightly to make a speed of light a convenient number.

@@sciencenerd7639 I'll put it on the idea list. My brother wrote a couple TED-ED videos, one of which hit some of the stuff you mentioned. Look up 'why the metric system matters'.

@@GuillotinedChemistry I went and watched it, good stuff

@@sciencenerd7639 he's my twin brother, so I'm not impartial, but I think all of his are pretty good!

You can do that multiple ways. But the big one was Perrin's work, based on Einstein's theories using Brownian motion. Sorry, the nuts and bolts of that were outside the scope of this video, unfortunately.

Thank you for the comment!

Honestly, I've never heard the value used. Are you sure it was avogadro's number? Or perhaps was your teacher mistaken? Very curious...

Thank you for stopping by! NightHawkInLight is the man. 😎

@@GuillotinedChemistry Agreed. I just loved your channel btw, great content! God bless for sharing such knowledge!

@@ulysses_grant I appreciate the kind words! I'm glad you've found some decent stuff here!

Who says I don't already have such a team combing over every word of my scripts? 😜

I think the idea that names shouldn't be translated it a great idea. We English speakers do like to pronounce and spell things in our own goofy ways... no doubt. I, for instance, added an extra 'i' at the end of Cannizaro and kept calling him Cannizario for some reason. Sigh.

That's a neat way of thinking about it!

I think they toyed around with the number of atoms in 12 grams of carbon-12 (and then in 16 grams of oxygen-16?) and then they defined it at its current value in 2019 regardless of any measurement. But you're right... pick out any element and look at it's molar mass, that should be around Avogadro's number.

@@GuillotinedChemistry you don't have to carefully choose your words with me :) 😀 I just realised the important part of this is the gram. All atoms will have a ratio with any unit of measurement, although it is interesting that the lightest element coincides pretty neatly with 1 gram

@@drfill9210 the precursor to the mole was the gram- atom or gram-molecule as I understand it. So it was Dalton's aspirational relative atomic masses scaled up to the lab measurement of grams. Since Dalton decided to make hydrogen '1' in his relative masses, it's definitely neat how '1' in grams of hydrogen would give you Avogadro's number in atoms.

@GuillotinedChemistry I thought you knew a large part of the story and were simply looking for a way to agree with me XD 10 points for diplomacy! The only thing I can add to this is that I think that a gram is calibrated to 1 mol unisotoped hydrogen and there is no chance involved. You alluded to that... also I get why avogadro is so respected now. He figured out 1 mol occupies 52 liters... at least he figured out the same space.... which means you can get 52 litres of stuff, 52 litres of other stuff, then solve the common ratio differentially. The weight of the atom or molecule is simply the smallest divisible number you take from your weights of your smallest common unit... I think

.6 cm³! There is a decimal there, but I definitely should've put a zero before it to make it easier to see. Question for you... how'd you get that superscript to show up in a comment? Is there an easy way to do that? (Asking for a friend...)

@@GuillotinedChemistry It's a german keyboard layout and the keys for 2 and 3 give " and § as caps characters and ² and ³ with the Alt Gr modifier key. But these are the only exponents one can usually do.

Yeah, this is a little early for you, but it'll make a lot more sense later in the year...

I didn't know what a trillard was... Thank you! 🙌

The fact that it is in of the fundamental constants certainly means the number is important, I agree. But IMHO, introductory classes over focus on that number and it is rarely used outside of trivia calculations at that level. I find students struggle with the more important idea that the mole represents a measurable amount of an equivalent amount of particles. Molar mass is way more ubiquitous in first year chemistry and a lot of students struggle with what it represents. I don't think most teachers clearly understand where the actual value came into common use, so those were all my motivations to devalue the number. I absolutely appreciate your perspective and thank you for taking the time to comment.

Ha, you're not the first to correct that! Not sure how I butchered that. 😎

Ha! Yeah, I guess you're right there! That would be a natural consequence of saying one gram of hydrogen is one mole. That's cool... Never really thought about it that way...

@@GuillotinedChemistry As a physicist, I would say that the inverse of A.N. is a quanta of atomic mass. Or all of the mass (99.9%) is made up of nucleons. And then Mendeleev comes along and hints at the quanta of atomic charge..

Hydrogen is one of the dozen or so elements with a range of values. 1.00784 is the lowest, I think. It can go as high as 1.00811 according to the IUPAC. I think it really depends on where you take the sample. iupac.qmul.ac.uk/AtWt/ What's a bungarrow, by the way?

@@GuillotinedChemistry wow that is fascinating. i would like to know mor3 about that. Like, it can’t be an isotope thing… i really can’t imagine what’s going on there. you say it depends where you take the sample? Is that a latitude consideration or a pressure consideration or something? btw, I take it back about the bungaree’s thing… it’s a Australian aboriginal name for a goana. it was kind of harmlessly chiding the error, but now I’m going to find out some more about that variance. thanks a lot.

@@antonychipman3088 Honestly I'd like to learn more about it too. There's a cited article that talks about the ranges. I'll have to read it so see if there's any explanation... www.degruyter.com/document/doi/10.1515/pac-2016-0302/html Thanks for your interest in this!

actually, i did the research. It is

​@@antonychipman3088interesting. I assume something similar for the other elements too. Thank you for taking the time to keep me in the loop!

You're not the first to point out that mistake! 😂 My apologies!

It is taught that way. I would say that a curious student would respond to your definition with, "you say it's useful. Why? What am I ever going to do with that conversion?" Or they might even ask, "where did that come from?" Or "how did scientists connect the atomic masses on the periodic table to laboratory mass equivalents without knowing Avogadro's Number?" Or even " why are atomic masses the same value as molar masses?" Those are the more interesting questions, IMHO. Scientists were doing a lot with the concepts behind the number long before they had the number. Perhaps I put it poorly, but we definitely need students to be curious about the content. I think your definitions, though correct, are not super interesting to most students as they don't seem relevant to any laboratory level experience. They'll memorize that definition for you, but if you poke them to go further, they'll probably just shrug their shoulders. Thank you for taking the time to comment! 🤘

Hi@@GuillotinedChemistry ! Sorry about the grumpy tone :-( I've fixed that. "Dalton's" (amus) are at a conceptual remove from protons and neutrons so are less approachable to the learners who haven't wrapped their heads around Avogadro yet. So that's why thinking of it in terms (roughly) as the number protons (or neutrons) is simplest. Grounding it so simply and deeply means there is essentially nothing to "remember", instead there is just this one, trivial, thing to understand. Thanks for your treatment of the material. I think your goals in this piece were different from what I've had to tutor learners about, re A's #.

@@smurp_com I wholeheartedly agree that stating avogadro's number is the number of protons/nucleons in a gram is a good way of anchoring that idea for students. I think it's a bummer that that is as far as most classrooms go, but if you're tutoring students then I'm probably already preaching to the choir. There's not much to do in first year chemistry with the value of Avogadro's number besides trivia calculations. I think it is way cooler for students to grapple the way early scientists tried to connect the atomic and laboratory scales. But maybe I'm an outlier. 😄 Thanks again for the thoughtful response.

I wish I had! It's a Sniglet!

😁😁@@GuillotinedChemistry

The question is how many digits.😂

Tell me more... Why would October 24th make more sense?

I fooled that RU-vid niche interested in Avogadro to click on a video about avogadro! You caught me 😂

@@GuillotinedChemistry nah you caught me

Most people just say they can't stand my voice, so that's a step up. :) Whenever I hear someone say OH, it reminds me of the movie Rushmore. But if you don't get the reference, I can see how it could offend.

@@GuillotinedChemistry I'll check out the movie. I've never seen it before. Thanks for the reply. Your voice is totally fine... I don't understand that opinion.

Sorry I didn't meet expectations! Thanks for giving it a shot ... The point of the video was that number itself is the least interesting thing about the concept, but I'll work on hitting the mark better next time. I appreciate the comment!

Which one are you referring to? I messed up a couple I think.

@@GuillotinedChemistry You keep saying avogado

I've definitely heard that before. 🙂 Which part in particular?

@Moonlight Gamers the barriers between academic subjects is rather arbitrary. But for the record I strongly disliked physical chemistry too, back in the day...

@Moonlight Gamers a lot of students have a love/hate relationship with chem! 😄

@Moonlight Gamers there is something for everyone in chemistry (but usually something you dislike too...)

@Moonlight Gamers thank you for subscribing! 🎇

I definitely mispronounced Cannizarro, but what's the right pronunciation of Dalton? (And what did I say?) 😄

I'll work on it! Thanks for stopping by!

if we were to define the value sanely, as a perfect cube, which we could do, since we defined the value, then it would also be nice to follow that up with some other very basic changes to the measurement system. for instance, all of the base units should be related to this number. so the base unit for mass should be the mass of this number of helium atoms. the base unit of time should be this number of beats at the frequency of D3. the base unit of distance should be how far light travels in this time. the base unit for electromagentism should be the voltage of this many electrons. etc. and the reason for using helium as the reference is that it's the most stable configuration of protons, over the widest range of conditions, known. so using anything else as your standard would do things like curve your temperature scale, as the Kelvin scale is, so that there is no meaningful correspondence between units of thermal energy and units of temperature. but, by all means, keep doing it wrong and bragging about how great the way you do it is. that's just charming.

at present we have things like the Coulomb, which is the charge of about 1 millionth of a mole of electrons. that's a scale disparity that we casually deal with in SI units all the time, so why not just actually make it a literal ratio of 1:1,000,000? but this also brings up the problem that a Coulomb isn't even physically realizable, because it's not a whole number. which means science is so absurdly broken that not only did nobody ever notice to link the mole and the Coulomb, but nobody ever bothered to rectify the fact that the Coulomb itself is an impossible quantity. good job. just amazing work you're doing there.

if we carried the principle of not being complete buffoons even further, then we'd find some nice anti-prime to define this value as. that way you could not only have a perfect cube of that many particles, and relate all the base units to that number, but you could also divide those things evenly by things like... oh, let's say... a number that all toddlers know, like 3. which is currently so unattainable with SI that 13 1/8" is almost an order of magnitude closer to 1/3 m than 333mm is. an obvious candidate would be something like 14,414,400^3, since this is only about 200 times smaller than avogadro's number. it's a perfect cube by definition, and it's divisible by everything from 1 to 16, and a whole lot more values between that and the square root of 14,414,400.

imagine being able to take 1 mole of a substance, put it into a perfect cube, and then perfectly divide that cube into a huge variety of smaller forms, down the particle. as it stands, the mole can't do anything close to any of that, because the value of avogadro's number is basically just completely random. but worse, we actively defined it to be that way, and have been proudly patting ourselves on the back for it for generations. that's up there with the dumbest things any religion does.

your concluding remarks are the hallmark of a charlatan. 'don't look behind the curtain'

I see what you did there. 😄

Good catch. Guess I like those ℹ️s... 🎇

Yeah, like the people who pronounce Goebbel's name [gu R bels] with an extra R.@@GuillotinedChemistry

​@@fagicawe do imagine a lot of stuff that isn't there, don't we? 😊

yes, like god, or the gods @@GuillotinedChemistry