An Actually Good Explanation of Moles

Moles (in chemistry) are really clever and useful. The definition involves a really big number called Avogadro's Number and on its own is really unhelpful when trying to understand what the Mole is actually for! The best way to get your head around this unit (Mol) is to look at the problem that is solves. Along the way you'll find out about Atomic Mass Units, isotopes and some dodgy chemical equations!

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[SteveMould]

This week should be a short video. This was supposed to be a short video. But then it turned out to be long. Hope you like it. And I hope you now understand Moles if you didn't already.

[davidguthary]

Fun fact: because of the importance of the mole in chemistry, it has its own unofficial holiday similar to Pi Day. Mole Day is celebrated every year on October 23 from 6:02 AM to 6:02 PM, in reference to Avogadro's Number 6.02*10^23.

[mesaprime]

"I have a drawer in my house that has half a mole of cables in it" thats what we call a premium joke

[blackmber]

Funny story about Beryllium Oxide. I dressed up as the compound for halloween with someone I dated - we each wore a t-shirt with the chemical symbols and some pom-poms to represent valence electrons. I think the ratio of our weights was about 16:9, because when we went rock climbing and I was belaying him, the rope suddenly lifted me off the ground and I ended up halfway up the wall while he dropped toward the ground. But the reason we decided to dress up as BeO is because of its incredibly strong bond, which I hoped would be a sweet metaphor for our relationship. Instead I discovered it's very toxic and hard to break up.

[bielsabas]

You make learning science, physics, and chemistry so "not anxiety inducing". Thank you for the work that you do! Your videos are so calming to listen to.

[CodeKujo]

"One micro Mole of sand grains on the earth" - wow, nice example just how big a Mole is / how small atoms are.

[jeffreybernath]

I love that Steve can't say "ounces" with a straight face, like it's the most ridiculous unit he could think of for this example.

[bestcreations]

I am a stem tutor and have run into a situation where I’ve had to explain why we use moles to a student who was getting frustrated with the idea of it. This video helped me put some thoughts into words but I also have found an explanation that I quite like to give. In the video, it is repeated that avagadros number is just a counting number used to describe a specific quantity of things. Thats a long winded explanation that some may not easily get. I love to compare it directly to other familiar numbers just like that for example my favourite is to use a bakers dozen. We all know a bakers dozen is 13. It’s just a name for a very specific number of things and can be used anywhere you like. Avagadros number is the exact same thing but designed to describe such small things that to have an amount on any relative human scale you need an unbelievable amount of them. Using avagadros number as the base unit lets us talk about quantities of atoms without needing to resort to long winded definitions or unreasonably large numbers.

A good example of where we use that exact same logic is in definitions of hours. An hour is sort of arbitrary, the base unit we typically use for time is seconds, so if we wanted to talk about an hours length of time using the base unit we would have to specify 3600 seconds. An hour just makes it easier to use on larger timescales. Another example but on the opposite side of size is the unit of solar mass or astronomical unit which represent a mass approximately equivalent to that of our sun, and a distance approximately equal to that between the earth and the Sun respectively. They are just a specific quantity of units which help in talking about and working with the units on larger scales.

[CharlesBurchill]

Thanks - my dad was a chemistry professor for about 30 years and it drove him nuts that my high school teachers (and others) got caught up in the size of a mole rather than the purpose - I think he would have wished your video was available back then.... :-)

[TheNasaDude]

My high school Chemistry professor must have been really good because this is exactly how she taught us about moles :)
She was strict, but she also really loved her science

[screwaccountnames]

How many atoms in a guaca-mole?






Avocado's number!

[Sublimeoo]

"But that's impractical" has the biggest understatement in history surely

[ferretyluv]

My teacher explained it to me as being the same as saying there’s “a dozen” or “a gross” of something. She also demonstrated it by showing us a mole of water, which was like half a jar-full of water. I don’t know why out of all the concepts in chemistry this was the easiest for me to grasp, especially when I have trouble with abstract concepts. Dimensional analysis took longer for me. But the mole, I guess just by seeing a jar of water, it clicked. It also helps to see the periodic table with the number underneath each element.
XKCD also has a great What If about what would happen if you had a mole of moles.

[bionshelden]

Placing moles in the same category as the offside rule was *brilliant* ! So incredibly true!

[PWJB]

I have had great success with:"Hey you know how 12 eggs are called a dozen? Same thing but not 12 but 6x10^23 instead"

[jasonpatterson]

Explaining moles by analogy to the dozen has always worked for me. The only trick is why 6.02x10^23, and that happens to be (approximately) the number of protons in 1g of protons.

[CroomTM]

So a mol is like saying "a dozen" of something?

[mayaluna]

best explanation I’ve ever seen 😭 literally have not understood this concept for years and I now feel enlightened

[Alexa_Kelley]

That was fantastic and I genuinely wish this video had existed years ago when I took chemistry with a rather awful teacher who couldn't properly convey to me what a mole was. TY for sharing and making this.

[krava]

I’ve been watching you for a while now Steve. And I have to say that your channel is consistently one of the best ones on youtube. Your positivity, humor, eloquence and charisma all make each one of your videos amazing. I especially love how you take something which seems mundane and boring and show how interesting it is. You are a perfect example of how we can find beautiful and interesting things all around us. Anyway, I just wanted to say this, I don’t usually comment on youtube. Keep up the great work.