 # Counting Atoms: Intro to Moles Part 2 In this video, we are going to look at how we can use

## moles

to count the number of

### atoms

we have in something so for example here I've got a container with a bunch of chunks of Carbon in it, I want to know how many Carbon

### atoms

do I have in here? You will learn how to figure that out here. So just a quick review of

## moles

. A mole is kind of like a dozen except there are 12 things in a dozen and there are 602 hexillion things in a mole and we often abbreviate this number in scientific notation as 6.02 times 10 to the 23rd (6.02 x 10^23). Now let's take a look at a mole. Right here, I have a mole of Sulfur

### atoms

which is just about 602 hexillion Sulfur

### atoms

. Now this is pretty crazy because it's such a giant number of Sulfur

### atoms

. Here's my question, how do I know that there are 602 hexillion Sulfur

### atoms

here, right? I couldn't count them out for two reasons. One,

### atoms

are way too tiny, we can't even see them with a very powerful microscope so there's no way that I could have seen the

### atoms

and counted them out. Second of all, even if I could count out the Sulfur

### atoms

, there are so many things in a mole that it would take 20 quadrillion years to count from 0 up to a mole. So even if I could see these

### atoms

, there is no way I could count them out. Yet, I'm pretty confident that there are pretty close to 602 hexillion Sulfur

### atoms

in here. How do I know that? Well, we're going to learn more about this but it turns out that I can figure out... how much a mole, 602 hexillion Sulfur

### atoms

, weighs and then I can put this thing on a scale and weigh out the number of Sulfur

### atoms

. Let's talk a little bit more about this so that it makes a little bit more sense. Okay, so here's an analogy. Let's say that I work at a candy factory and when someone places an order, it's my job to count out all the pieces of candy that they ordered. One day, a giant rush job comes in for 10,000 jellybeans and the person who placed this order wants exactly 10,000 jellybeans. What a pain this is going to be right? I have to count out 10,000 jellybeans! This is going to take all day! What could make my life a whole lot easier? One thing that would be really awesome is if I knew how much 10,000 jellybeans weigh. So what if I figured out that 10,000 jellybeans weigh 27,130 grams? That would be really awesome because all I would have to do is put a big bag on a scale and shovel the jellybeans in until I got 27,130 grams in them. So in other words instead of having to count, if I know how much 10,000 jellybeans weigh, all I have to do is weigh out that amount. We can do the exact same thing here with

## moles

. I told you there's about 602 hexillion Sulfur

### atoms

here, of course I didn't count that out, that's because I know that 602 hexillion Sulfur

### atoms

weigh just about 32.07 grams so all I have to do is put this container on a scale, weigh out 32.07 grams and I'll know that I have just about 602 hexillion of them. So... how did I know that a mole of Sulfur

### atoms

weighed 32.07 grams? Well, all you have to do is look at the periodic table. If I look Sulfur up on the periodic table, I've got element name and the abbreviation and stuff and then I have this number down here. This is what we call a molar mass and this number down here tells us how much one mole of this element weighs in grams. So 32.07 is how much one mole or 602 hexillion Sulfur

### atoms

weighs. Now let's go back to the candy factory. Imagine that I get all kind of orders for all sorts of different candies. I can figure out what 10,000 of many different types of candies weigh. So for example, maybe I have to do M&M's one day and I can find out 10,000 M&M's weigh 8,770 grams. They weigh less because one M&M is much lighter than one jellybean so 10,000 of them are going to weigh less. On the other hand, a candy like one of these chocolate malted balls are a bunch heavier than the jellybeans so 10,000 malted balls are going to weigh a bunch more at 154,600 grams. So it's the same way with

### atoms

, some are lighter and some are heavier. So Carbon for example is a little bit lighter than Sulfur and 602 hexillion Carbon

### atoms

only weigh about 12.01 grams because Carbon

### atoms

are just lighter than Sulfur

### atoms

. On the other hand, something like Zinc

### atoms

are heavier than Sulfur

### atoms

so 602 hexillion zinc

### atoms

or a mole of zinc

### atoms

weigh 65.38 grams and just as I did with Sulfur, I know how much the Carbon... and Zinc

## moles

weigh because I can look up the

### atoms

on the periodic table. So here we got Carbon, 12.01 is its molar mass, it's how much one mole weighs and Zinc, 65.38 and that tells me how much one mole of Zinc, 602 hexillion

### atoms

, weighs. So if I want 602 hexillion, one mole, of any kind of atom all I have to do is look at the periodic table and find out how much a mole of that atom weighs and I don't have to count any

### atoms

, all I have to do is just weigh out this amount on a scale. This is just like me being lazy in the candy factory. I don't want to have to count out these jellybeans or M&Ms, so I can just weigh them instead. I can do all my

## counting

by weighing and that's what I do with these

### atoms

, I count by weighing out their molar masses. So now that we know how to figure out how much a mole of

### atoms

weigh, let's go back to that original question I asked at the beginning of the video. I have here in this container a whole bunch of Carbon. I want to know how many

### atoms

of Carbon are in here. Let's see how we'll answer this. Okay so how many

### atoms

of Carbon do I have in this container? Well, let's think about

## moles

of Carbon. I look up Carbon on the periodic table and I find out that one mole weighs 12.01 grams and I also know that in that one mole there are 602 hexillion

### atoms

. The first thing I want to know is how many

## moles

of Carbon do I have here? In order to figure that out, we can do some weighing, alright? I know that one...
mole weighs 12.01 grams so let's weigh this and figure out how many total

## moles

we have. I put this on a scale and find out that there are 31.87 grams of Carbon

### atoms

in here. Now that's more than a mole. If we had 12.01 grams of Carbon we would have one mole but we have more than that so let's figure out how many total

## moles

we have. We'll do that by taking 31.87 grams, the total mass of Carbon

### atoms

here, and divide that by 12.01 grams which is how much one

## moles

weigh. When we do that we get 2.654

## moles

so that is how many

## moles

of Carbon I have in here. Okay, we'll take this number and hold on to it because it's going to be important for what we do next. So how many

### atoms

of Carbon do we have in here? Well we know that in each mole there are 602 hexillion

### atoms

but here I've got 2.654

## moles

. This isn't too hard though because all I have to do is multiply 2.654 by the number of

### atoms

that are in one mole. So I can do 2.654

## moles

times 602 hexillion

### atoms

. So now this is kind of a pain because I've got all these zeros so I'm going to rewrite this using a shortened version of this in scientific notation. I'm going to multiply this by 6.02 times 10 to the 23rd which is usually the version of 602 hexillion that we want to use when we're doing math. When I do this, I can just plug it into a calculator and I'm going to get 1.60x10^24 Carbon

### atoms

. Sometimes when you see things in scientific notation it can be a little bit scary...
so let's put this out of scientific notation and this is the number of Carbon

### atoms

that we have when we put all those zeros in. One hep-trillion six hundred hexillion Carbon

### atoms

. So that is how we can use

## moles

to figure out the number of

### atoms

we have in something. We can figure out how many

## moles

we have by weighing it and then once we know how many

## moles

we have, all we have to do is multiply that by the number of things that are in a mole and we get our final answer.