what is a mole so you're starting the quantitative aspects of chemical change otherwise known as stochiometry you're in grade 10 11 or 12 this video is for you we will be discussing what a mole is in chemistry let's go what is a mole a mole is defined as 6.022 * 10^ of 23 that's a huge number of some chemical unit such as atoms molecules or ions but what on Earth does this mean it's very important to understand that chemistry works with a massive massive amount of tiny tiny tiny particles therefore it doesn't make sense for scientists to work with individual atoms we cannot keep count of individual atoms scientists have tackled this problem by introducing the SI unit called the mole and the mole is the unit for the amount of substance so if someone says I have 2 moles of oxygen if someone says I have 2 moles of sodium they're telling you that they have a certain amount of oxygen or certain amounts of sodium so an SI unit is basically like some a unit that we use to measure something in so if I say the unit the SI unit for height is meters we measure your height in meters or we can say the SI unit is kilog or GRS we measure something in grams the weight or the mass of something in grams or kilograms so the SI unit for the amount of a substance is moles so I can have one mole of a substance or 1.5 moles of a substance or 2 moles or 20 moles it tells me the amount of substance but moles it's still confusing I want you to think of it like this if you are baking and you read a recipe and the recipe says say you need a dozen eggs okay that's a lot of eggs but let's pretend the recipe says you need a dozen eggs that means you need 12 eggs so instead of saying 12 we use the word dozen instead of saying I need a pair of shoe instead of saying I need two shoes we say I need a pair of shoes a pair means two so just like a dozen means 12 and a pair means two a mold means 6.022 * 10 23 particles so if I say I have 1 mole it means I have that many particles and what I've done is I've written out that number so 6.022 * 10 to the power of 23 so look at all of these zeros that is a huge amount of particles that number of particles that is one mole and just to give you an idea of how massive that number is if we had one mole of donuts so remember one mole consists of all of these numbers of particles that's a huge number so if I have one mole of donuts that one mole of donuts will form a layer around the entire circumference of the earth so remember an earth circle circumference is around the circle it will form a layer around the entire circumference of the earth that is 8 kilm deep that is huge if you are asked to Define one mole or to define or give the definition of a mole that is a definition up there it is the amount of substance that has the same number of particles as there are atoms in 12 G of carbon 12 now in earlier chapters in this year we learned about Isotopes carbon 12 is an isotope of carbon 12 is the atomic mass number it's the mass of this isotope of carbon so if I have 12 G that's the mass of carbon 12 12 is the atomic mass number that gives me 1 mole so if I had to take 12 G of carbon 12 so you take some carbon 12 carbon 12 is a specific isotope of carbon and you measure out 12 G now I have 12 G in my hand here and I had to count out all of the atoms okay prain we're doing this we're counting out how many atoms there are in this amount 12 G of carbon 12 we would get 6022 * 10 23 atoms so that's why it says there 12 G of carbon 12 contains 6022 * 10 23 particles or atoms that is one mole so the next bullet point says one mole always contains the same number of particles regardless of the substance so what that means if I have 1 mole of carbon as I've said already it means I have 6023 * 10 23 atoms of carbon if I have 1 mole of sodium I have 6023 * 10 23 atoms of sodium so one Mo always contains the same number of particles that number regardless of the substance and that number has a name it's called avagadro number or avagadro constant so avagadro number is 6022 so and so and so time 10 23 we often round it off to this number over here 6023 this is just round it off but it's called avagadro's number or avagadro's constant because it was avagadro that determined that there were that many atoms that huge number of atoms in 12 G of carbon 12 that's why we Define the mole in that way that's why it's called aagard number so how do we calculate moles well it all depends on what you are given so these formula come from your data sheet I copied and pasted it from a data sheet that comes in your final chemistry exam and as you can see in each of these formula one thing that they have in common is that they have n and n is the symbol for number of moles okay this one doesn't have it but these have n n is number of moles so if you are asked to calculate the number of moles you will use either one of these formula to calculate the number of moles it depends on what you are given so if you are given mass of a substance in gr and you can work out the molar mass using the periodic table you will use this formula to calculate number of moles I've included the unit of measurement for all of these variables however if you are given concentration and volume of a solution you use this formula to calculate number of moles n there's the unit for concentration moles per cubic decim and volume in cubic decimet so if you're given volume of a solution concentration you use this formula to calculate number of moles if you dealing with gases at STP you will be given the volume of that gas hopefully at STP measured in cubic decim or cubic cm but you'll just convert it then you use this formula to calculate number of moles VM is molar volume and at STP that is 224 cubic decim or lastly if you are given number of particles or atoms or molecules that is big n this is number of particles and this over here na is avagard number which we just discussed what that is avagadro's number 602 3 * 10 ^ 23 we can use this formula to calculate n baby n just keep in mind that baby n is number of moles now I have videos on every single one of these formula in the stochiometry playlist the quantitative aspects of chemical change playlist so if you want a video on how to calculate moles using this formula or a video on how to calculate moles using a godos number and this formula or working with concentration and solutions or working with gases at SCP all of these videos are in this playlist check out the link down below but most importantly these formula are used to calculate number of moles and why do I need to calculate number of moles well first of all remember chemists work with a massive amount of particles a huge huge huge number of atoms it doesn't make sense to work with atoms so they use the mole the mole is universally accepted accepted across the globe and scientists use it when working with chemical reactions so say for example scientists are producing water in a lb they're reacting hydrogen gas with oxygen gas to produce water we work with moles we say I want to know how many moles of water will be produced if I react 3 G of hydrogen for example so we need to know how to work with moles in order to work out how much product can be produced or made or to work out how much reactant is needed in a chemical reaction and when working with chemical reactions such as this one magnesium and oxy are my reactants those are the two things I react together and it gives me magnesium oxide that is my product this is a chemical reaction these big numbers that balance the reaction this tells me the number of moles so two moles of magnesium two reacts with one mole of oxygen there's an invisible one here to produce two moles of magnesium oxide so I need to work with moles when using a chemical reaction so for example if the question says I react 3 G of magnesium with excess oxygen calculate how much magnesium oxide I produce they're giving me information about magnesium they want to know how much magnesium oxide I produce in order to go from one substance to another we need to use something called a mole ratio what that means is I first need to convert the 3 G of magnesium to moles so we need to go from G of magnesium to moles of magnesium once we know the moles of one thing we can easily get the moles of something else using a mole ratio again mole ratios is something that I cover in this playlist so if you want more information about that please watch the other videos in this playlist this was just an introductory video to what on Earth a mole is I hoped I cleared up some confusion but again there's lots more to still work through so if you want to know how to calculate balls using the different formula I showed in this video and how to use more ratios with chemical reactions keep watching I'll see you in the next one bye everyone