this is an introduction to balancing chemical equations we're going to talk about what it means for an equation to be unbalanced or balanced and then we'll learn the process that you go through to balance a chemical equation I want to start with a few examples that show the concepts behind balancing equations so you can really understand what's going on when you work through these kind of problems we'll begin by looking at this chemical reaction hydrogen gas and chlorine gas combined to make hydrochloric acid so this is how we can express this chemical reaction using words and we often call this kind of thing a word equation now we can use this word equation to write a chemical equation by taking each one of these things and writing the chemical formula for it okay so the chemical equation looks like this hydrogen gas its chemical formulas h2 we have an the plus chlorine gas is CL 2 we get the arrow and then hydrochloric acid its chemical formula is H CL okay now if I wanted to be really precise about things I could put a G in parenthesis next to each one of these to show that they're gases but I'm trying to keep things simple for this video now in order to start talking about equation balancing which is the topic of this video we have to look at the atoms in this chemical equation we have to look at the number and type of atoms that we have on both sides of the arrow I've got some diagrams here so we can do this visually so we can actually see the atoms at how they recombine during this reaction okay so we got a molecule of hydrogen gas it looks like this we got two hydrogen atoms one two then we got some chlorine gas we got a molecule of that two chlorine atoms got our arrow and finally a molecule of hydrochloric acid so there it is one hydrogen and one chlorine okay so now we're going to start talking about balancing equations and balanced equations first thing that I want to do is figure out whether this equation here is a balanced equation so here's a definition for balanced equations a balanced equation has the same number of each type of atom on both sides of the arrow okay so keeping this definition mind what I have right here is this a balanced equation no it's not here's why on this side of the arrow I have two hydrogen atoms over on this side I only have one over here I have two chlorines and over here I only have one so this is not a balanced equation we don't have the same number of each type of atom on both sides this isn't a balanced equation so we call it an unbalanced equation unbalanced it's just the word for an equation that's not balanced it has different numbers of one or more of the types of atoms on the two sides of the arrow okay so this is currently an unbalanced equation now most the time in chemistry unbalanced equations aren't particularly useful to us and we have to make them balanced before we can use them for problem solving or for doing calculations so often chemistry we start out with unbalanced equations and then we have to figure out how to balance them so in order to balance this we're going to make a few adjustments here's how we do it to balance the chemical equation we change the number of these molecules that we have and we find a combination that gives us the same number of each type of atom on both sides okay it's a little bit like a puzzle so it might turn out that to balance this equation we need three of these and one of these and three of these or we might need two of these and two of these and one of these so we play around with the number of each one of these that we have finding a combination that gives us the same number of each type of atom on both sides okay so take a look at this equation can you figure out what we need to do to one or more of these in order to have the same number of each type of atom on both sides well here's what we do we have two hydrogens here two chlorines here one hydrogen one chlorine so if I get another one of these okay if I have two of these well then have two hydrogen's here two hydrogen's on this side two chlorines on this side two chlorines on this side and now this equation is balanced okay so we've balanced the visual the visual version of it to balance the written equation what we'll do is we'll put a two in front of the HCL here to show that we have two of these and now the equation is balanced okay so this is the combination this is the combination of these things in these things that we need to have the same number of each type of atom on both sides we need one of these one of these and two of these to end up with a balanced equation here's another chemical reaction hydrogen gas and oxygen gas combined to make water the chemical equation for this looks like this the chemical formula for hydrogen gas is h2 that oxygen gas is o2 and these combined to make water which is h2o now let's look at how we can represent this visually okay we've got one molecule of hydrogen gas h2 then we have one molecule of oxygen gas o2 we got our arrow here and h2o water is over here okay so just like we saw previously on this side of the equations what we start with it's our before we've got our reactants and over here is our after our products okay so take a look at this equation and these atoms here and think about this is this equation balanced the way it's written here an answer is no it is unbalanced here's why I've got two hydrogen's here and two hydrogens here's the hydrogens do balanced but the oxygens don't I have two oxygens here and only one over here so this equation is not balanced as it's written in order to change this we're going to adjust one or more of the numbers of these different compounds okay here's how we're going to do it take a look I've got two oxygens here and one here so the first thing I want to do is I want to try to balance these oxygens to get more oxygens on this side to get two oxygens on this side I'm going to add another one of these h2o and I have two of them alright so I have two oxygens here two oxygens here the oxygen is balanced but check this up by adding this water here I change something else my hydrogens used to balance but now I have four on this side I don't have two on this side but that's okay because I can change the number of these as well okay I used to have one so let me add another hydrogen here now I have four one two three four hydrogen atoms over here one two three four hydrogen atoms over here okay so now this is a representation of how the atoms balance in order to balance the chemical equation up here I'm going to put a two in front of the h2 because I have two of those and then I'm going to put a two in front of the h2o here because I have two h2s and now the equation is balanced here's a really common mistake I've got to tell you about when people are first learning this stuff a lot of the times they'll say hey I have a simpler way to balance this here's how you do it get rid of this 2 here get rid of this 2 here and then just put a little number 2 right under this oh here now you have h2 on this side h2 on this side Oh 2 on this side and o2 on the side it balances perfectly yeah but unfortunately it can do that these numbers here we call them subscripts you can't change them when you're balancing an equation they have to stay the same and here's why in this equation we're talking about water its formula is h2o and this is what a water molecule looks like if you put it to here we're not talking about water anymore we're not talking about h2o anymore we're talking about a molecule like this with two oxygens and two hydrogen's this isn't water this is now a compound called hydrogen peroxide so yeah by adding this to you might balance the equation but it's no longer the equation for hydrogen gas and oxygen gas making water it's now the equation for hydrogen gas and oxygen that's making hydrogen peroxide you totally change the meaning of the equation if you mess around with these subscripts so you can't do that the subscripts have to remain the same but you can put numbers in front of one or more of the compounds but the numbers always have to be in front you can't modify any of these subscripts when we first start off talking about balancing equations I love to use visuals like these of the atoms and molecules so you can really see what's going on but when you're gonna be balancing equations on homework or on quizzes you're not gonna be using drawings like this instead you want to be able to balance equations using charts doing a little bit of math so I'm going to show you one example here of how you do that okay so in this equation we have nitrogen and hydrogen now obviously we have those on both sides so I've made this little chart nitrogen and hydrogen on both sides so the first thing you want to do is you want to write in your chart how many of these atoms you have right so we have n2 so that means that we have two nitrogens on this side you can see that from the diagram h2 we have two hydrogen atoms on this side and then we have the arrow and then over here we have n so we have one nitrogen atom and then we have three hydrogen atoms so to start balancing this you want to look at where you have an imbalance of atoms where you don't have the same number of atoms and you want to think about what you could multiply one of these compounds by okay so let's let's look at nitrogen right here we have two nitrogens here we only have one here okay so one thing that we could do to start out balancing this is we could put a two in front of nh3 here so that would multiply this whole thing by two so now we'd have two of these and that would give us two nitrogens and now we have two times three which is going to give us six hydrogen's okay so that's how we use this chart now that kind of changed these numbers so let's look at what's going on over here okay so now the nitrogen is balanced but now the hydrogen's don't bounce I have six here and I have two here okay so what could I multiply something by here to fix the hydrogen's well I have two right now I want six so I could put a 3 in front of this it would look like this in our visual now we have two more hydrogens and that gives us 3 times 2 6 hydrogen's here so we can keep track of these adjustments that we make using charts like this that show us how many of each atom we have on both sides we multiply something by a number in front of it and then we change the number of atoms so the best way to get good at this is to just do a whole bunch of practice check out my video of balancing chemical equations practice problems you'll do a whole bunch of examples and it will really make sense