to be able to show what's happening in a chemical reaction you need to understand chemical equations one way to show reaction is with a word equation imagine we're told that methane burns in oxygen turning into carbon dioxide and water on the left hand side of our equation we have the methane and oxygen that reacted together and we call these the reactants on the right we have the molecules that are produced so in this case carbon dioxide and water which we call the products and in the middle we have a single arrow to show that the reactants react completely to form the products more often though instead of writing these word equations we write symbol equations using the chemical symbols of each molecule involved so we would have ch4 which is methane plus o2 going to form a co2 plus h2o notice that i've put o2 rather than o that's because oxygen exists as a molecule made up of two atoms so whenever you include oxygen in a reaction you have to put o2 just like for chlorine you would put cl2 and for nitrogen n2 anyway getting back to our equation it's not quite right just yet because we haven't balanced it in order to be balanced chemical equations need to have the same a total number of each type of atom on either side of the arrow in our example we can see that on the left of the arrow there's one carbon four hydrogens and two oxygens whilst on the right there's one carbon two hydrogens and three oxygens so our equation isn't balanced somehow we need to increase the number of oxygens on the left-hand side and increase the number of hydrogens on the right now it's absolutely fine if you can't work out how to balance it in one go often balancing equations is a process of trial and error where you keep on changing numbers until you get the answer the first rule of balancing equations is that we can't change any of the little numbers this is because doing so would mean that we were changing the actual type of chemicals in our equation for example we couldn't change our o2 to an o3 because o3 is an entirely different substance which isn't oxygen instead we have to rely on changing the big numbers in front of the different elements or compounds as this number just represents how many of that substance there are so to increase the number of oxygen atoms on the left we'd have to put a 2 in front of the o2 meaning we now have 2 oxygen molecules and therefore 4 oxygen atoms in total on the left hand side this might seem a bit weird as we only need three oxygen atoms to match the right hand side so shouldn't we just make it one and a half molecules of oxygen unfortunately we can't when balancing chemical equations another rule is that we need to keep the whole numbers and so we have to round up to two instead and keep four oxygen atoms this leaves us needing two more hydrogens and one more oxygen on the right which we can get by increasing the number of water molecules from one to two so we now have the same number of each type of atom on both sides of the reaction and so we're done let's quickly try one more example sulfuric acid plus sodium hydroxide goes to form a sodium sulfate plus water on the left we have three hydrogens one sulfur five oxygens and one sodium while on the right we have two hydrogens one sulfur five oxygens and two sodiums although it's up to you i recommend balancing the least common elements first which in this case would be sulfur and sodium as sulfur is already balanced with one on either side i'd look at sodium where we can see that we need one more on the left so to fix this i put a 2 in front of the sodium hydroxide giving us two sodiums then if we count all of our atoms again we can see that we need two more hydrogens and one more oxygen on the right hand side this is a pretty common problem to have and we can fix it by adding one more water molecule to the right as always when you think you're done just double check to see if it's balanced so we've got four hydrogens one sulfur six oxygens and two sodium atoms on each side so this is exactly balanced and we're finished anyway that's all for now so hope you enjoyed the video and we'll see you next time