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Current time:0:00Total duration:7:23

Video transcript

we humans have been curious about ranking things for example we have ranking of our cricketers based on their scores we have ranking of our superheroes based on their strength so this should not be a surprise that we wanted to rank our metals depending on the reactivity from most reactive metal to least reactive metal and for this we did some experiments and in this video we are going to burn metals to rank them basically if a metal burns vigorously or explosively then it is going to be more reactive whereas if a metal burns weakly then it's going to be less reactive so let's do that but before doing that let's see what happens chemically when a metal burns in air so we have seen earlier that if we take a shiny piece of magnesium ribbon and we burn it then we are left with a white powdery substance now see what's happening here is the magnesium atoms when they are burnt they combine with the oxygen molecules present in the air and they form magnesium oxide which is white in color mg plus O 2 gives mg o now if we take another example like copper which is also a shiny metal and if we heat it in air the color changes to black now what's happening here is that copper atoms they are combining with the oxygen molecule of the air and forming copper oxide which is the black color substance that you see so as a general thing you can notice that when metals are being burnt or heated in air their atoms combine with oxygen and form oxides whether you take aluminium or iron or sodium most of the metals they will combine with oxygen to form metal oxides most of the metals almost all because there are certain exceptions like gold and silver see gold and silver how much so ever you heat them they are not going to combine with oxygen we will not get oxides of silver and gold being form and that's why we say almost all metals combined with oxygen to form metal oxides so with this let's try to rank our metals according to how vigorously or how weakly they react with oxygen so first let's begin with sodium if you heat sodium in open-air it will catch fire and start burning very vigorously we will have a vigorous reaction in fact this can even become explosive in nature so be very careful while carrying out this reaction in fact we don't even need to heat it just keep it out in the open air and it might react automatically with oxygen and catch fire that's why we never keep sodium in the open we store it by dipping inside kerosene so it never comes in contact with air or water and just like sodium potassium is also very reactive its reaction with oxygen is also very vigorous in nature so these are the two top most reactive metals that we have next we have magnesium we have already seen that when we burn magnesium it catches fire and it burns with a dazzling white flame so it is also very reactive but in comparison to sodium and potassium it can only come second it's no match for them now next up I have metals such as aluminium zinc iron and copper now all of them react in a similar fashion with oxygen to form their oxides and that's why I have grouped them together in a single box it's pretty hard to actually tell which one among them is more reactive and their reaction is not as vigorous as sodium or magnesium and that's why I've put them at a third rank now even among them aluminium zinc and iron they will burn and react with oxygen to form their oxides whereas copper it does not burn it will get hot and then it will react with oxygen to form copper oxide whose color is black and that's why you will see a color change from copper - black color okay with this I have listed out few of the metals that will react with oxygen to form oxides now after this we have metals such as gold and silver now these two metals on being heated up they do not react with oxygen doesn't matter how much so ever you heat them there will be no reaction happening that's why these metals are called noble metals or peaceful metals these are the least reactive in our list so this is our list of reactivity here the metals sodium and potassium are most reactive then we have magnesium then we have these metals aluminium zinc iron and copper we are not sure which one is more reactive among them and then at last we have gold and silver now before we wrap up the video let me tell you one interesting fact see few of these metals they can react with oxygen and form oxides even at normal temperature without being heated up for example if I take a piece of aluminum metal and I leave it outside for some time now the outermost atoms the ones that are in contact with air they can react with oxygen and form oxide even at room temperature even at normal temperature something like this and they will form a protective layer a layer of oxide over this metal so what will happen is this layer will prevent the innermost atoms from reacting with oxygen because now oxygen cannot go through it and come in contact with the innermost atoms right so in one sense we can say that the outermost layer it sacrifices itself by reacting with oxygen and therefore it prevents or safeguards the innermost atoms from reacting with oxygen and this happens with many metals like magnesium zinc sodium they all will have a layer of metal oxide on top of them in this video we wanted to rank the metals in the order of their reactivity for this we reacted the metals with oxygen let them form oxides now depending on how vigorous the reaction was we put them in this particular order but there was a problem with this particular process see we did not get a detailed enough list for example if you look at position number three we have for metals clubbed for this particular position we can't detail them further enough right over here we have two metals grouped together over here we have two more metals grouped together so for this purpose we will be carrying out more reactions in future videos we will be reacting metals with water will be reacting metals with acid and with more information we will be detailing this list out