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Current time:0:00Total duration:11:12

Video transcript

let's rank metals from the most reactive to the least reactive for this we will have to do certain experiments and in this video we are going to react metals with water now depending on how vigorously each metal reacts we will list them in this particular series you might recall that in a previous video we attempted add something similar reacted metals with oxygen and depending on how vigorously they reacted we arrived at this particular list here sodium and potassium was most reactive and gold and silver they were the least reactive but there was a problem with this list see over here at rank 3 you can find these four metals being grouped together we weren't able to subber anchor them so our hope for this new experiment is that we will arrive at a more detailed a list more well organized list so let's begin so generally metals when they react with water they displace the hydrogen from water and form metal oxides so here in this case our products are going to be metal oxide plus hydrogen gas being evolved out now we also spoke about some metal oxide being soluble in water this means that if this metal oxide is soluble it will react with water to form metal hydroxide so either our products are metal hydroxide plus hydrogen gas or a suspension of metal oxide in water plus hydrogen gas so ok with this let's look at some examples so first let's react sodium with water so sodium will displace hydrogen that means hydrogen gas will be given out definitely and then sodium will react with oxygen to form sodium oxide and it whoa now sodium oxide is very much soluble in water so this will react with water to form sodium hydroxide let me replace this sodium hydroxide so these will be our products now along with this in the reaction you will also get a lot of heat energy being given out now let's look at the same thing in an actual reaction so here I have a beaker of normal water or cold water and I'm going to add sodium to it and yes sodium also reacts with cold water even with cold water now you can see that as soon as sodium touches it starts reacting it starts to dance on the surface of the water now why this is happening is because as soon as sodium touches the water reaction starts and hydrogen gas is given off now this hydrogen gas pushes the sodium into random direction and that's why sodium appears to be dancing on the surface of water now along with this we are also getting a lot of heat being evolved and this heat is so much that it can even burn the hydrogen gas being released so be very careful around this particular experiment this can be very explosive okay now you might notice one more thing how quickly did sodium metal get finished off and that's happening because sodium reacts very violently very quickly with water and gets converted into sodium hydroxide which is currently now dissolved in this water now how do we test this out so see sodium hydroxide is basic in nature so if I add a red litmus paper into it you can see that color is changing to blue now this definitely proves that this solution is basic and it has sodium hydroxide mix in it right so in this reaction we saw that sodium even reacts with cold water it is so reactive that it even reacts with cold water and it produces sodium hydroxide and hydrogen gas is released and along with this a lot of heat energy is given off which can even burn this hydrogen gas be very careful and potassium potassium also reacts in a very similar fashion it will also react with water to give potassium hydroxide and releasing hydrogen gas and lot of heat so these metals they are our most reactive metals they are ranked 1 when it comes to reactivity series now let's look at one more example so calcium this also reacts even with cold water just like sodium and potassium so here in this case calcium will displace hydrogen and will react with oxygen to form calcium oxide so these will be our products but cache em oxide this is soluble in water so this will react with the water to form calcium hydroxide Co h-hold twice and along with this we will also get a lot of heat being released and you can sense this because we started the reaction in a cold container of water but you can sense it that the water container will start getting warmer but let's compare the heat being released here with the heat being released in the case of sodium so in this case the heat was so much that it would even burn the hydrogen gas being escaping out right but here in the case of calcium the heat is not sufficient to burn the hydrogen gas its lesser in comparison to sodium and that's why we rank calcium as second in the reactivity series so in the case of sodium and potassium the heat would even burn the hydrogen whereas in the case of calcium the heat is not sufficient to burn the hydrogen gas in fact this hydrogen gas will start bubbling out of the water solution and it will stick to catch a metal and make it float in water you can check this out in the experiment in your lab now next we have magnesium metal and this also reacts with water but this can not react with cold water cold water does not have sufficient energy for magnesium to react with it so that's why we will need to heat the water so magnesium reacts only with hot water so this itself is an indication that magnesium is not as reactive as calcium so we will rank magnesium as third in the list so here also in this case magnesium will displace hydrogen and react with oxygen to form magnesium oxide and hydrogen gas will be given off and magnesium oxide is soluble in water so we will get magnesium hydroxide finally next we have as mininum reacting with water in fact aluminium iron and zinc they all react in a similar fashion with water which is they do not react with cold or hot water but they do react with steam which is basically h2o in gaseous form so this itself would tell us that all of these three are not as reactive as sodium calcium or magnesium and that's why I would rank them as forth in our reactivity series okay so in this reaction aluminium will displace hydrogen and form aluminium oxide and the different thing over here is that aluminium oxide is not soluble in water so this is not going to react with water to give us aluminum hydroxide no and how I like to remember this is that aluminium is used as aluminium foil to wrap our hot food in our lunchboxes now hot food will give out steam and that steam might react with aluminium to form some products now this product would have been aluminium hydroxide which is a base that might have spoiled our food so it's good that no base is being formed over here that's how I like to remember how steam reacts with aluminium to give me aluminium oxide only at last we have metals such as copper lead gold and silver and they all do not react at all with water there will be no reaction neither with cold water hot water or steam so okay with this let's rank our metals so we saw that sodium and potassium they even reacted with cold water and the hydrogen gas that was being released was set on fire because of the immense amount of heat being released at second we had calcium which also reacted with cold water but there was no fire and the hydrogen gas was bubbling out thirdly we have magnesium which reacts only with hot water not with cold water at 4th place we had aluminium iron and zinc which did not react with cold or hot water they reacted only with steam and at last we had copper led gold and silver which showed no reaction at all now with this new information let's go back and update our ranking of the metals so this was the old ranking that we had when we reacted metals with oxygen now let's compare and see what's new so here still sodium and potassium is at number one but we have calcium coming in at number two and magnesium at number three that means we will need to include calcium in between here let's update that and then we have aluminium iron and zinc at number four and we came to know that copper and lead are less reactive than aluminium iron and zinc so for sure we can update this particular rank and we can degrade copper to do our lower rank so something like this and we already knew that gold and silver they are the least reactive so this is our updated ranking of our metals after these two reactions but see this list is still not very detailed you can still see that at this rank we have three metals occupying the same position whereas over here we still do not know which one is more reactive between copper and lead so in future videos we will do more reactions and we will try to detail this particular list but for now let's summarize the video in this video we saw that when metals react with water they form metal oxide and and gas is released now if the metal oxide is soluble in water we will get metal hydroxide and we saw that how different different metals they react with water and depending on these we updated our ranking of metals