 Let's see what are the different processes to reduce some metal oxide to get metal. More importantly, let's continue learning about how to extract pure metals from their ores. And we saw that these were the four steps. And we already talked about the step number one and two. Basically first is enrichment of the ores. Here what happens is, we take a metal ore and we crush it into pieces. And then we separate the metal compounds from the impurities. Now if the metal compound was a metal sulfide or a metal carbonate, then first of all we need to convert it into metal oxide because it's easier to get the metal out from an oxide. And this is what happens in the second step. We saw that for sulfide ores, we use the process called roasting, whereas for carbonate ores, we use the process called calcination to convert them to oxides. Now let's move to the next step, which is reduction to metal. See after the second step, we got metal oxides. Now we need to extract the metal out of this, meaning we need to remove oxygen. And removal of oxygen is called reduction. So let's do that. So for example, if we have oxides of metal that are less reactive, for example, mercuric oxide and silver oxide. From the reactivity series, you might recall that these metals were somewhere towards the bottom, see mercury and silver. So that's why they are less reactive. So their oxides are not going to be very stable. And to get the metal out of them, we will only need to heat them. Just from the heat energy, these compounds, they decompose and finally we get the metal and oxygen is given out. So the oxides of low reactive metals, they just need to be heated. And they get reduced to their metals. Now let's talk about the oxides of medium reactive metals, such as zinc, manganese and iron. All of these are somewhere in the middle of reactivity series. And that's why they are medium reactive. Now we can't reduce them just by heating. We reduce them by displacement reaction. We react these metal oxides with a more reactive element. A more reactive element will displace a less reactive one from its compound. That's what is displacement reaction, right? So zinc oxide is reacted with carbon. Carbon is above zinc and is more reactive. It will displace zinc and form carbon monoxide. So this is how the reaction goes. Carbon is a very good reducing agent. It loves to snatch oxygen from different compounds like zinc oxide. And we get zinc metal reduced. Now in case of manganese dioxide, we react this with aluminium. Aluminium is above manganese and more reactive. It will displace manganese and reduce it. And this is how we get manganese metal. In fact, there is so much heat being given out in this reaction that the manganese metal being generated is made in liquid form. Similarly, in the case of iron oxide, we react this with aluminium. And this reduces the iron oxide to iron. And in this case, also a lot of heat is given out which melts the iron being generated and makes it in liquid form. This reaction is commonly used for the welding of iron equipment such as in the welding of iron railway tracks. And since this is commonly used, we give it a name. We call this thermite reaction. Okay, so far we have seen how to reduce low reactive and medium reactive metals. Now let's look at how to reduce high reactive metals. For example, sodium, calcium, magnesium and aluminium. So see, these metals are very reactive. So their compounds are also going to be very stable, very strongly bonded. And it would not be easy to break them apart or reduce them by just heating or by using carbon or other metals. For this, we take the help of electricity. For example, if I take the compound of aluminium, aluminium oxide, now I have to reduce this, meaning I want to take away oxygen, I want to separate aluminium and oxygen, right? So I will provide electrical energy and with that, they will break apart. Let's look at an example. So first of all, I will take aluminium oxide in molten state in a container, in liquid state. And the reason why I'm doing it is because after I have provided electricity, these will break into their ions and the ions can easily flow in a liquid state, right? Now to pass electricity, I will insert certain electrodes that will be connected to a battery. This is the positive electrode and this is the negative electrode. Now once I pass electricity, the aluminium oxide compound, this is going to break into its ions. We will get aluminium plus three ions and Oat minus two ions. Now the positive ion of aluminium, this will get attracted to the negative electrode. Over here, aluminium ion needs three electrons. It will take the three electrons from the negative electrode and will get converted to aluminium atom and the aluminium atoms will get deposited on the negative electrode over here, something like this. Similarly, the negative ion of oxygen will now get attracted to the positive electrode, opposite attract, right? So once it comes over here, it will deposit the extra electrons that it has and then will combine with other oxygen atoms to form O2 molecule. And these oxygen molecules will bubble out of the solution. So this is how by passing electricity, we can reduce the aluminium compound into aluminium and oxygen. Now let me give you one more example. This time, let's take the compound of sodium, sodium chloride. Now we will also pass electricity to reduce this. Now first of all, I will have to take sodium chloride in its molten state, in its liquid state. And then when I pass electricity, this compound is going to dissociate into its ions. I will get sodium plus ion and chlorine minus ion. Now the positive ion of sodium will get attracted to the negative electrode, also called as the cathode. Here, the sodium plus ion will receive an electron and will become sodium atom. Now these sodium atoms are going to be deposited on the cathode. Now the chlorine minus ion, they will get attracted towards the positive electrode, called the anode. And over here, chlorine ions, they are going to lose their extra electron and become chlorine atom. But see chlorine atoms are not stable, right? So basically, there are two chlorine ions and they both together lose their electrons and become chlorine molecules, Cl2. And we get two electrons over here. So to reduce the compounds of high reactive metals, we use electricity. And that's why this process is called electrolytic reduction. So okay, let me give you a quick overview. To reduce metals, we use heating for reducing the compounds of low reactive metal. We take the help of displacement reaction or reducing agents to reduce the compounds of medium reactive metals. And we use electrolytic reduction to reduce the compounds of high reactive metals. So far, we have got our metal out of the metal ore. We started with enrichment of the ore where we separated the metal compound from the impurities. Then we converted this metal compound into metal oxide. And then we reduce the metal oxide to get the metal. But this metal is still not 99.99% pure. It still has some impurity, some chemicals that we need to get rid of. And for this, we will have to refine the metal to get pure metal. We talk about the steps of refining in a separate video.