in this video we're going to look at how we can extract aluminium from its ore using the electrolysis of aluminium oxide you need to know how aluminium is extracted and also why it's done in this way aluminium is found in the ground as part of an ore called bauxite remember an ore is just a rock that contains enough of a metal compound that is financially worth us extracting it the metal compound that's found in bauxite is aluminium oxide which we can extract pure aluminium from lots of metals can be extracted from the oxide using carbon any metal that's less reactive than carbon for example zinc and iron can be displaced by carbon when carbon is reacted with its oxide so carbon can displace the zinc from zinc oxide for example but any metal that's more reactive than carbon can't be displaced by carbon from its oxide so we can't use carbon to extract aluminium from aluminium oxide because aluminium is more reactive than carbon instead we need to split up aluminium oxide using electrolysis the equipment we use for electrolysis is shown in the diagram below it looks quite different to the equipment we would use for electrolysis on a small scale in a lab and that's because this process is being done on an industrial scale but there are some similarities we start with a large steel case which holds the rest of the equipment we call this an electrolysis cell we then have our electrolyte which in this case is aluminium oxide it's important that the aluminium oxide is in liquid form either molten or dissolved this is so the ions are free to move and the electrolyte can conduct electricity aluminium oxide has a very high melting point so we dissolve the aluminium oxide in molten cryolite cryolite is a different compound of aluminium with a lower melting point this lowers the overall melting point of the electrolyte so we can use lower temperatures for the process this is good because it requires less energy and therefore makes the process much cheaper as always with electrolysis we need to use a dc power supply on the diagram i've shown it as a cell but in reality it would need to be a really big power supply connected to the negative terminal of the power supply is one of the electrodes the negative electrode is called the cathode and it's made of graphite which is a form of carbon this is because graphite can conduct electricity instead of being submerged into the electrolyte the cathode is lining the inside of the steel case so it goes all around the steel case connected to the positive terminal of the power supply are the anodes which are the positive electrodes and again these are going to be made from graphite which is a form of carbon because it can conduct electricity the electrolyte aluminium oxide contains aluminium ions which are positively charged and oxide ions which are negatively charged when electricity is passed through the electrolyte it splits up into its ions the positive aluminium ions are attracted to the negative cathode so they move towards it when they get there they gain electrons to turn back into neutral aluminium atoms so we collect molten aluminium at the bottom of the cell the negative oxide ions will be attracted to the positive anode so they move towards it when they get there they'll lose electrons to turn back into neutral oxygen atoms which tend to pair up to form oxygen gas or o2 so the process overall we're starting with aluminium oxide and we're splitting it up into aluminium and oxygen gas the word and symbol equations for this reaction are shown at the bottom of the screen when you do the symbol equation you need to make sure that it's balanced there is another accidental product which forms at the anode the anodes are made of carbon and because it's very hot in the electrolysis cell the carbon reacts with the oxygen that gets made there creating carbon dioxide this causes the anodes to wear away over time so we have to replace them every so often this adds to the cost of the process here are some practice questions for you to have a go at pause the video and give these questions a try the ore that contains lots of aluminium oxide is called bauxite we can't use carbon to extract aluminium from aluminium oxide because aluminium is more reactive than carbon which means carbon can't displace it from its oxide the electrodes we use are made of carbon specifically graphite we dissolve the electrolyte in molten cryolite to lower the melting point this means we can use lower temperatures which requires less energy and is therefore cheaper there are two products of electrolysis of aluminium oxide we produce oxygen at the anode and we produce molten aluminium at the cathode the word equation for the process is aluminium oxide splits up to produce aluminium and oxygen the anodes need to be replaced regularly because carbon anodes react with the oxygen that gets produced there forming carbon dioxide which causes the electrodes to wear away over time thank you for watching i hope this video has been helpful for you and i'll see you in the next one