KS3 Chemistry - Extracting Metals from Ores

In this video, we're learning about extracting metals from ores. So we'll cover how we get metals from the ground, and how we extract pure metals from their ores using carbon or electrolysis. So let's begin with how we get metals from the ground. Now, when we find metals in nature, they're usually found in metal ores, which are rocks that contain metal compounds, like metal oxides, mixed with some other impurities. To access the metals within the ores, first we need to get the metal ores out of the ground, which means we need to mine them, and then we process them by doing things like crushing the ores and sorting the different parts. To get pure metals out of the ores though, we also need to separate the metal ores from the impurities and extract the metal from the metal oxides. So, let's take a look at how we extract pure metals from their ores based on their reactivity. The method used to extract a metal depends on the metal's reactivity, so to understand this, we need to revisit the reactivity series, which is a list of metals arranged in order of how reactive they are, from the most reactive at the top, to the least reactive at the bottom. And remember, we generally include hydrogen and carbon as reference points, even though they're not metals. Now, in this context, the position of carbon in the reactivity series is especially important, because one common method of extracting pure metals is by reacting carbon with metal oxides. Now we do this because when we react carbon with a metal oxide that contains a metal that's less reactive than carbon, like these ones, carbon displaces the metal from the metal oxide to form a pure metal plus carbon dioxide. For example, when carbon reacts with iron oxide, the carbon displaces the iron, forming pure iron and carbon dioxide as a by-product. Importantly, we use the word displaces when we talk about carbon taking the place of the metal, because this is an example of a displacement reaction, which happens when a more reactive element displaces a less reactive element from a compound. Because carbon is more reactive than iron, it takes the oxygen from the iron oxide, displacing the iron and leaving behind the pure metal. This method only works with metals that are less reactive than carbon though, and if we tried this with one that's more reactive than carbon, like potassium, the reaction wouldn't happen at all because potassium is too reactive to be displaced by carbon, so we would need a different method. For all these metals that are more reactive than carbon, we can use electrolysis to extract the pure metal, which involves using electricity to split the ore into the elements it's made up of. By way of example, to extract calcium from calcium oxide, first we melt the ore and then we pass an electric current through the molten ore, which splits calcium oxide into calcium and oxygen. The oxygen is released as a gas and the pure calcium collects at the bottom of the container. There are some downsides to using electrolysis though, as it's more complex and expensive than using carbon to extract metals from metal oxides, but at the end of the day it is necessary for extracting metals that are really reactive. If you haven't heard yet, you can find all of our videos on our website, cognito.org. You'll also find questions, flashcards, exam-style questions, and past papers, and we track all of your progress so that you always know what to study next. So sign up for free by clicking here, or browse our playlist here on YouTube.