 how does it relate to the real world? So unreactive metals, so metals that are further down in our activity series, you can often find them in the ground as themselves. So gold nuggets, for example, are pretty much pure gold. You can find silver in the ground as silver. You would never find a lump of potassium or sodium or lithium in the ground because they're reactive. They've already reacted with something else in the environment. So you never find them as their native metal. They're very easily oxidized. They'll react with oxygen in the environment. They'll react with chlorine or carbon or many other substances, silicon. They'll react with those in the environment to produce a substance that is the metal ion locked up. To form the metal, you need to reduce the metal ion somehow and that's how more active metals are made. And we'll have a look at that in electrochemistry. So this relates to the discovery of metals too. Metals like copper, mercury, silver, even iron, tin and lead, they've been known about for a very long time because of their lack of reactivity they're relatively easy to find in the environment and also they're, for something like iron, reducing its ions is relatively easy to do. It doesn't require much energy to do that. So because of that, we've known about these for a long time, but these more active metals we haven't known about for as long. So something like aluminium, I'm going to talk about in a second, it's only been produced in large quantities for 150 years or so and substances like potassium and sodium, we didn't have solid lumps of those until people figured out the chemistry to produce really active metals. So let's have a talk about aluminium. So let's have a quick talk about aluminium. This is the Washington Monument in Washington DC. When I went and visited, there'd been an earthquake not long before, so they'd put a lot of scaffolding up and that also fenced it off so you couldn't get close to it because they were repairing it. It was the tallest obelisk in the world and right on top there is a pyramid of aluminium, which seems like a very odd thing to have on top of a monument like this. You might have something like gold, which was very precious, but at the time that this was built, aluminium was ridiculously precious because the production process for producing aluminium from its mineral bauxite, so this is bauxite down here, it had only just been invented, so solid aluminium was very rare. So this little pyramid was worth a lot more than gold would have been to put on top of the monument. If we go back here and we have a look at our activity, we can see that aluminium is quite reactive. So why would you put it on top of a monument if it's very reactive? The thing with aluminium is it's so reactive that it produces a coating of aluminium oxide that protects the metal underneath. So you get this coating of aluminium oxide where it's reactive with oxygen in the environment and that protects all the aluminium underneath. This is why we use aluminium in things like cans for soft drink or food. So the aluminium, it's quite light, which is an advantage, so it's easier to transport, but also because it produces an oxide layer, it protects itself. So today on Flipping Science we looked at the reactions of metals and the activity series and how that relates. That's it for Flipping Science today, see ya.