 This is about amphiprotism. Is this a big word? What does it mean? Well, it's like amphibian. So we know that amphibians can live on land as well as in water. These are species that according to the Bronsted Larry definition, that is proton donors and proton acceptors, these are species that can do both. They can both accept a proton and donate a proton. So one of the simplest ways of demonstrating amphiprotism is just to add water. One of the nice things about water is water itself is amphiprotic. Hopefully you'll notice that as we do a couple of these little examples, just to give you an idea. So in this particular example, we're going to demonstrate the hydrogen carbonate or bicarbonate ion acting as an acid. So let's say it's an acid. So if it's an acid, it's a proton donor. So it's going to lose a proton and therefore it's going to become C032 minus in solution. And it will lose that proton to the water. So the water will become an H3O plus ion. So if we use our understanding of conjugates, well, we can see that this was the acid, which means that water was acting as a base. And therefore this is now the conjugate base. It's the result of the hydrogen carbonate ion losing its hydrogen. And the hydronium ion will be the conjugate acid. Okay, so this is just an example of a Bronsted-Larry acid. But what about if we take exactly the same two reactants? But this time we switch them around so that the bicarbonate ion is acting as a base. So let me just write base underneath here, which means that this time the water is acting as an acid. So if it's acting as a base, this time it's actually going to accept a proton. And it's obviously going to do that from the water molecule. So if it accepts a proton, we now have H2CO3, which is carbonic acid. We know carbonic acid is a weak acid. It's the one that's involved in the equilibrium for soft drinks. And also what's left behind then this time is the hydroxide ion, which is also in the solution. So this is now the conjugate acid. And the hydroxide ion will be the conjugate base. Useful to put these pairs together because they're a useful way to help you remember these types of concepts.