 On the other hand, acid concentration is the ratio of solute to solvent, which is usually going to be acid or base to water. When the ratio of solute to solvent is high, we have a concentrated solution. When the ratio is low, we have a dilute solution. So in the first case here, you can see this is a concentrated solution. We're not worried here about whether there's a lot of molecules or ions. That's not relevant to our discussion. What we can see is there's lots of ions. So there's high solute to solvent. Lots of ions. In this case, because we have lots of them there, despite the fact that we have no molecules and therefore we would describe this as a strong acid, we would also describe it as concentrated because there's lots of ions in this solution. On the other hand, the one on the right is dilute. And it's dilute because there's few ions to water. Again, it must still be a strong acid because there are still no molecules. So both of these solutions are strong acids. They're both fully ionized. There's no molecules at all ions. But in the one on the left, we have lots of ions to a certain volume of water. And in the same volume of water on the right, there are much less ions. So this is dilute. These terms of strength and concentration are very important when we're describing solutions of acids and bases, particularly because we would describe concentrations in terms of their molarity. So we could talk about a one molar solution being a much more concentrated solution than a 0.01 molar solution. Of course, there are other differences that tell us about whether or not those are strong or weak. And we're going to continue to look at them as we progress through this module. Thanks for watching.