 Our final addition reaction is hydration. Hydration is the addition of water. Again, let's go with the same molecule we've been looking at throughout this particular video, which is ethene, and this time we're going to add water, H2O. Now, if you think about water as HOH, it's probably easier to understand exactly what's going to be happening here. So when we add water to our ethene, what we have is, again, the double bond breaking, the hydrogens where they were before, but this time we get a hydrogen on one of the carbons and an OH group on the other. The hydroxyl group is now one of the species that is added across this double bond. Often for this kind of thing, we might use a catalyst such as dilute sulfuric acid, and that sometimes is shown by putting that across the top of the arrow. I'll just put dilute here, so we're aware. And that water is going to be added across the double bond. So therefore, what I would have here is ethanol. Ethanol would be my product. Now, water can also be added across double bonds for other members of the alkenes in exactly the same way to create a range of different alcohols. These are just a small sample of the types of addition reactions that occur across the double bond of our unsaturated hydrocarbons. And obviously, what I haven't looked at is what would happen if we had an alkyne instead of an alkene. And what you might find there is that instead of adding a single water molecule across a double bond, I could add two water molecules across a triple bond. There's a few additional consequences of that, and they're probably worth exploring in class. So I'll let you do that on another day. Thanks for watching.