Question #4. Why is water wet?

Why is water wet? A question posed to me by my son quite some time ago. The only answer I could offer at the time that wouldn't completely bemuse him was that water is a fluid and if the water was dry it wouldn't be very good water. It was a good enough answer at the time.

Now, I had previously written a whole bunch of stuff  about states of matter and molecular cohesion but it has been lost somehow.  I presumed that it had been saved and left the page to do something else. I returned to the page and everything I had written was gone.
At this point all I will write is that there are 4 basic states of matter. The first 3 you typically learn in school (I know that I was not taught the fourth state when I was at school), They are Solid, Fluid, Gas, and the fourth is Plasma. There are other states such as non-classical states like glass, crystal, and liquid crystal states. There are Super fluids, Super solids, Bose-Einstien Condensates, High energy states, Dark matter. It's all really fascinating and had I not lost the previous version of this post you could have read it but it's gone and I'm not currently inclined to write it again. But do look it up elsewhere on the internet, I'll focus on the water here for now.

Water is probably the wettest of wet stuff. The thing that makes matter solid or fluid or gas is its molecular cohesion. It is in fact the molecular cohesion that matters. How strongly the molecules stick to each other determines whether the matter is solid or fluid and so on. Water molecules "like" other water molecules and they stick together but it is not just the molecular cohesion that makes water so wet, it is also its molecular adhesion. 
The difference between cohesion and adhesion is this. Cohesion is how strongly the molecules stick to other molecules of the same type. Adhesion is how strongly the molecules stick to molecules of a different type. Water likes everything so it will stick to pretty much anything. It has nearly the same level of molecular adhesion as it does molecular cohesion. 

Blobs of Mercury.

A good example to demonstrate is the observable differences between water and mercury. Both are liquids but place the same amounts of both liquids into containers (separately of course) and you will see that the water will spread out across the bottom of the container and cover as much of the container as physically possible. Move the container around and the water will flow and slosh around inside, tip it out and some of the water will still be stuck to the inside of the container. The mercury however will not spread out to fill the container. It will typically form a sort of "blob" that will roll around inside the container almost as if it were a solid. Tip the mercury out and none of it will be left in the container. (Just a tip. If you do have some mercury and want to conduct this experiment, Do Not Touch The Mercury! Mercury doesn't like you and it will hurt you. Water loves you though. Touch as much of that as you like. Put some soap in it as well, I can smell you from here!)

So, Why is water wet? Water is wet because of its level of both molecular cohesion and molecular adhesion. Which basically means that water loves everything else as much as it loves itself. This allows it to fill every part of any container it might find itself in, which is quite literally the ability to make the most of itself in any situation. As a liquid, water cannot be compressed, depressed or generally made to feel less about itself in any way at all. Water is inclusive of everything. Hydrogen is the most abundant chemical element in the entire universe. It combined here with Oxygen, the third most abundant element in the universe to create you and every other living organism on this planet. 

So when you hear the term "Be Like Water". Really be like water.