Why is water wet?

[jonathancook]

What is wetness? - How can you explain this to a four year old?

[Escher]

Everything is made up of very small things (atoms), which are so small you cannot see them unless there are lots of them in one place.

What makes things appear and feel the way they do, is how those small things (atoms) are joined together.

In bricks, the atoms are have strong joins (or bonds) so they are hard and stay in one piece mostly and feel dry.

In chocolate, the bonds are weaker and you can break them up fairly easily and even break them by the heat of your hand if you can wait that long.

Water has much weaker bonds (as do all liquids) and so the atoms will flow around and get everywhere and feel wet.

To carry on, if you have weaker bonds still, you get a gas. (ice to water to steam is a good example of weakening the bonds between the atoms by heating)

[bernardo]

That sort-of explains the difference between solid, liquid and gas, but it doesn't explain why water is "wet" whereas (e.g.) mercury isn't.

I think that water is wet mainly because of its high moisture content.

[newtron]

Bernardo, what do you mean?

[Escher]

You are right Bernado, I was pondering whether I'd answered the question on my drive home.

Wetness I suppose is an emotional thing (you "feel" wet), especially in the perspective of a child, rather than simply having a substance covering you (you don't feel wet when covered in honey, just sticky, maybe not a subject to get involved in until the children have gone to bed though :-) ).

So, maybe wetness has something more to do with heat conduction and your nerve endings? (sometimes when I touch a good conductor, ie metal I can get confused to whether it is wet or not). Or the fact that we are largely made up of water and when we come into contact with the same stuff, the feeling associated with it is called wet? Maybe anything that gets through our pores will feel wet? 

Anyone know?

PS, mercury is liquid due to a relativistic stretching (or is it shrinking) effect in its electron orbits. Not sure I want to to try sticking my hand in to she how wet it feels!

[CT]

Water conducts heat away from the body about 25 times faster than air.
I suppose wetness will be related to the way that heat is lost/gained from the water and the way that 'sticks' to the skin through surface tension.

[Marvin84]

Jonathon.... it's like trying to explain sight to a person who was born blind....

Probably the best way is by example; ".... this is wet.... this is not wet..."

But Echer is probably closest with the emotional aspect of feeling wet... and that might be the best explanation for a 4yo to grasp......

Best of Luck - let us know what you tell your 4yo!!

[erimus1]

It is to do with your central nervous system - the combination of pressure and temperature i.e. cold air would not feel "wet" by itself, but if your hand was covered in some respect, and was additionally cold, it would feel "wet" - try it in snow for instances - honest - it works - you can confuse the mind too as sight , to a degree assists. Try putting a rubber glove on then put your hand into cold water - it won't feel wet at first, but then it will.