Why Does Wet Stuff Dry?

[We Never Know]

It's been said already, evaporation.


A caution. Leaving dishes to air dry can leave bacteria on the dish.

Near everything we touch and deal with has bacteria unless its sanitized.

 

[exchemist]

Each water molecule is always moving, bouncing off of the others; but these molecules are also slightly sticky. This stickiness is caused by two very quick and temporary bonds: "Dipole-dipole" and "London dispersion forces." Always some of the molecules are breaking free and getting mixed into the air; but the ones in air are also quick to return to any liquid water that is nearby. There is constant traffic back and forth between the water and the air with water going into the air and air going into the water. The molecules mix a little bit. Drying happens when the air is warm enough to absorb all the water and keep the molecules bouncing in the air and keep them from sticking together too much.

On one point of detail, hydrogen bonding is thought to be more than just dipole-dipole attraction. It seems to be directional, involving the lone pairs of electrons on the more electronegative atom (in this case oxygen), which implies a degree of covalent character. But it seems even today to be a matter of research and debate, just as it was 50 years ago when I was an undergraduate. ( @Rival doesn't want to know any of this of course. It just puts 50p in my chemistry slot and make me light up for a bit. )

 

[exchemist]

I didn't say dangerous but it could cause stomach problems and you won't even know where the "bug" came from.

Do you have any evidence for this? My understanding has always been that it is the dishcloth that tends to harbour bacteria: Dish Cloths Should Only Be Used For One Thing, And Washed Often

 

[exchemist]

I know this sound stupid but I'm not a physicist or chemist.

Why does wet stuff dry? Say, you leave dishes slightly wet and then they're dry when you come back to them.

This has already been answered by others. But can you dry dishes satisfactoriy in your kitchen? I was slightly shocked by its lack of ventilation (ditto the bathroom) - unless you run the extractor a lot. Evaporation rate depends on the humidity of the air and the air in your kitchen is pretty humid.

 

[Rival]

This has already been answered by others. But can you dry dishes satisfactoriy in your kitchen? I was slightly shocked by its lack of ventilation (ditto the bathroom) - unless you run the extractor a lot. Evaporation rate depends on the humidity of the air and the air in your kitchen is pretty humid.

I towel them as dry as possible and that's really the extent of it, tbh. Hot water is obviously better, too.

 

[exchemist]

I towel them as dry as possible and that's really the extent of it, tbh. Hot water is obviously better, too.

Oh yes warm dishes dry far faster. Interestingly [yawn], I've found that things like plastic mixing bowls are very poor at drying by themselves, whereas crockery dries quite nicely on its own. I put that down to the higher heat capacity of crockery. Basically it stays warm for longer, once out of the hot water in the sink. Similarly, thick glass objects will often dry by themselves while thin glass, e.g my swanky Riedel wine glasses, often don't. (Mind you, it's always best to dry those with a cloth to avoid streaks from the hard water.)

 

[ChristineM]

Do you have any evidence for this? My understanding has always been that it is the dishcloth that tends to harbour bacteria: Dish Cloths Should Only Be Used For One Thing, And Washed Often

Something i read some years ago. I agree wash dishcloth often. Bacteria is everywhere certainly in dish water

 

[Rival]

Oh yes warm dishes dry far faster. Interestingly [yawn], I've found that things like plastic mixing bowls are very poor at drying by themselves, whereas crockery dries quite nicely on its own. I put that down to the higher heat capacity of crockery. Basically it stays warm for longer, once out of the hot water in the sink. Similarly, thick glass objects will often dry by themselves while thin glass, e.g my swanky Riedel wine glasses, often don't. (Mind you, it's always best to dry those with a cloth to avoid streaks from the hard water.)

Plastic is a nightmare. I have a plastic bowl and that one's the worst for drying. Proper crockery so to speak dries better.

 

[Ebionite]

Why does wet stuff dry?

Because the water molecules at the boundary of air and liquid water have a range of different kinetic energies. The kinetic energy of molecules in bulk is related to their temperature, and the hotter water is the more likely that it will exists in a gaseous state rather that a liquid one. At the boundary there is a constant exchange of water molecules from the liquid to the gaseous state, but the rates of exchange in either direction usually isn't the same - you can get evaporation or condensation depending on the temperature and humidity.