/sci/ - Science & Math

[Anonymous No.2315857]

sup /sci/, can you answer some of my questions about science?

>i) why does water evaporate under 100 degrees?
i thought water only evaporated at 100 degrees. i thought about this when i thought about my hair drying. im pretty sure my hair doesnt reach 100 degrees LOLOL.

ii) ok so 100 degrees is the temperature where water changes from water to a gas right? so when steam goes below 100 degrees it should transform back into water right?
>how can the temperature be, for example, 18 degrees? wouldn't all the water in the air turn back into liquid

this is not a troll thread, im just a dumbass LOL and i never listened in school + never did science

[Anonymous No.2315868]

Water boils at 100 degrees, its the temperature that all water turns to vapour. Lots of molecules still escape and turn to a vapour under this temperature though.
This is not an exact temperature that ALL water will change to vapour at exactly this temperature.

Its all to do with the bonds between the water molecules, and how many are able to break free from eachother; this is easier at higher temperatures.

[Anonymous No.2315873]

this was posted on /v/ a while ago

[Anonymous No.2315875]

>>2315873
i posted it on the wrong board
im usually on /v/ lol

i kinda get the first one now but then how do you turn steam back into water

[Anonymous No.2315894]

>18 degrees? wouldn't all the water in the air turn back into liquid?

i think it does?
at 18 degrees, the water in the air has turned to snow and hail and rain right?
when it's cold out, the air is dry, hence all the people with cracked, bloody knuckles in the winter

[Anonymous No.2315900]

>>2315894
Celsius, numpnuts.

[Anonymous No.2315923]

I'm starting to think the op isn't really Albert Einstein...

>>2315894
It's a single molecule. It's light enough to float around with the rest of the crap in the atmosphere, and it can't be liquid because there aren't enough.

Except in e.g. clouds, where some dust particle or other lump collects enough water from the air, so that eventually it does become heavy enough and falls out of the sky as a raindrop.

[Anonymous No.2316117]

>>2315923

Ah that makes sense. So the water in the air is liquid technically??

Does that mean water vapour =/= steam

[Anonymous No.2316120]

Air Pressure.

[Anonymous No.2316129]

Evaporation and ebullition are two different phenomenons.

[Anonymous No.2316135]

>>2316129
Ebullition is just a theory.

[Anonymous No.2316142]

Alright here we go. Vapor-liquid equilibrium, at any temperature for a liquid there is some amount that will escape into the vapor phase until an equilibrium is reached. If you put a cup of water in a closed vessel this equilibrium is achievable and as long as it's air tight you will always have water in the cup.

If you put that cup into an atmosphere, that's basically an infinite sink. The equilibrium is never reached. You have a slight bit of water escape into the local vapor (creating a local equilibrium) and this in turn cools the liquid water (heat of vaporization). This vapor then gets circulated, the water sample equilibrates (thermally) with surrounding. Then this whole process repeats until no more puddle/etc.

[Anonymous No.2316154]

>>2316135
a Gauss?

[Anonymous No.2316166]

In order to become a gas, liquid water molecules must have a certain amount of energy which breaks the bonds between them. This amount of energy, the activation energy, is supplied by heat. When liquid water molecules are given a certain temperature, say 70 degrees Celsius, some of the water molecules have this activation energy and become a gas, while others remain with energy below the activation energy and remain as a liquid.
The more you increase the temperature, the more likely it is that a certain molecule will have energy above the activation energy and therefore become a gas. At 100 degrees Celsius, almost all of the water molecules gain energy above the activation energy and therefore become a gas.