evaporation.. ?

[ColJack]

here's a thought i had today...

if the boiling point of water is 100 degrees C ( give or take a few for impurities..), then how do things dry out / off?

the water evaporates and is carried away in gaseous form...

I was under the impression that evaporation occurs when a liquid is heated to it's boiling point?

this happens at a lot lower temperature than 100 degrees C..

 

[markie]

Anything above 0 c will evaporate, wont it ? eg when it rains in winter/summer/spring/autum. the roads/paths etc etc dry out.

 

[gcol]

I was under the impression that evaporation occurs when a liquid is heated to it's boiling point?

Evaporation increases with temperature but it occurs at lower temperatures too.

 

[noseall]

I was under the impression that evaporation occurs when a liquid is heated to it's boiling point?

Evaporation increases with temperature but it occurs at lower temperatures too.

the height relative to sea level is a factor with liquids too.

boiling points of liquids are drastically reduced the higher above sea level you go, or increased the lower you go. the rarer the atmosphere the easier or more readily a liquid can evaporate. the water in a pressure cooker for instance will boil at a higher temperature because the space within the cooker is higher than sea level barometric pressure.

hope this makes sense.

 

[Softus]

Temperature is a factor, but much more important parameters are the vapour pressure of the liquid and the ambient pressure.

Note that, if the conditions are right, a solid can evaporate.

 

[noseall]

Temperature is a factor, but much more important parameters are the vapour pressure of the liquid and the ambient pressure.

...mmmm, i concur.

already.

 

[empip]

Sort of connected ... Interesting ...
http://www-saps.plantsci.cam.ac.uk/records/rec410.htm

 

[Softus]

Nice one empip; and it reminded me that the reason clothes dry quicker on a windy day is because the layer of saturated vapour at the surface of the liquid is being repeatedly moved away and replaced with a layer of unsaturated vapour.

 

[ricicle]

And the reason you feel hotter and sticky on a humid day is the fact that the air is already almost saturated so there is no more room for your sweat to evaporate so it remains on you.This hinders your evaportive cooling and thus the ability to stay cooler.

 

[notb665]

here's a thought i had today...

if the boiling point of water is 100 degrees C ( give or take a few for impurities..), then how do things dry out / off?

the water evaporates and is carried away in gaseous form...

I was under the impression that evaporation occurs when a liquid is heated to it's boiling point?

this happens at a lot lower temperature than 100 degrees C..

gcol was the nearest. One definition of boiling point is that the rate of molecules evaporating and condensing is equal. So at 100°C, the rate of water molecules leaving the liquid and re-joining the liquid is the same. In controlled conditions, you could keep water boiling and it wouldn't decrease in volume. So at lower temperatures, molecules are still leaving the liquid, just very slowly. And because of the wind/upper environment being completely un-dense with molecules, will be blown away never to come back.

 

[notb665]

Temperature is a factor, but much more important parameters are the vapour pressure of the liquid and the ambient pressure.

Note that, if the conditions are right, a solid can evaporate.

Yes, like dry ice (solid carbon dioxide). It is called sublimation. Check out 'phase diagrams' for more on this. They were about the only aspect of physical chemistry I enjoyed while at university. http://en.wikipedia.org/wiki/Phase_diagram

 

[notb665]

Water is a good one. Snow is considered another solid phase/state of water comparable to normal ice, liquid water and steam. Snow is formed where the conditions are right for hexagonal crystals to form - very pretty! There are lots of other states of water too, all formed around the same area on a phase diagram and dependant on relatively small pressure changes. http://www.mines.utah.edu/~tcerling/gg330/H2O_phases.JPG

 

[Macclesfield]

Very interesting, this would explain why sometimes my poo is hard and other times it's runny all to do with pressure.

 

[notb665]

Very interesting, this would explain why sometimes my poo is hard and other times it's runny all to do with pressure.

Your first post was about poo! Well done!