Atmosphere

[ccyy1993]

Q1. Does the atmospheric pressure affect the rate of boiling and evaporation?

Q2. When you go higher up the mountain etc., why do you feel cold and not feel hot?

[Eternity]

Check out http://www.atm.dal.ca/~folkins/physics1.html

 

I could of answered the question but would have taken quite some time, instead I decided the link above would do the trick.

[Peter Pedant]

Blimey the link is a bit technical ccyy

 Q1 yes it does - boiling - no it shouldnt -  evaporation

Q2 you would feel hotter if getting nearer the sun was the dominant effect - it isnt. As you go up, it gets colder, and as you go down it gets warmer.

Folkins page given above is obviously mmore detailed than this

[bernardo]

2. Because the temperature that you feel depends mostly on the pressure of the air - up a mountain, the air is thinner (because it has a smaller amount of air on top of it to squash it) and therefore colder.  The reason why low pressure feels colder is because "heat" is caused by zillions of air molecules bashing into you as they whizz around in the atmosphere.

[Rystan]

Air pressure effects both boiling and evaporation. If air pressure is high, there is more force on the molecules in the body of water, keeping them from moving easily. If pressure is low, the molecules have more room to bump around into each other and / or disperse into the air above.

As Bernardo pointed out, air pressure is lower at higher elevations. This means fewer molecules to bump into you but also, fewer molecules to themselves retain the heat reflecting off the earth's surface. The result is colder air.