Question

As we know water boils at 100 C at 1 atmospheric pressure but how it evaporates below its boiling point at 1 atmospheric pressure? please explain the mechanism clearly

Answer 1

If we're talking about pure water, then most of it becomes a gas at 100C. But the water molecules on the edge have less cohesive forces with surrounding water. Thus, a lower energy will excite the molecule to the point of becoming a gas.

A lower temperature than 100C can excite the gas.

I think there is also the issue of how much water is in the atmosphere around the water. It's similar to how you seem to sweat more when it's humid. It's just that the sweat doesn't evaporate as easily when there is more moisture in the air, and evaporates much easier when the environment is dry.

Good luck! I hope somebody else can be more specific than me! If you want to know more, maybe you can ask in the chemistry subject. I know some people don't like it when questions are posted it two places, but the viewpoints might differ significantly. This stuff is what I learned in chemistry, and I haven't studied molecules in physics yet. Maybe thermodynamics students would be able to help more!

Answer 2

i can give you a link...that may help you...
http://en.wikipedia.org/wiki/Evaporation

Answer 3

There is also a small Wikipedia article on cohesion. It looks like the water molecules make weak hydrogen bonds with each other. It would have fewer at the surface.
http://en.wikipedia.org/wiki/Cohesion_(chemistry)

Answer 4

From what i know boiling is a 'bulk phenomenon' while evaporation is a 'surface phenomenon'. Meaning ,at boiling point water molecules throughout the bulk of the liquid have attained the latent heat of vaporization and thus become 'gaseous' and escape out of the bulk of liquid. Meanwhile,in evaporation only the surface particles are able get the latent heat (from outside world) and are able to escape.