[kapital]

Can somebody please tell me why and where there is change in vapour pressure, due to curved interface?
Kelvin equation

[ramboacid]

I don't know exactly, but I know that vapor pressure isn't affected by an increase in surface area, si the change in surface are due to the curved interface likely isn't the answer. It might have to do with the difference in surface tension between the curved and non-curved interfaces, because the higher surface tensions indicate that the surface layer of liquid molecules are more strongly attracted to the bulk liquid and thus less likely to escape into the atmosphere and increase the vapor pressure.

[kapital]

I don't know exactly, but I know that vapor pressure isn't affected by an increase in surface area, si the change in surface are due to the curved interface likely isn't the answer. It might have to do with the difference in surface tension between the curved and non-curved interfaces, because the higher surface tensions indicate that the surface layer of liquid molecules are more strongly attracted to the bulk liquid and thus less likely to escape into the atmosphere and increase the vapor pressure.

Possibly. But still if I quote wikipedia first sentence:

The Kelvin equation describes the change in vapour pressure due to a curved liquid/vapor interface (meniscus) with radius r (for example, in a capillary or over a droplet).

And I really do not understand what this is telling.. Even more, to me that sentence dose not make any sense. As far as I know, the vapour pressure is parameter wich depends on the properties of compund, temperature and atmosferic pressure(or outer pressure) and I relly do not know what the curved surface(or interface) has to do with any of this.

And as far as I know, the surface tension is also the same over the whole area?

[Borek]

Pressure over the surface is a function of intermolecular forces between molecules in the liquid (how easy it is for the molecule to break all intermolecular bonds and "jump" away). Molecule lying on the surface is attracted by all molecules "touching" it from the liquid side. Number of these molecules is a function of the curvature of the liquid surface - in a small droplet molecule on the surface is more exposed, in the capillary it is surrounded by more molecules than on teh flat surface.

Even more, to me that sentence dose not make any sense. As far as I know, the vapour pressure is parameter wich depends on the properties of compund, temperature and atmosferic pressure(or outer pressure) and I relly do not know what the curved surface(or interface) has to do with any of this.

Just because you don't know doesn't mean something doesn't make sense.

[kapital]

I think I just partially understand what you have said. But nevertheless, can you tell me then where on this picture is vapour pressure different?

[Borek]

If curvature is constant, vapor pressure is constant as well.

[kapital]

Well, does not that implies somehow that this statement is a little weird:

The Kelvin equation describes the change in vapour pressure due to a curved liquid/vapor interface (meniscus) with radius r (for example, in a capillary or over a droplet).

Because I understand this like:

vapour pressure changes with curved interface.

But this is by my opinion that contradictory with picture comment.

[curiouscat]

But this is by my opinion that contradictory with picture comment.

Not sure what you mean.

[kapital]

Well I do not know to. ( I know what I want to say but it is probably wrong)

So can you explain what exatcle this equation tells?

[kapital]

If somebody tell what is wrong in my picture it woud also help.(mena wrong, in a way that you could use this equation)

[Borek]

Your picture doesn't contain anything that could be right or wrong, so it is not possible to comment.

Kelvin equation tells you what is saturated vapor pressure over a POINT on the liquid surface, not in a vessel.

[kapital]

Ok. Can you than make a picture, with two diffrent places with different capour pressures?

[curiouscat]

Ok. Can you than make a picture, with two diffrent places with different capour pressures?

Sometimes, just sometimes, don't you ever wonder to yourself if you are asking a lil' bit too much of the posters trying to help you out here?