Difference between adsorption and condensation So I just stumbled across the Wikipedia article on adsorption - and I asked myself, if there is a difference between (physical) adsorption and condensation on a surface? 
When I look at the water drops on a cold bottle of your favourite beverage, I think this is covered by what I know about adsorption. Or is this kind of condensation just one of many adsorption reactions?
Any help is appreciated :)
 A: Generally speaking we use the term adsorption when we're talking about a specific molecular interaction. In contrast the term condensation is really a phase transition of a bulk fluid.
Consider the interaction of water with a silica surface (this is a system I studied about 30 years (!!!) ago). A clean silica surface contains OH bonds that have a high dipole moment. These interact strongly with the OH bond in water, so a hydrogen bonded layer of water forms on the silica and this gives you a monolayer of water on the surface. That water layer then interacts with more water molecules via hydrogen bonds, so in practice silica will have more than a monolayer of water on its surface. Still, you are talking about a layer with a thickness of molecular dimensions. This type of behaviour is what I would refer to as adsorption.
Suppose you now change the conditions so your water vapour is supersaturated e.g. reduce the temperature to below the dew point. The water vapour would like to turn to a liquid, but the trouble is that condensation of the water vapour to water requires a nucleation step because there is an energy barrier to drop formation.
All sorts of things can act as nuclei, for example in clouds the water droplets are nucleated by dust particles or pollen grains. However surfaces are often good at providing nucleation points, especially if the surface contains defect or in the case of glass tiny scratches. At these points the energy barrier to droplet formation is lowered and droplets of water can condense from the vapour. This is the process I would refer to as condensation.
So the two processes are very different, and the way the surface acts in the two processes is very different.
A: Adsorption can catalyse condensation, but it's a distinct process. Molecules adsorb to a surface and then act as a (heterogeneous) nucleus for the gas-to-liquid phase transition (i.e. condensation).
