How does water condense onto glass

We wake up to hnd it is a bitterly cold day outside. We wish to wash, so we fill the bathroom sink with hot water but, as soon as we look up, we see how water condenses on the cold glass of the mirror. 

As soon as steam emanates from the water in the sink, it will rise (owing to eddy currents see Chapter 1). A tiny fraction of the airborne water (i.e. steam) will condense on the mirror, and soon a strongly bound chemisorbed layer forms to cover its whole surface. The layer is microscopically thin, making it wholly invisible to the eye. We will call this layer layer 1 . Each molecule of water in layer 1 is now physically distinct from normal water, since charge has been donated to the substrate. Each water molecule in layer 1 is, therefore, slightly charge deficient, compared with normal water. 

Further layers can physisorb, one above another. The extent of charge deficiency will decrease until, after about five or six layers have physisorbed, they are energetically indistinguishable. By the time we have about a dozen layers adsorbed on the glass, we are no longer able to speak about layers, and start to talk about bulk condensate of water. At this point, more water condenses onto this mass of water, causing its weight to increase, and eventually it runs down the mirror as warm condensation. 

Another example consider the adsorption of bromine on silica. We start by placing elemental bromine and silica at either end of a long sealed vessel. Having a relatively high vapour pressure, bromine volatilizes and molecules of bromine soon chemisorp onto the surface of the silica. When the chemisorbed monolayer is complete, successive layers of bromine form by physisorption. The first physisorbed layer is unique, 

The layer immediately adjacent to the substrate need not be physisorbed. 

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