Is Fog solid or gaseous mater? Can it reach the triple point of water? As per my research, fog rises only if its density is less than that of water as water vapor does, a fact that is forcing me to classify fog as a gaseous mater. Yet the only condition for fog to exist is when temperature is below the triple point of water,where we prospect to have liquid on transition to solid. This fact violates the idea for the triple point of water.
Standard everyday fog consists of a mixture of liquid water droplets suspended in water vapour in the air (it is an example of a 'liquid aerosol' colloid). A nice summary of the formation is given by the National Geographic website encyclopaedic entry about fog as:
Fog shows up when water vapor, or water in its gaseous form, condenses. During condensation, molecules of water vapor combine to make tiny liquid water droplets that hang in the air. You can see fog because of these tiny water droplets. Water vapor, a gas, is invisible.
There has to be a considerable amount of humidity and often, the presence of very small microscopic aerosols (dust, sea-salt etc etc) to condense on.
Fog is not a pure substance, so don't search for its phase. It's a mixture of water, water vapor and air. So No single PV or PT or any kind of diagram can represent its state.
BUT, As water vapor act approximately like gas, as long as we deal with "shot"s of the system, and because this mixture is approximately uniform in composition everywhere, we can say it is like water and water vapor system.
That's because It really act like that in practice, pressure will be constant for some isothermal compression as this PVT surface for water suggests.
The approximated system therefor lies in "vapor and liquid" part of this PVT surface.
If you intersect a horizontal plane with this surface, In between the critical point and the triple line. The resulting curve will be where approximated fog can exist. It is way higher than the pressure of the triple line.
Fog is a colloid, which is a type of mixture in which microscopic particles of one substance are suspended in a continuous medium. A colloid is distinguished from other types of suspension in that the suspended particles do not settle out of the suspension over practical time scales.
Both the suspended substance in a colloid and the medium in which it is suspended can be solid, liquid, or gas, except that there are no known gas-in-gas colloids. Different combinations of phases in colloids have different names. Liquid-in-gas colloids, like fog, and solid-in-gas colloids, like smoke, are called aerosols. Other well-known names for different kinds of colloids include foams (gas-in-liquid), emulsions (liquid-in-liquid), and gels (liquid-in-solid).