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.
[Physics] Physical state of Fog
everyday-lifethermodynamics
Related Solutions
[Physics] How does the temperature of the triple point of water depend on gravitational acceleration
This is perhaps similar to what mbq meant, but I will elaborate. The T-p phase diagram of water tells us, for a given temperature and pressure, what phase we will get if we have a bunch of that substance. If I apply different pressures to a bottle of water, I am moving around in the p-direction of the T-p plane. I am not changing the pressure of the triple point of water, just changing the pressure of that particular bottle of water! Similarly, if a tank of water is in a gravitational field, it affects the pressure. In fact, it leads to different pressures at different locations of the tank. It could lead some parts of the tank to freeze, for example. But it does not in any way change the triple point of water itself, which is an intrinsic property of that substance. So I would say that the question is ill-posed. It might be better to ask: what will happen to a tank of water at a given temperature and density if we now apply a gravitational field?
First, some might be interested in your reduced pressure. I guess you are working argon parameters of $\varepsilon = 119.8 \text K$ and $\sigma = 3.405 \overset{\circ}{\text A}$, thus your pressure of 1.0 MPa (10 atmospheres) in a reduced form:
$$p^* = \frac{p \sigma^3}{\varepsilon} \approx 0.024 $$
Anyway, let's see where are you. From your plot I've deduced several poins of yours:
ρ T
-----------
0.9 .7
0.7 .75
0.6 .9
0.5 1.05
0.4 1.1
0.3 1.15
0.2 1.25
and marked them on the density-temperature phase diagram of a Lennard-Jonesium:
I took the figure from the article I've already mentioned in your aother question, the article is by JP Hansen, L Verlet "Phase Transitions of the Lennard-Jones System." As you see, generally you start from a liquid+solid, then as you lower the density (or increase the temperature) solid melts into liquid, then somehow you reach the region of vapor-liquid coexistence where liquid gradually evaporates until you end up with mostly vapor phase.
Most of your process lies in a region of vapor-liquid coexistence, some part in the region of solid and liquid coexistence. The switch between the two occurs near $\rho =0.8$ and indeed your plot shows a peculiarity at these point. You should better resolve this region you may be near the triple point as Fabian suggests.
To sum up, $\rho(T)$ should be continuous, it is $\frac{d \rho}{d T}$ that should not. You plot seems to exhibit such a behavior, but I cannot tell for sure. You have to accurately measure the transition between the liquid and liquid+vapor to find the discontinuity of $\frac{d \rho}{d T}$. The problem is it can be hard to hit into liquid, since liquid for LJ (and argon) occupies only a small gap of $T$ and $\rho$. Why have you put $p$ to be 10 atm, maybe you wanted to have 1 atm?
You cannot rely on an RDF in the region of vapor-liquid coexistence, it has hardly any sense there --- basically you have bubbles of liquid floating in a vapor. Though due too the small size of your system it's hard to talk about bubbles.
You might want to study the system clearly exhibiting vapor-liquid interface, that is when the one part of your cell has vapor, the other one has liquid. Thus you could actually see how the amount of liquid diminishes due to evaporating. Given $z$ is a vertical axis, perpendicular to the surface of the liquid you can study $\rho(z)$ instead of RDF.
Last, but not least, obviously, I could not plot your points accurately on the phase diagram, be cautious not to rely on these too much, that's just an estimation. And the phase diagram itself is intended to reflect the true LJ, not the shifted and truncated one.
Best Answer
It is a colloid in which the dispersed phase is liquid and the medium in which it is dispersed is gas. This type of colloid is called aerosol.