From kinetic theory - why does heat rise? I know the explanation from fluid elements and densities however I don't find it satisfying.  Is there an explanation from kinetic theory?
 A: The following three factors are at play here: temperature $T$, pressure $p$, and molar density $\rho_M$ (inverse molar volume $\bar{V}$). "Heat" is associated colloquially with the first of the three factors more often than with the other two. This is not always the most appropriate of scientific connections to make. However, in kinetic theory, we do associate "hotter" gases with gases that have higher temperatures and therefore higher kinetic energy for their particles.
When we make the association that "heat" means hotter gas, what can we say about the other two factors?
First, recognize that kinetic theory leads directly to a derivation of the ideal gas law $p = \rho_M RT$ (with $R$ as the gas law constant). At this point, we can only take one of two approaches to decide what happens to the other two factors (pressure and molar density). 


*

*For the same PRESSURE, a hotter gas will have a lower density than a colder gas. In a gravitational field, a less dense (hotter) fluid (ideal gas) is forced by gravity to "float" above a denser (colder) fluid (ideal gas).

*For the same MOLAR DENSITY, a hotter gas will be at a higher pressure than a colder gas. Unfortunately, this perspective gives us no insights about as to why a higher pressure (colder) gas should sink below a lower pressure (hotter) gas in a gravitational field.
In summary, kinetic theory is not an avenue that can explain why "heat" rises. Kinetic theory is a way to explain why hotter gases are less dense than colder gases. The fact that hot gases float in a gravitational field is explained by basic physics principles of forces on fluids.
A: Think of it at the scale of individual particles and it clearly becomes a simple statistical issue.
Liquids in a gravitational field have a density distribution. If you consider a "low energy" liquid from any given location, one sees more particles below that spot and less above it.
Now take a bunch of "high energy" particles and fire them in random directions from that location. If they happen to be going up, they'll have less collisions over time and therefore travel further than the ones going down.
So, in bulk, "heat rises".
A: Heat doesn't rise.
Heated fluids rise relative to their surroundings if the surroundings are unheated quantities of the same fluid. 
