Why does heat rise?

Answer 1

"Heat" itself does not rise; heat transfers [moves] by conduction, radiation, and convection [convection is the one that best relates to what your question asks].

Your question refers to a warmer fluid [gasses as such as air for one example, or the same thing occurs in liquids, as water for one example] rising in cooler surrounding fluid.

The reason a warmer fluid [gas or liquid] rises in surrounding fluid is as answer one and two state, as both are correct in that both are causes, except that one is the cause for the other.

The combined answer is: As the average kinetic energy of the atoms of a fluid increases, the density of the fluid becomes less [it get "lighter"] and therefore rises ["floats"] in the surrounding fluid until it reaches a level where its temperature and density are the same as the surrounding fluid [equilibrium]. At that point the mass of fluid will cease to rise.

We refer to this process as "convection."j3h.

Answer Ok so we're all right.

Except that "right" is subjective and only correctly classified when we inject perspective. Heat will always rise with respect to the ground we walk on, no matter the temperature, state of matter, or any other physical property.

The true reason that heat rises is due to something not yet mentioned... GRAVITY! To be more precise, in a positively excited atom/molecule, the electrons create a larger orbital shell whereby making the atom/molecule as a whole more "empty" or "porous", void of matter. Believe it or not, this minutely small difference is enough to slightly loosen gravity's electromagnetic grip on the atom/molecule allowing it to slip further away from gravity's source... the planet's core. This is why even a lone positively excited atom/molecule in a vacuum will rise toward the top of the container, just as it would if there were trillions.

Answer - Rebuttal

Gravity as discussed above, is not the cause, but instead the DIFFERENCE IN BOUYANCY created by the "... more 'empty' or 'porus...' thus LESS DENSE weight of the fluid/gas molecule. The change in density does not change the mass of the molecule.

Answer 2

Heat rises because when air is heated, it becomes less dense and expands, causing it to become lighter than the surrounding cooler air. This lighter, warmer air then rises above the cooler air, creating convection currents and leading to the overall upward movement of heat.

Answer 3

Hot gases tend to rise because it is less dense. As molecular motion speeds up so does the distribution of molecules.