[Bishadi (OP)]

What makes an atom 'hot'?

and please, we talking about Atom number 1......  what makes that one HOT?

[Bored chemist]

Chemists can define heat. Perhaps Bishadi is a joke.

Defining the temperature of 1 atom is a bit meaningless- you could make some sort of estimate from its kinetic energy in your frame of reference or if it's in an electronicly excited state.
It's a bit like finding one member of a spercies- for example the last dodo- and asking if it's inteligent as dodos go.

[lyner]

Temperature is average KE so whatever the KE (in eV, perhaps - ionise it and accelerate so you could be sure of what it was) that would tell you. But it wouldn't mean a lot.

[lightarrow]

Temperature is average KE so whatever the KE (in eV, perhaps - ionise it and accelerate so you could be sure of what it was) that would tell you. But it wouldn't mean a lot.

Exactly. To make it more clear: let's take a gas at room T (25°C) in a container; there are molecules with velocity v distributed in some way, from 0 to (virtually) +infinite; now consider only the molecule with the higher velocity, let's say 299,000,000 m/s. Which is its temperature? The gas temperature is still 25°C, so should be that molecule's temperature...

In other words: its meaningless to define a single molecule's T because to do it you should associate that molecule to a specific system with a specific distribution, but you can do it for a system at room's T, for another at T = 10⁹°C, ecc.; which system does that molecule belong? It's undetermined, so as that single molecule's T.

[lyner]

Likeways, if you have a container of gas at 300K and suddenly shoot it off into space at 100km/s, the thermometer inside the container will still register 300K, although the 'average' KE of the container has considerably increased.
The concept of temperature describes the 'internal' energy.

[Bored chemist]

I wonder if we have been the victims of a "drive-by trolling".

[blakestyger]

What makes an atom 'hot'?

and please, we talking about Atom number 1......  what makes that one HOT?

We'll soon find out - maintaining a superiority complex whilst posting stuff like that takes a lot of mental effort and denial. [^]

[DoctorBeaver]

I wonder if we have been the victims of a "drive-by trolling".

 []

[lyner]

When a nebula starts to collapse, under its gravitational potential, all the atoms (with very few exceptions) will be moving inwards. The 'temperature' of one region would be very low, though, until the atoms get close enough to behave as described by kinetic theory  (bumping into each other, randomly).
Also, how about the 'temperature' of the gas ejected from an explosion?
And, of course, there is the odd fact that the temperature of the Sun's corona is 1+ million K, compared with the surface of about 5000K. The density of the plasma there is very low, however, so 'in the shade' it wouldn't actually feel that hot.
The word 'temperature' needs to be applied carefully.

[Bored chemist]

At the risk of prolongindg a thread which might be better left to die; I think temoperature is only validly defined for a system at or near equilibrium with its surroundings, or at least at equilibrium with itself.

[lyner]

You are probably right BC


RIP

[Bored chemist]

The goalposts have been moved.
Bishadi's original post has been changed.
It no longer includes the insulting, and irrational, idea that chemistry doesn't understand temperature.
Presumably that is because he realises that he was talking nonsense or that someone took that view on his behalf.

[chris]

I changed it because it was inconsistent with our format of posting questions, and it also make no sense.

Chris