Re: hot air rising

[John Denker <jsd@MONMOUTH.COM>]

At 01:45 PM 7/21/99 -0400, Robert A Cohen wrote:
> Hmmm...perhaps the difference is just one of terminology.  I would say
> that the floppy plastic bags prevent molecular mixing.  I was using mixing
> to describe the larger-scale exchange of air parcels,

Flow is not the same as mixing.

> students will typically
> not recognize that and will end up interpreting "adiabatic cooling" as
> cooling that occurs because the air parcels mix with the surrounding,
> cooler air.

Adiabatic cooling has everything to do with flow and nothing to do with mixing.

> I guess I am still confused.  If the hot air was "even hotter" before it
> went upstairs, then wouldn't it be "even hotter" on the lower floors?

That depends on what you mean by "it".  First, let's define _it_ to mean
the parcel of air that rose.  _It_ was was out of equilibrium with its
neighbors -- otherwise _it_ wouldn't have been hot and _it_ wouldn't have
risen.

Now define /it/ to be the ambient temperature.  /It/ is hotter upstairs
because of the accumulation of little parcels of air that came out of the
heating vent and have been hot ever since.