Sorry if this is slightly off-topic, but I know there are people here
who can enlighten my dull grey cells...

What, if any, is the difference between a gas and a vapour? I was trying
to explain steam to my 5 year old this morning and, as kids do, she
asked me this one that stumped me.

;-)


--
Posted via Mailgate.ORG Server - http://www.Mailgate.ORG

Because there's more to the internet than hits alone, Adam Coombes
wrote:

Sorry if this is slightly off-topic, but I know there are people here
who can enlighten my dull grey cells...

What, if any, is the difference between a gas and a vapour? I was trying
to explain steam to my 5 year old this morning and, as kids do, she
asked me this one that stumped me.

;-)

Since matter achieves its gaseous state (it e-vapor-ates) by absorbing
'Latent Heat of Vapourisation' I guess they must be the same thing.
However, you often hear people distingush between, for example, steam
and water vapour - steam being a gas (invisible), and water vapour
being lots of tiny little droplets of water (which defract light and
are thus visible as grey clouds).

I just looked up my old A-Level physics text book; it says

"A gas above its critical temerature cannot be liquefied. Early
attempts to liquefy gases such as air, by compression without cooling,
failed; and the gases were wrongly called 'permanent' gases. We still,
for convenience, refer to a gas as a vapour when it is below its
critical temperature, and as a gas when it is above it."

It goes on a bit to explain that this is not entirely accurate, but
the implication is, if a gas can be compressed to a liquid without the
need for additional cooling then it is a vapour. But a vapour still
falls into the category of 'gas'.




--

Stewart Hargrave

I run on beans - laser beans


For email, replace 'SpamOnlyToHere' with my name

On Fri, 02 Apr 2004 13:15:02 +0100, Stewart
wrote:

Because there's more to the internet than hits alone, Adam Coombes
wrote:

Sorry if this is slightly off-topic, but I know there are people here
who can enlighten my dull grey cells...

What, if any, is the difference between a gas and a vapour? I was trying
to explain steam to my 5 year old this morning and, as kids do, she
asked me this one that stumped me.

;-)

Since matter achieves its gaseous state (it e-vapor-ates) by absorbing
'Latent Heat of Vapourisation' I guess they must be the same thing.
However, you often hear people distingush between, for example, steam
and water vapour - steam being a gas (invisible), and water vapour
being lots of tiny little droplets of water (which defract light and
are thus visible as grey clouds).

I just looked up my old A-Level physics text book; it says

"A gas above its critical temerature cannot be liquefied. Early
attempts to liquefy gases such as air, by compression without cooling,
failed; and the gases were wrongly called 'permanent' gases. We still,
for convenience, refer to a gas as a vapour when it is below its
critical temperature, and as a gas when it is above it."

It goes on a bit to explain that this is not entirely accurate, but
the implication is, if a gas can be compressed to a liquid without the
need for additional cooling then it is a vapour. But a vapour still
falls into the category of 'gas'.

It's vapour if it's in contact with it's liquid phase. So when steam
comes out of the kettle it's vapour. The clouds are water vapour too
as they are just a highly visible concentration of vapour. The whole
atmosphere has invisible water vapour in it, which is in contact with
sea and rivers. The short distance from boiling kettle spout to
visible steam where the vapour is invisible is considered to be 'dry'
steam which as close to a gas as water gets on earth.

LPG and domestic propane is vapour in contact with liquid in the
tank/cylinder. Once the liquid is passed though the vapouriser and
boiled it is gas as it won't compress back to liquid. In the case of
domestic vapour draw off propane cylinders passing the vapour though
the regulator gives a pressure drop and propane gas results.

--
Peter Hill
Spamtrap reply domain as per NNTP-Posting-Host in header
Can of worms - what every fisherman wants.
Can of worms - what every PC owner gets!

"Peter Hill" wrote in message
...
On Fri, 02 Apr 2004 13:15:02 +0100, Stewart
wrote:

Because there's more to the internet than hits alone, Adam Coombes
wrote:

Sorry if this is slightly off-topic, but I know there are people here
who can enlighten my dull grey cells...

What, if any, is the difference between a gas and a vapour? I was trying
to explain steam to my 5 year old this morning and, as kids do, she
asked me this one that stumped me.

;-)

Since matter achieves its gaseous state (it e-vapor-ates) by absorbing
'Latent Heat of Vapourisation' I guess they must be the same thing.
However, you often hear people distingush between, for example, steam
and water vapour - steam being a gas (invisible), and water vapour
being lots of tiny little droplets of water (which defract light and
are thus visible as grey clouds).

I just looked up my old A-Level physics text book; it says

"A gas above its critical temerature cannot be liquefied. Early
attempts to liquefy gases such as air, by compression without cooling,
failed; and the gases were wrongly called 'permanent' gases. We still,
for convenience, refer to a gas as a vapour when it is below its
critical temperature, and as a gas when it is above it."

It goes on a bit to explain that this is not entirely accurate, but
the implication is, if a gas can be compressed to a liquid without the
need for additional cooling then it is a vapour. But a vapour still
falls into the category of 'gas'.

It's vapour if it's in contact with it's liquid phase. So when steam
comes out of the kettle it's vapour. The clouds are water vapour too
as they are just a highly visible concentration of vapour. The whole
atmosphere has invisible water vapour in it, which is in contact with
sea and rivers. The short distance from boiling kettle spout to
visible steam where the vapour is invisible is considered to be 'dry'
steam which as close to a gas as water gets on earth.

LPG and domestic propane is vapour in contact with liquid in the
tank/cylinder. Once the liquid is passed though the vapouriser and
boiled it is gas as it won't compress back to liquid. In the case of
domestic vapour draw off propane cylinders passing the vapour though
the regulator gives a pressure drop and propane gas results.

Ok, so now you know the answer, will you post a transcript of the
conversation when you explain it to your 5 year old! I think it could make
interesting reading!

"SimonJ" wrote in message



Ok, so now you know the answer, will you post a transcript of the
conversation when you explain it to your 5 year old! I think it could make
interesting reading!


Hmmm.... Yes! We'll have to see about that. ;-)

How is it kids always ask simple questions with complicated answers.
I've already struggled with 'How does the engine work?' and 'What does
the turbo do daddy?' This is from my daughter so Gods alone know what my
two new sons will be like when they get older. Maybe I'll sell the cars.


--
Posted via Mailgate.ORG Server - http://www.Mailgate.ORG

Ok, so now you know the answer, will you post a transcript of the
conversation when you explain it to your 5 year old! I think it could
make
interesting reading!


Hmmm.... Yes! We'll have to see about that. ;-)

How is it kids always ask simple questions with complicated answers.
I've already struggled with 'How does the engine work?' and 'What does
the turbo do daddy?' This is from my daughter so Gods alone know what my
two new sons will be like when they get older. Maybe I'll sell the cars.

You want to be thankful its just questions about cars

When I was a kid, at the stage where my parents were just in the middle of
explaining the 'birds and bees' stuff to me, I asked Mother, on a bus, at
the top of my voice................
"BUT MUMMY, HOW DID DADDY'S BABY SEED GET INTO YOUR TUMMY"
the result of course was a completely silent bus, and a bright crimson
mother!