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Solder properties? Irons?



 
 
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  #51  
Old June 29th 04, 03:26 PM
Javahut
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"Gene" wrote in message
...

"Moonraker" wrote in message
.. .

"O D" wrote in message
...
Don't know this as absolute fact of lead ingesting , but if you have a
change of state in the lead then you may have vapor being inhaled.

When
you go from asolid to a liquid there will be some small form of gas

that
is carried in the air stream.


Close.

Matter only has three properties, solid, liquid, or gas. Those states

for
every type of matter are attained at very specific temperatures.
Those temps are modified by adding some other matter to a pure

substance.
Similar to adding salt to ice, which lowers the melting (liquification
point) below 32*F. That's why adding tin and (whatever) to lead makes
solder work. Solder is an alloy that liquifies at a temperature lower

than
the melting point of the relatively pure lead came. Going from memory,
solder melts at about 425F, and lead melts at 621F. The boiling point

(not
melting point) of lead is nearly 3200F, and my soldering iron sure

doesn't
get THAT hot.

Gaseous states start only at the boiling point, by definition.


Close.

A "gaseous state" for the bulk of your material may start there, but gas
itself does not.

*Boiling* starts at the boiling point, not the release of material in
gaseous form.

The temperature of any object is a statistically determined number that is
related to
the velocity (*average* kinetic energy, actually) of the molecules that

are
dancing
around under the action of heat.

This number reflects the *average* kinetic energy, and many molecules

will
be moving at
greater or lesser velocities, including some that are moving at
*considerably* greater velocities,
all the way up to and including velocities that allow them to escape the
surface as a gas.

Even at room temperature, some molecules will inevitably be moving fast
enough (with enough
energy) to escape from the surface. You do not have to heat any liquid all
the way to boiling to
release its molecules into the air as a gas.

For a simple example most people will be familiar with, if you leave a
teaspoon or so of water
in a glass at room temperature for 2-3 days, you will probably not have a
teaspoon of water
in that glass anymore. Do you think the water just magically vanished, or
was somehow sucked
into the air mysteriously? No boiling flux here to sweep the water

molecules
up into the air,
either. In fact, a teaspoon of *ice*, sitting on your counter-top, is
releasing molecules into
the air, admittedly not very rapidly, but nevertheless it is losing

gaseous
vapor as you watch.
(And any objections to this based on the observation that if the humidity

in
the room is at
100%, the water doesn't vanish, are misleading because while molecules are
escaping from the
surface of the water, other molecules of water in the air are arriving and
replacing the lost
molecules, so that the teaspoon of water will *not* be the same teaspoon

of
water you started
with. In the case of ice, this is restricted to the near surface, but in

the
case of water the molecules
are free to diffuse throughout the volume.)

So that it is inevitably the case, among the molecules that are jostling
around (with their random
distribution of kinetic energies) under the influence of heat, even at 0
degrees celsius, will be
plenty that have a high enough velocity to escape the surface.

The boiling point of a substance is its *boiling* point, not the point at
which molecules of
the substance suddenly start drifting off into the air. *That* happens at
temps a lot lower
than the boiling point.

At the boiling point, essentially *all* of the molecules have enough

kinetic
energy to escape into
the air (against the air pressure, btw...lower the air pressure and you

need
less heat, i.e. a lower
temp.) OTOH, not *all*, but plenty (for a suitable definition of "plenty")
of molecules have enough kinetic energy to escape as gas at lower temps.

Now, *if* heat distributed energy *equally* to all the molecules, you

would
have been right to
have concluded that at less than the temperature of vaporization no gas at
all would be released.

Unfortunately, though, it doesnt.

HTH. HAND.

-Gene

Thank you Gene, certainly glad you cleared that up, I'm not nearly so
confused on that issue.


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