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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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