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Q. Take an open container of water up high enough and it will boil away. . .
Hi.
I understand if an open container of water is taken up to altitude high enough, that it will boil away. I take that to indicate when water is brought to a boil on our stove, at sea level, that the heat actually activates or motivates the water molecules to begin going crazy and rubbing against each other, and creating the vapor which must escape. But if one were to take that open, cold pot of watet to a given point above the earth's atmosphere, would the water get hot, as it would on the stove, while it boils away? Thanks, Jim |
#2
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Q. Take an open container of water up high enough and it will boil away. . .
"Jim" wrote in message ... Hi. I understand if an open container of water is taken up to altitude high enough, that it will boil away. I take that to indicate when water is brought to a boil on our stove, at sea level, that the heat actually activates or motivates the water molecules to begin going crazy and rubbing against each other, and creating the vapor which must escape. But if one were to take that open, cold pot of watet to a given point above the earth's atmosphere, would the water get hot, as it would on the stove, while it boils away? Thanks, Jim Anyone? Am I right in saying that though the water "boils" it does not however increase in temperature? And is this srictly on-topic? |
#3
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Q. Take an open container of water up high enough and it will boil away. . .
"Jim" wrote in message ... Hi. I understand if an open container of water is taken up to altitude high enough, that it will boil away. I take that to indicate when water is brought to a boil on our stove, at sea level, that the heat actually activates or motivates the water molecules to begin going crazy and rubbing against each other, and creating the vapor which must escape. But if one were to take that open, cold pot of watet to a given point above the earth's atmosphere, would the water get hot, as it would on the stove, while it boils away? Thanks, Jim Anyone? Am I right in saying that though the water "boils" it does not however increase in temperature? And is this srictly on-topic? |
#4
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Q. Take an open container of water up high enough and it will boil away. . .
my probably flawed guess:
it's not the temperature per se that causes the water to boil. It is actually the vapour energy of the water molecules vs the atmospheric pressure. At sea level, it gets converted to gas through high temperatures b/c we have higher pressure down here and thus the water molecules need more energy to escape. Remember that water molecules always have kinetic energy (which is probably what i'm referring to as vapour energy) and pressure of a container always works against this energy. just my $0.02 worth of what i remember from high school. Come to think of it, thats probably all its worth "Jim" wrote in message ... Hi. I understand if an open container of water is taken up to altitude high enough, that it will boil away. I take that to indicate when water is brought to a boil on our stove, at sea level, that the heat actually activates or motivates the water molecules to begin going crazy and rubbing against each other, and creating the vapor which must escape. But if one were to take that open, cold pot of watet to a given point above the earth's atmosphere, would the water get hot, as it would on the stove, while it boils away? Thanks, Jim |
#5
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Q. Take an open container of water up high enough and it will boil away. . .
my probably flawed guess:
it's not the temperature per se that causes the water to boil. It is actually the vapour energy of the water molecules vs the atmospheric pressure. At sea level, it gets converted to gas through high temperatures b/c we have higher pressure down here and thus the water molecules need more energy to escape. Remember that water molecules always have kinetic energy (which is probably what i'm referring to as vapour energy) and pressure of a container always works against this energy. just my $0.02 worth of what i remember from high school. Come to think of it, thats probably all its worth "Jim" wrote in message ... Hi. I understand if an open container of water is taken up to altitude high enough, that it will boil away. I take that to indicate when water is brought to a boil on our stove, at sea level, that the heat actually activates or motivates the water molecules to begin going crazy and rubbing against each other, and creating the vapor which must escape. But if one were to take that open, cold pot of watet to a given point above the earth's atmosphere, would the water get hot, as it would on the stove, while it boils away? Thanks, Jim |
#6
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Q. Take an open container of water up high enough and it will boilaway. . .
Jim wrote:
I understand if an open container of water is taken up to altitude high enough, that it will boil away. I take that to indicate when water is brought to a boil on our stove, at sea level, that the heat actually activates or motivates the water molecules to begin going crazy and rubbing against each other, and creating the vapor which must escape. More or less. The temperature indicates the average kinetic energy of the water molecules. But in order for the phase to change from liquid to vapour, additional heat is required. This is evidenced by the fact that as the pot is heated the water in it will reach 100°C quite a while before enough heat has been added to bring it to a full boil. In any open container of liquid there is an equilibrium between the rate at which molecules in the liquid phase evaporate from the surface and that at which vapour from the air condenses back into the liquid. Even at room temperature, if the air is dry enough, and especially if there's a wind to carry vapour away, a glass of water will evaporate. OTOH the water in a sealed pressure-cooker doesn't boil easily because of the high pressure inside, and can be brought to a temperature much higher than its normal boiling point while remaining in the liquid state. At any given temperature water -- and even ice -- has a characteristic "vapour pressure"; as long as the partial pressure of water vapour above the liquid is lower than the vapour pressure, more molecules will be lost to evaporation than are gained by condensation, and _vice versa_. We say a liquid is at its "boiling point" when its vapour pressure equals the atmospheric pressure. But if one were to take that open, cold pot of watet to a given point above the earth's atmosphere, would the water get hot, as it would on the stove, while it boils away? No. By taking the pot high into the atmosphere you're lowering the pressure; where this is lower than the vapour pressure appropriate to the water's temperature, boiling will take place. Since the escaping vapour carries heat away with it, the temperature of the water remaining in the pot will actually drop; the same principle underlies the cooling power of any refrigerator or air conditioner, except that water (which is extraordinarily resistant to vaporization for its molecular weight) is much less suitable for the purpose than Freon and other such substances. -- Odysseus |
#7
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Q. Take an open container of water up high enough and it will boilaway. . .
Jim wrote:
I understand if an open container of water is taken up to altitude high enough, that it will boil away. I take that to indicate when water is brought to a boil on our stove, at sea level, that the heat actually activates or motivates the water molecules to begin going crazy and rubbing against each other, and creating the vapor which must escape. More or less. The temperature indicates the average kinetic energy of the water molecules. But in order for the phase to change from liquid to vapour, additional heat is required. This is evidenced by the fact that as the pot is heated the water in it will reach 100°C quite a while before enough heat has been added to bring it to a full boil. In any open container of liquid there is an equilibrium between the rate at which molecules in the liquid phase evaporate from the surface and that at which vapour from the air condenses back into the liquid. Even at room temperature, if the air is dry enough, and especially if there's a wind to carry vapour away, a glass of water will evaporate. OTOH the water in a sealed pressure-cooker doesn't boil easily because of the high pressure inside, and can be brought to a temperature much higher than its normal boiling point while remaining in the liquid state. At any given temperature water -- and even ice -- has a characteristic "vapour pressure"; as long as the partial pressure of water vapour above the liquid is lower than the vapour pressure, more molecules will be lost to evaporation than are gained by condensation, and _vice versa_. We say a liquid is at its "boiling point" when its vapour pressure equals the atmospheric pressure. But if one were to take that open, cold pot of watet to a given point above the earth's atmosphere, would the water get hot, as it would on the stove, while it boils away? No. By taking the pot high into the atmosphere you're lowering the pressure; where this is lower than the vapour pressure appropriate to the water's temperature, boiling will take place. Since the escaping vapour carries heat away with it, the temperature of the water remaining in the pot will actually drop; the same principle underlies the cooling power of any refrigerator or air conditioner, except that water (which is extraordinarily resistant to vaporization for its molecular weight) is much less suitable for the purpose than Freon and other such substances. -- Odysseus |
#8
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"Jim" wrote in message ... Hi. I understand if an open container of water is taken up to altitude high enough, that it will boil away. I take that to indicate when water is brought to a boil on our stove, at sea level, that the heat actually activates or motivates the water molecules to begin going crazy and rubbing against each other, and creating the vapor which must escape. But if one were to take that open, cold pot of watet to a given point above the earth's atmosphere, would the water get hot, as it would on the stove, while it boils away? No: it will not get hot. What happens is that the lower the pressure is, the less heat is needed to make the water boil. At some point you will reach a pressure (or lack of it) where water will boil at room temperature. In other words, the boiling point of water is 212 degrees F at sea level. The higher you go, the lower the boiling point is. At an altitude where the boiling point is 98 degrees, your own body heat is sufficient to cause water to boil---and your own blood, too, for that matter. R |
#9
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"Logic" wrote in message...
... "Jim" wrote in message ... Hi. I understand if an open container of water is taken up to altitude high enough, that it will boil away. I take that to indicate when water is brought to a boil on our stove, at sea level, that the heat actually activates or motivates the water molecules to begin going crazy and rubbing against each other, and creating the vapor which must escape. But if one were to take that open, cold pot of watet to a given point above the earth's atmosphere, would the water get hot, as it would on the stove, while it boils away? Thanks, Jim Anyone? Am I right in saying that though the water "boils" it does not however increase in temperature? And is this srictly on-topic? 'Lo Logic 'n Jim -- Others have responded about the altitude effect on water. As far as the on-topic question is concerned, its application may become clear when one considers the effects of reduced pressure on the circulatory systems of astronauts. hth happy days and... starry starry nights! -- Sweet home, oh Precious Earth, The ONLY home we know, Tell us what you need of worth, And we can make it so. Do you want our hearts to beat And thrive within your air? Then teach us what we know we need So we can learn to care. Paine Ellsworth |
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