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Post by sigurdur on Aug 24, 2013 2:43:11 GMT
Let's discuss this in more detail.
Numerouno has me questioning a phase change with water vapor to liquid that I thought I understood. Maybe I don't, and would most certainly like to.
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Post by sigurdur on Aug 24, 2013 2:47:19 GMT
numerouno said:
"And as I said, the cooling is caused by the expanding water vapour carrying heat away. Were there no carrying away, there would only be a zero-sum phase change at where the water originates."
Ok, but the phase change from water vapor to water is a contraction, not an expansion which happens when water turns to vapor.
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Post by sigurdur on Aug 24, 2013 2:48:31 GMT
I am not trying to be difficult, but I must be missing something here.
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Post by icefisher on Aug 24, 2013 3:44:59 GMT
I am not trying to be difficult, but I must be missing something here. the heat is latent inside the H20. Its identical to potential energy. the conservation of energy law means though it has disappeared as heat and not been radiated or conducted away, its still there. The energy exits the H20 when it freezes, condenses or deposes without the H20 cooling. It enters the H20 when it melts, evaporates, or sublimates without the H20 warming. the environment typically warms or cools to receive or provide the energy for the H20 to do its state change. Conductivity of water is pretty high and the free convection of immersion is 20 times that of free convection air. My guess would be this event goes off in a massive way. When darkness hits the water an inversion layer forms at the surface and you get a lot of ice being created at one time. I would guess that if the spikes are fully attributable to this process that as the winter sets in and darkness covers a larger portion of the arctic 24/7 freeze events are kicked off by clearing of the skies. Another factor to consider that despite the fact that the heat of fusion is 7.5 times smaller than the heat of condensation, its also the case that this event is occurring in a very dry atmosphere. It also does not involve water vapor so the rate of atmosphere loss of this heat is very low. So it can accumulate more total heat. The arctic typically does not have convection, or at least not the upward motion of air. It has downwelling air from the large convection loops. Subsidence can create heavy marine overcasts. Over inversion layers near the surface. Thus you have a natural heat cap for an accumulation of near surface heat. Can it create a 10C warming spike? As shown in the DMI data? It would be nice to see some calculations on that I have to agree. I do know significant inversion layers can occur in temperate regions and cause frost to develop on your windshield when the ambient temperature is in the 40's F. I agree its an interesting process and I also would like to hear more about its details. I tend to believe NSIDC because the spikes only occur during times when freezing is occurring and are the largest and most frequent in the middle of winter.
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Post by sigurdur on Aug 24, 2013 3:49:14 GMT
Well put Icefisher. I thought I was getting old and feeble there for a minute.
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Post by Andrew on Aug 24, 2013 4:58:46 GMT
numerouno said: "And as I said, the cooling is caused by the expanding water vapour carrying heat away. Were there no carrying away, there would only be a zero-sum phase change at where the water originates." Ok, but the phase change from water vapor to water is a contraction, not an expansion which happens when water turns to vapor. We have to be clear that when water boils a huge amount of energy is added to the water via flame or hot metal to cause the phase change but we do not see a temperature change during the phase change, but we do produce vast amounts of hot steam spreading everywhere in proportion to the heat supplied to the water Then when water is cooled a huge amount of energy has to pass from the water to the cold atmosphere. Ie you are witnessing what happens when you have a force that can cause cooling. Without the cooling force the ice cannot form. So to boil water you need massive heating lets say and massive amounts of hot steam becomes present everywhere. No cooling becomes visible anywhere To freeze water you need massive cooling, you get massive amounts of cold ice everywhere and no massive heating becomes visible The latent heat of evaporation of water just means you have to supply more heat when you boil water and produce lots of hot steam The latent heat of fusion of water just means that when you cool water you need to supply more cooling to produce lots of ice than if the latent heat had a lower value.
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Post by nautonnier on Aug 24, 2013 11:17:26 GMT
Here are a couple of links. For Iceskater - you will note the age level of this explanation for Latent Heat. This module is for just after primary (elementary) school. It doesn't explain _why_ the latent heat is released or absorbed on state change but it does explain the changes in heat and temperature. So the next question is why don't fish die when the pond has ice on it? It is because ice floats. Ice floats because it is less dense than the water that froze. The reason being that the molecules form an ordered crystal lattice that keeps them further apart making ice molecules less densely packed. Less molecules in a given volume means that ice is lighter. When I was in school the next part was at ~14 - 15 years old. This crystal lattice is based on weak hydrogen bonds with the oxygen atoms in the H-O-H molecules. These hydrogen bonds appear in many molecules but water is easy to visualize. See this wikipedia explanation of hydrogen bonds in water. If you have a large 3 dimensional lattice with weak bonds as the energy is supplied it increases the vibrational energy of the molecules but not the kinetic energy (temperature) of the volume containing molecules. Eventually the vibrations are such that some of the lattice bonds break. This is the change of state when there are insufficient lattices absorbing energy to keep the overall kinetic energy of the molecules low the average kinetic energy of the molecules -the temperature- starts increasing. The molecules that are not in a lattice (liquid) are now closer together and therefore the liquid is denser than the ice state. The molecules of water are continually trying to coalesce into a lattice due to the hydrogen bonds - but at temperatures (kinetic energy levels) above freezing these bonds are breaking as fast or faster than they form. As water cools the reverse takes place and the conservation of energy laws mean that the kinetic energy is radiated as heat energy as the water molecule lattice forms. For Iceskater: This really is very basic physics. You seem to have the idea that you need a PhD to understand simple mechanisms in nature. This really is not the case.
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Post by numerouno on Aug 24, 2013 11:25:27 GMT
Water is an exceptional substance in that it expands while freezing. This property makes it float on water.
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Post by numerouno on Aug 24, 2013 11:29:36 GMT
numerouno said: "And as I said, the cooling is caused by the expanding water vapour carrying heat away. Were there no carrying away, there would only be a zero-sum phase change at where the water originates." Ok, but the phase change from water vapor to water is a contraction, not an expansion which happens when water turns to vapor. In evaporation, the heat content of the water that was stationary on the surfaces will be expanded, scattered around and removed. This will be the cooling you experience. Expanding gases requires energy that will come from the gas itself. The efficiency of this removal will be determined by the local conditions -- you will not feel equally cool after all rainfall in your fields.
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Post by Andrew on Aug 24, 2013 13:20:17 GMT
Here are a couple of links. For Iceskater - you will note the age level of this explanation for Latent Heat. This module is for just after primary (elementary) school. It doesn't explain _why_ the latent heat is released or absorbed on state change but it does explain the changes in heat and temperature. So the next question is why don't fish die when the pond has ice on it? It is because ice floats. Ice floats because it is less dense than the water that froze. The reason being that the molecules form an ordered crystal lattice that keeps them further apart making ice molecules less densely packed. Less molecules in a given volume means that ice is lighter. When I was in school the next part was at ~14 - 15 years old. This crystal lattice is based on weak hydrogen bonds with the oxygen atoms in the H-O-H molecules. These hydrogen bonds appear in many molecules but water is easy to visualize. See this wikipedia explanation of hydrogen bonds in water. If you have a large 3 dimensional lattice with weak bonds as the energy is supplied it increases the vibrational energy of the molecules but not the kinetic energy (temperature) of the volume containing molecules. Eventually the vibrations are such that some of the lattice bonds break. This is the change of state when there are insufficient lattices absorbing energy to keep the overall kinetic energy of the molecules low the average kinetic energy of the molecules -the temperature- starts increasing. The molecules that are not in a lattice (liquid) are now closer together and therefore the liquid is denser than the ice state. The molecules of water are continually trying to coalesce into a lattice due to the hydrogen bonds - but at temperatures (kinetic energy levels) above freezing these bonds are breaking as fast or faster than they form. As water cools the reverse takes place and the conservation of energy laws mean that the kinetic energy is radiated as heat energy as the water molecule lattice forms. For Iceskater: This really is very basic physics. You seem to have the idea that you need a PhD to understand simple mechanisms in nature. This really is not the case. Nautonnier you are muddled up. A child can understand the topic, no PhD is required Lets have a look at what you wrote for 14-15 year olds. If you have a large 3 dimensional lattice with weak bonds as the energy is supplied it increases the vibrational energy of the molecules but not the kinetic energy (temperature) of the volume containing molecules.the kinetic energy of the vibrational movement is essentially the temperature so you are mixed up there. There is not a special kind of kinetic energy in the way you are suggesting that separately creates temperature.Eventually the vibrations are such that some of the lattice bonds break. no problem with that.This is the change of state when there are insufficient lattices absorbing energy Again this is the bit you are muddled up on, the increases in the vibrations is the absorbed heat so that eventually the hydrogen bonding that was present before is no longer possible and the more chaotic next phase is enabled where the freer molecules can only exist while they have not lost the energy of movement that we call heat, and therefore it requires what we call heat to break them free from the previously more highly ordered structure. to keep the overall kinetic energy of the molecules low the average kinetic energy of the molecules -the temperature- starts increasing. This is totally muddled up The molecules that are not in a lattice (liquid) are now closer together and therefore the liquid is denser than the ice state. Water is loosely hydrogen bonded compared to ice which is more highly orderedThe molecules of water are continually trying to coalesce into a lattice due to the hydrogen bonds - but at temperatures (kinetic energy levels) above freezing these bonds are breaking as fast or faster than they form. yes As water cools the reverse takes place and the conservation of energy laws mean that the kinetic energy is radiated as heat energy as the water molecule lattice forms. The kinetic energy of waters vibrations is the heat. To get ice to form, that kinetic energy has to be removed by the presence of something colder that the water can radiate to or be in contact with.
There is no spare heat that gets beamed out of the water to warm the atmosphere other than the heat that 0C water has that can warm -10C air. You obviously have knowledge but even so you are muddled up.
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Post by sigurdur on Aug 24, 2013 13:44:01 GMT
Thought about this last night/this morning.
Latent heat is a measure of energy.
It is somewhat like potential energy.
A rock balanced on the top of a hill has stored energy because of its mass. We know it is there because of the position of the rock and we know what work it can do because of physics. While stationary, it is all potential, measurable, etc.
IF the rock never moves, the energy sits there.
Latent heat is a measurement of potential energy. The phase change releases that energy OR absorbs energy, depending on the state of the mass.
make any sense?
I do know that when sprinkling water on orchards etc, the insulation value of the ice is used to help, but the heat released when forming that ice is the primary source of warmth to keep the orchard from freezing for short periods of time.
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Post by sigurdur on Aug 24, 2013 13:46:22 GMT
Also, tiz why we don't worry too much if it freezes and we are getting a heavy dew. Same principle applies.
But on a dry night....offfffffta. Plants die.
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Post by Andrew on Aug 24, 2013 17:30:58 GMT
Latent heat is a measurement of potential energy. Latent heat of Fusion is kinetic energy. It is the active vibrational movement of water that has to be removed to enable a more rigid less vibrationally active structure to form. The energy is removed by cooling. It cannot heat anything other than whatever is causing the cooling.
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Post by nautonnier on Aug 24, 2013 19:50:03 GMT
Here are a couple of links. For Iceskater - you will note the age level of this explanation for Latent Heat. This module is for just after primary (elementary) school. It doesn't explain _why_ the latent heat is released or absorbed on state change but it does explain the changes in heat and temperature. So the next question is why don't fish die when the pond has ice on it? It is because ice floats. Ice floats because it is less dense than the water that froze. The reason being that the molecules form an ordered crystal lattice that keeps them further apart making ice molecules less densely packed. Less molecules in a given volume means that ice is lighter. When I was in school the next part was at ~14 - 15 years old. This crystal lattice is based on weak hydrogen bonds with the oxygen atoms in the H-O-H molecules. These hydrogen bonds appear in many molecules but water is easy to visualize. See this wikipedia explanation of hydrogen bonds in water. If you have a large 3 dimensional lattice with weak bonds as the energy is supplied it increases the vibrational energy of the molecules but not the kinetic energy (temperature) of the volume containing molecules. Eventually the vibrations are such that some of the lattice bonds break. This is the change of state when there are insufficient lattices absorbing energy to keep the overall kinetic energy of the molecules low the average kinetic energy of the molecules -the temperature- starts increasing. The molecules that are not in a lattice (liquid) are now closer together and therefore the liquid is denser than the ice state. The molecules of water are continually trying to coalesce into a lattice due to the hydrogen bonds - but at temperatures (kinetic energy levels) above freezing these bonds are breaking as fast or faster than they form. As water cools the reverse takes place and the conservation of energy laws mean that the kinetic energy is radiated as heat energy as the water molecule lattice forms. For Iceskater: This really is very basic physics. You seem to have the idea that you need a PhD to understand simple mechanisms in nature. This really is not the case. Nautonnier you are muddled up. A child can understand the topic, no PhD is required Lets have a look at what you wrote for 14-15 year olds. If you have a large 3 dimensional lattice with weak bonds as the energy is supplied it increases the vibrational energy of the molecules but not the kinetic energy (temperature) of the volume containing molecules.the kinetic energy of the vibrational movement is essentially the temperature so you are mixed up there. There is not a special kind of kinetic energy in the way you are suggesting that separately creates temperature.Eventually the vibrations are such that some of the lattice bonds break. no problem with that.This is the change of state when there are insufficient lattices absorbing energy Again this is the bit you are muddled up on, the increases in the vibrations is the absorbed heat so that eventually the hydrogen bonding that was present before is no longer possible and the more chaotic next phase is enabled where the freer molecules can only exist while they have not lost the energy of movement that we call heat, and therefore it requires what we call heat to break them free from the previously more highly ordered structure. to keep the overall kinetic energy of the molecules low the average kinetic energy of the molecules -the temperature- starts increasing. This is totally muddled up The molecules that are not in a lattice (liquid) are now closer together and therefore the liquid is denser than the ice state. Water is loosely hydrogen bonded compared to ice which is more highly orderedThe molecules of water are continually trying to coalesce into a lattice due to the hydrogen bonds - but at temperatures (kinetic energy levels) above freezing these bonds are breaking as fast or faster than they form. yes As water cools the reverse takes place and the conservation of energy laws mean that the kinetic energy is radiated as heat energy as the water molecule lattice forms. The kinetic energy of waters vibrations is the heat. To get ice to form, that kinetic energy has to be removed by the presence of something colder that the water can radiate to or be in contact with.
There is no spare heat that gets beamed out of the water to warm the atmosphere other than the heat that 0C water has that can warm -10C air. You obviously have knowledge but even so you are muddled up.Iceskater - you seem to delight in trying to split hairs in non-formal descriptions. Fine. That is not the point of this forum. Your initial claim was that "no energy was released" on state change condensing or freezing. The references I provided show that you are WRONG. I suggest that you go to some of the simple sites set up for elementary and middle school children and read them. You will then find that the state change DOES indeed liberate energy. Obfuscating your mistake by 'clever comments' does not win any points.
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Post by nautonnier on Aug 24, 2013 19:52:16 GMT
Latent heat is a measurement of potential energy. Latent heat of Fusion is kinetic energy. It is the active vibrational movement of water that has to be removed to enable a more rigid less vibrationally active structure to form. The energy is removed by cooling. It cannot heat anything other than whatever is causing the cooling. There is a difference between vibrational energy while still held in a crystal lattice and the kinetic energy of a free molecule with its own separate velocity vector. Until you understand that point you will not understand latent heat.
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