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Can ice conduct heat?

by sgstudent
Tags: conduct, heat
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sgstudent
#1
Jan16-13, 07:09 AM
P: 645
1. The problem statement, all variables and given/known data
When ice at 0 degrees is placed into an environment that is colder than it, the ice will transfer heat to it's environment. However, if one layer of ice (meaning 2 molecules of H2O thin) is heated with just enough heat energy to melt it, will heat still be conducted?

2. Relevant equations

none

3. The attempt at a solution
I'm quite confused because when the heat is absorbed the water molecules vibrate more so they become further apart. However, as they vibrate more won't the neighboring water molecules also get pushed around and vibrate as a result. So by the conservation of energy the exact amount to free 2 molecules by allow that one molecule to vibrate so intensely isn't enough due to some energy loss to the second layer?
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256bits
#2
Jan16-13, 10:06 AM
P: 1,478
I am not exactly sure what your explanation means, but the question isn't asking about 1 or 2 molecules but about a layer of ice 2 molecules thick. Think about the temperature of the ice and the temperature of the the layer just after it has melted.
hms.tech
#3
Jan16-13, 10:47 AM
P: 247
Of course it can !

However I think a better way to phrase this question should have been :
"how good is ice as a conductor of heat

Conduction is given by this mathematical expression given in the attachment .
Let me define the terms :
L is the length
A is the cross sectional area
ΔT is the temperature difference
k is the most important part to answer your question (the thermal conductivity and it is an intrinsic property of the material)

Now, for ice according to Wikipedia
k=2.2

Just to give u an idea of what the variation of the values of "k" :

One of the best conductors of heat is Silver metal and it has a thermal conductivity of
k=430
Attached Thumbnails
Equation of Conduction.PNG  

sgstudent
#4
Jan16-13, 11:17 AM
P: 645
Can ice conduct heat?

Quote Quote by 256bits View Post
I am not exactly sure what your explanation means, but the question isn't asking about 1 or 2 molecules but about a layer of ice 2 molecules thick. Think about the temperature of the ice and the temperature of the the layer just after it has melted.
Oh I'm going in in to the first layer of ice like as in: http://postimage.org/image/o9fj8i40j/full/

So for example when i apply just enough heat to melt them so they start vibrating more and more. But as they do so won't they collide with the second layer of molecules? So if i just apply just enough heat to break the bonds of the first layer, it won't be enough as some energy will be lost to the second layer?
256bits
#5
Jan16-13, 12:00 PM
P: 1,478
You did not answer the question about what temperature is the layer of water when melted. By the way, this is not a question about vibrating molecules.
sgstudent
#6
Jan16-13, 08:52 PM
P: 645
Quote Quote by 256bits View Post
You did not answer the question about what temperature is the layer of water when melted. By the way, this is not a question about vibrating molecules.
Oh but actiually my question from the start is this: I'm saying when just enough heat (Q=ml) is provided to break this first layer http://postimage.org/image/o9fj8i40j/full/ will those molecules will vibrate (as they go further apart from each other). So in that process they might collide with the second layer of water molecules. Applying the conservation of energy here, won't there be not enough energy to melt
sgstudent
#7
Jan16-13, 09:02 PM
P: 645
Quote Quote by hms.tech View Post
Of course it can !

However I think a better way to phrase this question should have been :
"how good is ice as a conductor of heat

Conduction is given by this mathematical expression given in the attachment .
Let me define the terms :
L is the length
A is the cross sectional area
ΔT is the temperature difference
k is the most important part to answer your question (the thermal conductivity and it is an intrinsic property of the material)

Now, for ice according to Wikipedia
k=2.2

Just to give u an idea of what the variation of the values of "k" :

One of the best conductors of heat is Silver metal and it has a thermal conductivity of
k=430
But when heat is supplied to ice, won't those first few molecules melt? Or will they happen together. I learned that the molecules go further apart during the melting process so they will vibrate more as well. Hence, will both processes go together?
256bits
#8
Jan16-13, 09:44 PM
P: 1,478
If I understand you correctly you are saying that there was only enough energy to melt the first layer, so no more layers will melt by conservation of energy.
Ok. You get half marks for that part of your answer, since you have used an aspect of one of the laws of thermodynamics..

Is there another law also applicable here, such as what does the zeroeth law tell you.

Your statement about the atoms getting farther apart as the ice turns into water is incorrect. The density of ice is less than water, which is the reason ice will float on water. In fact water is most dense at around 4C. Less dense means that the ice molecules are on a whole farther apart than that of the more dense water molecules. Your explanation using the vibrating molecule does not follow the actual physics.

Have you heard of the laws of thermodynamics. What does the zeroeth law tell you that might apply here ( remeber I asked you about the temperature of the water layer )
sgstudent
#9
Jan16-13, 10:12 PM
P: 645
Quote Quote by 256bits View Post
If I understand you correctly you are saying that there was only enough energy to melt the first layer, so no more layers will melt by conservation of energy.
Ok. You get half marks for that part of your answer, since you have used an aspect of one of the laws of thermodynamics..

Is there another law also applicable here, such as what does the zeroeth law tell you.

Your statement about the atoms getting farther apart as the ice turns into water is incorrect. The density of ice is less than water, which is the reason ice will float on water. In fact water is most dense at around 4C. Less dense means that the ice molecules are on a whole farther apart than that of the more dense water molecules. Your explanation using the vibrating molecule does not follow the actual physics.

Have you heard of the laws of thermodynamics. What does the zeroeth law tell you that might apply here ( remeber I asked you about the temperature of the water layer )
Hi, I just read it up and it is: a generalization principle of thermal equilibrium among bodies, or thermodynamic systems, in contact. The temperature of the water is also at 0 degrees i think?

So ice contracts when heated. So in that case how will conduction be possible?
256bits
#10
Jan17-13, 04:10 AM
P: 1,478
Ice does not contract when it experiences a rise in temperature.

The phase change from ice ( a solid ) to water ( a liquid ) is when the change in density occurs, and this is a particular feature of water. Most other compounds, if not all, have a decrease in density with phase change.

Water, as a solid (ice) forms a lattice structure where the molecules line up in a set way to form a crystal. As such, the way the H2O behaves, ice will take up more space since the molecules can only set up a certain way. You may be interested in why snowflakes have the appearance they do.
As the ice melts, the crystal structure is destroyed and the molecules of H20 can now freely move around and rotate, and doing so can fill in the empty space that was there in the ice cystal.

So water as a liquid has molecules that are mobile, or in your usage of terms, vibrate more. You should note that the molecules in ice are also vibrating but without sufficient added energy to break the bonds between molecules, ice will remain as ice. Given enough added energy, a molecule can break the bonds that holds it to its neighboring H20 molecules, and that molecule can now be considered a liquid water molecule.
sgstudent
#11
Jan17-13, 04:48 AM
P: 645
Quote Quote by 256bits View Post
Ice does not contract when it experiences a rise in temperature.

The phase change from ice ( a solid ) to water ( a liquid ) is when the change in density occurs, and this is a particular feature of water. Most other compounds, if not all, have a decrease in density with phase change.

Water, as a solid (ice) forms a lattice structure where the molecules line up in a set way to form a crystal. As such, the way the H2O behaves, ice will take up more space since the molecules can only set up a certain way. You may be interested in why snowflakes have the appearance they do.
As the ice melts, the crystal structure is destroyed and the molecules of H20 can now freely move around and rotate, and doing so can fill in the empty space that was there in the ice cystal.

So water as a liquid has molecules that are mobile, or in your usage of terms, vibrate more. You should note that the molecules in ice are also vibrating but without sufficient added energy to break the bonds between molecules, ice will remain as ice. Given enough added energy, a molecule can break the bonds that holds it to its neighboring H20 molecules, and that molecule can now be considered a liquid water molecule.
Actually during the melting of the other liquids, will the particles start to vibrate more? Or do they just move apart at a constant velocity. Because during a state change temperature which is the average KE of the liquid remains constant. So if they increase in velocity then the average KE is increased which is wrong.

Since water is a unique let's ignore this for a while. Eg Liquid A (not water) has a freezing point at 0 degrees so it contracts during the freezing process. So when it is at a solid state and heat is supplied to it, what happens? Because now the particles that is directly exposed to the heat should have a larger distance between each other (melting breaks the bond). However, while that bond is being broken the distance between the two particles increases. From this expansion won't the particles collide with the the set of particles causing them to heat up as well?

Thanks for the help 256bits
256bits
#12
Jan18-13, 03:39 AM
P: 1,478
My pleasure,

Some molecules will have greater KE than average and some less. As they jiggle about, they exchange energy with one another all the time at the atomic level.
For the liquid A , as it melts, what you say is correct. The "melted" particles do collide with the "solid" particles, and energy could be exchanged. So some of the solid particles could turn into liquid, while at the same time some liquid particles into solid. If only so much energy is supplied to the material ( or you can say if the material has only so much energy ), the material will remain in a certain equiibrium state forever. The equilibrium state cannot change unless energy is exchanged with the surroundings.

Consider a slushy drink of water and very fine ice. Remove enough heat and the slush will all turn to ice. Add enough heat and the drink turns into water. Put the drink in a controlled environment at the same temperature as the drink so that no net energy is exchanged between drink and enviroment, and the drink will last forever as a slush. ( bear in mind that this assumes pressure, for instance is constant ). At the atomic level all the molecules are josling each other around and doing some liquid molecules form a bond with some solid molecules and some solid molecules become part of the liquid.
sgstudent
#13
Jan28-13, 09:23 AM
P: 645
Quote Quote by 256bits View Post
My pleasure,

Some molecules will have greater KE than average and some less. As they jiggle about, they exchange energy with one another all the time at the atomic level.
For the liquid A , as it melts, what you say is correct. The "melted" particles do collide with the "solid" particles, and energy could be exchanged. So some of the solid particles could turn into liquid, while at the same time some liquid particles into solid. If only so much energy is supplied to the material ( or you can say if the material has only so much energy ), the material will remain in a certain equiibrium state forever. The equilibrium state cannot change unless energy is exchanged with the surroundings.

Consider a slushy drink of water and very fine ice. Remove enough heat and the slush will all turn to ice. Add enough heat and the drink turns into water. Put the drink in a controlled environment at the same temperature as the drink so that no net energy is exchanged between drink and enviroment, and the drink will last forever as a slush. ( bear in mind that this assumes pressure, for instance is constant ). At the atomic level all the molecules are josling each other around and doing some liquid molecules form a bond with some solid molecules and some solid molecules become part of the liquid.
Oh then how will it conduct the heat? Since when I apply some heat to it, some particles would move apart from each other (not enough to break the bonds) and transfer some heat to the neighboring particle. So wouldn't it be not enough to break any bonds? Because when that happens the neighbouring particles will move apart as well so the heat cannot be enough to melt the one layer due to the inefficiency?

Or does this occur: the few particles move away from the neighbouring particle such that it becomes a liquid. And sometimes it randomly collided with the ice and transfers its energy to the solid. So how will the energy be transferred or is this too micro to be studied?

Thanks for the help :)


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