Why does ice have a lower specific heat capacity ?


by elemis
Tags: capacity, heat, specific
elemis
elemis is offline
#1
May3-12, 03:15 AM
P: 157
Throughout my time doing physics I have noticed that ice has a lower specific heat capacity than water.

I dont understand why.

To me it seems that the bonds between water molecules in a solid are stronger and hence require a greater deal of thermal energy to break. Hence, the PE of the system increases.

So what is the explanation ?
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castro94
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#2
May3-12, 04:23 AM
P: 23
http://www.physicsforums.com/showthread.php?t=131151
read this thread
the conclusion is that the enregy given to liquid water is used to other things that just "rising" the temperature.
elemis
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#3
May3-12, 08:23 AM
P: 157
From my knowledge of Chemistry there are hydrogen bonds in both ice and water. Hence, the thermal energy must be going into breaking these strings H-bonds in both the liquid and solid state.

Therefore both should be very large.

castro94
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#4
May4-12, 08:13 AM
P: 23

Why does ice have a lower specific heat capacity ?


the process where the intermolecular force are being broken , and loosen up is measused in something other than specific heat capacity , it is called latent heat. during these process, melting/evaporating, the energy given is not used to increase temperature but to break or loosen the bonds.
Water molecule has two h-bonds, when it is cold it forms an structure that alouds both of the H-bonds to be "used" this structure makes it less dense , the molecule are fast holden but relativ far from each other . when liquid it has another molecular strucutre here only one of the H-bonds is being "used" , this alouds it to move more freely.
The temperature is the measument of the kinectic energy the molecules have . the differense is that in ice the molecules are so fast holden by the intermolecular forces that the energy given can only be transformed to vibrating kinectic energy . When liquid the molecules are more fre so they can move in different ways , more than just vibrating , so the energy given is "distrubed" into diferen types of kinectic energy , as rotational kinectic energy , translational kinectic energy and vibrational kinectic energy. so it will give a lower increase in the general temperature of the liquid.

this can be summarized by saying that the energy given to water in liquid form is distrubed between different forms of kinectic energy, while that given to ice is only transformed to ONE form of kinectic energy therefore more energy is needed to rise the general temperature of water. or at least thats what i have understood from my chemistry studies


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