Talk:Ice pack

Enthalpy of Vaporisation, not specific heat capacity.

I've changed most of the article (every bit I could find) to clarify the fact that it's the melting of the ice that absorbs energy, not the temperature change. If you doubt this, go ahead and calculate the temperature change that water would require to absorb as much heat as an identical quantity of water melting. I get a temperature change of 80°C, far in excess of the range for a normal ice pack. From this it should immediately be clear that for a small change in temperature, the ice-water transition can absorb a gigantic amount of energy, and then go on to absorb that little bit more from actually changing temperature.

I'm not really certain of whether additives are used to improve the enthalpy of fusion of the water (or if there are completely different substances that are better). The best alternative to water that I can come up with is pure ammonia (or liquefied hydrogen perhaps), but it has an awkwardly low melting point so I don't think it's used in medical packs (or anything that goes in a household freezer). As such I reduced the additives mentioned to just anti-bacterial action inside the pack and the gelling agents, since I can't seem to find a better example of heat absorption. If there is a better chemical for absorbing heat around that temperature by anything reversible (perhaps a dehydration reaction of some kind) and it's in use, it'd help to mention it.

The explanation having to involve moles is awkward, especially since the Enthalpy of Fusion page states that the SI units are kJ/mol, but then lists a bunch of kJ/kg measurements. I'm not aware of a special name for enthalpy of fusion per kilogram not mole, but if it exists it would massively simplify that explanation. I think it reads awkwardly, but I can't think of a way to reword it without losing continuity or flow. 118.208.103.227 (talk) 08:48, 4 February 2011 (UTC)

The term you are looking for is Specific Enthalpy. Specific is a commonly used term in thermodynamics to describe quantities (volumes, enthalpies, heat capacities etc etc) per kilogram. There is a page on Wikipedia for Enthalpy - all is described therein. Enthalpy — Preceding unsigned comment added by 81.171.244.180 (talk) 10:08, 30 June 2011 (UTC)

You wrote Enthalpy of Vaporization in your title. I think you meant Enthalpy of Fusion. Vmelkon (talk) 05:21, 10 January 2015 (UTC)

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