I did some keyword searching to try to find some kind of estimate of the rate of evaporation of ice in a freezer. It's actually a popular experiment - Freeze a weighed amount of water in your freezer in a bowl and leave it in the freezer for a week, then weigh it again, to find that it now weighs less. But there are a number of variables - vapor pressure of water in the freezer (humidity), the temperature, the amount of surface area exposed to the air, the air movement over the surface, how often the freezer door is opened, how often the defroster runs, etc. Well, if you have a few days you could do this experiment and get an actual estimate of how long it will take the ice to evaporate! An example problem here gives a rate of loss of six grams per week which sounds reasonable, so you might want to use that. This way, it's not necessary to try to answer the question just from the heat absorbed perspective, defrost cycle, and so forth. If we assume all of the heat is transferred to the ice, it won't last very long! But, that would not be the case anyway. But your teacher may like all the calculations - moles of ice, heat of fusion, heat of vaporization, and all that good stuff! It's certainly a good "thinking" problem! Steve |
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