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It's a simple question, but this post asking why it is that tea cools faster when it is evenly divided into two different cups, made me wonder if it's a similar case for solid food. An answer to the tea question is that the tea cools mostly by evaporation, and that there is more surface area after it has been divided.

Sometimes when I'm trying to get a batch of food to cool down, I split it into several containers because I know it will cool down more quickly than if it had remained in one large pot. I figured that it has something to do with an increase in surface area, but is there also a similar evaporation effect that happens with solid food?

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  • $\begingroup$ If you're a chef, you don't want your food to undergo too much evaporation before it's served. Increasing the surface area definitely increases the susceptibility to evaporation. If you keep the food undivided, kinetic energy (heat) will be transferred to the outer surface more slowly, but with less evaporation of the juices. $\endgroup$ – Ernie Jul 26 '15 at 22:25
  • $\begingroup$ @Ernie I'm not a chef, but I am often asked to make pasta salad, which will be served cold. Does this make a difference? $\endgroup$ – matryoshka Jul 26 '15 at 22:29
  • $\begingroup$ As long as you don't let it stand in the open air too long, the outer surface of the pasta shouldn't dry out too much. But you also don't want the pasta in the center to be mushy. Probably fast cooling in a refrigerator is the best way. Experiment would be instructive. $\endgroup$ – Ernie Jul 26 '15 at 22:35
  • $\begingroup$ Too bad there isn't a non-instrusive "anti-microwave" that would produce more uniform cooling in chunky objects. Things simply have to cool from the outside in. Increased surface area helps. Stirring does, too. $\endgroup$ – Bill N Jul 26 '15 at 22:50
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Heat is lost by one or more of three methods, radiation, conduction or convection. Evaporation, to me would be convection, heating the air and it rises up and away, cooling air coming in to replace it and the temperature of the food drops.

So food heat can be lost, probably mostly by a bigger surface area, (conduction) as with the tea in two or more cups to increase the surface area and by evaporation/convection as above, or, especially if its really hot, by radiation.

You probably most likely will feel radiation loss when you open a hot oven door, less likely as a heat loss source with food, if it's that hot, it's probably burnt beyond hope:).

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