39. KE = 1/2*m*v^2.
As the more energetic molecules of water (from the sweat) leave due to evaporation, the average energy of the remaining molecules is decreased and lower energy means lower T. Another way of saying the same thing is that energy to help the molecules escape (evaporate) must come from someplace and that place is from the sweat itself. That lowers the temperature of the remaining water.
40. Specific heat of something is how much energy it takes to heat it up or the energy lost in cooling it. In general terms, low specific heat materials heat up fast and cool down fast. An example is a piece of metal--just a little heat added is enough to get it hot enough to burn your finger. Conversely, just a little time is all it needs to cool down so the metal can be picked up safely. For high specific heat materials (water is an example), just a little added heat hardly raises the temperature at all so a lot of heat is required to heat a pot of water BUT a lot of time must go by before it is cool enough to drink. Think of coffee.
All of that is a preamble. The crust has a low specific heat; cheese has a high specific heat.
39. Explain why sweating cools you down in terms of molecular kinetic energy.
40. You take a pizza out of the oven and let it cool briefly. When you bite into it, the crust is not too hot but the cheese burns your mouth. Explain why this happens in terms of specific heat capacity.
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