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Homework Help: A question about heat

  1. Nov 14, 2006 #1
    why we use water, but not alcohol as a coolant in the car engine?can you give me three reasons?
  2. jcsd
  3. Nov 14, 2006 #2
    Alcohol has a lower heat capcity than water
    It boils at a lower temperature than water
    It evaporates at a lower temperatuer than water

    Why would we use alcohol as a coolant?
  4. Nov 14, 2006 #3
    Thx A Lot~
  5. Nov 14, 2006 #4
    Np. All 3 reasons are related. Because it has a higher heat capacity, it takes more engergy to boil, which also means more engergy to evaporate. Was this a hw question, or were you just wondering?
  6. Nov 14, 2006 #5
    actually this is a hw question.
    i am just a secondary 3 student.
    can i say water is cheaper and alcohol is flamable?
  7. Nov 14, 2006 #6
    I'm not sure those would be better reasons than the ones I listed above. The fact that alcohol is flamable shouldnt be a factor because it is never exposed to a spark, only the gasoline is. If the water was ever present where the combustion took place, the engine wouldn't run. Also, inside the radior, some of the water does boil; that's why you dont open a radior cap on a hot engine. Not all of the water boils because it's under pressure. If alcohol were used, more of it would boil and you wouldn't have the same volume of cooling liquid inside the radior; more would exist in a vaporous form than with water.
  8. Nov 14, 2006 #7
    THX for your detailed explanation!!!!You are really a enthusiast!!!
  9. Nov 14, 2006 #8
    Haha. I do love cars, and the test I'm studying for right now deals with heat capacity. Good thing you asked when you did.
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