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When should I add the ice?

  1. Nov 11, 2014 #1
    Hi everyone,
    I have just brewed some tea for myself and my brother,and I am confused with the timing of the addition of ice cubes.
    I had prepared 2 cups,label them A and B.
    At the beginning,A was empty and B was filled with 2 ice cubes.
    Soon the water boils,I pour a roughly equal amount of tea into both cups.Then I put 2 ice cubes in A.
    Assume that everything was the same(e.g.The material of the cups,the size of ice cubes...) except the time of addition of ice,which cup will have the lowest final temperature?(So that next time I will follow that order when I want to have some ice tea :).)

    Hope someone can give a theoretical explanation on this,Thx ;)
     
  2. jcsd
  3. Nov 11, 2014 #2
    If you put the ice cubes in before the hot water, then the enviroment will cause the ice cube to start melting before the water is added which will lead to a (slightly) higher temperature than if you add the ice afterwards. Ideally you would want to keep the ice in the freezer until you've added the hot water for the lowest temperature although I suspect the difference is actually quite small.
     
  4. Nov 11, 2014 #3
    In fact I put the ice cubes into B right after the kettle boils,I wonder would there be any temperature difference between pouring the boiling tea into A,and adding ice cubes into B after the addition of tea.

    Perhaps I should give a better example.Suppose there are two identical and very tall tanks,X and Y.
    I am going to pour a huge amount of hot water into it.
    A thin ice sheet(so that it will soon be covered by the hot tea) is placed in X(right before addition of water to minimize the amount of heat gain from surrounding ).On the other hand,Y is empty.
    Assume there is no heat gain from surrounding,
    which tank will have a lower final temp?

    If you consider tank X,during the addition process,the thin ice sheet would probably have completely dissolved after a small amount of hot water is added.
    That means the amount of ice is used to dissolve a small amount of hot water,so at this point its temperature will be smaller (compared to the final temperature of Y,where the ice sheet will dissolve in a whole container of hot water.)
    However,if you continue to add the remaining water into X,the temperature of the mixture will undoubtedly increase.

    This comes to my question------To sum it up,which tank will have a lower temperature?
     
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