Latent heat

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  • #1
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Homework Statement


You are given 2.5 102 g of coffee (same specific heat as water) at 70.0°C. In order to cool this to 60.0°C, how much ice (at 0.0°C) must be added? Neglect heat content of the cup and heat exchanges with the surroundings.


Homework Equations


Q=(m ice)(c ice)(delta T ice+ m ice)(Lf)
Q=(m coffee)(c coffee)(delta T coffee)


The Attempt at a Solution


If these are the right formulas I still have the problem that there are 2 variables, since I don't know Q or m ice.
 

Answers and Replies

  • #2
mgb_phys
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The Q's in both equations are the same, energy lost by coffee = energy gained by ice.
so you simply set the two equations equal to eahc other
 
  • #3
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do you mean (m ice)(c ice)(delta T ice+ m ice)(Lf)=(m coffee)(c coffee)(delta T coffee)?
 
  • #4
mgb_phys
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Almost, remember ther is energy to melt the ice (which doesn't depend on temperature) and then the energy to heat the resulting water to the final temperature.
 

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