Thermos Coffee Cooling: What is the Final Temperature?

[Saladsamurai]

Homework Statement

A thermos contains 150 cm³ of coffee at 85 ^oC. To cool the coffee, you drop two 11g ice cubes into the thermos. The ice cubesare initially at 0 ^oC
and melt completely. What is the final temperature of the coffee? (Treat the coffee as if it were water)

Homework Equations

Q_f = mL_fusion
Q = mcΔT

The Attempt at a Solution

I am trying to help someone with this problem. They have yet to learn about internal energy, so I am a little lost (forgetful) as to how to approach this problem
and explain it so that it makes sense.



How would you approach this problem?

Thanks,
Casey

 

[Saladsamurai]

I know that the final temps of coffee and ice will be the same since they reach equilibrium. I also know that there should (probably) be 3 terms: Q of the coffee, Q of the ice melting, and Q of the melt-water changing temp.

But I cannot figure out out to set up a balanced equation...

 

[Saladsamurai]

I got it...Total heat transfer with environment = 0...piece of cake...