A 25-kg steel tank initially at −10°C is filled with 100 kg of milk (assumed to have the same properties as water) at 30°C. The milk and the steel come to a uniform temperature of +5°C in a storage room. How much heat transfer is needed for this process?

Step 1 of 3</p>

We need to find out how much heat transfer is needed for the milk and the steel to reach a uniform temperature of .

Step 2 of 3</p>

From the first law of thermodynamics,

In this case the volume is constant so there is no work.

Implies,