If 75 grams of steam at +140C is cooled to the point that it becomes ice at -5C, how many calories of heat will be released?
Divide your problem into the sections that we have:
1. we have steam at 140 C going to 100 C
2. when steam reaches 100 C it will also loose some heat by becoming a liquid. this would be the (DeltaH) of condensation which is a constant for water ofcourse
3. the liquid then loses energy as its temperature drops from 100 to 0
4. water at 0 will become Ice at 0 and so losing more energy this step is (deltaH) fusion
5. ice then loses more enrgy ...
We also know that energy released by system = energy taken by environment. We also know that mc(DT) (where DT is delta temperature) would actually define the heat gain or loss (we know the mass and the C and the DT). So we ca say total energy released = mc(DT)(gas from 140-100) + DHcond. + mcDT(liq 100-0) + DHfreez. + mcDT(ice 0 to -5).