EasyPhysicsHigh School (11–12)Heat & Thermodynamics › Calorimetry and Change of StateNumericalBoard ExamAPA-LevelIB
2.0 kg of water at 65 °C is mixed with 1.5 kg at 25 °C…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
- of water at is mixed with at . Find the final temperature.
- How much water at must be added to at to bring it to ?
Need a reminder? The key ideaShow
Method of mixtures: heat lost by the hot bodies heat gained by the cold ones, if none escapes. A calorimeter's water equivalent is .
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Step 1. (a) .
Step 2. (b) , so .
Answer: (a) . (b) .
Check. In (b), is halfway between and , so equal masses make sense.
Watch out. The specific heat cancels only because both are water.
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