Simple heat problems:
Simple heat problems are those where one thing undergoes a single change (a change in temperature or a change in phase). To solve such a problem we simply decide what formula to use (q=mcΔT for temperature changes and q=mΔH for phase changes), determine what we know and what we don’t and then solve for the missing piece.
Here are some fully worked out examples:
- How much heat is needed to warm 150.0 g of water from 24 oC to 47 oC?
We can see that this problem involves a change in temperature so the correct formula is
Now what do we know?
|m||150.0 g water|
|c||1.000 cal/g oC (known)|
|ΔT||47-24 = 23oC|
As the table shows, the only thing we don’t know is heat, and (not surprisingly) that’s what the question asks us to find.
We can therefore just substitute into the formula and solve:
Math imageThermo problem 1