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 we determine what we know

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:

Let's try another...