# Temperature Question (answ=neg#-?)

1. Jan 8, 2008

### grantP

[SOLVED] Temperature Question (answ=neg#-???)

1. The problem statement, all variables and given/known data
A .03kg piece of iron is heated to 100 degrees celsius and then dropped into cool water where the iron's temperature drops to 30 degrees celsuis. How many joules does it lose to the water?(Specific Heat Capacity of Iron=450J)

2. Relevant equations
change-in-energy=(SHC)(m)(Tf-Ti)

3. The attempt at a solution

change-in-energy=(450)(.03)(30-100)
=-945J
does it matter that my answer is a negative number?

2. Jan 8, 2008

### blochwave

You found the change in energy, which is the final energy-the initial energy

the fact that it's negative implies what? Does that seem correct?

3. Jan 8, 2008

### Staff: Mentor

Reread the phrasing of the question. (If the change in the amount of money in your wallet after playing poker is -\$5, how much did you lose?)

4. Jan 8, 2008

### grantP

ok so i think my answer should just simply be 945J instead of -945J because the negative implies that is what i lost, and evidently is exactly what was asked in the question!
is this thinking right?

5. Jan 8, 2008

Correct