# Homework Help: Thermo Mixing Question

1. May 8, 2005

### cogs24

hi guys, i have a thermodynamics question.

a 2.50 kg iron object is initially at 650 degrees celsius and dropped into a bucket containing 20kg of water at 25 degrees celsius, what is the final temperature?

As always it just a matter of applying the formula, but i dont seem to be applying the right one?
Thanx

2. May 8, 2005

### Staff: Mentor

Consider that the net exchange of thermal energy must be zero. Whatever heat flows out of the iron ($Q = m c \Delta T$) must be equal to the heat flowing into the water. And, once they reach equilibrium, both iron and water end up at the same final temperature.

3. May 8, 2005

### cogs24

is delta t, t final - t initial or vice versa?

4. May 8, 2005

### Staff: Mentor

I suggest using $\Delta T = T_f - T_i$. In which case, $Q_{water} = - Q_{iron}$. (The iron cools down, so its $\Delta T$ is negative.)

5. May 9, 2005

### cogs24

ok, the specific heat capacity of iron is 440J per degree celsius, right?
if so i have all the values i need, i just need to transpose the formula to find the final temperature