How Much Energy Does Ice Release When Cooled in a Freezer?

[roxxyroxx]

Homework Statement

A 3.0kg block of ice made in a fridge has an initial temp. of -5.0$$\circ$$C. It
is then moved to a much colder freezer. how much thermal energy is released by the ice as it cools to -40.0$$\circ$$C?

Homework Equations

E_H = mc$$\Delta$$T
for water, c = 4186 J/kg/$$\circ$$C

The Attempt at a Solution

E_H = mc$$\Delta$$T
E_H = (3.0kg)(4186 J/kg/$$\circ$$C)(-40.0$$\circ$$C - -5.0$$\circ$$C)
= -439530 J
but the answer should be 2.2 x 10^5 J
help?

 

[LowlyPion]

The specific heat of ice is different from that of water.

 

[nlightner]

I would like to offer some suggestions to help you with this problem. First, make sure that you are using the correct value for the specific heat capacity of ice, which is different from the specific heat capacity of water. The specific heat capacity of ice is 2093 J/kg/\circC. Also, when calculating the change in temperature, make sure to use the absolute value of the difference between the final and initial temperatures. So in this case, it would be 40.0\circC - 5.0\circC. This should give you the correct answer of 2.2 x 10^5 J. Additionally, it is always a good idea to double check your units and make sure they are consistent throughout your calculations. I hope this helps!