How Much Heat Must Be Removed to Make Ice from Water at Different Temperatures?

[Yanbeast]

Homework Statement

How much heat (in kcal) must be removed to make ice at –10°C from 2 kg of water at 20°C? (The specific heat of ice is 0.5 cal/g °C.)

Homework Equations

Q=cmT

The Attempt at a Solution

I thought this problem was simple,
Q=0.5x2000x30
Then diving by 1000 again to put it into Kcal. 30 is not the right answer.

 

[Mark44]

Homework Statement

How much heat (in kcal) must be removed to make ice at –10°C from 2 kg of water at 20°C? (The specific heat of ice is 0.5 cal/g °C.)

And the specific heat of water is 1.0 cal/g °C.

Homework Equations

Q=cmT

The Attempt at a Solution

I thought this problem was simple,
Q=0.5x2000x30
Then diving by 1000 again to put it into Kcal. 30 is not the right answer.

There are three things you have to account for:
The water has to be cooled 20°C.
The water at 0°C has to be converted to ice. (80C/g)
The ice at 0°C has to be cooled to -10°C.