Including a heat for a phase change or not?

[catzmeow]

Hi PF!

I just took a test for my class and there is one problem I can't get my mind off of. I'm not necessarily looking for the correct solution here, just if my thinking was correct. It went more or less like this: there is 40g of ice at 0 degrees C in 200g of water in an aluminum calorimeter. Both water and calorimeter are at 0C. There is also a bit of copper at 98C. The system's final temp is 2 C.

Was I right to include a phase change of ice to water to rise to 2C? I also included the change in heat using the specific heat of water and another step including the specific heat of ice?

Did I include too much/over think this?

Thanks!

 

[Andrew Mason]

Hi PF!

I just took a test for my class and there is one problem I can't get my mind off of. I'm not necessarily looking for the correct solution here, just if my thinking was correct. It went more or less like this: there is 40g of ice at 0 degrees C in 200g of water in an aluminum calorimeter. Both water and calorimeter are at 0C. There is also a bit of copper at 98C. The system's final temp is 2 C.

Was I right to include a phase change of ice to water to rise to 2C? I also included the change in heat using the specific heat of water and another step including the specific heat of ice?

Did I include too much/over think this?

Thanks!

Do you think there will be any ice at 2C? If not, you were quite right to take into account the phase change.

AM

 

[catzmeow]

Haha yes very true. For some reason I feel like I shouldn't have included the specific heat of water or of ice... I'm not sure. Something felt off about it but I can't put my finger on it...

 

[Chestermiller]

You shouldn't have used the specific heat of ice for the portion originally ice that was heated from 0 to 2. You should have used the specific heat of water for this.

 

[catzmeow]

Hmmm I only wish I could go back and change it! Thank you, chestermiller, I'll have to remember this for the next test...

 

[CWatters]

Was I right to include a phase change of ice to water to rise to 2C? I also included the change in heat using the specific heat of water and another step including the specific heat of ice?

Yes, should include the heat for the phase change but it should be..

Specific Heat of the original water
+ Latent heat for the ice->water
+ Specific Heat of the ice that is now water

 

[catzmeow]

I want to say I did do that, I can't exactly remember now. I wasn't sure if I included to many changes or not...thanks for your input!