Including a heat for a phase change or not?

In summary, the conversation discusses a test question involving a system with 40g of ice at 0 degrees C, 200g of water at 0C, and a bit of copper at 98C. The final temperature of the system is 2 C. The question is whether the correct solution should include the phase change of ice to water and the specific heat of water and ice. It is determined that the phase change should be included but the specific heat of ice should only be used for the portion of ice that is now water. The person regrets not using the correct specific heat and thanks the expert for their input.
  • #1
catzmeow
18
0
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!
 
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  • #2
catzmeow said:
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
 
  • #3
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...
 
  • #4
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.
 
  • #5
Hmmm I only wish I could go back and change it! Thank you, chestermiller, I'll have to remember this for the next test...
 
  • #6
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
 
  • #7
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!
 

1. What is a phase change?

A phase change is the process in which matter transitions from one physical state to another, such as from a solid to a liquid or from a liquid to a gas.

2. What factors determine if heat should be included for a phase change?

The factors that determine whether heat should be included for a phase change include the type of substance, the initial and final temperatures, and the amount of heat required for the phase change to occur.

3. Why is it important to include heat for a phase change?

Including heat for a phase change is important because it affects the amount of energy needed to break the bonds between molecules and change the physical state of the substance. This can have significant impacts on processes such as cooking, industrial production, and climate change.

4. How does the addition of heat affect a phase change?

The addition of heat increases the kinetic energy of the molecules, causing them to move faster and break the bonds holding them together. This allows the substance to transition from one phase to another.

5. Can heat ever be excluded for a phase change?

In some cases, such as for certain substances like dry ice (solid carbon dioxide), heat can be excluded for a phase change to occur. This is because these substances undergo sublimation, where they transition directly from a solid to a gas without going through a liquid phase.

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