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Phase Change Problems

  • #1

Homework Statement



I have three questions I need help on. Can someone please explain to me how to do them, how to correctly set up the problem, and what I need to know. I have a test tomorrow. Thanks!

Q1: How much heat is released freezing 75 grams of steam at 110 degrees C into ice at -5.1 degrees C

Q2: How much heat is released in condensing 43 grams of steam at 100 degrees C and then cooling the water to 20 degrees C.

Q3: I make a cup of tea with 43 g of water at 99 degrees C. To cool it, I add 5.1g of ice at 0 degrees C. By how much will the temperature of the tea come down by once I add the ice? (Treat tea the same as regular water)



Homework Equations



Change in Heat= mass*specific heat*change in temperature
Change in Heat=mass*latent heat




The Attempt at a Solution

 

Answers and Replies

  • #2
157
0
Q1 is straight forward. Just use the first equation you posted.

[tex] \Delta Heat = m (Cp) ( \Delta Temp) [/tex]

Cp is specific to the material and you can look it up for homework and will most likely be provided for tests.

Q2 is the same as Q1. Let me know if you don't understand the first two. It should just be plugging in numbers for each variable with change in temperature equal to final temp minus the starting temp.

Q3 I don't remember.
 

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