Block of ice melts - entropy of ice?

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Homework Help Overview

The problem involves calculating the change in entropy of a 2.00 kg block of ice at 0.0˚C as it melts. The context is centered around thermodynamics and the concept of entropy during phase changes.

Discussion Character

  • Exploratory, Conceptual clarification, Mathematical reasoning

Approaches and Questions Raised

  • Participants discuss the calculation of heat (Q) and its relation to temperature change, questioning the appropriateness of using a temperature change equation when the temperature remains constant during melting.
  • There is exploration of using latent heat for the phase change to determine Q, with some participants suggesting looking up the relevant values.

Discussion Status

The discussion is ongoing, with participants providing feedback on each other's approaches. Some guidance has been offered regarding the use of latent heat, and there is a recognition of the need to adjust calculations based on the phase change rather than temperature change.

Contextual Notes

Participants are navigating the constraints of using equations that may not apply due to the nature of the phase change, and there is a focus on ensuring the correct values for latent heat are utilized in calculations.

ally1h
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Homework Statement


A 2.00 kg block of ice at 0.0˚C melts. What is the change in entropy of the ice as a result of this process?


Homework Equations


Q = mcΔT
ΔS = Q/T



The Attempt at a Solution


Q = (2.00 kg)(2.1 kJ/kg*K)(273 K)
Q = 1092 J

ΔS = 1092 J / 273 K
ΔS = 4 J/K


Any good?
 
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Not good. Why would you calculate Q using an equation with ΔT? The temperature change is zero, not 273 K. I like your second equation, though, which assumes constant temperature.

How about getting the energy from the phase change?
 


Then I'm not sure how to do the problem, the first part anyway, because then Q = 0 and if Q = 0 then ΔS = 0 as well...
 


How about looking up the energy associated with the phase change?
 


Ahhh... so I'm looking at latent heat then?
Q = mass x latent heat of fusion
Q = (2.00 kg)(333.7 kJ/kg)
Q = 667.4 kJBetter? And then plug that into the second equation?
 


Better.
 

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