Change in entropy of system and universe

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SUMMARY

The discussion focuses on calculating the change in entropy for a system consisting of 50.0g of water at 30°C being frozen to ice at -10°C. The relevant equation for entropy change is ΔS=Q/T=∫Ti..Tf(CpdT)/T. Participants emphasize the need to consider both the water and the ice during the calculation, as well as the entropy change of the freezer, which is treated as a large reservoir with a constant temperature. The heat flow out of the water is crucial for determining the entropy change of the surroundings.

PREREQUISITES
  • Understanding of thermodynamics principles, particularly entropy.
  • Familiarity with the specific heat capacity (Cp) of water and ice.
  • Knowledge of phase changes and their effects on entropy.
  • Ability to perform integral calculus for temperature-dependent processes.
NEXT STEPS
  • Calculate the change in entropy for the phase transition from water to ice using specific heat values.
  • Learn about the concept of thermal equilibrium and its implications in thermodynamic systems.
  • Explore the role of heat flow in entropy calculations, particularly in closed systems.
  • Investigate the effects of temperature on entropy changes in various materials.
USEFUL FOR

Students studying thermodynamics, physics enthusiasts, and anyone involved in calculating entropy changes in chemical or physical processes.

sfgoat
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Homework Statement



50.0g of water (the system) at 30C is frozen to ice at a final temp of -10C in a freezer. Assuming that the volume of water remains the same during the process, calculate the change in entropy of the system and the change of entropy of the thermal universe when the system reaches thermal equilibrium.
constants.jpg


Homework Equations


ΔS=Q/T=∫Ti..Tf(CpdT)/T

The Attempt at a Solution


See attached image for attempt at solution. I already missed the question in class and just want to know how to properly do it at this point. Thanks.
CCI11212014_0001.jpg
 
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sfgoat said:

Homework Statement



50.0g of water (the system) at 30C is frozen to ice at a final temp of -10C in a freezer. Assuming that the volume of water remains the same during the process, calculate the change in entropy of the system and the change of entropy of the thermal universe when the system reaches thermal equilibrium.

Homework Equations


ΔS=Q/T=∫Ti..Tf(CpdT)/T
This is correct for the entropy change for the water. What about the ice part?
 
sfgoat said:

Homework Statement



50.0g of water (the system) at 30C is frozen to ice at a final temp of -10C in a freezer. Assuming that the volume of water remains the same during the process, calculate the change in entropy of the system and the change of entropy of the thermal universe when the system reaches thermal equilibrium.
View attachment 75716

Homework Equations


ΔS=Q/T=∫Ti..Tf(CpdT)

In order to calculate the change in entropy of the freezer (i.e the surroundings) assume that the freezer is so large that its temperature does not change during the process. In that case, the change in entropy is -Q/Tfreezer where Q is the heat flow out of the water. What is the heat flow out of the water?

AM
 

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