Change in entropy of system and universe

AI Thread Summary
The discussion focuses on calculating the change in entropy for a system where 50.0g of water at 30°C is frozen to ice at -10°C. The relevant equation for entropy change is ΔS=Q/T, and the calculation involves integrating the specific heat capacity over the temperature range. Participants emphasize the need to account for both the water and ice phases in the entropy change. Additionally, they note that the freezer's temperature remains constant, allowing for the calculation of the surroundings' entropy change as -Q/Tfreezer. The conversation highlights the importance of understanding heat flow during phase changes to determine total entropy changes accurately.
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
 
Thread 'Variable mass system : water sprayed into a moving container'

Thread 'Variable mass system : water sprayed into a moving container'

Starting with the mass considerations #m(t)# is mass of water #M_{c}# mass of container and #M(t)# mass of total system $$M(t) = M_{C} + m(t)$$ $$\Rightarrow \frac{dM(t)}{dt} = \frac{dm(t)}{dt}$$ $$P_i = Mv + u \, dm$$ $$P_f = (M + dm)(v + dv)$$ $$\Delta P = M \, dv + (v - u) \, dm$$ $$F = \frac{dP}{dt} = M \frac{dv}{dt} + (v - u) \frac{dm}{dt}$$ $$F = u \frac{dm}{dt} = \rho A u^2$$ from conservation of momentum , the cannon recoils with the same force which it applies. $$\quad \frac{dm}{dt}...
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