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## Homework Statement

A 10 gram block of iron metal (Sp=0.449 J/gK) at 400 K is placed in contact with a 20 gram block of aluminum (Sp=0.903 J/gK) at 300 K. Heat flows between the two until equilibrium is reached. Find the equilibrium temp and the change in entropy for the process.

## Homework Equations

q=m(Sp)([tex]\Delta[/tex]T)

and for a process involving a temperature change i think we use:

[tex]\Delta[/tex]S = [tex]\int[/tex]Cp*dT/T

## The Attempt at a Solution

First of all I was able to find the final temperature by using the first equation. It should be = 319.9 K. Where I get confused is do I use the Sp in place of Cp and then integrate? The reason I don't think I am doing this right is because there is a problem almost identical to it in the book (except that the metals and masses are the same) and I can't even get close to a right answer. Also in the one in the book, it asks for the change in the entropy for the universe and says that it is a positive non-zero number. How can that be true if the system is isolated and even if it isn't isolated how could you calculate the entopy change for the surroundings? I've tried it every way I can think of. please help!!!

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