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Physics 7B
WS T7 (rev. 3.0)
Page 1
T7. Entropy: Other Topics
Part 1: Entropy with Calorimetry
Questions for discussion (Part 1)
1
. The melting point of lead is 327.5
o
C. To melt one kilogram of lead at this temperature, you must
add about 25,000 J of heat. When you do this, does the entropy of the lead change? (See if you can
answer based on the qualitative idea of “order vs. disorder.”)
2
. In Discussion Question 1, if you said that the entropy of the system changes, then by how much?
(Give a numerical answer.)
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View Full DocumentPhysics 7B
WS T7 (rev. 3.0)
Page 2
Problems (Part 1)
1
. A small lead block, of mass M and initial
temperature 3T, is placed in contact with a
large lead block, of mass 4M and initial
temperature T. The system as a whole is
isolated, so that no heat is lost to the
surroundings.
a)
Will the final temperature of the twoblock
system be less than 2T, greater than 2T, or
equal to 2T?
b)
Find the final temperature T
f
in terms of T.
Was your answer to part (a) correct?
c)
Find the change in the entropy of the small
block during this process. (Denote the specific
heat of lead by c
L
.) Is your answer consistent
with the Second Law?
d)
Next, find the change in entropy of the large
block during this process. Is your answer
consistent with the Second Law?
e)
Finally, find the change in entropy of the two
block system. Is your answer consistent with
the Second Law?
2
. A lead block of mass M is at initial
temperature T
L
. The block is placed within a
thermally insulated canister of water. The
water has mass m and is initially at
temperature T
W
.
If M = 12 kg, m = 75 g, and T
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 Fall '10
 yildiz
 Physics, Entropy

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