Two copper blocks, each of mass 2.26 kg,initially have different temperatures, t

Question

Two copper blocks, each of mass 2.26 kg,initially have different temperatures,t1 =17° C and t2 =29° C. The blocks are placed incontact with each other and come to thermal equilibrium. No heat islost to the surroundings.
(a) Find the final temperature of theblocks.
1°C

Find the heat transferred between them.
2 J

(b) Find the entropy change of each block during the time intervalin which the first joule of heat flows.
S1 = 3 J/K S2 = 4 J/K
(c) Estimate the entropy change of each block after it has reachedthermal equilibrium. Use each block's average temperature duringthe process in calculating the estimated values ofS.
S1 = 5 J/K S2 = 6 J/K (a) Find the final temperature of theblocks.
1°C

Find the heat transferred between them.
2 J

(b) Find the entropy change of each block during the time intervalin which the first joule of heat flows.
S1 = 3 J/K S2 = 4 J/K
(c) Estimate the entropy change of each block after it has reachedthermal equilibrium. Use each block's average temperature duringthe process in calculating the estimated values ofS.
S1 = 5 J/K S2 = 6 J/K S1 = 3 J/K S2 = 4 J/K

Explanation / Answer

(a) The final equilibrium temperature of the two blocks when theykept in contact with each other is                 T = (t1 + t2)/2                    = (17oC + 29oC) / 2                    = 23oC (b) The amount of heat lost by one copper block is equal to theamount of heat gained by the another copper block. So the amount of heat transferred is              Q = mcT                 = (2.26kg)(385J/kg.K)(23oC - 17oC)                  =5220.6 J (c) Formula for the entropy is              S = Q / T

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