1. Heat Transfer Problems

2. 12-4 – Case #1 Silver Spoon Steel Spoon m = 10.0 g m = 10.0 g
Boiling Water Baths at 100 oC
Ti = 25.0 oC
Ti = 25.0 oC
s = J/ g oC
s = J/ g oC

3. Graph of Temp v Time T emp E R A U 100 oC Silver silver steel Time
20 minutes
2) At 20 min, both metals have equilibrated to the temp. of surroundings.

4. 3) Which Spoon’s atom’s have a greater average kinetic energy?
Temperature is directly proportional to average kinetic energy.
BOTH ARE AT SAME TEMPERATURE THUS KINETIC ENERGIES ARE THE SAME.

5. HW 12-4 #4) Which spoon has more stored heat Q?
Steel. It takes 0.51 J to raise the temp. of 1 g of Steel by 1oC. It takes only .23 J of energy to raise the temperature of 1 g of silver by 1 oC.

6. 4) Calculate Q absorbed after 20 min. TF = 100oC of spoons;
Q = sm∆T
Silver:
Q = (0.23 J/g oC)(10.0 g) (100oC – 25oC)
Q = = 170 J (2 SF)
Steel:
Q = (0.51 J/g oC)(10.0 g) (100oC – 25oC)
Q = = 380 J (2 SF)

7. Q = sm∆T ; ∆T = Q/ sm; ∆T = Tf – Ti; Tf = ∆T + Ti ∆T = 1000. J
Case 2 – If two objects absorb the exact same amount of heat energy in joules, will they be at same final temperature?
Q = sm∆T ; ∆T = Q/ sm; ∆T = Tf – Ti; Tf = ∆T + Ti
∆T = J
Silver
=434.7= 430 (2 SF)
(0.23 J/ g oC)( 10.0 g)
Tf = ∆T + Ti; Tf = = 455 oC
Steel:
∆T = J
(0.51 J/g oC) (10.0 g)
= 196 = 200 (2 SF)
Different s values causes different ∆T
Tf = ∆T + Ti; Tf = = 225 oC

8. Analogy to Case #1: Is the same energy required to lift a bowling ball and ping ball to the same height?
Energy required to move each objective is analogous to heat added
Arrows are analogous to force (energy) required to lift
Height difference is analogous to ∆T
10 pounds
1/1760 of a pound
Different masses analogous to different specific heat capacity

9. Analogy to Case #2: If the same energy is applied to the bowling ball and ping ball will they rise to the same height?
= Force =
Energy required to move each objective is analogous to heat added
Height difference is analogous to ∆T
10 pounds
1/1760 of a pound
Different masses analogous to different specific heat capacity