Heat is added to a 1.0-kg solid sample of a material at -200 °C. The figure shows the temperature of the material as a function of the heat added.
-What is the latent heat of fusion of this material?
A)50 cal/g
B)100 cal/g
C)150 cal/g
D)300 cal/g
E)450 cal/g

Question

Heat is added to a 1.0-kg solid sample of a material at -200 °C. The figure shows the temperature of the material as a function of the heat added. 
-What is the latent heat of fusion of this material?
A)50 cal/g 
B)100 cal/g 
C)150 cal/g 
D)300 cal/g 
E)450 cal/g

Quizplus · Accepted Answer

The temperature of the material remains steady at -200°C until all of the solid material has heated up and melted. This means that all of the heat added during this time is being used for the phase change from solid to liquid, so the heat added is equal to the latent heat of fusion. From the graph, we can see that the heat added during this phase change is approximately 1000 cal. Since the mass of the sample is 1 kg, the latent heat of fusion is:
Latent heat of fusion = heat added/mass = 1000 cal/1000 g = 1 cal/g = 100 cal/kg
Therefore, the answer is B, 100 cal/g.

Heat Is Added to a 1