Question

Consider the heating curve below. The graph represents temperature changes for a substance as heat is added at a steady rate. From the graph, we would most likely conclude which of the following?

• A. The specific heat of the substance in the liquid phase is very small
• B. The latent heat of fusion of the substance is very large
• C. The latent heat of vaporization of the substance is very large
• D. The latent heat of fusion of the substance is very small
• E. The latent heat of vaporization of the substance is very small

Answer 1

The correct option is D The latent heat of fusion of the substance is very small

Latent heat of is defined as the heat required to change the state of a substance, without any change in its temperature.

We can see from above graph, when the substance is changing from solid to liquid state and from liquid to vapour, its temperature is constant though heat is added to it continuouslyat a steady rate, in the given graph, temperature is constant for very little time when substance is changing into liquid i.e. we have added small amount of heat to change its state from solid to liquid as heat is added at a steady state (heat added $\propto time$) which means the latent heat of fusion of substance is very small.

Due to a long constant time, when substance is changing from liquid to vapour, substance has a large latent heat of vaporisation.