A solid material is supplied with heat at a constant rate. The temperature of the material is changing with the heat input as shown in the graph in figure. Study the graph carefully and answer the following questions:

(i) What do the horizontal regions AB and CD represent?
If CD is equal to 2AB, what do you infer?
What does the slope of DE represents?
The slope of OAgtthe slope of BC. What does this indicate?

Answer

A

Explanation

(i) Region AB: Heat is absorbed by the material at a
constant temperature called the melting point.
The phase changes from solid to liquid.
Region CD: Heat is absorbed by the material at a
constant temperature called the boiling point. The
phase changes from liquid to gas.
(ii) Latent heat of vaporisation =2(latent heat of fusion)
(iii) `Q=mc_gDeltaT.`
The slope `DE=(DeltaT)/Q=1/(mc_g)`
(iv) The reciprocal of heat capacity in solid state is greater
than the reciprocal of heat capacity in liquid state
`(1/(mc))_(solid)gt(1/(mc))_(liquid)gt(mc)_(solid)`
`rArrc_(liquid)gtc_(solid)`