Question

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 1

(a) in horizontal portions AB and CD, temperature remains same hence these portionas show change of state.
AB: conversion from solid to liquid state.
CD: conversion from liquid to vapour.
(b) When range of state takes place, `DeltaQ=mL`
Lenght of line `prop` Letent heat
`CD=2AB`
`DeltaQ_(CD)=2DeltaQ_(AB)`
`mL_v=2mL_l`
`L_v=2L_l`
Latent heat of vapourization is two times of latent heat of fusion
(c ) `DeltaQ=msDeltaQ`
`(Deltatheta)/(DeltaQ)=` Slope of inclined line
`=(1)/(ms)=(1)/("Thermal capacity")`
The slope of line DE represents reciprocal of heat capacity.
(d) Slope of `OAgt` slope of BC
`(1)/((ms)_s)gt(1)/((ms)_l)`
`s_lgts_S`
The specific heat of liquid is greater than that of specific heat of solid.