A solid material is supplied heat at a constant rate. The temperature of the material is changing with the heat input as shown in figure. Study the graph carefully and answer the following questions: (i) What do the horizontal regions AB and CD represent? (ii) If CD = 2AB, what do you infer? (iii) The slope of OA gt the slope of BC. What does this indicate? (iv) What does the slope DE represent ?

A solid material is supplied heat at a constant rate. The temperature

1.	A solid material is supplied heat at a constant rate. The temperature of the material is changing with the heat input as shown in figure. Study the graph carefully and answer the following questions: (i) What do the horizontal regions AB and CD represent? (ii) If CD = 2AB, what do you infer? (iii) The slope of OA gt the slope of BC. What does this indicate? (iv) What does the slope DE represent ?
Answer» Solution :(i) In the regions AB and CD the temperature of the material REMAIN constant. So AB represents fusion and CD represents vaporisation. (ii) `CD = 2AB or Q_(4) = 2Q_(2)`, it shows that latent heat of vaporisation is twice than that of latent of fusion. (iii) Let `C_(1)` and `C_(2)` are the specific heats of SOLID and liquid states respectively, then `Q_(1) = mC_(1) Delta T_(1) (or) C_(1) = 1/(m((DeltaT_(1))/Q_(1)))=1/(mxx "slope of" OA)` Similarly `C_(2) = 1/(m XX "slope of" BC)` , Since slope of `OA gt` slope of BC, `therefore C_(1) gt C_(2)`. (iv) If `C_(3)` is the specific heat of vapour state (region DE), then `C_(3) = 1/ (m xx "slope of" DE)` (or) Slope of `DE = 1/(mC_(3))=1/("heat capacity"). `