Question

A block of lead of mass 250 g, at 27°C was heated in a furnace till it completely melted. Find the quantity of heat required
(a) To bring the lead block upto its melting point,
(b) To completely melt the block at its melting point (Melting point of lead is 327°C, Sp. heat cap. of lead is 0.13 J/gk and latent heat of fusion of lead is 26 J/g)

Answer 1

Mass of lead block, m = 250 g

Change in temperature, ΔT = 327°C - 27°C = 300°C = 300 K

C = 0.13 J/gK

Amount of heat required to raise the temperature to 327°C

Q = m x C ΔT

= 250 x 0.13 x 300 = 9750 J

Amount of heat required to completely melt the block upto its melting point

Q = m x L

= 250 x 26 = 6500 J