Question

A hydrocarbon of mass 1.5 kg is just kept in the molten state by a heater of 500 W. If the heater is switched off, the temperature starts dropping after 4 min. Calculate sp. latent heat of fusion of the hydrocarbon.

Answer 1

The heat supplied while the hydrocarbon changes state is Q = Pt.

Time = 4 × 60 = 240 s

Q = 500 × 240 = 120000 J

Using Q = mL

$$L = \frac{Q}{m}$$

$$= \frac{120000}{1.5}$$

= 80000 Jkg⁻¹