Question

An electric heater of 500 W is used to melt 200 g of dry ice at 0°C. Find the time required to melt ice. Assume all the heat energy supplied by the heater is absorbed by the ice, and the specific latent heat of fusion of ice is 336000 J kg⁻¹.

Answer 1

Given: mass of ice, m = 200 g = 0.2 kg

Specific latent heat of fusion of ice, L = 336000 J kg⁻¹

Heat required to melt ice:

Q = mL

= 0.2 × 336000

= 67200 J

Power of heater, P = 500 W = 500 J/s

Since all heat supplied is absorbed by ice, the time required:

$$t = \frac{Q}{P}$$

$$= \frac{67200}{500}$$

= 134.4 s

Therefore, the time required is 134.4 seconds, i.e., 2 minutes and 14.4 seconds.