Question

50 g of ice at –20°C is heated on an electric heater till it forms water at 100°C. Calculate:

1. Heat energy required to raise the temperature of ice to 0°C.
2. Heat energy required to melt ice so as to form water at 0°С.
3. Heat energy required to bring water to the temperature of 100°C.

[Take specific latent heat of fusion of ice = 340 Jg⁻¹, specific heat capacity of water = 4.2 Jg⁻¹°C⁻¹ and specific heat capacity of ice = 2.1 Jg⁻¹°C⁻¹].

Answer 1

(a) Heat energy required to raise the temperature of ice to 0°C.

H = mcθ_R

= 50 g × 2.1 Jg⁻¹°C⁻¹ × 20°C

= 2100 J

(b) Heat energy required to melt ice

H = mL

= 50 g × 340 Jg⁻¹

= 17000 J

(c) Heat energy required to bring water to 100°C.

H = mcθ_R

= 50 g × 4.2 Jg⁻¹°C⁻¹ × 100°C

= 21000 J