Question

How much heat is transferred in the process of completely melting a 1.6kg block of ice starting at -15 degrees Celsius? Is this process endothermic or exothermic?

Answer 1

Answer:

• a) Heat = 590 kJ

• b) Endothermic

Explanation:

Endothermic processes absorb energy. The final state contains more energy than the initial state.

Since ice absorbs heat energy in the process of completely melting this is an endothermic process.

The process involves two stages: 1) heating the ice up to the melting point, which is 0ºC, and 2) melting the ice.

1. Heating the ice from -15ºC to 0ºC

a) Formula: Q = m×C×ΔT

• m = 1.6 kg

• C = 2.108 kJ/kg.ºC (specific heat of ice)

• ΔT = 15ºC

b) Calculations:

• Q = m×C×ΔT = 1.6 kg × 2.108 kJ/kg.ºC  × 15ºC = 50.592 kJ

2. Melting the ice at 0ºC

a) Formula:  L = m × ΔHf

• m = 1.6 kg

• ΔHf = 334 kJ/kg (latent heat of fussion)

b) Calculations

•    L = m × ΔHf = 1.6 kg × 334 kJ/kg = 534.40 kJ

2. Total heat

• 50.592 kJ + 534.40 kJ = 584.992 kJ ≈ 590 kJ (rounded to 2 significant figures)