Question: What is the entropy change when 1 kg of water at 100°C is converted to steam at 100°C?

Options:

1. 2260 J/K
2. 100 J/K
3. 540 J/K
4. 0 J/K

Correct Answer: 2260 J/K

Solution:

The entropy change for phase change at constant temperature is ΔS = Q/T. For 1 kg of water to steam, Q = 2260 kJ, T = 373 K, so ΔS = 2260 kJ / 373 K = 6.06 kJ/K.