Which of the following does NOT represent a step on the heating curve of water?

• A. Condensation of steam to liquid water
• B. Boiling of liquid water to steam
• C. Melting of ice to liquid water
• D. Heating of liquid water

Answer: (A)

Verified step by step guidance

1. Understand what a heating curve represents: it shows the temperature change of a substance as heat is added, including phase changes and temperature increases within phases.
2. Identify the typical steps on the heating curve of water: heating ice (solid) from below 0°C to 0°C, melting ice to liquid water at 0°C, heating liquid water from 0°C to 100°C, boiling liquid water to steam at 100°C, and heating steam above 100°C.
3. Recognize that all these steps involve adding heat to increase temperature or change phase from solid to liquid or liquid to gas (endothermic processes).
4. Note that condensation (steam to liquid water) is the reverse of boiling and involves removing heat (exothermic), so it does not appear on a heating curve, which only shows heating steps.
5. Conclude that 'Condensation of steam to liquid water' is not a step on the heating curve of water because it represents cooling and phase change in the opposite direction.