According to the cooling curve of water, which segment represents the phase change from liquid to solid?

• A. The flat segment at 100°C
• B. The sloped segment above 0°C
• C. The flat segment at 0°C
• D. The sloped segment below 0°C

Answer: (C)

Verified step by step guidance

1. Understand that a cooling curve shows temperature changes of a substance as it loses heat over time.
2. Identify that during a phase change, the temperature remains constant because the energy is used to change the phase, not to change temperature.
3. Recognize that the phase change from liquid to solid (freezing) for water occurs at 0°C, so the flat segment at 0°C represents this phase change.
4. Note that the flat segment at 100°C corresponds to the phase change from gas to liquid (condensation) or liquid to gas (boiling), not freezing.
5. Understand that sloped segments represent temperature changes within a single phase (liquid above 0°C or solid below 0°C), not phase changes.