Under what condition does water begin to boil in a refrigeration system?

• A. When the temperature increases
• B. When the temperature decreases
• C. When the pressure is lowered
• D. When it is heated above 100°C

Answer: (C)

Water begins to boil when the pressure is lowered because boiling occurs when a liquid's vapor pressure equals the surrounding atmospheric pressure. In a refrigeration system, if the pressure around the water is reduced, the boiling point decreases. This means that under lower pressure, water can boil at temperatures below its normal boiling point of 100°C at standard atmospheric pressure. This principle is crucial in refrigeration cycles, where low pressure is used to facilitate the evaporation or boiling process, allowing heat absorption from the surrounding environment. Other factors, such as temperature or heating above 100°C, do not directly relate to the boiling process under the typical conditions applied within refrigeration systems.