Which physical phenomenon is the Celsius temperature scale based on?

• A. The freezing and boiling points of water at 1 atm pressure
• B. The average kinetic energy of gas molecules
• C. The triple point of water
• D. The absolute zero of temperature

Answer: (A)

Verified step by step guidance

1. Understand that temperature scales are defined based on specific physical phenomena or reference points that can be reliably reproduced.
2. Recall that the Celsius temperature scale is historically based on two fixed points related to water: the freezing point and the boiling point at standard atmospheric pressure (1 atm).
3. Recognize that the freezing point of water is defined as 0°C and the boiling point as 100°C on the Celsius scale, creating a 100-degree interval between these two physical states.
4. Note that other temperature scales, such as Kelvin, are based on different phenomena like absolute zero or the triple point of water, but these are not the basis for the Celsius scale.
5. Conclude that the Celsius scale is specifically based on the freezing and boiling points of water at 1 atm pressure, making these physical phenomena the defining reference for this scale.