The absolute zero temperature is 0 Kelvin. In °C unit, which one of the following is the absolute zero temperature?
- A.0 °C
- B.-100 °C
- C.-273.15 °C
- D.-173.15 °C
Correct answer
Explanation
The correct answer is C, -273.15 °C. Zero on the Kelvin scale lies 273.15 degrees below the freezing point of water.
The Kelvin and Celsius scales have degrees of the same size, so T(K) = t(°C) + 273.15. Putting T = 0 K gives t = -273.15 °C. Absolute zero is the lowest possible temperature, at which the particles of matter have the least possible energy; it can be approached in laboratories but never actually reached. The kelvin is the SI unit of temperature, and on this scale water freezes at 273.15 K and boils at 373.15 K.
A is wrong because 0 °C is the freezing point of water, which is 273.15 K.
B is wrong because -100 °C equals 173.15 K, well above absolute zero.
D is wrong because -173.15 °C equals 100 K, not 0 K.
Exam tip: K = °C + 273.15; absolute zero = 0 K = -273.15 °C = -459.67 °F; -40 is the same on the Celsius and Fahrenheit scales.
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