The SI unit kelvin is used to measure which quantity?

• A. Temperature
• B. Distance
• C. Time
• D. Mass

Answer: (A)

Kelvin is the unit used to measure temperature, specifically thermodynamic temperature. It’s the SI unit because it starts at absolute zero—the point where particles have minimum thermal motion. This makes Kelvin an absolute scale, which is especially useful in science because temperature changes are directly related to energy and can be used in formulas without negative values. One kelvin represents the same magnitude of temperature change as one degree Celsius, but the zero point is different: 0 K equals −273.15 °C. For example, water freezes at 273.15 K and boils at 373.15 K at one atmosphere of pressure.

This quantity is not used for measuring distance, time, or mass, which are measured in meters, seconds, and kilograms respectively.