IB Physics Higher Level (HL) Practice Exam

Absolute zero is defined as the theoretical temperature at which all molecular motion ceases, and is considered the lowest possible temperature. In the Kelvin scale, absolute zero is established as 0 K. This temperature corresponds to -273.15°C in the Celsius scale. The Kelvin scale is an absolute temperature scale used in scientific contexts, which starts from absolute zero and does not include negative values, making 0 K the foundational reference point.

The other choices either represent temperatures above absolute zero or are conversions that may lead to misunderstandings. Understanding that absolute zero signifies a complete absence of thermal energy is crucial in various scientific disciplines, including physics, and highlights its importance in thermodynamics and the behavior of matter at low temperatures.