What is the primary characteristic of absolute zero?

The primary characteristic of absolute zero is that it represents a state where there is no kinetic energy among the particles of a substance. At absolute zero, which is defined as 0 Kelvin or -273.15 degrees Celsius, the molecular motion that contributes to thermal energy effectively ceases, resulting in a state of minimal thermal energy. This means that the particles are in their lowest energy state, and although quantum effects still may exist, the traditional views of temperature and kinetic energy break down.

In practical terms, reaching absolute zero is impossible due to the third law of thermodynamics, but it serves as a theoretical point indicating the absence of thermal motion. The concept of maximum kinetic energy is not applicable in the context of absolute zero, nor do states of matter such as liquid or gaseous exist at that temperature; all gases would condense to liquids or solids at extreme low temperatures. Thus, the definition and physical implications of absolute zero center strictly on the absence of kinetic energy.