At which temperature is it said that all molecular motion completely ceases?

The temperature at which all molecular motion is said to completely cease is known as absolute zero, which is defined as 0 Kelvin (K). At this temperature, a system reaches its minimum energy state, and the thermal motion of particles is theoretically absent. Absolute zero represents the lower limit of the thermodynamic temperature scale, and it is equivalent to -273.15 degrees Celsius.

This concept is fundamental in the study of thermodynamics and provides a reference point for the Kelvin scale, which is widely used in scientific contexts. The molecular motion that we refer to encompasses all forms of kinetic energy, meaning that as you approach absolute zero, the movement of atoms and molecules slows down significantly, ultimately leading to a complete cessation of motion at 0 K.

Other temperature choices do not correspond to the point at which all molecular motion ceases; for instance, 273.15 K is the freezing point of water, and temperatures such as -273.15 K are not physically achievable according to the laws of physics.