What is the relationship between absolute zero, kinetic theory and the Kelvin scale?
According to Kinetic Molecular Theory, the average kinetic energy of molecules depends on the temperature.
All kinetic energy of motion supposedly ceases at absolute zero.
This makes it convenient to design a temperature scale that starts at absolute zero. Nothing can be colder than absolute zero, so all temperatures on such a scale will be positive numbers.
The Kelvin scale starts at absolute zero (0 K) and has degrees that are the same size as Celsius degrees.