When the weather is hot, the air atoms are moving. But when will the atoms stop their movement. For example oxygen, the boiling point is –182.97⁰C, the melting point is –209.86⁰C. In gas form, it moves freely, in liquid form, it moves freely too but slower than in gas form. And in solid form, it can only moves in a small area, Although in solid form, the atoms still moving. But at –273.15⁰C, it stops, no atoms can move at this temperature. And at this temperature, the kinetic energy of the atoms is 0.

Arrangement in different form

In gas form in liquid form in solid form