BBs in a pan are shaken by a speaker hooked to a signal generator.  The pan is tipped slightly so the BBs move to the lower end and pack like a crystalline solid. The shaking represents atomic motion or kinetic energy or temperature.  Turning up the amplitude of shaking (at about 30 Hz) “melts” the solid when the BBs can move by one another.  Larger amplitude shaking produces a gas, where the BBs move everywhere.  Adding larger ball bearings demonstrates that the same energy gives lower speed to the larger balls