You heat a piece of iron from 200 to 400 k what happens to the atom's energy of random motion

When you heat a piece of iron from 200 degree Kelvin to 400 degree Kelvin, then the kinetic energy of the molecules increases and so they start travelling faster at a random motion. Whenever the temperature of any object increases the atoms and molecules present within the object start moving faster as they are boosted by additional kinetic energy. Under normal circumstances the particles of the iron are held together in an orderly fashion and with increased heat, this orderliness starts dissipating as the particles gain in energy and start moving faster randomly.