7. Nitrogen has two naturally occurring isotopes: nitrogen -14 (99.632%; isotopic mass=14.003074 amu) and nitrogen -15 (0.31 %; isotopic mass = 15.00010 amu). Calculate the atomic weight of nitrogen

Alidded glass container is filled with a colored gas. after a period of time, it is observed that the gas is uniformly spread throughout the box and that the movement has slowed considerably. next, a warm iron plate is carefully placed under the box. why is there resumed movement of the gas in the container?