sodium methoxide is a strong base and nucleophile. What would be the product of an Sn2 reaction of sodium methoxide and ethyl iodide

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?