The half-life of iodine-131 is 8.1 days. How long will it take for three-fourths of a sample of iodine-131 to decay? (1-3/4 = 1/4; 1/4 = 1/2 x 1/2 = 2 half lives) will brainlist

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?